ADOPTS WITH AMENDMENTS:

International Building Code 2018 (IBC 2018)

Heads up: There are no amended sections in this chapter.

Section O101 Applicability and Scope

AMENDMENT
This section has been amended at the state or city level.

O101.1 General

AMENDMENT
This section has been amended at the state or city level.
The structural design and construction of new qualified one and two story reinforced concrete buildings can be performed in accordance with these alternate provisions, as an alternate to those included in the 2018 Puerto Rico Building Code (IBC 2018) and the Puerto Rico Residential Code 2018. For additions or modifications of existing structures, follow the Puerto Rico Existing Building Code 2018. A qualified building shall meet the requirements set forth in this section as follows:
  1. The building consists of a reinforced concrete structure with or without concrete block infill walls. The floor area of each story shall not exceed five thousand (5,000) square feet and any story level shall not exceed 12 feet in height.
  2. The building shall have a nearly symmetrical plan configuration in both principal directions. The distance between the center of mass and the center of rigidity of the building shall not exceed five (5) percent of the plan dimension measured normal to the direction of the load.
  3. All reinforced concrete structural elements supporting vertical and lateral loads shall be castin- place.
  4. A lateral force resisting system (LFRS), consisting of moment frames or shear walls or a combination of both, shall be provided in both principal directions of the building. The outof- plane stiffness of the walls shall not be considered as part of the LFRS.
  5. All vertical structural elements shall be continuous down to the foundation, with no horizontal offset and no reduction in sectional area. Rigid structural systems on the second level, like reinforced concrete or concrete block shear walls that are supported by frame systems on the first level, shall be identified as a soft story at the first level and shall not be allowed.
  6. The maximum difference in base elevation between adjacent footings shall not exceed twelve (12) inches. Additionally, the final grading elevation around the building shall not exceed three (3) feet above the ground slab elevation.
  7. The second-floor slab area shall not exceed that of the ground floor, except that for balconies or overhangs the second-floor slabs are permitted up to six (6) feet from the faces of the four façades of the building, but not larger than 1/3 of the adjacent interior span.
  8. The resulting design seismic base shear, calculated as per these alternate provisions, shall not be reduced due to ductility considerations.
  9. These provisions shall apply only to buildings with Occupancy Category I and II as defined in Table O102.2 or Table 1604.5 (IBC 2018) (Minimum Design Loads for Buildings and Other Structures). The qualified buildings shall not have an Importance Factor greater than 1.0.

Section O102 Design Loads

AMENDMENT
This section has been amended at the state or city level.

O102.1 Permanent Loads

AMENDMENT
This section has been amended at the state or city level.
Dead, fixed and permanent loads used for the design shall be as per the IBC 2018 provisions.

Table O102.1:
Design Wind Pressures for Components and Cladding
TYPE OF Component and Cladding DESIGN pressure NORMAL to surface (IN psf)
Wall components and their connections to LFRS, including, but not limited to, structural members, concrete block walls, exterior wall panels, doors, windows, permanent terrace covers and nonretractable shade curtains and all exterior architectural components, All Roof structure components. 90 (inward or outward) at edge zone and 65(inward or outward) elsewhere
All equipment and components supported by the roof including, but not limited to, solar water heaters, solar panels, water cisterns, A/C units, equipment, and associated conduit and ductwork and all attachments. Also, skylights, ventilation and extraction fans and all their attachments. 90 (acting in any direction) 54 (acting upward and downward)
All parapets or extension of wall elements above roof elevation. 90 (acting inward, outward or upward
Roof membranes installed for impermeabilization and climate control purposes. 90 (acting inward or outward) 110 (acting upward) at edge zones and flashings and 65 (acting upward) elsewhere

O102.2 Live Loads

AMENDMENT
This section has been amended at the state or city level.
Design live loads shall be as per the IBC 2018 provisions or PRBC-2018 amendments.

O102.3 Lateral Forces

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This section has been amended at the state or city level.
The general provisions for the calculation of the design lateral loads shall be as per this section.

