CODES

ADOPTS WITHOUT AMENDMENTS:

International Existing Building Code 2012 (IEBC 2012)

Copyright

Preface

Effective Use of the International Existing Building Code

Legislation

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 Compliance Methods

Chapter 4 Prescriptive Compliance Method

Chapter 5 Classification of Work

Chapter 6 Repairs

Chapter 7 Alterations—Level 1

Chapter 8 Alterations—Level 2

Chapter 9 Alterations—Level 3

Chapter 10 Change of Occupancy

Chapter 11 Additions

Chapter 12 Historic Buildings

Chapter 13 Relocated or Moved Buildings

Chapter 14 Performance Compliance Methods

Chapter 15 Construction Safeguards

Chapter 16 Referenced Standards

Appendix A Guidelines for the Seismic Retrofit of Existing Buildings

Chapter A1 Seismic Strengthening Provisions for Unreinforced Masonry Bearing Wall Buildings
Chapter A2 Earthquake Hazard Reduction in Existing Reinforced Concrete and Reinforced Masonry Wall Buildings with Flexible Diaphragms
Chapter A3 Prescriptive Provisions for Seismic Strengthening of Cripple Walls and Sill Plate Anchorage of Light, Wood-Frame Residential Buildings
Chapter A4 Earthquake Risk Reduction in Wood-Frame Residential Buildings with Soft, Weak or Open Front Walls
Chapter A5 Earthquake Hazard Reduction in Existing Concrete Buildings

Appendix B Supplementary Accessibility Requirements for Existing Buildings and Facilities

Appendix C Guidelines for the Wind Retrofit of Existing Buildings

Resource A Guidelines on Fire Ratings of Archaic Materials and Assemblies

Appendix

ASCE/SEIAmerican Society of Civil Engineers
Structural Engineering Institute
1801 Alexander Bell Drive
Reston, VA 20191-4400
Standard
reference
number
TitleReferenced
in code
section number
7—-10 Minimum Design Loads for Buildings and Other Structures with Supplement No. 1 A104, A403.3
31—-03 Seismic Evaluation of Existing BuildingsA504.1, A505.1
41—06Seismic Rehabilitation of Existing BuildingsA503.2, A506.3.2,A507.1
ASTMASTM International
100 Barr Harbor Drive
West Conshohocken, PA 19428-2959
Standard
reference
Number
Title Referenced
in code
section number
A653/A653M—08Standard Specification for Steel Sheet, Zinc Coated (Galvanized) or
Zinc-Iron Alloy-Coated (Galvannealed) by Hot-Dip Process
A304.2.6
C90—2003 Standard Specification for Load-bearing Concrete Masonry Units A505.2.3
C496—96 Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens A104, A106.3.3.2
E519—00e1 Standard Test Method for Diagonal Tension (Shear) in Masonry Assemblages A104, A106.3.3.2
DOCU.S. Department of Commerce
National Institute of Standards and Technology
100 Bureau Drive Stop 3460
Gaithersburg, MD 20899
Standard
reference
Number
Title Referenced
in code
section number
PS-1—95Construction and Industrial PlywoodA302
PS-2—92Performance Standard for Wood-based Structural-use PanelsA302
ICCInternational Code Council
500 New Jersey Avenue, NW, 6th Floor
Washington, DC 20001
Standard
reference
Number
Title Referenced
in code
section number
BNBC—93BOCA National Building Code®A502
BNBC—96BOCA National Building Code®A502
BNBC—99BOCA National Building Code®A202
IBC—00International Building Code®A202.1, A502.1
IBC—03International Building Code®A202.1, A502.1
IBC—06International Building Code®A202.1, A502.1
IBC—09International Building Code®A202.1, A502.1
IBC—12International Building Code®A102.2, A108.2, A202.1, A203, A206.3, A206.9,
A403.1, A405.1, A407.1, A502.1, A503.3, A506.4,
SBC—94Standard Building Code®A502
SBC—97Standard Building Code®A502
SBC—99Standard Building Code®A202
UBC—76Uniform Building Code®A502
UBC—97Uniform Building Code®A102.2, A103, A104, A108.2, A202, A203, A206.2, A301.2, A401.2, A403.1, A403.2, A403.3,
A403.4, A403.7, A403.11.2.2, A405.2.3,
A406.2, A406.3.2.1, A408.1, A502
UBC—Standard 21-4Hollow and Solid Load-bearing Concrete Masonry UnitsA106.2
UBC—Standard 21-6In-place Masonry Shear TestsA104
UBC—Standard 21-7Tests of Anchors in Unreinforced MasonryA105.3, A107.3, A107.4, Table A1-E
UBC—Standard 21-8Pointing of Unreinforced Masonry WallsA103, A106.3.3.9

Chapter A1 Seismic Strengthening Provisions for Unreinforced Masonry Bearing Wall Buildings

The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on existing unreinforced masonry bearing wall buildings.

The provisions of this chapter are intended as minimum standards for structural seismic resistance, and are established primarily to reduce the risk of life loss or injury. Compliance with these provisions will not necessarily prevent loss of life or injury, or prevent earthquake damage to rehabilitated buildings.

The provisions of this chapter shall apply to all existing buildings having at least one unreinforced masonry bearing wall. The elements regulated by this chapter shall be determined in accordance with Table A1-A. Except as provided herein, other structural provisions of the building code shall apply. This chapter does not apply to the alteration of existing electrical, plumbing, mechanical or fire safety systems.
The provisions of this chapter shall not apply to the strengthening of buildings in Risk Categories III or IV. Such buildings shall be strengthened to meet the requirements of the International Building Code for new buildings of the same risk category or other such criteria approved by the code official.

For the purpose of this chapter, the applicable definitions in the building code shall also apply.

Deleted
[B] COLLAR JOINT. The vertical space between adjacent wythes. A collar joint may contain mortar or grout.
[B] CROSSWALL. A new or existing wall that meets the requirements of Section A111.3 and the definition of Section A111.3. A crosswall is not a shear wall.
[B] CROSSWALL SHEAR CAPACITY. The unit shear value times the length of the crosswall, νcLc.
[B] DIAPHRAGM EDGE. The intersection of the horizontal diaphragm and a shear wall.
[B] DIAPHRAGM SHEAR CAPACITY. The unit shear value times the depth of the diaphragm, νuD.
Deleted
[B] FLEXIBLE DIAPHRAGM. A diaphragm of wood or untopped metal deck construction.
[B] NORMAL WALL. A wall perpendicular to the direction of seismic forces.
[B] OPEN FRONT. An exterior building wall line without vertical elements of the lateral force-resisting system in one or more stories.
[B] POINTING. The partial reconstruction of the bed joints of an unreinforced masonry wall as defined in UBC Standard 21-8.
[B] RIGID DIAPHRAGM. A diaphragm of concrete construction.
[B] UNREINFORCED MASONRY. Includes burned clay, concrete or sand-lime brick; hollow clay or concrete block; plain concrete; and hollow clay tile. These materials shall comply with the requirements of Section A106 as applicable.
[B] UNREINFORCED MASONRY BEARING WALL. A URM wall that provides the vertical support for the reaction of floor or roof-framing members.
[B] UNREINFORCED MASONRY (URM) WALL. A masonry wall that relies on the tensile strength of masonry units, mortar and grout in resisting design loads, and in which the area of reinforcement is less than 25 percent of the minimum ratio required by the building code for reinforced masonry.
[B] YIELD STORY DRIFT. The lateral displacement of one level relative to the level above or below at which yield stress is first developed in a frame member.

For the purpose of this chapter, the following notations supplement the applicable symbols and notations in the building code.

an =Diameter of core multiplied by its length or the area of the side of a square prism.
A =Cross-sectional area of unreinforced masonry pier or wall, square inches (10-6 m2).
Ab =Total area of the bed joints above and below the test specimen for each in-place shear test, square inches (10-6 m2).
D =In-plane width dimension of pier, inches (10-3 m), or depth of diaphragm, feet (m).
DCR =Demand-capacity ratio specified in Section A111.4.2.
f 'm=Compressive strength of masonry.
f sp =Tensile-splitting strength of masonry.
Fwx =Force applied to a wall at level x , pounds (N).
H =Least clear height of opening on either side of a pier, inches (10-3 m).
h/t =Height-to-thickness ratio of URM wall. Height, h, is measured between wall anchorage levels and/or slab-on-grade.
L =Span of diaphragm between shear walls, or span between shear wall and open front, feet (m).
Lc =Length of crosswall, feet (m).
Li =Effective span for an open-front building specified in Section A111.8, feet (m).
P =Applied force as determined by standard test method of ASTM C 496 or ASTM E 519, pounds (N).
PD =Superimposed dead load at the location under consideration, pounds (kN). For determination of the rocking shear capacity, dead load at the top of the pier under consideration shall be used.
PD+L =Press resulting from the dead plus actual live load in place at the time of testing, pounds per square inch (kPa).
Pw =Weight of wall, pounds (N).
R =Response modification factor for Ordinary plain masonry shear walls in Bearing Wall System from Table 12.2-1 of ASCE 7, where R = 1.5.
SDS =Design spectral acceleration at short period, in g units.
SD1 =Design spectral acceleration at 1-second period, in g units.
νa =The shear strength of any URM pier, νm A/1.5 pounds (N).
νc =Unit shear capacity value for a crosswall sheathed with any of the materials given in Table A1-D or A1-E, pounds per foot (N/m).
νm =Shear strength of unreinforced masonry, pounds per square inch (kPa).
Vaa =The shear strength of any URM pier or wall, pounds (N).
Vca =Total shear capacity of crosswalls in the direction of analysis immediately above the diaphragm level being investigated, νcLc, pounds (N).
Vcb =Total shear capacity of crosswalls in the direction of analysis immediately below the diaphragm level being investigated, νcLc, pounds (N).
Vp =Shear force assigned to a pier on the basis of its relative shear rigidity, pounds (N).
Vr =Pier rocking shear capacity of any URM wall or wall pier, pounds (N).
νt =Mortar shear strength as specified in Section A106.3.3.5, pounds per square inch (kPa).
Vtest =Load at incipient cracking for each in-place shear test per UBC Standard 21-6, pounds (kN).
νto =Mortar shear test values as specified in Section A106.3.3.5, pounds per square inch (kPa).
νu =Unit shear capacity value for a diaphragm sheathed with any of the materials given in Table A1-D or A1-E, pounds per foot (N/m).
Vwx =Total shear force resisted by a shear wall at the level under consideration, pounds (N).
W =Total seismic dead load as defined in the building code, pounds (N).
Wd =Total dead load tributary to a diaphragm level, pounds (N).
Ww =Total dead load of a URM wall above the level under consideration or above an open-front building, pounds (N).
Wwx =Dead load of a URM wall assigned to level x halfway above and below the level under consideration, pounds (N).
ΣνuD =Sum of diaphragm shear capacities of both ends of the diaphragm, pounds (N).
ΣΣνuD =For diaphragms coupled with crosswalls, νuD includes the sum of shear capacities of both ends of diaphragms coupled at and above the level under consideration, pounds (N).
ΣWd =Total dead load of all the diaphragms at and above the level under consideration, pounds (N).
The seismic force-resisting system specified in this chapter shall comply with the building code, except as modified herein.
Alterations and repairs required to meet the provisions of this chapter shall comply with applicable structural requirements of the building code unless specifically provided for in this chapter.
The following construction information shall be included in the plans required by this chapter:
1. Dimensioned floor and roof plans showing existing walls and the size and spacing of floor and roof-framing members and sheathing materials. The plans shall indicate all existing and new crosswalls and shear walls and their materials of construction. The location of these walls and their openings shall be fully dimensioned and drawn to scale on the plans.
2. Dimensioned wall elevations showing openings, piers, wall classes as defined in Section A106.3.3.8, thickness, heights, wall shear test locations, cracks or damaged portions requiring repairs, the general condition of the mortar joints, and if and where pointing is required. Where the exterior face is veneer, the type of veneer, its thickness and its bonding and/or ties to the structural wall masonry shall also be noted.
3. The type of interior wall and ceiling materials, and framing.
4. The extent and type of existing wall anchorage to floors and roof when used in the design.
5. The extent and type of parapet corrections that were previously performed, if any.
6. Repair details, if any, of cracked or damaged unreinforced masonry walls required to resist forces specified in this chapter.
7. All other plans, sections and details necessary to delineate required retrofit construction.
8. The design procedure used shall be stated on both the plans and the permit application.
9. Details of the anchor prequalification program required by UBC Standard 21-7, if used, including location and results of all tests.
Structural observation, in accordance with Section 1709 of the International Building Code, shall be required for all structures in which seismic retrofit is being performed in accordance with this chapter. Structural observation shall include visual observation of work for conformance with the approved construction documents and confirmation of existing conditions assumed during design.

