The provisions of this division are minimum standards for structural seismic resistance established primarily to reduce the risk of loss of life or injury and will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. This division shall not require existing electrical, plumbing, mechanical or fire-safety systems to be altered unless they constitute a hazard to life or property.
This division provides systematic procedures and standards for identification and classification of unreinforced masonry bearing wall buildings based on their current use. Priorities, time periods and standards are also established under which these buildings are required to be structurally analyzed and anchored. Where the analysis determines deficiencies, this division requires the building to be strengthened or demolished.
HIGH-RISK BUILDING is any building not classified as an essential building having an occupant load, as determined by CBC Section 1004.1, of 100 occupants or more.
- Any building having exterior walls braced with masonry cross walls or wood-frame cross walls spaced less than 40 feet (12 192 mm) apart in each story. Cross walls shall be full-story height with a minimum length of 1 1/2 times the story height.
- Any building used for its intended purpose, as determined by the Department, for less than 20 hours per week.
LOW-RISK BUILDING is any building not classified as an essential building having an occupant load as determined by CBC Section 1004.1 of less than 20 occupants.
MEDIUM-RISK BUILDING is any building not classified as a high-risk building or an essential building having an occupant load as determined by CBC Section 1004.1 of 20 occupants or more.
UNREINFORCED MASONRY BEARING WALL is a masonry wall having all the following characteristics:
- For the purpose of this division, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications.
- For the purpose of this division, to establish the rating classification of a building containing one or more artist in residence spaces, as defined in Section 91.8501 of this Code, the occupant load of each artist in residence space shall be one for each space less than 2,000 square feet (186 m2) in area and two for each space 2,000 square feet (186 m2) or more in area.
The owner of a building within the scope of this division shall comply with the requirements set forth above by submitting to the Department for review within the stated time limits:
- Within 270 days after the service of the order, a structural analysis. Such analysis, which is subject to approval by the Department, shall demonstrate that the building meets the minimum requirements of this division, or
- Within 270 days after the service of the order, the structural analysis and plans for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or
- Within 120 days after service of the order, plans for the installation of wall anchors in accordance with the requirements specified in Section 91.8808.3, or
- Within 270 days after the service of the order, plans for the demolition of the building.
Owners electing to comply with Item 3 are also required to comply with Items 2 and 4, provided, however, that the 270 day period provided for in Items 2 and 4 and the time limits for obtaining a building permit, commencing construction and completing construction for complete structural alterations or building demolition set forth in Table No. 88-B shall be extended in accordance with Table No. 88-C. Each such extended time limit, except the time limit for commencing construction, shall begin to run from the date the order is served in accordance with Section 91.8806.2. The time limit for commencing construction shall commence to run from the date the building permit is issued.
Appeals or requests for slight modifications from any other determinations, orders or actions by the Department pursuant to this division shall be made in accordance with the procedures established in Section 98.0403.2 of the Los Angeles Municipal Code.
If the building is either demolished, found not to be within the scope of this division, or is structurally capable of resisting minimum seismic forces required by this division as a result of structural alterations or an analysis, the Department shall file with the Office of the County Recorder a certificate terminating the status of the subject building as being classified within the scope of this division.
V = IKCSW (8-1)
The value of IKCS need not exceed the values set forth in Table No. 88-D based on the applicable rating classification of the building.
Fp = ICpSWp (8-2)
For the provisions of this Section, the product of IS need not exceed the values as set forth in Table No. 88-E.
The value of Cp need not exceed the values set forth in Table No. 88-F.
In addition, the compatibility of the roof diaphragm stiffness with the out-of-plane stability of the unreinforced masonry bearing walls of the story immediately below the roof system shall be verified in accordance with the provisions of Section 91.8811.
Substantial changes in wall thickness or stiffness shall be considered in the analysis for out-of-plane and in-plane wall stability, and the wall shall be restrained against out-of- plane instability by anchorage and bracing to the roof or floor diaphragm in accordance with Section 91.8808.3 of this Code.
