A masonry wall must be designed and built to withstand earthquake forces. The vertical forces can be as great as the horizontal forces but are not usually a big problem for a masonry wall, since there is plenty of reserve strength vertically. Horizontal (or lateral) loads, however, require special attention. This article discusses some of the basic seismic requirements for masonry and looks at the products used to achieve safe masonry designs.There are different concerns for masonry veneer and for loadbearing masonry. For veneer, the primary concern is keeping it attached to the backing material. For loadbearing masonry buildings, the concerns include attachment of masonry walls to floor and roof diaphragms, foundation anchorage, and adequate structural reinforcement.
The Uniform Building Code (UBC) and the Masonry Standards Joint Committee's ACI 530/ASCE 5/TMS 402 Building Code Requirements for Masonry Structures (MSJC Code) specify how the masonry veneer is to be connected to the backing as well as tie size, spacing, and physical properties. There are additional requirements for support of the veneer, anchor spacing, and minimum reinforcement.
The requirements of the 1997 UBC and the 1999 MSJC Code for anchored veneer created the need for a way to directly connect the required horizontal joint reinforcement to the masonry veneer wall tie. This requirement led to the development of a number of rather simple clips, which are listed here:
- Veneer Anchors, Seismic Strap Anchor, and Seismic Dur-O-Eye and Ladur-Eye Systems manufactured by Dur-O-Wal Inc.
- Seismic Tab Notch and No. 370 Seismic Hook Tab, manufactured by Heckmann Building Products
- SEISMICLIP Interlock System, Seismic-Notch Anchors, and T-LOK TIE, manufactured by Hohmann & Barnard
- WIRE-BOND Clip, manufactured by Masonry Reinforcing Corp. of America
- Fleming Masonry Anchoring System, manufactured by Halfen Anchoring Systems and represented exclusively in the United States by Meadow-Burke Products
- SCP-"QUAKE-TIE," manufactured by Southern Construction Products
Model building codes contain many special requirements for structural, or loadbearing, masonry built to withstand seismic forces. Both the UBC and the MSJC Code dictate minimum reinforcement and address the strength required for the connection of masonry walls to other building elements.
The 1997 UBC also contains requirements for different types of anchorage. The ways to anchor masonry walls to floors, roofs, and steel columns and beams are almost limitless. The products shown here represent only a sampling of what is available, particularly the straps and anchors used in low seismic risk areas.
- Masonry wall to steel column/beam. Manufacturers include: Dur-O-Wal, Heckmann Building Products, Hohmann & Barnard, Masonry Reinforcing Corp. of America, Meadow Burke/Halfen, and Southern Construction Products.
- Masonry wall to concrete or masonry wall/column. Manufacturers include: Dur-O-Wal, Heckmann Building Products, Hohmann & Barnard, Masonry Reinforcing Corporation, Meadow Burke/Halfen, Simpson Strong-Tie, and Southern Construction Products.
- Masonry wall to floor/roof diaphragm. Manufacturers include Meadow Burke/Halfen and others.
- Reinforcing bar confinement. Dur-O-Wal's Seismic Comb provides vertical reinforcing bar confinement.
The article also includes an explanation of seismic performance categories.