O102.3.1 Hurricane Wind Loads

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This section has been amended at the state or city level.

O102.3.1.1 General

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This section has been amended at the state or city level.
All buildings and their components, and accessories and their attachments subject to wind loads, shall be designed to withstand the pressures and meet the requirements of this section. Building components, such as windows, panels, doors, roof equipment, antennas and the architectural features exposed to the wind shall be designed for the wind loads specified. The wind shall be assumed as approaching the structure from any horizontal direction. Reductions on the design wind pressures shall not be permitted. Reductions in load associated with protection or shielding provided by adjacent structures shall not be permitted. However, the calculated capacity of the components may be increased by a factor of 1.3 to account for the short duration of the wind loads.

O102.3.1.2 Basic Wind Speed

AMENDMENT
This section has been amended at the state or city level.
Wind pressures listed in this section are based on a wind speed of three (3) seconds gust criteria, as defined by the ASCE 7 design standard. Design wind pressures as per this section are unfactored service loads.

O102.3.1.3 Design Wind Pressure

AMENDMENT
This section has been amended at the state or city level.
The net wind pressure, at strength load condition, acting on the main wind force resisting system shall not be less than 54 psf, acting normal to both the windward (positive pressure) and leeward (negative pressure) façades of the building, concurrently with a roof vertical pressure of 54 psf acting on the roof upward or 42 psf acting on the roof downward. The two load cases specified above shall be considered separately and the structural element shall be designed for the larger load combination. The total shear force induced by wind shall be calculated based on these criteria.

O102.3.1.4 Components and Cladding

AMENDMENT
This section has been amended at the state or city level.
The wind pressures acting on any structural or non-structural component or cladding element shall not be less than those listed on Table I. Designer shall refer to ASCE 7 standard, to obtain the design wind pressures for those components not listed in this section. Wall edge zones shall be defined as the portion of the wall located within a distance of ten (10) feet measured horizontally from the corners of the building.

O102.3.2 Earthquake Loads

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This section has been amended at the state or city level.

O102.3.2.1 General

AMENDMENT
This section has been amended at the state or city level.
All qualified buildings and all their components shall be designed to meet the seismic requirements of this section.

O102.3.2.2 Seismic Loads

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This section has been amended at the state or city level.
The design horizontal seismic force shall be applied at the level of each story and located at a distance of plus or minus five (5) percent of the maximum plan dimension normal to the direction of the load from the center of rigidity of each story. This distance shall be considered the accidental eccentricity. The seismic load need not be applied concurrently along both principal directions of the building. For all non-structural components, the design seismic force shall be applied at their center of mass. The seismic forces calculated as per these alternate provisions are factored loads based on the elastic structural behavior and shall not be reduced to account for any ductility considerations.

O102.3.2.3 Minimum Design Seismic Force

AMENDMENT
This section has been amended at the state or city level.
The design seismic load shall not be less than that calculated by the following formula:

Vu = 0.50 W

where;

W = Total weight of the structure including all structural and non-structural components, equipment and any other permanent attachment to the structure that modifies the inertial properties of the structure.
Vu = Total horizontal base shear force at factored level.


For one story structures, the total base shear, Vu, shall be applied to the roof level. For two story structures, Vu shall be applied in equal proportions to the first and roof levels.

O102.3.2.4

AMENDMENT
This section has been amended at the state or city level.
Horizontal Distribution of Seismic Force. The total shear force applied at each level shall be distributed among all components of the LFRS in proportion to their relative stiffness. The floor and roof slabs shall be used as horizontal rigid diaphragms. Slabs thickness shall not be less than four (4) inches and shall be cast-in-place without horizontal construction joints.

O102.3.2.5

AMENDMENT
This section has been amended at the state or city level.
Minimum horizontal design seismic forces on nonstructural components: All non-structural components and their attachments to the principal structure shall be designed to withstand as a minimum, the lateral loads calculated in accordance with the following formula:

Fp = 0.60 Wp

where,

Wp = Total weight of the non-structural components or equipment.
Fp = Total design horizontal seismic force at factored level.