No allowable tension stress will be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this division shall be strengthened or shall be removed and replaced.
- Unreinforced masonry walls in buildings not classified as a Rating Classification I pursuant to Table No. 88-A may be analyzed in accordance with Section 91.8809 of this Code.
- Unreinforced masonry walls which carry no design loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements.
All units of both bearing and nonbearing walls shall be laid with full shoved mortar joints; all head, bed and wall (collar) joints shall be solidly filled with mortar; and the bonding of adjacent wythes of multiwythe walls shall be as follows:
The facing and backing shall be bonded so that not less than 4 percent of the wall surface of each face is composed of headers extending not less than four inches (102 mm) into the backing. The distance between adjacent full-length headers shall not exceed 24 inches (610 mm) either vertically or horizontally. In walls in which a single header does not extend through the wall, headers from the opposite sides shall overlap at least four inches (102 mm), or headers from opposite sides shall be covered with another header course overlapping the header below at least four inches (102 mm).
Wythes of walls not bonded as described above shall be considered as veneer. The veneer wythe shall not be included in the effective thickness used in calculating the height-to-thickness ratio and the shear capacity of the wall.
Tension stresses due to seismic forces normal to the wall may be neglected if the wall does not exceed the height-to-thickness ratio in Table No. 88-G and the in-plane shear stresses due to seismic loads as set forth in Table No. 88-J.
If the wall height-to-thickness ratio exceeds the specified limits, the wall may be supported by vertical bracing members designed in accordance with Division 16 of this Code. The deflection of such bracing member at design loads shall not exceed one tenth of the wall thickness.
All 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 the unsupported height of the wall or 10 feet (3048 mm).
The wall height may be measured vertically to bracing elements other than a floor or roof. Spacing of the bracing elements and wall anchors shall not exceed six feet (1829 mm). Bracing elements shall be detailed to minimize the horizontal displacement of the wall by components of vertical displacements of the floor or roof.
The existence and condition of existing veneer anchor ties shall be verified as follows:
- An approved testing laboratory shall verify the location and spacing of the ties and shall submit a report to the Department for approval as a part of the structural analysis.
- The veneer in a selected area shall be removed to expose a representative sample of ties (not less than four) for inspection by the Department.
The vertical wall joint between wythes (collar joints) shall be inspected at the test location after the in-place shear tests, and an estimate of the percentage of wythe-to-wythe mortar coverage shall be reported along with the results of the in-place shear tests. 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 reported.
Alternative methods of testing may be approved by the Department. Nothing shall prevent pointing with mortar of all the masonry wall joints before the tests are first made. Prior to any pointing, the mortar joints must be raked and cleaned to remove loose and deteriorated mortar. Mortar for pointing shall be Type S or N except masonry cements shall not be used. All preparation and mortar pointing shall be done under the continuous inspection of a registered deputy inspector. At the conclusion of the inspection, the inspector shall submit a written report to the licensed engineer or architect responsible for the seismic analysis of the building setting forth the result of the work inspected. Such report shall be submitted to the Department for approval as part of the structural analysis.
All testing shall meet Department-approved testing method parameters (including rate of load application) and shall be performed in accordance with the requirements specified in this section by a testing agency approved by the Department.
An accurate record of all such tests and their location in the building shall be recorded and these results shall be submitted to the Department for approval as part of the structural analysis.
- At each of both the first and top stories, not less than two per wall line or line of wall elements providing a common line of resistance to lateral forces.
- At each of all other stories, not less than one per wall element providing a common line of resistance to lateral forces.
- In any case, not less than one per 1,500 square feet (139.4 m 2 ) of wall surface and a total of eight.
The exact test or core location shall be determined at the building site by the licensed engineer or architect responsible for the seismic analysis of the subject building.
An internal caliper, graduated in 0.001 of an inch (0.025 mm) increments shall be used to measure movement of the masonry unit. A hydraulic jack equipped with a pressure gauge graduated in increments of 50 psi (345 kPa) or less shall be used. The jack load shall be applied at a rate not exceeding 5,000 pounds (22 240 N) per minute.