Structural testing and inspection for new construction materials shall be in accordance with the building code, except as modified by this chapter.

Materials permitted by this chapter, including their appropriate strength design values and those existing configurations of materials specified herein, may be used to meet the requirements of this chapter.
Existing materials used as part of the required vertical load-carrying or lateral force-resisting system shall be in sound condition, or shall be repaired or removed and replaced with new materials. All other unreinforced masonry materials shall comply with the following requirements:
1. The lay-up of the masonry units shall comply with Section A106.3.2, and the quality of bond between the units has been verified to the satisfaction of the building official;
2. Concrete masonry units are verified to be load-bearing units complying with UBC Standard 21-4 or such other standard as is acceptable to the building official; and
3. The compressive strength of plain concrete walls shall be determined based on cores taken from each class of concrete wall. The location and number of tests shall be the same as those prescribed for tensile-splitting strength tests in Sections A106.3.3.3 and A106.3.3.4, or in Section A108.1.

The use of materials not specified herein or in Section A108.1 shall be based on substantiating research data or engineering judgment, with the approval of the building official.

Unreinforced masonry walls used to carry vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this section. All masonry that does not meet the minimum standards established by this chapter shall be removed and replaced with new materials, or alternatively, shall have its structural functions replaced with new materials and shall be anchored to supporting elements.
The facing and backing shall be bonded so that not less than 10 percent of the exposed face area is composed of solid headers extending not less than 4 inches (102 mm) into the backing. The clear distance between adjacent full-length headers shall not exceed 24 inches (610 mm) vertically or horizontally. Where the backing consists of two or more wythes, the headers shall extend not less than 4 inches (102 mm) into the most distant wythe, or the backing wythes shall be bonded together with separate headers with their area and spacing conforming to the foregoing. Wythes of walls not bonded as described above shall be considered veneer. Veneer wythes shall not be included in the effective thickness used in calculating the height-to-thickness ratio and the shear capacity of the wall.

Exception: Veneer wythes anchored as specified in the building code and made composite with backup masonry may be used for calculation of the effective thickness, where SD1 exceeds 0.3.

Grouted or ungrouted hollow concrete or clay block and structural hollow clay tile shall be laid in a running bond pattern.
Lay-up patterns other than those specified in Sections A106.3.2.1 and A106.3.2.2 above are allowed if their performance can be justified.
The quality of mortar in all masonry walls shall be determined by performing in-place shear tests in accordance with the following:
1. The bed joints of the outer wythe of the masonry should be tested in shear by laterally displacing a single brick relative to the adjacent bricks in the same wythe. The head joint opposite the loaded end of the test brick should be carefully excavated and cleared. The brick adjacent to the loaded end of the test brick should be carefully removed by sawing or drilling and excavating to provide space for a hydraulic ram and steel loading blocks. Steel blocks, the size of the end of the brick, should be used on each end of the ram to distribute the load to the brick. The blocks should not contact the mortar joints. The load should be applied horizontally, in the plane of the wythe. The load recorded at first movement of the test brick as indicated by spalling of the face of the mortar bed joints is Vtest in Equation A1-3.
2. Alternative procedures for testing shall be used where in-place testing is not practical because of crushing or other failure mode of the masonry unit (see Section A106.3.3.2).
The tensile-splitting strength of existing masonry, fsp, or the prism strength of existing masonry, f'm, may be determined in accordance with one of the following procedures:
1. Wythes of solid masonry units shall be tested by sampling the masonry by drilled cores of not less than 8 inches (203 mm) in diameter. A bed joint intersection with a head joint shall be in the center of the core. The tensile-splitting strength of these cores should be determined by the standard test method of ASTM C 496. The core should be placed in the test apparatus with the bed joint 45 degrees from the horizontal. The tensile-splitting strength should be determined by the following equation:
(Equation A1-1)
2. Hollow unit masonry constructed of through-the-wall units shall be tested by sampling the masonry by a sawn square prism of not less than 18 inches square (11 613 mm2). The tensile-splitting strength should be determined by the standardtest method of ASTM E 519. The diagonal of the prism should be placed in a vertical position. The tensile-splitting strength should be determined by the following equation:
(Equation A1-2)
3. An alternative to material testing is estimation of the f'm of the existing masonry. This alternative should be limited to recently constructed masonry. The determination of f'm requires that the unit correspond to a specification of the unit by an ASTM standard and classification of the mortar by type.
The shear tests shall be taken at locations representative of the mortar conditions throughout the entire building, taking into account variations in workmanship at different building height levels, variations in weathering of the exterior surfaces, and variations in the condition of the interior surfaces due to deterioration caused by leaks and condensation of water and/or by the deleterious effects of other substances contained within the building. The exact test locations shall be determined at the building site by the engineer or architect in responsible charge of the structural design work. An accurate record of all such tests and their locations in the building shall be recorded, and these results shall be submitted to the building department for approval as part of the structural analysis.
The minimum number of tests per class shall be as follows:
1. At each of both the first and top stories, not less than two tests per wall or line of wall elements providing a common line of resistance to lateral forces.
2. At each of all other stories, not less than one test per wall or line of wall elements providing a common line of resistance to lateral forces.
3. In any case, not less than one test per 1,500 square feet (139.4 m2) of wall surface and not less than a total of eight tests.
1. Mortar shear test values, νto, in pounds per square inch (kPa) shall be obtained for each in-place shear test in accordance with the following equation:
vto = (Vtest/Ab) - PD+L(Equation A1-3)
2. Individual unreinforced masonry walls with νto consistently less than 30 pounds per square inch (207 kPa) shall be entirely pointed prior to retesting.
3. The mortar shear strength, νt, is the value in pounds per square inch (kPa) that is exceeded by 80 percent of the mortar shear test values, νto.
4. Unreinforced masonry with mortar shear strength, νt, less than 30 pounds per square inch (207 kPa) shall be removed, pointed and retested or shall have its structural function replaced, and shall be anchored to supporting elements in accordance with Sections A106.3.1 and A113.8. When existing mortar in any wythe is pointed to increase its shear strength and is retested, the condition of the mortar in the adjacent bed joints of the inner wythe or wythes and the opposite outer wythe shall be examined for extent of deterioration. The shear strength of any wall class shall be no greater than that of the weakest wythe of that class.
1. The minimum average value of tensile-splitting strength determined by Equation A1-1 or A1-2 shall be 50 pounds per square inch (344.7 kPa). The minimum value of f'm determined by categorization of the masonry units and mortar should be 1,000 pounds per square inch (6895 kPa).
2. Individual unreinforced masonry walls with average tensile-splitting strength of less than 50 pounds per square inch (344.7 kPa) shall be entirely pointed prior to retesting.
3. Hollow unit unreinforced masonry walls with estimated prism compressive strength of less than 1,000 pounds per square inch (6895 kPa) shall be grouted to increase the average net area compressive strength.
The collar joints shall be inspected at the test locations during each in-place shear test, and estimates of the percentage of adjacent wythe surfaces that are covered with mortar shall be reported along with the results of the in-place shear tests.
Existing unreinforced masonry shall be categorized into one or more classes based on shear strength, quality of construction, state of repair, deterioration and weathering. A class shall be characterized by the allowable masonry shear stress determined in accordance with Section A108.2. Classes shall be defined for whole walls, not for small areas of masonry within a wall.
Deteriorated mortar joints in unreinforced masonry walls shall be pointed according to UBC Standard 2 1-8. Nothing shall prevent pointing of any deteriorated masonry wall joints before the tests are made, except as required in Section A107.1.
Preparation and mortar pointing shall be performed with special inspection.
Exception: At the discretion of the building official, incidental pointing may be performed without special inspection.
In-place masonry shear tests shall comply with Section A106.3.3.1. Testing of masonry for determination of tensile-splitting strength shall comply with Section A106.3.3.2.
Existing wall anchors used as all or part of the required tension anchors shall be tested in pullout according to UBC Standard 21-7. The minimum number of anchors tested shall be four per floor, with two tests at walls with joists framing into the wall and two tests at walls with joists parallel to the wall, but not less than 10 percent of the total number of existing tension anchors at each level.
All new embedded bolts shall be subject to periodic special inspection in accordance with the building code, prior to placement of the bolt and grout or adhesive in the drilled hole. Five percent of all bolts that do not extend through the wall shall be subject to a direct-tension test, and an additional 20 percent shall be tested using a calibrated torque wrench. Testing shall be performed in accordance with UBC Standard 21-7. New bolts that extend through the wall with steel plates on the far side of the wall need not be tested.
Exception: Special inspection in accordance with the building code may be provided during installation of new anchors in lieu of testing.

All new embedded bolts resisting tension forces or a combination of tension and shear forces shall be subject to periodic special inspection in accordance with the building code, prior to placement of the bolt and grout or adhesive in the drilled hole. Five percent of all bolts resisting tension forces shall be subject to a direct-tension test, and an additional 20 percent shall be tested using a calibrated torque wrench. Testing shall be performed in accordance with UBC Standard 21-7. New through-bolts need not be tested.

1. Strength values for existing materials are given in Table A1-D and for new materials in Table A1-E.
2. Capacity reduction factors need not be used.
3. The use of new materials not specified herein shall be based on substantiating research data or engineering judgment, with the approval of the building official.
The unreinforced masonry shear strength, νm, shall be determined for each masonry class from one of the following equations:
1. The unreinforced masonry shear strength, νm, shall be determined by Equation A1-4 when the mortar shear strength has been determined by Section A106.3.3.1.
(Equation A1-4)

The mortar shear strength values, νt, shall be determined in accordance with Section A106.3.3.5 and shall not exceed 100 pounds per square inch (689.5 kPa) for the determination of νm.

2. The unreinforced masonry shear, νm, shall be determined by Equation A1-5 when tensile-splitting strength has been determined in accordance with Section A106.3.3.2, Item 1 or 2.
(Equation A1-5)
3. When f'm has been estimated by categorization of the units and mortar in accordance with Section 2105.2.2.1 of the International Building Code, the unreinforced masonry shear strength, νm, shall not exceed 200 pounds per square inch (1380 kPa) or the lesser of the following:
a)
b)
c)(Equation A1-6)
For SI: 1 psi = 6.895 kPa.
where:
ν=62.5 psi (430 kPa) for running bond masonry not grouted solid.
ν=100 psi (690 kPa) for running bond masonry grouted solid.
ν=25 psi (170 kPa) for stack bond grouted solid.
Where any increase in dead plus live compression stress occurs, the compression stress in unreinforced masonry shall not exceed 300 pounds per square inch (2070 kPa).
Unreinforced masonry shall be assumed to have no tensile capacity.
The resistance values of the existing anchors shall be the average of the tension tests of existing anchors having the same wall thickness and joist orientation.
For existing foundations, new total dead loads may be increased over the existing dead load by 25 percent. New total dead load plus live load plus seismic forces may be increased over the existing dead load plus live load by 50 percent. Higher values may be justified only in conjunction with a geotechnical investigation.
The elements of buildings hereby required to be analyzed are specified in Table A1-A.
Buildings with rigid diaphragms shall be analyzed by the general procedure of Section A110, which is based on the building code. Buildings with flexible diaphragms shall be analyzed by the general procedure or, when applicable, may be analyzed by the special procedure of Section A111.
Buildings shall be analyzed to resist minimum lateral forces assumed to act nonconcurrently in the direction of each of the main axes of the structure in accordance with the following:
(Equation A1-7)
Parts and portions of a structure not covered in Sections A110.3 shall be analyzed and designed per the current building code, using force levels defined in Section A110.1.
Exceptions:
1. Unreinforced masonry walls for which height-to-thickness ratios do not exceed ratios set forth in Table A1-B need not be analyzed for out-of-plane loading. Unreinforced masonry walls that exceed the allowable h/t ratios of Table A1-B shall be braced according to Section A113.5.
2. Parapets complying with Section A113.6 need not be analyzed for out-of-plane loading.
3. Where walls are to be anchored to flexible floor and roof diaphragms, the anchorage shall be in accordance with Section A113.1.
Vertical lateral load-resisting elements shall be analyzed in accordance with Section A112.
Any redundancy or overstrength factors contained in the building code may be taken as unity. The vertical component of earthquake load (Eν) may be taken as zero.
The special procedures of this section may be applied only to buildings having the following characteristics:
1. Flexible diaphragms at all levels above the base of the structure.
2. Vertical elements of the lateral force-resisting system consisting predominantly of masonry or concrete shear walls.
3. Except for single-story buildings with an open front on one side only, a minimum of two lines of vertical elements of the lateral force-resisting system parallel to each axis of the building (see Section A111.8 for open-front buildings).
With the exception of the provisions in Sections A111.4 through A111.7, elements of structures shall comply with Sections A110.2 through A110.4.
Crosswalls shall meet the requirements of this section.
A crosswall is a wood-framed wall sheathed with any of the materials described in Table A1-D or A1-E or other system as defined in Section A111.3.5. Crosswalls shall be spaced no more than 40 feet (12 192 mm) on center measured perpendicular to the direction of consideration, and shall be placed in each story of the building. Crosswalls shall extend the full story height between diaphragms.

