Masonry Magazine October 1997 Page. 28
Masonry Wall Bracing Standard
The Council for Masonry Wall Bracing, an industry adjunct organization, is developing a bracing standard for masonry walls. The standard will address the bracing of masonry walls during construction, before they are permanently connected to the structure. The standard will provide guidelines for the design and installation of bracing systems, and will cover a variety of bracing methods.
The standard will address the following topics:
* Wind loads on masonry walls
* Bracing requirements for different wall heights and thicknesses
* Bracing methods, including metal braces, wood braces, and post-tensioning
* Anchorage of bracing to the structure
* Inspection and maintenance of bracing systems
The standard will also include a series of sample designs using different bracing schemes to test the practicality of the approach and to help contractors understand how the standard will work in practice. Designs using metal braces and strongbacks, wood braces and strongbacks and sequential post-tensioning will be performed.
The strength of masonry will be considered at the initial stage which is defined as 8 hours old, and the intermediate stage which is defined as the period between the initial stage and the time when the wall is permanently connected to the structure, or it has achieved its design strength. Generally the strength of masonry in this stage will be that strength attained at 24 hours. Design can be based on ultimate strength or working stresses using the Masonry Standards Joint Committee (MSJC) "Building Code Requirements for Masonry Structures" as the basis for design. Allowable stresses at the initial stage and intermediate stage will be 30% and 50% respectively of the allowable stresses published in the above code.
Anchorage of bracing at the face of walls will be capable of resisting tension and compression so that the walls can be braced from one side. Braces will be attached to floor slabs, grade beams or "dead men" capable of resisting the tension and compression loads from the braces. Cable braces, capable of resisting only tension, will be allowed when bracing is installed on both sides of a wall.
Before issuing the standard, the committee will develop a series of sample designs using different bracing schemes to test the practicality of the approach and to help contractors understand how the standard will work in practice. Designs using metal braces and strongbacks, wood braces and strongbacks and sequential post-tensioning will be performed.
The committee will distribute the draft document to a broad base of industry representatives for review prior to adoption.
This activity is a significant "first step" by the MCAA to enter into the codes and standards arena. By being pro-active in these matters, the industry can prevent regulations from being written which have a negative impact on its members. To accomplish the goals of this effort, the MCAA needs and solicits input from its members and others in the industry so that the needs of everyone can be considered.
Editors note: Mario Catani is Chairman of the Council for Masonry Wall Bracing, an industry adjunct organization with the assigned responsibility to develop a bracing guidelines for masonry walls. Catani is also President of Dur-O-Wal Corporation.
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