O102.4 Load Combinations

AMENDMENT
This section has been amended at the state or city level.
The required strength of the structure and all its components shall be determined from the Load and Resistance Factor Design load combinations and load factors provided in Section 1605 of the IBC 2018.

Section O103 Foundations

AMENDMENT
This section has been amended at the state or city level.

O103.1 General

AMENDMENT
This section has been amended at the state or city level.
The foundation design of qualified buildings shall meet the requirements of this section. Structures designed as per these alternate provisions may be supported by isolated or combined footings or by a mat foundation. Minimum concrete compressive strength is 3,000 psi at 28 days and 60,000 ksi for steel reinforcement conforming to ASTM A615-09. Welding of reinforcement bars shall not be permitted.

O103.2 Minimum Foundation Thickness

AMENDMENT
This section has been amended at the state or city level.
The foundation thickness shall not be less than the following:
  1. For spread footings under load bearing walls twelve (12) inches.
  2. For spread footings under columns twelve (12) inches.
  3. For mat foundations, twelve (12) inches under concrete walls, twelve (12) inches under columns and six (6) inches elsewhere. Changes in thickness shall be done gradually in a 1:1 slope down towards the thickened portion.

O103.3 Minimum Foundation Width

AMENDMENT
This section has been amended at the state or city level.
The foundation width shall not be less than the following:
  1. For combined footings and mat foundations under interior load bearing walls, twelve (12) inches measured from each face of the wall. For the case of combined footings and mat foundations under exterior load bearing walls, fifteen (15) inches measured from each face of the wall.
  2. For spread footings and combined footings under interior and exterior columns, eighteen (18) inches measured from each face of the column. For the case of mat foundations under interior columns, eighteen (18) inches measured from each face of the column. For the case of mat foundations under exterior columns, fifteen (15) inches measured from each face of the column.

O103.4 Minimum Steel Reinforcement

AMENDMENT
This section has been amended at the state or city level.
Foundation reinforcement shall not be less than 0.002 of the gross sectional area.

O103.5 Minimum Concrete Cover

AMENDMENT
This section has been amended at the state or city level.
The concrete clear cover of steel reinforcement cast against earth or permanently exposed to earth, shall not be less than three (3) inches or two (2) inches if the complete foundation is cast against an unperforated bituminous or plastic vapor barrier membrane conforming to ASTM E-1993 and ASTM 1745 of at least six thousandths of an inch (6 mils) thick. Membrane installation shall be as per ASTM 1643.

O103.6 Type L Footings

AMENDMENT
This section has been amended at the state or city level.
Type "L" footings shall not be used except at those instances required to avoid conflicts with property lines. In such cases, their design shall consider soil bearing pressure variations caused by the eccentricity of the applied load. The full footprint of the foundation shall remain in bearing contact with the soil when subjected to service level loads combinations as per IBC 2018.

Section O104 Reinforced Concrete Frames

AMENDMENT
This section has been amended at the state or city level.

O104.1 General

AMENDMENT
This section has been amended at the state or city level.
The design of reinforced concrete frames designated to be part of the LFRS shall meet the provisions of this section.

O104.2 Materials

AMENDMENT
This section has been amended at the state or city level.
The specified materials shall satisfy or exceed the following minimum requirements:
  1. Concrete. The specified 28 days concrete compressive strength for all components of the frame components shall not be less than three thousand pounds per square inches (3,000 psi).
  2. Steel. All steel reinforcement shall consist of deformed bars with a minimum yield stress, Fy, of sixty thousand pounds per square inches (60,000 psi) conforming to ASTM A615-09. Welding of steel reinforcement bars shall not be permitted.