Exceptions:

1. Crosswalls need not be provided at all levels when used in accordance with Section A111.4.2, Item 4.
2. Existing crosswalls need not be continuous below a wood diaphragm at or within 4 feet (1219 mm) of grade, provided:
2.1. Shear connections and anchorage requirements of Section A111.5 are satisfied at all edges of the diaphragm.
2.2. Crosswalls with total shear capacity of 0.5SD1σWd interconnect the diaphragm to the foundation.
2.3. The demand-capacity ratio of the diaphragm between the crosswalls that are continuous to their foundations does not exceed 2.5, calculated as follows:
(Equation A1-8)
Within any 40 feet (12 192 mm) measured along the span of the diaphragm, the sum of the crosswall shear capacities shall be at least 30 percent of the diaphragm shear capacity of the strongest diaphragm at or above the level under consideration.
Existing crosswalls shall have a maximum height-to-length ratio between openings of 1.5 to 1. Existing crosswall connections to diaphragms need not be investigated as long as the crosswall extends to the framing of the diaphragms above and below.
New crosswall connections to the diaphragm shall develop the crosswall shear capacity. New crosswalls shall have the capacity to resist an overturning moment equal to the crosswall shear capacity times the story height. Crosswall overturning moments need not be cumulative over more than two stories.
Other systems, such as moment-resisting frames, may be used as crosswalls provided that the yield story drift does not exceed 1 inch (25.4 mm) in any story.
A diaphragm is acceptable if the point (L,DCR) on Figure A1-1 falls within Region 1, 2 or 3.
Demand-capacity ratios shall be calculated for the diaphragm at any level according to the following formulas:
1. For a diaphragm without qualifying crosswalls at levels immediately above or below:
(Equation A1-9)
2. For a diaphragm in a single-story building with qualifying crosswalls, or for a roof diaphragm coupled by crosswalls to the diaphragm directly below:
(Equation A1-10)
3. For diaphragms in a multistory building with qualifying crosswalls in all levels:
(Equation A1-11)

DCR shall be calculated at each level for the set of diaphragms at and above the level under consideration. In addition, the roof diaphragm shall also meet the requirements of Equation A1-10.

4. For a roof diaphragm and the diaphragm directly below, if coupled by crosswalls:
(Equation A1-12)
An analysis for diaphragm flexure need not be made, and chords need not be provided.
An analysis of diaphragm collector forces shall be made for the transfer of diaphragm edge shears into vertical elements of the lateral force-resisting system. Collector forces may be resisted by new or existing elements. [B] A111.4.5 Diaphragm openings.
1. Diaphragm forces at corners of openings shall be investigated and shall be developed into the diaphragm by new or existing materials.
2. In addition to the demand-capacity ratios of Section A111.4.2, the demand-capacity ratio of the portion of the diaphragm adjacent to an opening shall be calculated using the opening dimension as the span.
3. Where an opening occurs in the end quarter of the diaphragm span, the calculation of vuD for the demand-capacity ratio shall be based on the net depth of the diaphragm.
Diaphragms shall be connected to shear walls with connections capable of developing the diaphragm-loading tributary to the shear wall given by the lesser of the following formulas:
(Equation A1-13)

using the Cp values in Table A1-C, or

(Equation A1-14)
The wall story force distributed to a shear wall at any diaphragm level shall be the lesser value calculated as:
(Equation A1-15)

but need not exceed

(Equation A1-16)
The wall story shear shall be the sum of the wall story forces at and above the level of consideration.
(Equation A1-17)
Shear walls shall comply with Section A112.
Moment frames used in place of shear walls shall be designed as required by the building code, except that the forces shall be as specified in Section A111.6.1, and the story drift ratio shall be limited to 0.015, except as further limited by Section A112.4.2.
The provisions of Section A110.2 are applicable, except the allowable height-to-thickness ratios given in Table A1-B shall be determined from Figure A1-1 as follows:
1. In Region 1, height-to-thickness ratios for buildings with crosswalls may be used if qualifying crosswalls are present in all stories.
2. In Region 2, height-to-thickness ratios for buildings with crosswalls may be used whether or not qualifying crosswalls are present.
3. In Region 3, height-to-thickness ratios for “all other buildings” shall be used whether or not qualifying crosswalls are present.
When diaphragms above and below the wall under consideration have demand-capacity ratios in different regions of Figure A1-1, the lesser height-to-thickness ratio shall be used.
A single-story building with an open front on one side and crosswalls parallel to the open front may be designed by the following procedure:
1. Effective diaphragm span, Li, for use in Figure A1-1 shall be determined in accordance with the following formula:
Li = 2[(Ww/Wd)L + L](Equation A1-18)
2. Diaphragm demand-capacity ratio shall be calculated as:
DCR = 2.1SD1(Wd + Ww)/[(vuD) + Vcb](Equation A1-19)
The following requirements are applicable to both the general procedure and the special procedure for analyzing vertical elements of the lateral force-resisting system.
Flexural components of deflection may be neglected in determining the rigidity of an unreinforced masonry wall.
Wall piers shall be analyzed according to the following procedure, which is diagramed in Figure A1-2.
1. For any pier,
1.1. The pier shear capacity shall be calculated as:
Va = vmA/1.5(Equation A1-20)
1.2. The pier rocking shear capacity shall be calculated as:
Vr= 0.9PDD/H(Equation A1-21)
2. The wall piers at any level are acceptable if they comply with one of the following modes of behavior:
2.1. Rocking controlled mode. When the pier rocking shear capacity is less than the pier shear capacity, i.e., Vr < Va for each pier in a level, forces in the wall at that level, Vwx, shall be distributed to each pier in proportion to PDD/H.

For the wall at that level:

(Equation A1-22)

2.2. Shear controlled mode. Where the pier shear capacity is less than the pier rocking capacity, i.e., Va < Vr in at least one pier in a level, forces in the wall at the level, Vwx, shall be distributed to each pier in proportion to D/H.

For each pier at that level:

Vp < Va(Equation A1-23)

and

Vp < Vr(Equation A1-24)

If Vp < Va for each pier and Vp > Vr for one or more piers, such piers shall be omitted from the analysis, and the procedure shall be repeated for the remaining piers, unless the wall is strengthened and reanalyzed.

3. Masonry pier tension stress. Unreinforced masonry wall piers need not be analyzed for tension stress.
Shear walls without openings shall be analyzed the same as for walls with openings, except that Vr shall be calculated as follows:
(Equation A1-25)
Plywood-sheathed shear walls may be used to resist lateral forces for buildings with flexible diaphragms analyzed according to provisions of Section A111. Plywood-sheathed shear walls may not be used to share lateral forces with other materials along the same line of resistance.
Lateral forces shall be distributed among the vertical-resisting elements in proportion to their relative rigidities, except that moment-resisting frames shall comply with Section A112.4.2.
Moment-resisting frames shall not be used with an unreinforced masonry wall in a single line of resistance unless the wall has piers that have adequate shear capacity to sustain rocking in accordance with Section A112.2.2. The frames shall be designed in accordance with the building code to carry 100 percent of the lateral forces tributary to that line of resistance, as determined from Equation A1-7. The story drift ratio shall be limited to 0.0075.
Unreinforced masonry walls shall be anchored at the roof and floor levels as required in Section A110.2. Ceilings of plaster or similar materials, when not attached directly to roof or floor framing and where abutting masonry walls, shall either be anchored to the walls at a maximum spacing of 6 feet (1829 mm), or be removed.
Anchors shall consist of bolts installed through the wall as specified in Table A1-E, or an approved equivalent at a maximum anchor spacing of 6 feet (1829 mm). All wall anchors shall be secured to the joists to develop the required forces.
Anchorage of masonry walls to each floor or roof shall resist a minimum force determined as 0.9SDS times the tributary weight or 200 pounds per linear foot (2920 N/m), whichever is greater, acting normal to the wall at the level of the floor or roof. Existing wall anchors, if used, must meet the requirements of this chapter or must be upgraded.
At the roof and floor levels, both shear and tension anchors shall be provided within 2 feet (610 mm) horizontally from the inside of the corners of the walls.
Bolts transmitting shear forces shall have a maximum bolt spacing of 6 feet (1829 mm) and shall have nuts installed over malleable iron or plate washers when bearing on wood, and heavy-cut washers when bearing on steel.
Collector elements shall be provided that are capable of transferring the seismic forces originating in other portions of the building to the element providing the resistance to those forces.
Ties and continuity shall conform to the requirements of the building code.
Where a wall height-to-thickness ratio exceeds the specified limits, the wall may be laterally supported by vertical bracing members per Section A113.5.2 or by reducing the wall height by bracing per Section A113.5.3.
Vertical bracing members shall be attached to floor and roof construction for their design loads independently of required wall anchors. Horizontal spacing of vertical bracing members shall not exceed one-half of the unsupported height of the wall or 10 feet (3048 mm). Deflection of such bracing members at design loads shall not exceed one-tenth of the wall thickness.
The wall height may be reduced by bracing elements connected to the floor or roof. Horizontal spacing of the bracing elements and wall anchors shall be as required by design, but shall not exceed 6 feet (1829 mm) on center. Bracing elements shall be detailed to minimize the horizontal displacement of the wall by the vertical displacement of the floor or roof.
Parapets and exterior wall appendages not conforming to this chapter shall be removed, or stabilized or braced to ensure that the parapets and appendages remain in their original positions.

The maximum height of an unbraced unreinforced masonry parapet above the lower of either the level of tension anchors or the roof sheathing shall not exceed the height-to-thickness ratio shown in Table A1-F. If the required parapet height exceeds this maximum height, a bracing system designed for the forces determined in accordance with the building code shall support the top of the parapet. Parapet corrective work must be performed in conjunction with the installation of tension roof anchors.

The minimum height of a parapet above any wall anchor shall be 12 inches (305 mm).

Exception: If a reinforced concrete beam is provided at the top of the wall, the minimum height above the wall anchor may be 6 inches (152 mm).
1. Veneer shall be anchored with approved anchor ties conforming to the required design capacity specified in the building code and shall be placed at a maximum spacing of 24 inches (610 mm) with a maximum supported area of 4 square feet (0.372 m2).

Exception: Existing anchor ties for attaching brick veneer to brick backing may be acceptable, provided the ties are in good condition and conform to the following minimum size and material requirements.

Existing veneer anchor ties may be considered adequate if they are of corrugated galvanized iron strips not less than 1 inch (25.4 mm) in width, 8 inches (203 mm) in length and 1/16 inch (1.6 mm) in thickness, or the equivalent.

2. The location and condition of existing veneer anchor ties shall be verified as follows:
2.1. An approved testing laboratory shall verify the location and spacing of the ties and shall submit a report to the building official for approval as part of the structural analysis.
2.2. The veneer in a selected area shall be removed to expose a representative sample of ties (not less than four) for inspection by the building official.
Unreinforced masonry walls that carry no design vertical or lateral loads and that are not required by the design to be part of the lateral force-resisting system shall be adequately anchored to new or existing supporting elements. The anchors and elements shall be designed for the out-of-plane forces specified in the building code. The height- or length-to-thickness ratio between such supporting elements for such walls shall not exceed nine.
Where trusses and beams other than rafters or joists are supported on masonry, independent secondary columns shall be installed to support vertical loads of the roof or floor members.

Exception: Secondary supports are not required where SD1 is less than 0.3g.

Where elements of adjacent buildings do not have a separation of at least 5 inches (127 mm), the allowable height-to-thickness ratios for “all other buildings” per Table A1-B shall be used in the direction of consideration.
Walls of unburned clay, adobe or stone masonry construction shall conform to the following:
1. Walls of unburned clay, adobe or stone masonry shall not exceed a height- or length-to-thickness ratio specified in Table A1-G.
2. Adobe may be allowed a maximum value of 9 pounds per square inch (62.1 kPa) for shear unless higher values are justified by test.
3. Mortar for repointing may be of the same soil composition and stabilization as the brick, in lieu of cement-mortar.

