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2109.2 Lateral Stability
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For SI: 1 pound per square inch = 0.006895 mPa.
Where the structure depends upon masonry walls for lateral stability, shear walls shall be provided parallel to the direction of the lateral forces resisted.
Minimum nominal thickness of masonry shear walls shall be 8 inches (203 mm).
Exception: Shear walls of one-story buildings are permitted to be a minimum nominal thickness of 6 inches (152 mm).
In each direction in which shear walls are required for lateral stability, shear walls shall be positioned in two separate planes. The minimum cumulative length of shear walls provided shall be 0.4 times the long dimension of the building. Cumulative length of shear walls shall not include openings or any element whose length is less than one-half its height.
Masonry shear walls shall be spaced so that the length-to-width ratio of each diaphragm transferring lateral forces to the shear walls does not exceed the values given in Table 2109.2.1.3.
| FLOOR OR ROOF DIAPHRAGM CONSTRUCTION | MAXIMUM LENGTH-TO-WIDTH RATIO OF DIAPHRAGM PANEL |
|---|---|
| Cast-in-place concrete | 5:1 |
| Precast concrete | 4:1 |
| Metal deck with concrete fill | 3:1 |
| Metal deck with no fill | 2:1 |
| Wood | 2:1 |
The roof construction shall be designed so as not to impart out-of-plane lateral thrust to the walls under roof gravity load.
Dry-stacked, surface-bonded concrete masonry walls shall comply with the requirements of this code for masonry wall construction, except where otherwise noted in this section.
Dry-stacked, surface-bonded concrete masonry walls shall be of adequate strength and proportions to support all superimposed loads without exceeding the allowable stresses listed in Table 2109.2.3.1. Allowable stresses not specified in Table 2109.2.3.1 shall comply with the requirements of ACI 530/ASCE 5/TMS 402.
DESCRIPTION |
MAXIMUM ALLOWABLE STRESS (psi) |
|---|---|
| Compression standard block | 45 |
| Shear | 10 |
Flexural tension Vertical span Horizontal span |
18 30 |
Construction of dry-stacked, surface-bonded masonry walls, including stacking and leveling of units, mixing and application of mortar and curing and protection shall comply with ASTM C 946.
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