Masonry Magazine April 1992 Page. 29
9.8.2.3
Walls shall be anchored by joint reinforcement spaced at a maximum distance of 8 in. (200 mm). Longitudinal rods of such reinforcement shall be at least 9 gage (W 1.7) and shall extend at least 30 in. (762 mm) in each direction at the intersection.
9.8.2.4
Interior non-loadbearing walls shall be anchored at their intersection, at vertical intervals of not more than 16 in. (400 mm) with joint reinforcement or in. (6.4 mm) mesh galvanized hardware cloth.
9.8.2.5
Other metal ties, joint reinforcement or anchors, if used, shall be spaced to provide equivalent area of anchorage to that required by this section.
9.8.3
Floor and roof anchorage Floor and roof diaphragms providing lateral support to masonry shall be connected to the masonry by one of the following methods:
9.8.3.1
Wood floor joists bearing on masonry walls shall be anchored to the wall at intervals not to exceed 6 ft (1.8 m) by metal strap anchors. Joists parallel to the wall shall be anchored with metal straps spaced not more than 6 ft (1.8 m) on centers extending over or under and secured to at least 3 joists. Blocking shall be provided between joists at each strap anchor.
9.8.3.2
Steel floor joists shall be anchored to masonry walls with % in. (9.5 mm) round bars, or their equivalent, spaced not more than 6 ft (1.8 m) on center. Where joists are parallel to the wall, anchors shall be located at joists cross bridging.
9.8.3.3
Roof structures shall be anchored to masonry walls with % in. (12.7 mm) bolts 6 ft (1.8 m) on center or their equivalent. Bolts shall extend and be embedded at least 15 in. (381 mm) into the masonry, or be hooked or welded to not less than 0.20 in² (129 mm²) of bond beam reinforcement placed not less than 6 in. (150 mm) from the top of the wall.
9.8.4
Walls adjoining structural framing - Where walls are dependent upon the structural frame for lateral support they shall be anchored to the structural members with metal anchors or otherwise keyed to the structural members. Metal anchors shall consist of % in. (12.7 mm) bolts spaced at 4 ft (1.2 m) on center embedded 4 in. (100 mm) into the masonry, or their equivalent area.
Miscellaneous Requirements (9.9)
General limitations for masonry structures such as masonry over chases and recesses, lintels over openings, noncombustible supports for masonry walls and corbeling have empirical requirements for proper design and construction.
Chases and recesses in masonry walls are sometimes used for visual effects or to receive pipes, conduits or ducts. When chases or recesses are wider than 12 in. (300 mm), the masonry above the chase must be supported by noncombustible lintels, which could be steel angle lintels or reinforced brick masonry lintels.
The design of lintels must be in accordance with Section 5.6 which stipulates that the deflection of lintels due to vertical loads should not exceed the span divided by 600 nor 0.3 in. (7.6 mm) when supporting un-reinforced masonry. Minimum bearing for lintels is 4 in. (100 mm) on each end of the masonry opening.
Masonry is not permitted to be supported by combustible construction. i.e. wood. Even though wood construction may meet the deflection requirements for lintels, this restriction is a fire safety requirement.
Corbeling limitations are the same as those required by the model building codes used throughout the country. The maximum corbeled projection beyond the plane of the wall should not be more than one-half of the wall thickness or one-half the wythe thickness for hollow walls. The maximum projection of any single course of masonry should not exceed one-half the unit height or one-third the unit thickness. Solid units are required for corbeled courses of masonry. Figure 5 illustrates these criteria for corbeling masonry.
Seismic Considerations for Empirically
Designed Masonry
Appendix A of ACI 530/ASCE 5 contains special requirements for masonry in seismic zones as specified in ASCE 7 (formerly ANSI A58.1). The provisions of Chapter 9 on empirical design of masonry may be used in Seismic Zones 0, 1 and 2, and are modified by Appendix A. Empirical design cannot be used in buildings located in Seismic Zones 3 and 4.
For Seismic Zones 0 and 1, all provisions of Chapter 9 apply without modification. There are no restrictions on materials or design methods since these areas of the country represent low seismic risk.
Masonry elements in Seismic Zone 2 must meet more stringent requirements. Connections are strengthened and minimum vertical and horizontal reinforcement is required in order to provide more ductility in the structure. All materials also are permitted to be used in the structure.
Seismic requirements for buildings or structures in Seismic Zone 2 as contained in Appendix A are as follows:
"A.3.5 Veneer and units not specifically intended for structural use shall not be designed to resist loads other than their own weight or their own shear loads.
A.3.6 Masonry walls shall be anchored to all floors and roofs which provide lateral support for the walls. Such anchorage shall provide direct connection capable of resisting horizontal forces required in Section 5.2 or a minimum of 200 lb (90.9 kg) per lineal foot (meter) of wall, whichever is greater. Walls shall be designed to resist bending between anchors where anchor spacing exceeds 4 ft (1.2 m). Anchors