[B] TABLE A1-A
ELEMENTS REGULATED BY THIS CHAPTER

BUILDING ELEMENTSSD1
≥ 0.067g < 0.133g ≥ 0.133g < 0.20g ≥ 0.20g < 0.30g > 0.30g
ParapetsXXXX
Walls, anchorageXXXX
Walls, h/t ratiosXXX
Walls, in-plane shearXXX
DiaphragmsaXX
Diaphragms, shear transferbXXX
Diaphragms, demand-capacity ratiosbXX
a. Applies only to buildings designed according to the general procedures of Section A110.
b. Applies only to buildings designed according to the special procedures of Section A111.

[B] TABLE A1-B
ALLOWABLE VALUE OF HEIGHT-TO-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS

WALL TYPES 0.13gSD1 < 0.25g 0.25gSD1 < 0.4g SD1 ≥ 0.4g
BUILDINGS WITH CROSSWALLSa
SD1 > 0.4g
ALL OTHER BUILDINGS
Walls of one-story buildings 20 16 16b,c 13
First-story wall of multistory building 20 18 16 15
Walls in top story of multistory building 14 14 14b,c 9
All other walls 20 16 16 13
a. Applies to the special procedures of Section A111 only. See Section A111.7 for other restrictions.
b. This value of height-to-thickness ratio may be used only where mortar shear tests establish a tested mortar shear strength, νt, of not less than 100 pounds per square inch (690 kPa). This value may also be used where the tested mortar shear strength is not less than 60 pounds per square inch (414 kPa), and where a visual examination of the collar joint indicates not less than 50-percent mortar coverage.
c. Where a visual examination of the collar joint indicates not less than 50-percent mortar coverage, and the tested mortar shear strength, νt, is greater than 30 pounds per square inch (207 kPa) but less than 60 pounds per square inch (414 kPa), the allowable height-to-thickness ratio may be determined by linear interpolation between the larger and smaller ratios in direct proportion to the tested mortar shear strength.

[B] TABLE A1-C
HORIZONTAL FORCE FACTOR, Cp

CONFIGURATION OF MATERIALS Cp
Roofs with straight or diagonal sheathing and roofing applied directly to the sheathing, or floors with straight tongue-and- groove sheathing.
Diaphragms with double or mulitple layers of boards with edges offset, and blocked plywood systems.
Diaphragms of metal deck without topping:
Minimal welding or mechanical attachment.
Welded or mechanically attached for seismic resistance.
0.50

0.75

0.6
0.68

[B] TABLE A1-D
STRENGTH VALUES FOR EXISTING MATERIALS

EXISTING MATERIALS OR CONFIGURATION OF MATERIALSa STRENGTH VALUES
x 14.594 for N/m
Horizontal
diaphragms
Roofs with straight sheathing and roofing applied directly to the sheathing. 300 lbs. per ft. for seismic shear
Roofs with diagonal sheathing and roofing applied directly to the sheathing. 750 lbs. per ft. for seismic shear
Floors with straight tongue-and-groove sheathing. 300 lbs. per ft. for seismic shear
Floors with straight sheathing and finished wood flooring with board edges offset or perpendicular. 1,500 lbs. per ft. for seismic shear
Floors with diagonal sheathing and finished wood flooring. 1,800 lbs. per ft. for seismic shear
Metal deck welded with minimal welding.c 1,800 lbs, per ft. for seismic shear
Metal deck welded for seismic resistance.d 3,000 lbs. per ft. for seismic shear
Crosswallsb Plaster on wood or metal lath. 600 lbs. per ft. for seismic shear
Plaster on gypsum lath. 550 lbs. per ft. for seismic shear
Gypsum wallboard, unblocked edges. 200 lbs. per ft. for seismic shear
Gypsum wallboard, blocked edges. 400 lbs. per ft. for seismic shear
Existing footing, wood framing, structural steel, reinforcing steel Plain concrete footings. f'c = 1,500 psi (10.34 MPa) unless otherwise shown by tests
Douglas fir wood. Same as D.F. No. 1
Reinforcing steel. Fy= 40,000 psi (124.1 N/mm2) maximum
Structural steel. Fy= 33,000 psi (137.9 N/mm2) maximum
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 pound = 4.4 N.
a. Material must be sound and in good condition.
b. Shear values of these materials may be combined, except the total combined value should not exceed 900 pounds per foot (4380 N/m).
c. Minimum 22-gage steel deck with welds to supports satisfying the standards of the Steel Deck Institute.
d. Minimum 22-gage steel deck with 3/4 φ plug welds at an average spacing not exceeding 8 inches (203 mm) and with sidelap welds appropriate for the deck span.

[B] TABLE A1-E
STRENGTH VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION

NEW MATERIALS OR CONFIGURATION OF MATERIALS STRENGTH VALUES
Horizontal diaphragms Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing on joists or rafters and edges of plywood located on center of individual sheathing boards. 675 lbs. per ft.
Crosswalls Plywood sheathing applied directly over wood studs; no value should be given to plywood applied over existing plaster or wood sheathing. 1.2 times the value specified in the current building code.
Drywall or plaster applied directly over wood studs. The value specified in the current building code.
Drywall or plaster applied to sheathing over existing wood studs. 50 percent of the value specified in the
current building code.
Tension boltse Bolts extending entirely through unreinforced masonry wall secured with bearing plates on far side of a three-wythe- minimum wall with at least 30 square inches of area.b,c5,400 lbs. per bolt.
2,700 lbs. for two-wythe walls.
Shear boltse Bolts embedded a minimum of 8 inches into unreinforced masonry walls; bolts should be centered in 21/2-inch-diameter holes with dry-pack or nonshrink grout around the circumference of the bolt. The value for plain masonry specified for solid masonry in the current building code; no value larger than those given for 3/4-inch bolts should be used.
Combined tension and shear bolts Through-bolts—bolts meeting the requirements for shear and for tension bolts.b,c Tension—same as for tension bolts.
Shear—same as for shear bolts.
Embedded bolts—bolts extending to the exterior face of the wall with a 21/2-inch round plate under the head and drilled at an angle of 221/2degrees to the horizontal; installed as specified for shear bolts.a,b,c Tension—3,600 lbs. per bolt.
Shear—same as for shear bolts.
Infilled walls Reinforced masonry infilled openings in existing unreinforced masonry walls; provide keys or dowels to match reinforcing. Same as values specified for unreinforced masonry walls.
Reinforced masonryd Masonry piers and walls reinforced per the current building code. The value specified in the current building code for strength design.
Reinforced concreted Concrete footings, walls and piers reinforced as specified in the
current building code.
The value specified in the current building code for strength design.
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 pound = 4.4 N.
a. Embedded bolts to be tested as specified in Section A107.4.
b. Bolts to be 1/2 inch (12.7 mm) minimum in diameter.
c. Drilling for bolts and dowels shall be done with an electric rotary drill; impact tools should not be used for drilling holes or tightening anchors and shear bolt nuts.
d. No load factors or capacity reduction factor shall be used.
e. Other bolt sizes, values and installation methods may be used, provided a testing program is conducted in accordance with UBC Standard 21-7. The useable value shall be determined by multiplying the calculated allowable value, as determined by UBC Standard 21-7, by 3.0, and the useable value shall be limited to a maximum of 1.5 times the value given in the table. Bolt spacing shall not exceed 6 feet (1829 mm) on center and shall not be less than 12 inches (305 mm) on center.

[B] TABLE A1-F
MAXIMUM ALLOWABLE HEIGHT-TO-THICKNESS RATIOS FOR PARAPETS

SD1
0.13gSD1< 0.25g 0.25gSD1 < 0.4g SD1 ≥ 0.4g
Maximum allowable height-to-thickness ratios 2.5 2.5 1.5

[B] TABLE A1-G
MAXIMUM HEIGHT-TO-THICKNESS RATIOS FOR ADOBE OR STONE WALLS

SD1
0.13g SD1 < 0.25g0.25g SD1 < 0.4gSD1 ≥ 0.4g
One-story buildings
Two-story buildings
First story
Second story
12

14
12
10

11
10
8

9
8

[B] FIGURE A1-1
ACCEPTABLE DIAPHRAGM SPAN

[B] FIGURE A1-2
ANALYSIS OF URM WALL IN-PLANE SHEAR FORCES

Chapter A2 Earthquake Hazard Reduction in Existing Reinforced Concrete and Reinforced Masonry Wall Buildings with Flexible Diaphragms

The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on reinforced concrete and reinforced masonry wall buildings with flexible diaphragms. Based on past earthquakes, these buildings have been categorized as being potentially hazardous and prone to significant damage, including possible collapse in a moderate to major earthquake. The provisions of this chapter are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury on both subject and adjacent properties. These provisions will not necessarily prevent loss of life or injury, or prevent earthquake damage to an existing building that complies with these standards.
The provisions of this chapter shall apply to wall anchorage systems that resist out-of-plane forces and to collectors in existing reinforced concrete or reinforced masonry buildings with flexible diaphragms. Wall anchorage systems that were designed and constructed in accordance with the 1997 Uniform Building Code, 1999 BOCA National Building Code, 1999 Standard Building Code or the 2000 and subsequent editions of the International Building Code shall be deemed to comply with these provisions.
For the purpose of this chapter, the applicable definitions listed in Chapters 16, 19, 21, 22 and 23 of the International Building Code and the following shall apply:
[B] FLEXIBLE DIAPHRAGMS. Roofs and floors including, but not limited to, those sheathed with plywood, wood decking (1-by or 2-by) or metal decks without concrete topping slabs.
For the purpose of this chapter, the applicable symbols and notations in the International Building Code shall apply.
The seismic-resisting elements specified in this chapter shall comply with provisions of Section 1613 of the International Building Code, except as modified herein.
Alterations and repairs required to meet the provisions of this chapter shall comply with applicable structural requirements of the building code unless specifically modified in this chapter.
The plans shall accurately reflect the results of the engineering investigation and design and shall show all pertinent dimensions and sizes for plan review and construction. The following shall be provided:
1. Floor plans and roof plans shall show existing framing construction, diaphragm construction, proposed wall anchors, cross-ties and collectors. Existing nailing, anchors, cross-ties and collectors shall also be shown on the plans if they are considered part of the lateral force-resisting systems.
2. At elevations where there are alterations or damage, details shall show roof and floor heights, dimensions of openings, location and extent of existing damage and proposed repair.
3. Typical wall panel details and sections with panel thickness, height, pilasters and location of anchors shall be provided.
4. Details shall include existing and new anchors and the method of developing anchor forces into the diaphragm framing, existing and/or new cross-ties, and existing and/or new or improved support of roof and floor girders at pilasters or walls.
5. The basis for design and the building code used for the design shall be stated on the plans.
Structural observation, in accordance with Section 1709 of the International Building Code, shall be required for all structures in which seismic retrofit is being performed in accordance with this chapter. Structural observation shall include visual observation of work for conformance to the approved construction documents and confirmation of existing conditions assumed during design.

Structural testing and inspection for new construction materials shall be in accordance with the building code, except as modified by this chapter.

Concrete and masonry walls shall be anchored to all floors and roofs that provide lateral support for the wall. The anchorage shall provide a positive direct connection between the wall and floor or roof construction capable of resisting 75 percent of the horizontal forces specified in Section 1613 of the International Building Code.
The steel elements of the wall anchorage system shall be designed in accordance with the building code without the use of the 1.33 short duration allowable stress increase when using allowable stress design.

Wall anchors shall be provided to resist out-of-plane forces, independent of existing shear anchors.

Exception: Existing cast-in-place shear anchors are allowed to be used as wall anchors if the tie element can be readily attached to the anchors, and if the engineer or architect can establish tension values for the existing anchors through the use of approved as-built plans or testing and through analysis showing that the bolts are capable of resisting the total shear load (including dead load) while being acted upon by the maximum tension force due to an earthquake. Criteria for analysis and testing shall be determined by the building official.

Expansion anchors are only allowed with special inspection and approved testing for seismic loading.

Attaching the edge of plywood sheathing to steel ledgers is not considered compliant with the positive anchoring requirements of this chapter. Attaching the edge of steel decks to steel ledgers is not considered as providing the positive anchorage of this chapter unless testing and/or analysis are performed to establish shear values for the attachment perpendicular to the edge of the deck. Where steel decking is used as a wall anchor system, the existing connections shall be subject to field verification and the new connections shall be subject to special inspection.