The test shall be conducted by a minimum of two technicians. Load and displacement readings shall be recorded at the following intervals:
- At a caliper reading of 0.001 inch (0.025 mm);
- At first visually observed sign of movement or cracking of the mortar or masonry unit;
- At a caliper reading of 0.02 inch (0.51 mm); and
- The ultimate load on the unit.
Walls with mortar values which are consistently low and do not meet the minimum quality values specified in this Section shall be entirely pointed per Chapter A1, Section A103 and A22.214.171.124 of 2007 California Existing Building Code except that the depth of joint penetration shall be 1-l/2 inch (38 mm) in lieu of the 3/4 inch (19 mm) specified.
5/8-inch-diameter bolts or dowels — 50 foot-pounds.
3/4-inch-diameter bolts or dowels — 60 foot-pounds.
For SI: 1 inch = 25.4 mm, 1 foot-pound = 1.356 Nm
No bolts exceeding 3/4-inch (19.1 mm) shall be used. All nuts shall be installed over malleable iron or plate washers when bearing on wood and heavy cut washers when bearing on steel.
Design stresses shall be related to test results obtained in accordance with Table No. 88-J. Intermediate values between 3 and 10 psi (20.7 kPa and 69 kPa) may be interpolated.
- All unreinforced masonry walls shall be anchored at the roof and ceiling levels by tension bolts through the wall as specified in Table No. 88-I, or by an approved equivalent at a maximum anchor spacing of six feet (1829 mm). Anchors installed in accordance with Section 91.8114 of this Code shall be accepted as conforming to this requirement.
All unreinforced masonry walls shall be anchored at all floors and ceiling with tension bolts through the wall or by existing rod anchors at a maximum anchor spacing of six feet (1829 mm). All existing rod anchors shall be secured to the joists to develop the required forces. The Department may require testing to verify the adequacy of the embedded ends of existing rod anchors. Tests, when required, shall conform to Section 91.8809.8.
EXCEPTION: Walls need not be anchored to ceiling systems that, because of their low mass and/or relative location with respect to the floor or roof systems, would not impose significant normal forces on the wall and cause out-of-plane wall failures.
At the roof and all floor levels, the anchors nearest the building corners shall be combination shear and tension anchors located not more than two feet (610 mm) horizontally from the inside corners of the walls.
When access to the exterior face of the masonry wall is prevented by proximity of an existing building, wall anchors conforming to Items 5 and 7 in Table No. 88-I may be used.
Alternative devices to be used in lieu of tension bolts for masonry wall anchorage shall be tested as specified in Section 91.8809.9.
- Diaphragm chord stresses of horizontal diaphragms shall be developed in existing materials or by addition of new materials.
- 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.
- Parapets and exterior wall appendages not capable of resisting the forces specified in this division shall be removed, stabilized or braced to ensure that the parapets and appendages remain in their original position.
The maximum height of an unbraced, unreinforced masonry parapet above the lower of either the level of tension anchors or roof sheathing shall not exceed one and one half times the thickness of the parapet wall. If the required parapet height exceeds this maximum height, a bracing system designed for the force factors specified in Table Nos. 88-E and 88-F for walls shall support the top of the parapet. Parapet corrective work must be performed in conjunction with the installation of tension roof anchors.
- All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N mortar. Prior to any pointing, the wall surface must be raked and cleaned to remove loose and deteriorated mortar. All preparation and pointing shall be done under the continuous inspection of a registered deputy inspector certified to inspect masonry or concrete. At the conclusion of the project, the inspector shall submit a written report to the Department setting forth the portion of work inspected.
- Repair details of any cracked or damaged unreinforced masonry wall required to resist forces specified in this division.
- The type and dimensions of existing walls and the size and spacing of floor and roof members.
- The extent and type of existing wall anchorage to floors and roof.