O104.3 Minimum Element Dimensions

AMENDMENT
This section has been amended at the state or city level.
The depth of frame elements in the plane of the lateral load under consideration, shall not be less than twelve (12) inches in columns and eighteen (18) inches in beams, including the slab thickness when cast monolithically. In no case any frame element shall have a dimension of less than eight (8) inches. In addition, the minimum column cross sectional area shall not be less than one hundred forty-four (144) square inches.

O104.4 Minimum Reinforcement

AMENDMENT
This section has been amended at the state or city level.
The beams of the frame shall be provided with at least two (2) #5 longitudinal reinforcing bars at bottom and top. In no case shall the minimum reinforcement provided in beams be less than the provisions of Section 10.5 of ACI 318-14. Transverse reinforcement shall consist of at least #3 closed stirrups spaced no farther apart than six (6) inches on center. The center of the splice for the positive (bottom) reinforcement shall be located at a distance of one-fourth (1/4) the clear span from the face of the support and shall have a splice length of thirty-six (36) times the bar diameter or eighteen (18) inches, whichever is greater. The negative (top) reinforcement shall be continuous throughout the supports, and the center of the splice shall be located at mid-span with an overlapping length of thirty (30) times the bar diameter or twelve (12) inches, whichever is greater. The longitudinal top and bottom reinforcement of beams shall terminate on exterior columns anchored with 90 degree standard hooks. The longitudinal reinforcement in columns shall not be less than eight (8) #5 bars. The longitudinal reinforcement of columns shall terminate anchored with 90 degree standard hooks. The footing dowels shall be spliced with the column longitudinal reinforcement at column mid-height with an overlapping of thirty-six (36) times the diameter of the longitudinal bars. Column transverse reinforcement shall consist of at least #3 closed ties spaced no farther than six (6) inches on center. Beam stirrups and column ties shall consist of closed hoops in accordance with ACI standards. In all columns, ties shall be extended through the column-beam joints.

O104.5 Minimum Area of Concrete Columns

AMENDMENT
This section has been amended at the state or city level.
The sum of the gross area of all concrete columns, in square inches and on the base floor must be at least 0.00325 times the total horizontal base shear Vu, in pounds.

O104.6 Required Analysis of Moment Frames

AMENDMENT
This section has been amended at the state or city level.
The structural analysis of moment frames shall be performed by means of a rational analytical method accepted by the engineering community. The stiffness contribution and effects of moment frames with Concrete Masonry Units (CMU) infill shall be considered as per these provisions.

Section O105 Reinforced Concrete Walls

AMENDMENT
This section has been amended at the state or city level.

O105.1 General

AMENDMENT
This section has been amended at the state or city level.
The design of reinforced concrete walls designated to be part of the LFRS shall meet the provisions of this section.

O105.2 Materials

AMENDMENT
This section has been amended at the state or city level.
The specified materials shall satisfy or exceed the following minimum requirements:
  1. Concrete — The specified 28 days concrete compressive strength for all walls shall not be less than three thousand pounds per square inches (3,000 psi).
  2. Steel — All steel reinforcement shall consist of deformed bars with a minimum yield stress, Fy, of sixty thousand pounds per square inches (60,000 psi) conforming to ASTM A615-09. Welding of steel reinforcement bars shall not be permitted.

O105.3 Minimum Element Dimensions

AMENDMENT
This section has been amended at the state or city level.
The length of the wall in the direction of the lateral load under consideration, shall not be less than forty-eight (48) inches. The perpendicular dimension of the wall shall not be less than eight (8) inches.

O105.4 Minimum Reinforcement

AMENDMENT
This section has been amended at the state or city level.
The walls shall be provided with at least two (2) #5 longitudinal reinforcing bars at each end of the wall cross section, confined with #3 ties or hairpins spaced at six (6) inches along the wall height. In no case shall the minimum horizontal and vertical reinforcement provided in walls be less than 0.0025 times the gross area of the wall. The vertical and horizontal reinforcements shall not be spaced further apart than eighteen (18) inches. The longitudinal reinforcement of walls shall be anchored with 90 degree standard hooks. The footing dowels shall be spliced with the wall longitudinal reinforcement with an overlapping length of thirty-six (36) times the diameter of the longitudinal bars.