Development of anchor loads into roof and floor diaphragms shall comply with Section 1613 of the International Building Code using horizontal forces that are 75 percent of those used for new construction.
Exception: If continuously tied girders are present, the maximum spacing of the continuity ties is the greater of the girder spacing or 24 feet (7315 mm).

In wood diaphragms, anchorage shall not be accomplished by use of toenails or nails subject to withdrawal. Wood ledgers, top plates or framing shall not be used in cross-grain bending or cross-grain tension. The continuous ties required in Section 1613 of the International Building Code shall be in addition to the diaphragm sheathing.

Lengths of development of anchor loads in wood diaphragms shall be based on existing field nailing of the sheathing unless existing edge nailing is positively identified on the original construction plans or at the site.

Anchorage at pilasters shall be designed for the tributary wall-anchoring load per Section A206.1, considering the wall as a two-way slab. The edges of the two-way slab shall be considered fixed when there is continuity at pilasters and shall be considered pinned at roof and floor. The pilasters or the walls immediately adjacent to the pilasters shall be anchored directly to the roof framing such that the existing vertical anchor bolts at the top of the pilasters are bypassed without permitting tension or shear failure at the top of the pilasters.
Exception: If existing vertical anchor bolts at the top of the pilasters are used for the anchorage, additional exterior confinement shall be provided as required to resist the total anchorage force.

The minimum anchorage force at a floor or roof between the pilasters shall be that specified in Section A206.1.

Symmetry of wall anchorage and continuity connectors about the minor axis of the framing member is required.
Exception: Eccentricity may be allowed when it can be shown that all components of forces are positively resisted. The resistance must be supported by calculations or tests.
Wood members used to develop anchorage forces to the diaphragm must be at least 3-inch (76 mm) nominal members for new construction and replacement. All such members must be checked for gravity and earthquake loading as part of the wall-anchorage system.
Exception: Existing 2-inch (51 mm) nominal members may be doubled and internailed to meet the strength requirement.
New anchors used in combination on a single framing member shall be of compatible behavior and stiffness.
Existing interior reinforced concrete or reinforced masonry walls that extend to the floor above or to the roof diaphragm shall be anchored for out-of-plane forces per Sections A206.1 and A206.3.Walls extending through the roof diaphragm shall be anchored for out-of-plane forces on both sides, and continuity ties shall be spliced across or continuous through the interior wall to provide diaphragm continuity.
If collectors are not present at reentrant corners or interior shear walls, they shall be provided. Existing or new collectors shall be designed for the capacity required to develop into the diaphragm a force equal to the lesser of the rocking or shear capacity of the reentrant wall or the tributary shear based on 75 percent of the horizontal forces specified in Chapter 16 of the International Building Code. The capacity of the collector need not exceed the capacity of the diaphragm to deliver loads to the collector. A connection shall be provided from the collector to the reentrant wall to transfer the full collector force (load). If a truss or beam other than a rafter or purlin is supported by the reentrant wall or by a column integral with the reentrant wall, then an independent secondary column is required to support the roof or floor members whenever rocking or shear capacity of the reentrant wall is less than the tributary shear.
Existing mezzanines relying on reinforced concrete or reinforced masonry walls for vertical and/or lateral support shall be anchored to the walls for the tributary mezzanine load. Walls depending on the mezzanine for lateral support shall be anchored per Sections A206.1, A206.2 and A206.3.
Exception: Existing mezzanines that have independent lateral and vertical support need not be anchored to the walls.
All materials permitted by the building code, including their appropriate strength or allowable stresses, may be used to meet the requirements of this chapter.

Chapter A3 Prescriptive Provisions for Seismic Strengthening of Cripple Walls and Sill Plate Anchorage of Light, Wood-Frame Residential Buildings

The provisions of this chapter are intended to promote public safety and welfare by reducing the risk of earthquake-induced damage to existing wood-frame residential buildings. The requirements contained in this chapter are prescriptive minimum standards intended to improve the seismic performance of residential buildings; however, they will not necessarily prevent earthquake damage.

This chapter sets standards for strengthening that may be approved by the code official without requiring plans or calculations prepared by a registered design professional. The provisions of this chapter are not intended to prevent the use of any material or method of construction not prescribed herein. The code official may require that construction documents for strengthening using alternative materials or methods be prepared by a registered design professional.

The provisions of this chapter apply to residential buildings of light-frame wood construction containing one or more of the structural weaknesses specified in Section A303.
Exception: The provisions of this chapter do not apply to the buildings, or elements thereof, listed below. These buildings or elements require analysis by a registered design professional in accordance with Section A301.3 to determine appropriate strengthening:
1. Group R-1, R-2 or R-4 occupancies with more than four dwelling units.
2. Buildings with a lateral force-resisting system using poles or columns embedded in the ground.
3. Cripple walls that exceed 4 feet (1219 mm) in height.
4. Buildings exceeding three stories in height and any three-story building with cripple wall studs exceeding 14 inches (356 mm) in height.
5. Buildings where the code official determines that conditions exist that are beyond the scope of the prescriptive requirements of this chapter.
6. Buildings or portions thereof constructed on concrete slabs on grade.
Deleted
The details and prescriptive provisions herein are not intended to be the only acceptable strengthening methods permitted. Alternative details and methods may be used where designed by a registered design professional and approved by the code official. Approval of alternatives shall be based on a demonstration that the method or material used is at least equivalent in terms of strength, deflection and capacity to that provided by the prescriptive methods and materials.

Where analysis by a registered design professional is required, such analysis shall be in accordance with all requirements of the building code, except that the seismic forces may be taken as 75 percent of those specified in the building code.

For the purpose of this chapter, in addition to the applicable definitions in the building code, certain additional terms are defined as follows:

[B] ADHESIVE ANCHOR. An assembly consisting of a threaded rod, washer, nut, and chemical adhesive approved by the code official for installation in existing concrete or masonry.
Deleted
[B] COMPOSITE PANEL. A wood structural panel product composed of a combination of wood veneer and wood-based material, and bonded with waterproof adhesive.
[B] CRIPPLE WALL. A wood-frame stud wall extending from the top of the foundation to the underside of the lowest floor framing.
Deleted
[B] EXPANSION ANCHOR. An approved post-installed anchor, inserted into a pre-drilled hole in existing concrete or masonry, that transfers loads to or from the concrete or masonry by direct bearing or friction or both.
[B] ORIENTED STRAND BOARD (OSB). A mat-formed wood structural panel product composed of thin rectangular wood strands or wafers arranged in oriented layers and bonded with waterproof adhesive.
[B] PERIMETER FOUNDATION. A foundation system that is located under the exterior walls of a building.
[B] PLYWOOD. A wood structural panel product composed of sheets of wood veneer bonded together with the grain of adjacent layers oriented at right angles to one another.
[B] SNUG-TIGHT. As tight as an individual can torque a nut on a bolt by hand, using a wrench with a 10-inch-long (254 mm) handle, and the point at which the full surface of the plate washer is contacting the wood member and slightly indenting the wood surface.
[B] WAFERBOARD. A mat-formed wood structural panel product composed of thin rectangular wood wafers arranged in random layers and bonded with waterproof adhesive.
[B] WOOD STRUCTURAL PANEL. A structural panel product composed primarily of wood and meeting the requirements of United States Voluntary Product Standard PS 1 and United States Voluntary Product Standard PS 2. Wood structural panels include all-veneer plywood, composite panels containing a combination of veneer and wood-based material, and mat-formed panels such as oriented strand board and waferboard.
For the purpose of this chapter, structural weaknesses shall be as specified below.
1. Sill plates or floor framing that are supported directly on the ground without a foundation system that conforms to the building code.
2. A perimeter foundation system that is constructed only of wood posts supported on isolated pad footings.
3. Perimeter foundation systems that are not continuous.

Exceptions:

1. Existing single-story exterior walls not exceeding 10 feet (3048 mm) in length, forming an extension of floor area beyond the line of an existing continuous perimeter foundation.
2. Porches, storage rooms and similar spaces not containing fuel-burning appliances.

4. A perimeter foundation system that is constructed of unreinforced masonry or stone.

5. Sill plates that are not connected to the foundation or that are connected with less than what is required by the building code.

Exception: Where approved by the code official, connections of a sill plate to the foundation made with other than sill bolts may be accepted if the capacity of the connection is equivalent to that required by the building code.

6. Cripple walls that are not braced in accordance with the requirements of Section A304.4 and Table A3-A, or cripple walls not braced with diagonal sheathing or wood structural panels in accordance with the building code.

The structural weaknesses noted in Section A303 shall be strengthened in accordance with the requirements of this section. Strengthening work may include both new construction and alteration of existing construction. Except as provided herein, all strengthening work and materials shall comply with the applicable provisions of the building code.
All existing wood materials that will be a part of the strengthening work (sills, studs, sheathing, etc.) shall be in a sound condition and free from defects that substantially reduce the capacity of the member. Any wood material found to contain fungus infection shall be removed and replaced with new material. Any wood material found to be infested with insects or to have been infested with insects shall be strengthened or replaced with new materials to provide a net dimension of sound wood at least equal to its undamaged original dimension.
Floor joists framed perpendicular or at an angle to perimeter foundations shall be restrained either by an existing nominal 2-inch-wide (51 mm) continuous rim joist or by a nominal 2-inch-wide (51 mm) full-depth block between alternate joists in one-and two-story buildings, and between each joist in three-story buildings. Existing blocking for multistory buildings must occur at each joist space above a braced cripple wall panel.
Existing connections at the top and bottom edges of an existing rim joist or blocking need not be verified in one-story buildings. In multistory buildings, the existing top edge connection need not be verified; however, the bottom edge connection to either the foundation sill plate or the top plate of a cripple wall shall be verified. The minimum existing bottom edge connection shall consist of 8d toenails spaced 6 inches (152 mm) apart for a continuous rim joist, or three 8d toenails per block. When this minimum bottom edge-connection is not present or cannot be verified, a supplemental connection installed as shown in Figure A3-8A or A3-8C shall be provided.
Where an existing continuous rim joist or the minimum existing blocking does not occur, new 3/4-inch (19 mm) or 23/32-inch (18 mm) wood structural panel blocking installed tightly between floor joists and nailed as shown in Figure A3-9 shall be provided at the inside face of the cripple wall. In lieu of wood structural panel blocking, tight fitting, full-depth 2-inch (51 mm) blocking may be used. New blocking may be omitted where it will interfere with vents or plumbing that penetrates the wall.
Where existing floor joists are parallel to the perimeter foundations, the end joist shall be located over the foundation and, except for required ventilation openings, shall be continuous and in continuous contact with the foundation sill plate or the top plate of the cripple wall. Existing connections at the top and bottom edges of the end joist need not be verified in one-story buildings. In multistory buildings, the existing top edge connection of the end joist need not be verified; however, the bottom edge connection to either the foundation sill plate or the top plate of a cripple wall shall be verified. The minimum bottom edge connection shall be 8d toenails spaced 6 inches (152 mm) apart. If this minimum bottom edge connection is not present or cannot be verified, a supplemental connection installed as shown in Figure A3-8B, A3-8C or A3-9 shall be provided.
New perimeter foundations shall be provided for structures with the structural weaknesses noted in Items 1 and 2 of Section A303. Soil investigations or geotechnical studies are not required for this work unless the building is located in a special study zone as designated by the code official or other authority having jurisdiction.
Partial perimeter foundations or unreinforced masonry foundations shall be evaluated by a registered design professional for the force levels specified in Section A301.3. Test reports or other substantiating data to determine existing foundation material strengths shall be submitted to the code official. Where approved by the code official, these existing foundation systems may be strengthened in accordance with the recommendations included with the evaluation in lieu of being replaced.

Exception: In lieu of testing existing foundations to determine material strengths, and where approved by the code official, a new nonperimeter foundation system designed for the forces specified in Section A301.3 may be used to resist lateral forces from perimeter walls. A registered design professional shall confirm the ability of the existing diaphragm to transfer seismic forces to the new nonperimeter foundations.

All new perimeter foundations shall be continuous and constructed according to either Figure A3-1 or A3-2. All new construction materials shall comply with the requirements of building code. Where approved by the code official, the existing clearance between existing floor joists or girders and existing grade below the floor need not comply with the building code.

Exception: Where designed by a registered design professional and approved by the code official, partial perimeter foundations may be used in lieu of a continuous perimeter foundation.