- The extent and type of parapet corrections which were performed in accordance with Section 91.8114 of this Code.
- Accurately dimensioned floor plans and masonry wall elevations showing dimensioned openings, piers, wall thickness and heights, and veneer and anchorages.
- The location of cracks or damaged portions of unreinforced masonry walls requiring repairs.
- The type of interior wall surfaces and ceilings, and if reinstalling or anchoring existing plaster is necessary.
- The general condition of the mortar joints and if the joints need pointing.
- The location of the shear tests shall be shown on the floor plans and building wall elevations, and the complete test report shall be reproduced on the approved plans.
Section 91.8811 Design Check — Compatibility of Roof Diaphragm Stiffness to Unreinforced Masonry Wall Out-Of-Plane Stability
- Two to one for wood structural panels.
- One to one for gypsum board, gypsum lath, cement plaster or diagonal sheathing.
- Demand = lateral forces due to 33 percent of the weight of the diaphragm and the tributary weight of the walls and other elements anchored to the diaphragm.
- Capacity = diaphragm total shear strength in the direction under consideration as determined using the values in Table No. 88-K or Table No. 88-L.
h/t = height-to-thickness ratio of an unreinforced masonry wall. The height shall be measured between wall anchorage levels and the thickness shall be measured through the wall cross section.
L = span of diaphragm between masonry shear walls or steel frames.
Vc = total shear capacity of cross walls in the direction of analysis immediately below the diaphragm level being investigated as determined by using Tables Nos. 88-K and 88-L.
vu = maximum shear strength in pounds per foot for a diaphragm sheathed with any of the materials given in Tables Nos. 88-K and 88-L.
Wd = total dead load of the diaphragm plus the tributary weight of the walls anchored to the diaphragm, the tributary ceiling and partitions and the weight of any other permanent building elements at the diaphragm level under investigation.
DCR = 0.33Wd /2vuD (11-3)
DCR = 0.33Wd /(2vuD + Vc ) (11-4)
Any person who violates, causes or permits another person to violate this provision is guilty of a misdemeanor. Any person includes an owner, lessor, sublessor, manager or person in control of a building subject to this division. This term shall not include any person who is merely a tenant or other individual occupying any dwelling unit, efficiency dwelling unit, guest room or suite in a building. The legal owner of a building is that person, firm, corporation, partnership or other entity whose name or title appears on the record with the Office of the County Recorder, as well as all successors or assignees of these persons.
- For a one-story building with wall anchors installed pursuant to Section 91.8808.3, either before or within 60 days after notice is given by the Department:
Within 180 days after notice is given pursuant to this section, the owner shall submit to the Department either plans and a structural analysis for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or an application for demolition of the building or structure.
If the owner elects to perform the proposed structural alterations, then within 270 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; within 90 days of obtaining a permit to strengthen the building, the owner shall commence strengthening work; and within 18 months after notice is given pursuant to this section, the owner shall complete all strengthening work.
If the owner elects to demolish the building, then within 210 days after notice is given pursuant to this section, the owner shall obtain permits for the demolition of the building or structure; within 21 days of obtaining a demolition permit, the owner shall commence demolition; and within 300 days after notice is given pursuant to this section the owner shall complete the demolition of the building or structure.
- Time for compliance for all other buildings:
Within 60 days after notice is given pursuant to this section, the owner shall submit to the Department either plans and a structural analysis for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or an application for demolition of the building or structure.
If the owner elects to perform the necessary alterations, then within 120 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; within 21 days of obtaining a permit, the owner shall begin work; and within 365 days after notice is given pursuant to this section, the owner shall complete all strengthening work.
