Section A112

ANALYSIS AND DESIGN

[BS] A112.1 General. The following requirements are applicable to both the general procedure and the special procedure for analyzing vertical elements of the lateral force-resisting system.

Fwx = 0.8 SD1 ( Wwx + Wd /2)

but need not exceed

Fwx = 0.8 SD1Wwx + vuD

(Equation A1-13)

(Equation A1-14)

Copyright © 2022 by, or licensed to, International Code Council, Inc. (ALL RIGHTS RESERVED); licensed to California Building Standards Commission pursuant to License Agreement. No further reproductions is authorized. Any unauthorized reproduction or distribution is a violation of the federal copyright act and the license agreement, and subject to civil and criminal penalties thereunder.

APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

[BS] A112.2 In-plane shear of unreinforced masonry walls.

[BS] A112.2.1 Flexural rigidity. Flexural components of deflection need not be considered in determining the rigidity of an unreinforced masonry wall.

[BS] A112.2.2 Shear walls with openings. Wall piers shall be analyzed according to the following procedure, which is diagrammed in Figure A112.2.2.

1. For any pier, 1.1. The pier shear capacity shall be calculated as:

va = vmAn (Equation A1-18)

where:

An = area of net mortared or grouted

section of a wall or wall pier.

1.2. The pier rocking shear capacity shall be calculated as:

Vr = 0.9 PDD / H (Equation A1-19)

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. Where the pier rocking shear capacity is less than the pier shear capacity, in other words, 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:

0.7 Vwx < Σ Vr (Equation A1-20)

2.2. Shear controlled mode. Where the pier shear capacity is less than the pier rocking capac

PIER IS OVERSTRESSED IN SHEAR

Va = Allowable shear strength of a pier.

Vp = Shear force assigned to a pier on the basis of a relative shear rigidity analysis.

RETURN

Vr

VWX

∑ Vr

= Rocking shear capacity of pier.

= Total shear force resisted by the wall.

= Rocking shear capacity of all piers in the wall.

[BS] FIGURE A112.2.2 ANALYSIS OF URM WALL IN-PLANE SHEAR FORCES

APPENDIX A-14 2022 CALIFORNIA EXISTING BUILDING CODE

Copyright © 2022 by, or licensed to, International Code Council, Inc. (ALL RIGHTS RESERVED); licensed to California Building Standards Commission pursuant to License Agreement. No further reproductions is authorized. Any unauthorized reproduction or distribution is a violation of the federal copyright act and the license agreement, and subject to civil and criminal penalties thereunder.

APPENDIX A—GUIDELINES FOR THE SEISMIC RETROFIT OF EXISTING BUILDINGS

ity, in other words, va < Vr in one or more pier(s) 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 A1-21)

and

Vp < Vr (Equation A1-22)

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.

[BS] A112.2.3 Shear walls without openings. Shear walls without openings shall be analyzed the same as for walls with openings, except that Vr shall be calculated as follows:

Vr = 0.9( PD + 0.5 Pw ) D / H (Equation A1-23)

[BS] A112.3 Plywood-sheathed shear walls. Plywoodsheathed shear walls may be used to resist lateral forces for URM buildings with flexible diaphragms analyzed according to provisions of Section A111. Plywood-sheathed shear walls shall not be used to share lateral forces with other materials along the same line of resistance.

[BS] A112.4 Combinations of vertical elements.

[BS] A112.4.1 Seismic force distribution. Seismic 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.

[BS] A112.4.2 Moment-resisting frames. 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 resist 100 percent of the seismic forces tributary to that line of resistance, as determined from Section A111.2. The story drift ratio shall be limited to 0.0075.