Section A110 General Procedure
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:
- Unreinforced masonry walls for which height-to-thickness ratios do not exceed ratios set forth in Table A110.2 need not be analyzed for out-of-plane loading. Unreinforced masonry walls that exceed the allowable h/t ratios of Table A110.2 shall be braced according to Section A113.5.
- Parapets complying with Section A113.6 need not be analyzed for out-of-plane loading.
- Where walls are to be anchored to flexible floor and roof diaphragms, the anchorage shall be in accordance with Section A113.1.
[BS] TABLE A110.2
ALLOWABLE VALUE OF HEIGHT-TO-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS
|WALL TYPES||0.13g ≤ SD1 < 0.25g||0.25g ≤ SD1 < 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 multiple-story building||20||18||16||15|
|Walls in top story of multiple-story building||14||14||14b,c||9|
|All other walls||20||16||16||13|
For SI: 1 pound per square inch = 6894.75 N/m2
- Applies to the special procedures of Section A111A only. See Section A111.7 for other restrictions.
- This value of height-to-thickness ratio shall be used where mortar shear tests establish a tested mortar shear strength, vt, of not less than 100 pounds per square inch. This value shall also be used where the tested mortar shear strength is not less than 60 pounds per square inch, and where a visual examination of the collar joint indicates not less than 50-percent mortar coverage.
- Where a visual examination of the collar joint indicates not less than 50-percent mortar coverage, and the tested mortar shear strength, vt, is greater than 30 pounds per square inch but less than 60 pounds per square inch, 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.