If the owner elects to perform the necessary alterations, then within 120 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; and within 120 days after obtaining the demolition permit, the owner shall complete the demolition of the building or structure.
|TYPE OF BUILDING||CLASSIFICATION|
|High Risk Building||II|
|Medium Risk Building||III|
|Low Risk Building||IV|
|REQUIRED ACTION BY OWNER||OBTAIN BUILDING PERMIT WITHIN||COMMENCE CONSTRUCTION WITHIN||COMPLETE CONSTRUCTION WITHIN|
|Complete Structural Alterations or Building Demolition||1 year||180 days*||3 years|
|Wall Anchor Installation||180 days||270 days||1 year|
*Measured from date of building permit issuance.
|Rating Occupant Classification||Extension of Time if Wall Anchors Load||Minimum Time Periods are Installed||Service of Order|
|I (Highest Priority)||Any||One Year||0|
|II||100 or more||One Year||90 Days|
|III||100 or more||One Year||One Year|
|More than 50, but less than 100||One Year||Two Years|
|More than 19, but less than 51||One Year||Three Years|
|IV (Lowest Priority)||less than 20||One Year||Four Years|
**Buildings that have obtained a building permit for wall anchors and met the time schedule in Table 88-B for wall anchor installation may utilize the time extensions, which are permitted in Table 88-C prior to the adoption of this ordinance.
|III & IV||0.100|
|III & IV||0.75|
|PART OR PORTION OF BUILDINGS||DIRECTION OF FORCE||VALUE OF Cp|
|Exterior bearing and nonbearing walls; interior bearing walls and partitions; interior nonbearing walls and partitions over 10 feet in height; masonry fences over 6 feet in height||Normal to flat surface||0.20|
|Cantilever parapet and other cantilever walls, except retaining walls.||Normal to flat surface||1.00|
|Exterior and interior ornamentations and appendages.||Any direction||1.00|
|When connected to or a part of a building: towers, tanks, towers and tanks plus contents, racks over 8 feet 3 inches in height plus contents, chimneys, smokestacks and penthouses.||Any direction||0.202,4|
|When connected to or a part of a building: rigid and rigidly mounted equipment and machinery not required for continued operation of essential occupancies. 5||Any horizontal direction||0.203|
|Tanks plus effective contents resting on the ground.||Any direction||0.12|
|Floors and roofs acting as diaphragms.||In the plane of the diaphragm||0.126|
|Prefabricated structural elements, other than walls, with force applied at center of gravity of assembly.||Any horizontal direction||0.30|
|Connections for exterior panels or elements.||Any direction||2.00|
For SI: 1 inch = 25.4 mm, 1 foot = 305 mm.
- See Section 91.8808.2 for use of Cp.
- When located in the upper portion of any building with a height to depth ratio of 5 to 1 or greater, the value shall be increased by 50 percent.
- For flexible and flexible mounted equipment and machinery, the appropriate values for Cp shall be determined with consideration given to both the dynamic properties of the equipment and machinery and to the building and building or structure in which it is placed.
- The Wp for storage racks shall be the weight of the racks plus contents. The value of Cp for racks over two storage support levels in height shall be 0.16 for the levels below the top two levels.
- The design of the equipment and machinery and their anchorage is an integral part of the design and specification of that equipment and machinery. The structure to which the equipment or machinery is mounted shall be capable of resisting the anchorage forces (see also Section 13.6.5 of ASCE-7).
- Floor and roofs acting as diaphragms shall be designed for a minimum force resulting from a Cp of 0.12 applied to Wp unless a greater force results from the distribution of lateral forces in accordance with Section 12.8.3 of ASCE-7.
|BUILDINGS W/ CROSS WALLS AS DEFINED BY SECTION 91.8803||ALL OTHER BUILDINGS|
|Walls of One-story Buildings||13 - 16 3, 4, 5||13|
|First-Story Wall of Multi-story Buildings||16||15|
|Walls in Top Story of Multi-story Buildings||9 - 14 3, 4, 5||9|
|All Other Walls||16||13|
- 1. Minimum quality mortar shall be determined by laboratory testing in accordance with Section 91.8809.5 of this Code.
- 2. This table is not applicable to buildings of Rating Classification I. Walls of buildings within Rating Classification I shall be analyzed in accordance with Section 91.8808.6 of this Code.
