Section 2106A

SEISMIC DESIGN

2106 A .1 Seismic design requirements for masonry. Masonry structures and components shall comply with the requirements in Chapter 7 of TMS 402 depending on the structure’s seismic design category.

2106A.1.1 TMS 402, Sections 5.3.1.4(a) and 5.3.1.4(b). Replace TMS 402, Sections 5.3.1.4(a) and 5.3.1.4(b) as follows:

a. Ties shall be at least ³ /8 inch (10 mm) in diameter

and shall be embedded in grout. Top tie shall be within 2 inches (51 mm) of the top of the column or of the bottom of the horizontal bar in the supported beam.

b. The spacing of column ties shall be as follows: not

greater than 8 bar diameters, 24 tie diameters, or one half the least dimension of the column, or 8 inches (203 mm) for the full column height.

2106A.1.2 TMS 402, Chapter 5. Add TMS 402, Section 5.6 as follows:

5.6 – Lateral Support of Members

5.6.1 – Lateral support of masonry may be provided by cross walls, columns, pilasters, counterforts or buttresses where spanning horizontally, or by floors, beams, girts or roofs where spanning vertically. Where walls are supported laterally by vertical elements, the stiffness of each vertical element shall exceed that of the tributary area of the wall.

2106A.1.3 TMS 402, Sections 7.4.4.1 and 7.4.5.1. Replace TMS 402, Section 7.4.4.1 as follows and delete Section 7.4.5.1:

7.4.4.1 Minimum reinforcement requirements for masonry walls. The total area of reinforcement in rein- forced masonry walls shall not be less than 0.003 times the sectional area of the wall. Neither the horizontal nor the vertical reinforcement shall be less than one third of the total. Horizontal and vertical reinforcement shall be spaced at not more than 24 inches (610 mm) center to center. Where stack bond is used in reinforced hollow-unit masonry, the open-end type of unit shall be used with vertical reinforcement spaced a maximum of 16 inches (406 mm) on center.

Exception: Reinforced hollow-unit masonry used for freestanding site walls or interior nonbearing nonshear wall partitions shall have horizontal rein- forcing spaced not more than 4’-0” on center, except for locations in Seismic Design Category F, and may be grouted only in cells containing vertical and hori- zontal reinforcement..

7.4.4.1.1 The minimum reinforcing shall be No. 4, except that No. 3 bars may be used for ties and stirrups. Vertical wall reinforcement shall have dowels of equal size and equally matched spacing in all footings. Rein- forcement shall be continuous around wall corners and through intersections. Only reinforcement which is continuous in the wall shall be considered in comput- ing the minimum area of reinforcement. Reinforcement with splices conforming to TMS 402 shall be consid- ered as continuous reinforcement.

ment shall have dowels of equal_ size and equally matched spacing in all footings. Rein- forcement shall be continuous around wall corners and through intersections. Only reinforcement which is continuous in the wall shall be considered in comput- ing the minimum area of reinforcement. Reinforcement with splices conforming to TMS 402 shall be consid- ered as continuous reinforcement.

7.4.4.1.2 Horizontal reinforcing bars in bond beams shall be provided in the top of footings, at the top of wall openings, at roof and floor levels, and at the top of parapet walls. For walls 12 inches (nominal) (305 mm) or more in thickness, horizontal and vertical reinforcement shall be equally divided into two layers, except where designed as retaining walls. Where reinforcement is added above the minimum requirements, such additional reinforcement need not be so divided.

7.4.4.1.3 In bearing walls of every type of reinforced masonry, there shall be trim reinforcement of not less

21A-8 2022 CALIFORNIA BUILDING CODE

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than one No. 5 bar or two No. 4 bars on all sides of, and adjacent to, every opening which exceeds 16 inches (406 mm) in either direction, and such bars shall extend not less than 48 diameters, but in no case less than 24 inches (610 mm) beyond the corners of the opening. The bars required by this paragraph shall be in addition to the minimum rein- forcement required elsewhere.

7.4.4.1.4 When the reinforcement in bearing walls is designed, placed and anchored in position as for columns, the allowable stresses shall be as for columns.

7.4.4.1.5 Joint reinforcement shall not be used as principal reinforcement in masonry.