New concrete foundations shall have a minimum compressive strength of 2,500 pounds per square inch (17.24 MPa) at 28 days.
New hollow-unit masonry foundations shall be solidly grouted. The grout shall have minimum compressive strength of 2,000 pounds per square inch (13.79 MPa). Mortar shall be Type M or S.
Where new sill plates are used in conjunction with new foundations, they shall be minimum 2x nominal thickness and shall be preservative-treated wood or naturally durable wood permitted by the building code for similar applications, and shall be marked or branded by an approved agency. Nails in contact with preservative-treated wood shall be hot-dip galvanized or other material permitted by the building code for similar applications. Metal framing anchors in contact with preservative treated wood shall be galvanized in accordance with ASTM A 653 with a G185 coating.
Where the building has an existing continuous perimeter foundation, all perimeter wall sill plates shall be anchored to the foundation with adhesive anchors or expansion anchors in accordance with Table A3-A.
Anchors shall be installed in accordance with Figure A3-3, with the plate washer installed between the nut and the sill plate. The nut shall be tightened to a snug-tight condition after curing is complete for adhesive anchors and after expansion wedge engagement for expansion anchors. All anchors shall be installed in accordance with manufacturer’s recommendations. Where existing conditions prevent anchor installations through the sill plate, this connection may be made in accordance with Figure A3-4A, A3-4B, or A3-4C. The spacing of these alternate connections shall comply with the maximum spacing requirements of Table A3-A. Expansion anchors shall not be used where the installation causes surface cracking of the foundation wall at the locations of the bolt.
Anchors shall be placed within 12 inches (305 mm), but not less than 9 inches (229 mm), from the ends of sill plates and shall be placed in the center of the stud space closest to the required spacing. New sill plates may be installed in pieces where necessary because of existing conditions. For lengths of sill plates greater than 12 feet (3658 mm), anchors or bolts shall be spaced along the sill plate as specified in Table A3-A. For other lengths of sill plate, anchor placement shall be in accordance with Table A3-B.

Exception: Where physical obstructions such as fireplaces, plumbing or heating ducts interfere with the placement of an anchor, the anchor shall be placed as close to the obstruction as possible, but not less than 9 inches (229 mm) from the end of the plate. Center-to-center spacing of the anchors shall be reduced as necessary to provide the minimum total number of anchors required based on the full length of the wall. Center-to-center spacing shall not be less than 12 inches (305 mm).

Sill plates for new perimeter foundations shall be anchored in accordance with Table A3-A and as shown in Figure A3-1 or A3-2.
Exterior cripple walls not exceeding 4 feet (1219 mm) in height shall be permitted to be specified by the prescriptive bracing method in Section A304.4. Cripple walls over 4 feet (1219 mm) in height require analysis by a registered design professional in accordance with Section A301.3.
Wood structural panel sheathing shall not be less than 15/32-inch (12 mm) thick and shall be installed in accordance with Figure A3-5 or A3-6. All individual pieces of wood structural panels shall be nailed with 8d common nails spaced 4 inches (102 mm) on center at all edges and 12 inches (305 mm) on center at each intermediate support with not less than two nails for each stud. Nails shall be driven so that their heads are flush with the surface of the sheathing and shall penetrate the supporting member a minimum of 11/2 inches (38 mm). When a nail fractures the surface, it shall be left in place and not counted as part of the required nailing. A new 8d nail shall be located within 2 inches (51 mm) of the discounted nail and be hand-driven flush with the sheathing surface. Where the installation involves horizontal joints, those joints shall occur over nominal 2-inch by 4-inch (51 mm by 102 mm) blocking installed with the nominal 4-inch (102 mm) dimension against the face of the plywood.

Vertical joints at adjoining pieces of wood structural panels shall be centered on studs such that there is a minimum 1/8 inch (3.2 mm) between the panels, and such that the nails are placed a minimum of 1/2 inch (12.7 mm) from the edges of the existing stud. Where such edge distances cannot be maintained because of the width of the existing stud, a new stud shall be added adjacent to the existing studs and connected in accordance with Figure A3-7.

See Table A3-A and Figure A3-10 for the distribution and amount of bracing required for each wall line. Each braced panel length must be at least two times the height of the cripple stud. Where the minimum amount of bracing prescribed in Table A3-A cannot be installed along any walls, the bracing must be designed in accordance with Section A301.3.

Exception: Where physical obstructions such as fireplaces, plumbing or heating ducts interfere with the placement of cripple wall bracing, the bracing shall then be placed as close to the obstruction as possible. The total amount of bracing required shall not be reduced because of obstructions.

When bracing materials are installed on the interior face of studs forming an enclosed space between the new bracing and the existing exterior finish, each braced stud space must be ventilated. Adequate ventilation and access for future inspection shall be provided by drilling one 2-inch to 3-inch-diameter (51 mm to 76 mm) round hole through the sheathing, nearly centered between each stud at the top and bottom of the cripple wall. Such holes should be spaced a minimum of 1 inch (25 mm) clear from the sill or top plates. In stud spaces containing sill bolts, the hole shall be located on the center line of the sill bolt but not closer than 1 inch (25 mm) clear from the nailing edge of the sheathing. When existing blocking occurs within the stud space, additional ventilation holes shall be placed above and below the blocking, or the existing block shall be removed and a new nominal 2-inch by 4-inch (51 mm by 102 mm) block shall be installed with the nominal 4-inch (102 mm) dimension against the face of the plywood. For stud heights less than 18 inches (457 mm), only one ventilation hole need be provided.
Existing underfloor ventilation shall not be reduced without providing equivalent new ventilation as close to the existing ventilation as possible. Braced panels may include underfloor ventilation openings when the height of the opening, measured from the top of the foundation wall to the top of the opening, does not exceed 25 percent of the height of the cripple stud wall; however, the length of the panel shall be increased a distance equal to the length of the opening or one stud space minimum. Where an opening exceeds 25 percent of the cripple wall height, braced panels shall not be located where the opening occurs. See Figure A3-7.

Exception: For homes with a post and pier foundation system where a new continuous perimeter foundation system is being installed, new ventilation shall be provided in accordance with the building code.

All work shall be subject to inspection by the code official including, but not limited to:

1. Placement and installation of new adhesive or expansion anchors installed in existing foundations. Special inspection is not required for adhesive anchors installed in existing foundations regulated by the prescriptive provisions of this chapter.

2. Installation and nailing of new cripple wall bracing.

3. Any work may be subject to special inspection when required by the code official in accordance with the building code.

All nails specified in this chapter shall be common wire nails of the following diameters and lengths: 8d nails shall be 0.131 inch by 21/2 inches. 10d nails shall be 0.148 inch by 3 inches. 12d nails shall be 0.148 inch by 31/4 inches. 16d nails shall be 0.162 inch by 31/2 inches. Nails used to attach metal framing connectors directly to wood members shall be as specified by the connector manufacturer in an approved report. Deleted

[B] TABLE A3-A
SILL PLATE ANCHORAGE AND CRIPPLE WALL BRACING

NUMBER OF STORIES
ABOVE CRIPPLE WALLS
MINIMUM SILL PLATE CONNECTION
AND MAXIMUM SPACINGa, b
AMOUNT OF BRACING FOR EACH WALL LINEc,d,e
A Combination of Exterior Walls
Finished with Portland Cement Plaster
and Roofing Using Clay Tile or
Concrete Tile Weighing More than 6 psf
(287 N/m2)
All Other Conditions
One story 1/2 inch (12.7 mm) spaced 6 feet, 0
inch (1829 mm) center-to-center with washer plate
Each end and not less than 50
percent of the wall length
Each end and not less than 40
percent of the wall length
Two stories 1/2 inch (12.7 mm) spaced 4 feet, 0
inch (1219 mm) center-to-center with washer plate; or 5/8 inch (15.9 mm) spaced 6 feet, 0 inch (1829 mm) center-to-center with washer plate
Each end and not less than 70
percent of the wall length
Each end and not less than 50
percent of the wall length
Three stories 5/8 inch (15.9 mm) spaced 4 feet, 0
inch (1219 mm) center-to-center with washer plate
100 percent of the wall lengthf Each end and not less than 80
percent of the wall lengthf
a. Sill plate anchors shall be chemical anchors or expansion bolts in accordance with Section A304.3.1.
b. All washer plates shall be 2 inches by 2 inches by 3/16 inch (51 mm by 51 mm by 4.8 mm) minimum.
c. See Figure A3-10 for braced panel layout.
d. Braced panels at ends of walls shall be located as near to the end as possible.
e. All panels along a wall shall be nearly equal in length and shall be nearly equal in spacing along the length of the wall.
f. The minimum required underfloor ventilation openings are permitted in accordance with Section A304.4.4.

[B] TABLE A3-B
SILL PLATE ANCHORAGE FOR VARIOUS LENGTHS OF SILL PLATEa,b

NUMBER OF STORIES LENGTHS OF SILL PLATE
Less than 12 feet (3658 mm) to
6 feet (1829 mm)
Less than 6 feet (1829 mm)
to 30 inches (762 mm)
Less than 30 inches
(762 mm)c
One story Three connections Two connections One connection
Two stories Four connections for 1/2-inch (12.7 mm) anchors or bolts or three connections for 5/8-inch (15.9 mm) anchors or bolts Two connections One connection
Three stories Four connections Two connections One connection
a. Connections shall be either chemical anchors or expansion bolts.
b. See Section A304.3.2 for minimum end distances.
c. Connections shall be placed as near to the center of the length of plate as possible.
MINIMUM FOUNDATION DIMENSIONSMINIMUM FOUNDATION REINFORCING
NUMBER OF STORIESW FDa, b, cTHVERTICAL REINFORCING
Single-pour wall and footingFooting placed separate from wall
112 inches
(305 mm)
6 inches
(152 mm)
12 inches
(305 mm)
6 inches
(152 mm)
≤ 24 inches
(610 mm)
#4 @ 48 inches
(1219 mm) on center
#4 @ 32 inches
(813 mm) on center
215 inches
(381 mm)
7 inches
(178 mm)
18 inches
(457 mm)
8 inches
(203 mm)
≥ 36 inches
(914 mm)
#4 @ 48 inches
(1219 mm) on center
#4 @ 32 inches
(813 mm) on center
318 inches
(457 mm)
8 inches
(203 mm)
24 inches
(610 mm)
10 inches
(254 mm)
≥ 36 inches
(914 mm)
#4 @ 48 inches
(1219 mm) on center
#4 @ 18 inches
(457 mm) on center
a. Where frost conditions occur, the minimum depth shall extend below the frost line.
b. The ground surface along the interior side of the foundation may be excavated to the elevation of the top of the footing.
c. When expansive soil is encountered, the foundation depth and reinforcement shall be as directed by the building official.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

[B] FIGURE A3-1
NEW REINFORCED CONCRETE FOUNDATION SYSTEM

MINIMUM FOUNDATION DIMENSIONSMINIMUM FOUNDATION REINFORCING
NUMBER OF STORIESWFD a, b, cTHVERTICAL
REINFORCING
HORIZONTAL
REINFORCING
1 12 inches (305 mm)6 inches
(152 mm)
12 inches
(305 mm)
6 inches
(152 mm)
≤ 24 inches
(610 mm)
#4 @ 24 inches
(610 mm) on center
#4 continuous at top of stem wall
2 15 inches (381 mm)7 inches
(178 mm)
18 inches
(457 mm)
8 inches
(203 mm)
≥ 24 inches
(610 mm)
#4 @ 24 inches
(610 mm) on center
#4 @ 16 inches
(406 mm) on center
3 18 inches (457 mm 8 inches
(203 mm)
24 inches
(610 mm)
10 inches
(254 mm)
≥ 36 inches
(914 mm)
#4 @ 24 inches
(610 mm) on center
#4 @ 16 inches
(406 mm) on center
a. Where frost conditions occur, the minimum depth shall extend below the frost line.
b. The ground surface along the interior side of the foundation may be excavated to the elevation of the top of the footing.
c. When expansive soil is encountered, the foundation depth and reinforcement shall be as directed by the building official.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

[B] FIGURE A3-2
NEW MASONRY CONCRETE FOUNDATION

For SI: 1 inch = 25.4 mm.

NOTES:

1. Plate washers shall comply with the following:

1/2 in. anchor or bolt—3 in. x 3 in. x 0.229 in. minimum.

5/8 in. anchor or bolt—3 in. x 3 in. x 0.229 in. minimum.

2. See Figure A3-5 or A3-6 for cripple wall bracing.

[B] FIGURE A3-3
SILL PLATE BOLTING TO EXISTING FOUNDATION

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
NOTES:
1. If shim space exceeds 11/2 in., alternate details will be required.
2. Where required, single piece shim shall be foundation grade redwood or preservative-treated wood. If perservative-treated wood is used, it shall be isolated from the foundation system with a moisture barrier.