O105.5 Minimum Area of Concrete Walls

AMENDMENT
This section has been amended at the state or city level.
The sum of the gross area of all concrete walls at the base floor must be at least 0.005 times the total gross area of the ground level.

Section O106 Concrete Masonry Walls

AMENDMENT
This section has been amended at the state or city level.

O106.1 General

AMENDMENT
This section has been amended at the state or city level.
The design of concrete masonry (CMU) walls shall meet the provisions of this section. The out-of-plane stiffness and strength of all CMU walls shall not be considered in the LFRS.

The design lateral forces shall be resisted by the designated structural walls comprising the LFRS. The seismic loads shall be distributed among all wall components in proportion to their relative in-plane stiffness. Only walls properly connected to a horizontal rigid diaphragm shall be considered to be part of the LFRS.

CMU walls designated to be part of the LFRS, shall not have their horizontal sectional area reduced by more than fifty (50) percent at any location. Larger reductions may be permitted, when caused by the presence of embedded components such as vertical conduits, drainage pipes or any other required accessories to be installed within the wall, if the discontinuity in the horizontal sectional area is considered in the structural analysis and design. The affected wall shall not be considered to act as a whole unit. Instead they shall be modeled and designed as independent wall segments delimited by each vertical disruption. The structural designer shall coordinate with other disciplines in order to determine and consider all the instances in which such condition would occur.

O106.2 Materials

AMENDMENT
This section has been amended at the state or city level.
The materials to be used in the construction of the load bearing and transverse CMU walls shall satisfy the minimum quality requirements specified below:
  1. Concrete Masonry Units (CMU) — All CMU must meet all minimum requirements specified in Chapter 21, Section 2103 of IBC 2018
  2. Mortar — must meet all minimum requirements specified in Chapter 21, Section 2103 of IBC 2018.
  3. Cement Grout must meet all the minimum requirements specified in Chapter 21, Section 2103 of IBC 2018.
  4. Concrete — The concrete used in the structural confining elements shall have a minimum compressive strength of three thousand psi (3,000 psi) at twenty-eight (28) days.
  5. Steel Reinforcement — The reinforcement shall have a minimum yield strength of sixty thousand psi (60,000 psi) and shall comply with ASTM A615-09.

O106.3 Dimensions

AMENDMENT
This section has been amended at the state or city level.
All load bearing and transverse CMU walls shall meet the following requirements related to their dimensions. The free distance, horizontal or vertical between supports or confining elements, shall not exceed twenty-five (25) times the thickness of the wall. For this limitation, the vertical distance from top of foundation to bottom of confining beam, or the distance from top of slab to bottom of confining beam shall be considered. The horizontal distance to be considered shall be the distance between confining columns or transverse walls. No structural CMU walls shall be constructed using a thickness less than six inches (6"). No finishes or plaster shall be considered to determine wall thicknesses.

O106.4 Wall Confinements

AMENDMENT
This section has been amended at the state or city level.
The CMU wall and its confining frame, acting as a structural unit, shall be designed to withstand the vertical and lateral loads. The minimum dimensions for the beams and columns shall be as established in sections O106.5 and O106.6 of this regulation.

To guarantee that individual and group behavior will be adequate, the confined CMU walls shall be located symmetrically and must provide the highest possible torsional stiffness of the building. This could be achieved by locating confined walls as close as possible to the perimeter of the structure.

The openings located on load bearing and transverse CMU walls that form part of the LFRS shall meet the following:
  1. The total area of the openings shall not exceed thirty-five percent (35%) of the total CMU wall area enclosed by the horizontal and vertical confinement elements.
  2. The aggregate of the horizontal length of the openings, within the CMU wall, shall not exceed half (1/2) the distance between confinement column elements.
  3. The horizontal distance between an opening edge and the CMU wall edge shall not be less than one fourth (1/4) the opening height.
  4. The clear horizontal distance between openings shall not be less than one half (1/2) the smaller height of the openings, nor less than twenty inches (20").
  5. The clear vertical distance between openings shall not be less than one half (1/2) the width of the widest opening, nor less than twenty inches (20").
When any CMU wall does not comply with one or more of the requirements above in this subsection, the wall shall not be considered part of the LFRS. Nevertheless, this wall shall be designed to withstand all applicable local horizontal and vertical forces.