- 3. The minimum mortar shear strengths required in Footnotes 4 and 5 shall be that shear strength without the effect of axial stress in the wall at the point of the test.
- 4. The larger height-to-thickness ratio may be used where mortar shear tests in accordance with Section 91.8809.5.3 of this Code establish a minimum mortar shear strength of not less than 100 psi (690 kPa) or where the tested mortar shear strength is not less than 60 psi (414 kPa) and a visual examination of the vertical wythe-to-wythe wall joint (collar joint) indicates not less than 50 percent mortar coverage.
- 5. Where a visual examination of the collar joint indicates not less than 50 percent mortar coverage and the minimum mortar shear strength when established in accordance with Section 91.8809.5.3 of this Code is greater than 30 psi (207 kPa) but less than 60 psi (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 mortar shear strength.
|EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1||ALLOWABLE VALUES|
|1. HORIZONTAL DIAPHRAGMS|
|(a) Roofs with straight sheathing and roofing applied directly to the sheathing.||100 lbs. per foot for seismic shear.|
|(b) Roofs with diagonal sheathing and roofing applied directly to the sheathing.||400 lbs. per foot for seismic shear.|
|(c) Floors with straight tongue-and-groove sheathing.||150 lbs. per foot for seismic shear.|
|(d) Floors with straight sheathing and finished wood flooring.||300 lbs. per foot for seismic shear.|
|(e) Floors with diagonal sheathing and finished wood flooring.||450 lbs. per foot for seismic shear.|
|(f) Floors or roofs with straight sheathing and plaster applied to the joist or values for items 1(a) and 1(c) rafters.2||Add 50 lbs. per foot to the allowable values for items 1(a) and 1(c).|
|2. SHEAR WALL
Wood stud walls with lath and plaster
|100 lbs. per foot each side for seismic shear.|
|3. PLAIN CONCRETE FOOTINGS||fc’ = 1500 psi unless otherwise shown by tests|
|4. DOUGLAS FIR WOOD||Allowable stress same as No. 1 D.F. 3|
|5. REINFORCING STEEL||fy = 18,000 lbs. per square inch maximum|
|6. STRUCTURAL STEEL||fy = 20,000 lbs. per square inch maximum|
For SI: 1 pound per foot = 0.0146 N/m, 1 pound per square inch (psi) = 6.895 kPa.
- 1. Material must be sound and in good condition.
- 2. The wood lath and plaster must be reattached to existing joists or rafters in a manner approved by the Department.
- 3. Stresses given may be increased for combinations of loads as specified in Section 91.8808.7.2 of this Code.
|NEW MATERIALS OR CONFIGURATION OF MATERIALS 1||ALLOWABLE VALUES|
|1. HORIZONTAL DIAPHRAGMS|
|Same as specified in CBC Table 2306.2.1.(1) and 2306.2.1.(2) for blocked diaphragms.|
|2. SHEAR WALLS|
|Same as values specified in CBC Table 2306.3 for shear walls.|
b. Dry wall or plaster applied directly over existing wood studs.
|75 percent of the values specified in CBC Table 2306.7.|
|33 1/3 percent of the values specified in CBC Table 2306.7.|
|3. SHEAR BOLTS|
|133 percent of the values for plain solid masonry specified in Table No. 88-M. No values larger than those given for 3/4 inch bolts shall be used.|
|4. TENSION BOLTS|
|1200 lbs. per bolt or dowel.|
|5. COMBINATION SHEAR AND TENSION WALL ANCHORS|
a. Bolts extending to the exterior face of the wall with a 2-1/2 inch round plate under the head. Install as specified for shear bolts. Spaced not closer than 12 inches on centers. 1, 2, 3
|600 lbs. per bolt for tension.4 See Item 3 (SHEAR BOLTS) for shear values.|
b. Bolts or dowels extending to the exterior face of the wall with a 2-1/2 inch round plate under the head and drill at an angle of 22-1/2 degrees to the horizontal. Installed as specified for shear bolts. 1, 2, 3
|1200 lbs per bolt or dowel for tension.4 See Item 3 (SHEAR BOLTS) for shear values.|
c. Through bolt with bearing plate for tension per Item 4. Combined with minimum eight-inch grouted section for shear per Item 3.