[B] FIGURE A3-4A
ALTERNATE SILL PLATE ANCHORING IN EXISTING FOUNDATION—
WITHOUT CRIPPLE WALLS AND FLOOR FRAMING NOT PARALLEL TO FOUNDATIONS

For SI: 1 inch = 25.4 mm.

[B] FIGURE A3-4B
ALTERNATE SILL PLATE ANCHOR TO EXISTING FOUNDATION WITHOUT CRIPPLE
WALL AND FLOOR FRAMING PARALLEL TO FOUNDATIONS

For SI: 1 inch = 25.4 mm.

[B] FIGURE A3-4C
SILL PLATE ANCHORING TO EXISTING FOUNDATION—ALTERNATE CONNECTION FOR BATTERED FOOTING

For SI: 1 inch = 25.4 mm.
NOTE: See Figure A3-3 for sill plate anchoring.

[B] FIGURE A3-5
CRIPPLE WALL BRACING WITH NEW WOOD STRUCTURAL PANEL ON EXTERIOR FACE OF CRIPPLE STUDS

For SI: 1 inch = 25.4 mm.

[B] FIGURE A3-6
CRIPPLE WALL BRACING WITH WOOD STRUCTURAL PANEL ON INTERIOR FACE OF CRIPPLE STUDS

For SI: 1 inch = 25.4 mm.

[B] FIGURE A3-7
PARTIAL CRIPPLE STUD WALL ELEVATION

For SI: 1 inch = 25.4 mm, 1 pound = 4.4 N.
NOTE: See manufacturing instructions for nail sizes associated with metal framing clips.

[B] FIGURE A3-8A
TYPICAL FLOOR TO CRIPPLE WALL CONNECTION (FLOOR JOISTS NOT PARALLEL TO FOUNDATIONS)

For SI: 1 inch = 25.4 mm, 1 pound = 4.4 N.

NOTE: See manufacturing instructions for nail sizes associated with metal framing clips.

[B] FIGURE A3-8B
TYPICAL FLOOR TO CRIPPLE WALL CONNECTION (FLOOR JOISTS PARALLEL TO FOUNDATIONS)

For SI: 1 inch = 25.4 mm.

NOTES:

1. See Section A304.3 for sill plate anchorage.
2. See manufacturing instructions for nail sizes associated with metal framing clips.

[B] FIGURE A3-8C
TYPICAL FLOOR TO MUDSILL CONNECTIONS

For SI: 1 inch = 25.4 mm, 1 pound = 4.4N.
NOTE: See Section A304.4 for cripple wall bracing.

[B] FIGURE A3-9
ALTERNATE FLOOR FRAMING TO CRIPPLE WALL CONNECTION

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

[B] FIGURE A3-10—
FLOOR PLAN-CRIPPLE WALL BRACING LAYOUT

Chapter A4 Earthquake Risk Reduction in Wood-Frame Residential Buildings with Soft, Weak or Open Front Walls

The purpose of this chapter is to promote public welfare and safety by reducing the risk of death or injury that may result from the effects of earthquakes on existing wood-frame, multiunit residential buildings. The ground motions of past earthquakes have caused the loss of human life, personal injury and property damage in these types of buildings. This chapter creates minimum standards to strengthen the more vulnerable portions of these structures. When fully followed, these minimum standards will improve the performance of these buildings but will not necessarily prevent all earthquake-related damage.
The provisions of this chapter shall apply to all existing Occupancy Group R-1 and R-2 buildings of wood construction or portions thereof where the structure has a soft, weak, or open-front wall line, and there exists one or more stories above. Deleted

Notwithstanding the applicable definitions, symbols and notations in the building code, the following definitions shall apply for the purposes of this chapter:

[B] ASPECT RATIO. The span-width ratio for horizontal diaphragms and the height-length ratio for shear walls.
Deleted
[B] GROUND FLOOR. Any floor whose elevation is immediately accessible from an adjacent grade by vehicles or pedestrians. The ground floor portion of the structure does not include any floor that is completely below adjacent grades.
[B] NONCONFORMING STRUCTURAL MATERIALS. Wall bracing materials other than wood structural panels or diagonal sheathing.
[B] OPEN-FRONT WALL LINE. An exterior wall line, without vertical elements of the lateral force-resisting system, that requires tributary seismic forces to be resisted by diaphragm rotation or excessive cantilever beyond parallel lines of shear walls. Diaphragms that cantilever more than 25 percent of the distance between lines of lateral force-resisting elements from which the diaphragm cantilevers shall be considered excessive. Exterior exit balconies of 6 feet (1829 mm) or less in width shall not be considered excessive cantilevers.
[B] RETROFIT. An improvement of the lateral force-resisting system by alteration of existing structural elements or addition of new structural elements.
[B] SOFT WALL LINE. A wall line whose lateral stiffness is less than that required by story drift limitations or deformation compatibility requirements of this chapter. In lieu of analysis, a soft wall line may be defined as a wall line in a story where the story stiffness is less than 70 percent of the story above for the direction under consideration.
[B] STORY. A story as defined by the building code, including any basement or underfloor space of a building with cripple walls exceeding 4 feet (1219 mm) in height.
[B] STORY STRENGTH. The total strength of all seismic-resisting elements sharing the same story shear in the direction under consideration.
[B] WALL LINE. Any length of wall along a principal axis of the building used to provide resistance to lateral loads. Parallel wall lines separated by less than 4 feet (1219 mm) shall be considered one wall line for the distribution of loads.
[B] WEAK WALL LINE. A wall line in a story where the story strength is less than 80 percent of the story above in the direction under consideration.
All modifications required by the provisions in this chapter shall be designed in accordance with the International Building Code provisions for new construction, except as modified by this chapter.
Exception: Buildings for which the prescriptive measures provided in Section A404 apply and are used.

No alteration of the existing lateral force-resisting system or vertical load-carrying system shall reduce the strength or stiffness of the existing structure, unless the altered structure would remain in conformance to the building code and this chapter.

This chapter requires the alteration, repair, replacement or addition of structural elements and their connections to meet the strength and stiffness requirements herein. The lateral-load-path analysis shall include the resisting elements and connections from the wood diaphragm immediately above any soft, weak or open-front wall lines to the foundation soil interface or to the uppermost story of a podium structure comprised of steel, masonry, or concrete structural systems that supports the upper, wood-framed structure. Stories above the uppermost story with a soft, weak, or open-front wall line shall be considered in the analysis but need not be modified. The lateral-load-path analysis for added structural elements shall also include evaluation of the allowable soil-bearing and lateral pressures in accordance with the building code. Where any portion of a building within the scope of this chapter is constructed on or into a slope steeper than one unit vertical in three units horizontal (33-percent slope), the lateral force-resisting system at and below the base level diaphragm shall be analyzed for the effects of concentrated lateral forces at the base caused by this hillside condition.
Exception: When an open-front, weak or soft wall line exists because of parking at the ground floor of a two-story building and the parking area is less than 20 percent of the ground floor area, then only the wall lines in the open, weak or soft directions of the enclosed parking area need comply with the provisions of this chapter.
The design base shear in a given direction shall be permitted to be 75 percent of the value required for similar new construction in accordance with the building code. The value of R used in the design of the strengthening of any story shall not exceed the lowest value of R used in the same direction at any story above. The system overstrength factor, Δ0, and the deflection amplification factor, Cd, shall not be less than the largest respective value corresponding to the R factor being used in the direction under consideration.
Exceptions:
1. For structures assigned to Seismic Design Category B, values of R, Δ0 and Cd shall be permitted to be based on the seismic force-resisting system being used to achieve the required strengthening.
2. For structures assigned to Seismic Design Category C or D, values of R, Δ0 and Cd shall be permitted to be based on the seismic force-resisting system being used to achieve the required strengthening, provided that when the strengthening is complete, the strengthened structure will not have an extreme weak story irregularity defined as Type 5b in ASCE 7 Table 12.3-2.
3. For structures assigned to Seismic Design Category E, values of R, Δ0 and Cd shall be permitted to be based on the seismic force-resisting system being used to achieve the required strengthening, provided that when the strengthening is complete, the strengthened structure will not have an extreme soft story, a weak story, or an extreme weak story irregularity defined, respectively, as Types 1b, 5a and 5b in ASCE 7 Table 12.3-2.
Deleted
The calculated story drift for each retrofitted story shall not exceed the allowable deformation compatible with all vertical load-resisting elements and 0.025 times the story height. The calculated story drift shall not be reduced by the effects of horizontal diaphragm stiffness but shall be increased when these effects produce rotation. Drift calculations shall be in accordance with the building code.
The effects of rotation and soil stiffness shall be included in the calculated story drift where lateral loads are resisted by vertical elements whose required depth of embedment is determined by pole formulas. The coefficient of subgrade reaction used in deflection calculations shall be based on a geotechnical investigation conducted in accordance with the building code.
The requirements of the building code shall apply, except as modified herein. All structural framing elements and their connections not required by design to be part of the lateral force-resisting system shall be designed and/or detailed to be adequate to maintain support of design dead plus live loads when subjected to the expected deformations caused by seismic forces. The stress analysis of cantilever columns shall use a buckling factor of 2.1 for the direction normal to the axis of the beam.
All parts of the structure included in the scope of Section A403.2 shall be interconnected as required by the building code. Deleted
Collector elements shall be provided that can transfer the seismic forces originating in other portions of the building to the elements within the scope of Section A403.2 that provide resistance to those forces.
The strength of an existing horizontal diaphragm sheathed with wood structural panels or diagonal sheathing need not be investigated unless the diaphragm is required to transfer lateral forces from vertical elements of the seismic force-resisting system above the diaphragm to elements below the diaphragm because of an offset in placement of the elements.

Wood diaphragms with stories above shall not be allowed to transmit lateral forces by rotation or cantilever except as allowed by the building code; however, rotational effects shall be accounted for when unsymmetric wall stiffness increases shear demands.