When all openings are surrounded by interior confinement columns and beams as defined below on these provisions, the edge distance requirements above in this subsection are no longer required. The confinement columns that surround the openings shall extend from the foundations or inferior diaphragm to the next superior diaphragm, and shall be properly anchored on both sides.

O106.5 Interior Confinement Beams

AMENDMENT
This section has been amended at the state or city level.
The minimum width for the interior confinement beams shall be eight (8) inches. Interior confinement beams shall not have a total depth smaller than twelve (12) inches and shall comply with the requirements of Section O104.3.

The confinement beams shall have a minimum reinforcement as required on this section. Minimum reinforcement shall consist of four (4) longitudinal #4 bars (2 bars top and two bars bottom) with #3 stirrups spaced at eight inches (8") on the beams located at intermediate floor levels and roof. The interior confinement beams for load bearing and transverse CMU walls must fit inside the intermediate floor system to guarantee the diaphragm effect. The superior level of the interior confinement beam will correspond to the superior level of the intermediate floor level.

The beams shall be cast on top of the CMU wall to anchor the vertical reinforcement of the walls. As an alternate, the CMU wall shall be constructed so that the wall reinforcement is effectively anchored to the beam and columns through splices and the wall is provided with a mechanism to transfer the shear forces acting in all directions.

O106.6 Interior Confinement Columns

AMENDMENT
This section has been amended at the state or city level.
The interior confinement columns are interior vertical reinforced elements that confine the walls. These Confinement columns will be used wherever the required CMU walls are part of the LFRS or at the intersection between two load bearing or transverse walls, or at intermediate locations of the load bearing and transverse walls with a separation not to exceed the limits established in these provisions.

The minimum width of the confinement columns shall be the eight (8) inches, and the cross-sectional area shall not be less than ninety-six square inches (96 in2). The confinement columns shall extend from the inferior beam up to the superior beam properly anchored to these elements. The reinforcement of the columns shall be anchored with standard 90 degree hooks to the foundation.

The confinement columns minimum reinforcement shall be six (6) #4 longitudinal bars with #3 ties spaced at six (6) inches.

The columns shall be cast against the CMU walls, and the forms shall be placed only to the sides with no walls. As an alternate, the CMU wall shall be constructed so that the wall reinforcement is effectively anchored to the beam and columns through splices and the wall is provided with a mechanism to transfer the shear forces acting in all directions.

O106.7 Cmu Walls Subjected to Lateral Loads Design

AMENDMENT
This section has been amended at the state or city level.
The wall elements shall be designed according to the following criteria:
  1. Lateral Loads — The lateral loads specified in this regulation shall be used.
  2. Analysis — Each CMU wall will be modeled as a frame of articulated joints comprised of confinement beams and columns and diagonal elements formed by masonry equivalent elements. Those diagonal elements shall have an equivalent width no greater than twenty-five percent (25%) of the clear diagonal length within joints and a depth equal to the thickness of the wall. The elasticity modulus of the equivalent element shall be equal to the masonry modulus of elasticity to be taken as Em = 900f'm.
  3. Design — For the loads specified in section O102 and the mathematical model described above, the internal forces in tension or compression of the different columns will be determined, and each will be designed for the predominant forces.
The diagonal equivalent elements forces shall not exceed the diagonal strength of the wall, estimated as,

Rc = (2/3) a t f'm sec θ

Where,

Rc = Ultimate strength of the equivalent diagonal element.
t = Equivalent element depth, in other words, the thickness of the wall, in inches.
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