|See Item 4 (TENSION BOLTS) for tension values.4 See Item 3 (SHEAR BOLTS) for shear values.|
|6. INFILLED WALLS|
|Same as values specified for unreinforced masonry walls.|
|7. REINFORCED MASONRY|
|Same as values determined per CBC Section 2106.|
|8. REINFORCED CONCRETE|
|Same as values specified in Division 19 of this Code.|
|9. EXISTING FOUNDATION LOADS|
Foundation loads for structures exhibiting no evidence of settlement.
|Calculated existing foundation loads due to maximum dead load plus live load may be increased 25 percent for deadload, and may be increased 50 percent for dead load plus seismic load required by this division.|
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm 2 , 1 pound = 4.45 N.
- 1. Bolts and dowels to be tested as specified in Section91.8809.6 of this Code.
- 2. Bolts and dowels to be 1/2-inch minimum in diameter.
- 3. Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools shall not be used for drilling holes or tightening anchor and shear bolt nuts.
- 4. Allowable bolt and dowel values specified are for installations in minimum three wythe walls. For installations in two wythe walls, use 50 percent of the value specified, except that no value shall be given to tension bolts that do not extend entirely through the wall and are secured with bearing plates on the far side.
|Eighty percent of test results in psi not less than||Average test results of cores in psi||Seismic in-plane shear based on gross area|
|30 plus axial stress||20||3 psi*|
|40 plus axial stress||27||4 psi*|
|50 plus axial stress||33||5 psi*|
|100 plus axial stress or more||67 or more||10 psi max*|
* Allowable shear stress may be increased by addition of 10% of the axial stress due to the weight of the wall directly above.
|EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1||ALLOWABLE VALUES|
|1. HORIZONTAL DIAPHRAGMS|
a. Roofs with straight sheathing and roofing applied directly to the sheathing.
|100 lbs. per foot for seismic shear.|
b. Roofs with diagonal sheathing and roofing applied directly to the sheathing.
|250 lbs. per foot for seismic shear.|
|2. CROSSWALLS 2, 3|
|a. Plaster on wood or metal lath.||per side: 200 lbs. per foot for seismic shear.|
|b. Plaster on gypsum lath.||175 lbs. per foot for seismic shear.|
|c. Gypsum wall board, unlocked edges.||75 lbs. per foot for seismic shear.|
|d. Gypsum wall board, blocked edges.||125 lbs. per foot for seismic shear.|
- 1. Materials must be sound and in good condition.
- 2. For crosswalls, values of all materials may be combined, except the total combined value shall not exceed 300 lbs. per foot for seismic shear.
- 3. The cross wall aspect ratio for plaster on wood, metal, or gypsum lath and gypsum wall board shall be a maximum height to width ratio of 1:1.
|NEW MATERIALS OR CONFIGURATION OF ALLOWABLE VALUES||NEW AND EXISTING MATERIALS 1|
|1. HORIZONTAL DIAPHRAGMS|
|225 lbs. per foot for seismic shear.|
|2. CROSS WALLS 2, 3|
|1.33 times the values specified in CBC Table 2306.3 for shear walls.|
b. Drywall or plaster applied directly over existing wood studs.
|100 percent of the values specified in CBC Table 2306.7.|
- 1. Materials must be sound and in good condition.
- 2. For cross walls, values of all materials may be combined, except the total combined value shall not exceed 300 lbs. per foot for seismic shear.
- 3. The cross wall aspect ratio for drywall, plaster and gypsum wall board shall be a maximum height to width ratio of 1:1, and for plywood shall be a maximum height to width ratio of 2:1.
(shear in pounds)
(shear in pounds)