Exception: Diaphragms that cantilever 25 percent or less of the distance between lines of lateral load-resisting elements from which the diaphragm cantilevers may transmit their shears by cantilever, provided that rotational effects on shear walls parallel and perpendicular to the load are taken into account.
Wood-framed shear walls shall have strength and stiffness sufficient to resist the seismic loads and shall conform to the requirements of this section.
Gypsum or cement plaster products shall not be used to provide lateral resistance in a soft or weak story or in a story with an open-front wall line, whether or not new elements are added to mitigate the soft, weak or open-front condition.
Wood structural panel shear walls shall meet the story drift limitation of Section A403.4. Conformance to the story drift limitation shall be determined by approved testing or calculation. Individual shear panels shall be permitted to exceed the maximum aspect ratio, provided the allowable story drift and allowable shear capacities are not exceeded.
Shear walls are permitted to be designed for continuity around openings in accordance with the building code. Blocking and steel strapping shall be provided at corners of the openings to transfer forces from discontinuous boundary elements into adjoining panel elements. Alternatively, perforated shear wall provisions of the building code are permitted to be used. Deleted
Expansion anchors that provide tension strength by friction resistance shall not be used to connect hold-down devices to existing concrete or masonry elements.
The required depth of embedment or edge distance for the anchor used in the hold-down connector shall be provided in the concrete or masonry below any plain concrete slab unless satisfactory evidence is submitted to the code official that shows that the concrete slab and footings are of monolithic construction. Deleted
These prescriptive measures shall apply only to two-story buildings and only when deemed appropriate by the code official. These prescriptive measures rely on rotation of the second floor diaphragm to distribute the seismic load between the side and rear walls of the ground floor open area. In the absence of an existing floor diaphragm of wood structural panel or diagonal sheathing, a new wood structural panel diaphragm of minimum thickness of 3/4 inch (19 mm) and with 10d common nails at 6 inches (152 mm) on center shall be applied.
To qualify for these prescriptive measures, the following additional conditions need to be satisfied by the retrofitted structure:
1. Diaphragm aspect ratio L/W is less than 0.67, where W is the diaphragm dimension parallel to the soft, weak or open-front wall line and L is the distance in the orthogonal direction between that wall line and the rear wall of the ground floor open area.
2. Minimum length of side shear walls = 20 feet (6096 mm).
3. Minimum length of rear shear wall = three-fourths of the total rear wall length.
4. No plan or vertical irregularities other than a soft, weak or open-front wall line.
5. Roofing weight less than or equal to 5 pounds per square foot (240 N/m2).
6. Aspect ratio of the full second floor diaphragm meets the requirements of the building code for new construction.
The anchor size and spacing shall be a minimum of 3/4 inch (19 mm) in diameter at 32 inches (813 mm) on center. Where existing anchors are inadequate, supplemental or alternative approved connectors (such as new steel plates bolted to the side of the foundation and nailed to the sill) shall be used.
Shear wall top plates shall be connected to blocking or rim joist at upper floor with a minimum of 18-gage galvanized steel angle clips 41/2 inches (114 mm) long with 12-8d nails spaced no farther than 16 inches (406 mm) on center, or by equivalent shear transfer methods.
The shear wall sheathing shall be a minimum of 15/32 inch (11.9 mm) 5-Ply Structural I with 10d nails at 4 inches (102 mm) on center at edges and 12 inches (305 mm) on center at field; blocked all edges with 3 by 4 board or larger. Where existing sill plates are less than 3-by thick, place flat 2-by on top of sill between studs, with flat 18-gage galvanized steel clips 41/2 inches (114 mm) long with 12-8d nails or 3/8-inch-diameter (9.5 mm) lags through blocking for shear transfer to sill plate. Stagger nailing from wall sheathing between existing sill and new blocking. Anchor new blocking to foundation as specified above.
Shear walls shall be provided with hold-down anchors at each end. Two hold-down anchors are required at intersecting corners. Hold-downs shall be approved connectors with a minimum 5/8-inch-diameter (15.9 mm) threaded rod or other approved anchor with a minimum allowable load of 4,000 pounds (17.8 kN). Anchor embedment in concrete shall not be less than 5 inches (127 mm). Tie-rod systems shall not be less than 5/8 inch (15.9 mm) in diameter unless using high-strength cable. Threaded rod or high-strength cable elongation shall not exceed 5/8 inch (15.9 mm) using design forces.
New materials shall meet the requirements of the International Building Code, except where allowed by this chapter.
The use of default values from the building code for continuous and isolated concrete spread footings shall be permitted. For soil that supports embedded vertical elements, Section A403.4.1 shall apply.
The physical condition, strengths, and stiffnesses of existing building materials shall be taken into account in any analysis required by this chapter. The verification of existing materials conditions and their conformance to these requirements shall be made by physical observation, material testing or record drawings as determined by the registered design professional subject to the approval of the code official. Deleted
When the required calculations rely on design values for common nails or surfaced dry lumber, their use in construction shall be verified by exposure.
When verification of the existing plywood is by use of record drawings alone, plywood shall be assumed to be of three plies.
Wood framing is permitted to use the design stresses specified in the building code under which the building was constructed or other stress criteria approved by the code official.
All existing structural steel shall be permitted to be assumed to comply with ASTM A 36. Existing pipe or tube columns shall be assumed to be of minimum wall thickness unless verified by testing or exposure.
All existing concrete footings shall be permitted to be assumed to be plain concrete with a compressive strength of 2,000 pounds per square inch (13.8 MPa). Existing concrete compressive strength taken greater than 2,000 pounds per square inch (13.8 MPa) shall be verified by testing, record drawings or department records.
The analysis of existing cast-in-place anchors shall be permitted to assume proper anchor embedment for purposes of evaluating shear resistance to lateral loads.
The plans shall show all information necessary for plan review and for construction and shall accurately reflect the results of the engineering investigation and design. The plans shall contain a note that states that this retrofit was designed in compliance with the criteria of this chapter.
The plans shall show existing diaphragm and shear wall sheathing and framing materials; fastener type and spacing; diaphragm and shear wall connections; continuity ties; and collector elements. The plans shall also show the portion of the existing materials that needs verification during construction.
The foundation plan shall include the size, type, location and spacing of all anchor bolts with the required depth of embedment, edge and end distance; the location and size of all shear walls and all columns for braced frames or moment frames; referenced details for the connection of shear walls, braced frames or moment-resisting frames to their footing; and referenced sections for any grade beams and footings.
The framing plan shall include the length, location and material of shear walls; the location and material of frames; references on details for the column-to-beam connectors, beam-to-wall connections and shear transfers at floor and roof diaphragms; and the required nailing and length for wall top plate splices.
Shear walls shall have a referenced schedule on the plans that includes the correct shear wall capacity in pounds per foot (N/m); the required fastener type, length, gauge and head size; and a complete specification for the sheathing material and its thickness. The schedule shall also show the required location of 3-inch (76 mm) nominal or two 2-inch (51 mm) nominal edge members; the spacing of shear transfer elements such as framing anchors or added sill plate nails; the required hold-down with its bolt, screw or nail sizes; and the dimensions, lumber grade and species of the attached framing member.
Notes shall show required edge distance for fasteners on structural wood panels and framing members; required flush nailing at the plywood surface; limits of mechanical penetrations; and the sill plate material assumed in the design. The limits of mechanical penetrations shall also be detailed showing the maximum notching and drilled hole sizes.
General notes shall show the requirements for material testing, special inspection and structural observation.
Structural observation, in accordance with Section 1709 of the International Building Code, shall be required for all structures in which seismic retrofit is being performed in accordance with this chapter. Structural observation shall include visual observation of work for conformance to the approved construction documents and confirmation of existing conditions assumed during design.

Structural testing and inspection for new construction materials shall be in accordance with the building code, except as modified by this chapter.

Deleted

Chapter A5 Earthquake Hazard Reduction in Existing Concrete Buildings

The purpose of this chapter is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on concrete buildings and concrete frame buildings.

The provisions of this chapter are intended as minimum standards for structural seismic resistance, and are established primarily to reduce the risk of life loss or injury. Compliance with the provisions in this chapter will not necessarily prevent loss of life or injury or prevent earthquake damage to the rehabilitated buildings.

The provisions of this chapter shall apply to all buildings having concrete floors or roofs supported by reinforced concrete walls or by concrete frames and columns. This chapter shall not apply to buildings with roof diaphragms that are defined as flexible diaphragms by the building code, and shall not apply to concrete frame buildings with masonry infilled walls.

Buildings that were designed and constructed in accordance with the seismic provisions of the 1993 BOCA National Building Code, the 1994 Standard Building Code, the 1976 Uniform Building Code, the 2000 International Building Code or later editions of these codes shall be deemed to comply with these provisions, unless the seismicity of the region has increased since the design of the building.

Exception: This chapter shall not apply to concrete buildings where Seismic Design Category A is permitted.
This chapter provides a three-tiered procedure to evaluate the need for seismic rehabilitation of existing concrete buildings. The evaluation shall show that the existing building is in compliance with the appropriate part of the evaluation procedure as described in Sections A505, A506 and A507, or shall be modified to conform to the respective acceptance criteria. This chapter does not preclude a building from being evaluated or modified to conform to the acceptance criteria using other well-established procedures, based on rational methods of analysis in accordance with principles of mechanics and approved by the authority having jurisdiction.
Except where specifically permitted herein, the stress-strain relationship of concrete and reinforcement shall be determined from published data or by testing. All available information, including building plans, original calculations and design criteria, site observations, testing and records of typical materials and construction practices prevalent at the time of construction, shall be considered when determining material properties.

For Tier 3 analysis, expected material properties shall be used in lieu of nominal properties in the calculation of strength, stiffness and deformabiltity of building components.

The procedure for testing and determination of material properties shall be from Section 6.2 of ASCE 41-06.

Structural observation, in accordance with Section 1709 of the International Building Code shall be required for all structures in which seismic retrofit is being performed in accordance with this chapter. Structural observation shall include visual observation of work for conformance to the approved construction documents and confirmation of existing conditions assumed during design.

Structural testing and inspection for new construction materials shall be in accordance with the building code, except as modified by this chapter.

The earthquake loading used for the determination of demand on elements of the structure shall correspond to that required by ASCE 31 Tier 1.
The earthquake loading used for the determination of demand on elements and the structure shall conform to 75 percent of that required by the building code.
The site ground motion shall be an elastic design response spectrum prepared in conformance to the building code but having spectral acceleration values equal to 75 percent of the code design response spectrum. The spectral acceleration values shall be increased by the occupancy importance factor when required by the building code.
Structures conforming to the requirements of the ASCE 31 Tier 1, Screening Phase, are permitted to be shown to be in conformance to this chapter by submission of a report to the building official as described in this section.
The registered design professional shall prepare a report summarizing the analysis conducted in compliance with this section. As a minimum, the report shall include the following items:
1. Building description.
2. Site inspection summary.
3. Summary of reviewed record documents.
4. Earthquake design data used for the evaluation of the building.
5. Completed checklists.
6. Quick-check analysis calculations.
7. Summary of deficiencies.
A Tier 2 analysis includes an analysis using the following linear methods: Static or equivalent lateral force procedures. A linear dynamic analysis may be used to determine the distribution of the base shear over the height of the structure. The analysis, as a minimum, shall address all potential deficiencies identified in Tier 1, using procedures specified in this section.

If a Tier 2 analysis identifies a nonconforming condition, such condition shall be modified to conform to the acceptance criteria. Alternatively, the design professional may choose to perform a Tier 3 analysis to verify the adequacy of the structure.

A Tier 2 analysis procedure may be used if:
1. There is no in-plane offset in the lateral force-resisting system.
2. There is no out-of-plane offset in the lateral force-resisting system.
3. There is no torsional irregularity present in any story. A torsional irregularity may be deemed to exist in a story when the maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drifts at the two ends of the structure.
4. There is no weak story irregularity at any floor level on any axis of the building. A weak story is one in which the story strength is less than 80 percent of that in the story above. The story strength is the total strength of all seismic-resisting elements sharing the story shear for the direction under consideration.
Exception: Static or equivalent lateral force procedures shall not be used if:
1. The building is more than 100 feet (30 480 mm) in height.
2. The building has a vertical mass or stiffness irregularity (soft story). Mass irregularity shall be considered to exist where the effective mass of any story is more than 150 percent of the effective mass of any adjacent story. A soft story is one in which the lateral stiffness is less than 70 percent of that in the story above or less than 80 percent of the average stiffness of the three stories above.
3. The building has a vertical geometric irregularity. Vertical geometric irregularity shall be considered to exist where the horizontal dimension of the lateral force-resisting system in any story is more than 130 percent of that in an adjacent story.
4. The building has a nonorthogonal lateral force-resisting system.
A structural analysis shall be performed for all structures in accordance with the requirements of the building code, except as modified in Section A506. The response modification factor, R, shall be selected based on the type of seismic force-resisting system employed and shall comply with the requirements of Section 301.1.4.1.
The three-dimensional mathematical model of the physical structure shall represent the spatial distribution of mass and stiffness of the structure to an extent that is adequate for the calculation of the significant features of its distribution of lateral forces. All concrete and masonry elements shall be included in the model of the physical structure.

Exception: Concrete or masonry partitions that are isolated from the concrete frame members and the floor above.

Cast-in-place reinforced concrete floors with span-to-depth ratios less than three-to-one may be assumed to be rigid diaphragms. Other floors, including floors constructed of precast elements with or without a reinforced concrete topping, shall be analyzed in conformance to the building code to determine if they must be considered semi-rigid diaphragms. The effective in-plane stiffness of the diaphragm, including effects of cracking and discontinuity between precast elements, shall be considered. Parking structures that have ramps rather than a single floor level shall be modeled as having mass appropriately distributed on each ramp. The lateral stiffness of the ramp may be calculated as having properties based on the uncracked cross section of the slab exclusive of beams and girders.

Component stiffness shall be calculated based on the approximate values shown in Table 6-5 of ASCE 41.
The design and detailing of new components of the seismic force-resisting system shall comply with the requirements of the International Building Code, unless specifically modified herein.
The calculated strength of a member shall not be less than the load effects on that member.
For load and resistance factor design (strength design), structures and all portions thereof shall resist the most critical effects from the combinations of factored loads prescribed in the building code.

Exception: For concrete beams and columns, the shear effect shall be determined based on the most critical load combinations prescribed in the building code. The shear load effect, because of seismic forces, shall be multiplied by a factor of Cd, but combined shear load effect need not be greater than Ve, as calculated in accordance with Equation A5-4. Mpr1 and Mpr2 are the end moments, assumed to be in the same direction (clockwise or counter clockwise), based on steel tensile stress being equal to 1.25 fy, where fy is the specified yield strength.

(Equation A5-1)

where:

Wg= Total gravity loads on the beam
The strength of a member shall be determined by multiplying the nominal strength of the member by a strength reduction factor, φ. The nominal strength of the member shall be determined in accordance with the building code.
A Tier 3 evaluation shall be performed using the nonlinear procedures of Section 6.3.1.2.2. of ASCE 41. The general assumptions and requirements of Section 6.0, excluding concrete frames with in-fills shall be used in the evaluation. Site-ground motions in accordance with Section A504.3 are permitted for this evaluation.
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