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Efficient Masonry Design
Efficient Masonry Design: Computer Programs
and Simplified Design Methods
For all its attributes, masonry presents challenges for designers
working with it. Building codes allow several methods for designing
structural masonry—allowable stress, strength design, and
empirical—some of which can be time-consuming. To address
this, several interested parties in the masonry industry have developed
computer programs and a simplified method for designing masonry
buildings.
New Software
For simple structures, the National
Concrete Masonry Association (NCMA) has software that is easy
to use for the design of masonry. For more complex structures, NCMA
and the International
Masonry Institute (IMI) have been working with the Bentley software
development group to create a RAM structural masonry design module.
This software is intended to fill the gap of providing structural
engineers with a comprehensive, commercially available software
design package for masonry that complements existing structural
design software commonly used by structural design firms. In the
August 2008 The Construction Specifier, engineers Keith
Lashway and Diane Throop of IMI discuss the new software package,
which is based on the finite element method, to help speed the design
of reinforced masonry structures.
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| Modeling of a load-bearing masonry structural
system. |
Developed with joint support from IMI and NCMA, the software can
be used for designing “hybrid masonry.” This term has
come to mean structural frames infilled with reinforced masonry,
where the masonry helps carry in- and out-of-plane loads so that
the frame works more efficiently. The pairing of steel frames with
masonry infill eliminates the need for cross bracing (which is otherwise
necessary to make the frame more rigid), and removes the interference
between the frame and the infill. Efficiency is improved because
the frame can be smaller and construction easier.
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| Model of a hybrid masonry system. |
Direct Design
Another approach for speeding the (structural) design of simple
masonry structures comes for the Design Practices Committee of The
Masonry Society. The method, known as Direct Design, is a procedure
for designing single-story concrete masonry structures. The procedure
applies to masonry subjected to factored combinations of dead, roof,
live, wind, seismic, snow, and rain loads in accordance with the
strength design provisions of the 2005 MSJC Code and the 2006 International
Building Code. This activity is being overseen by the Design
Practices Committee of The Masonry Society and the first of several
documents (based on the use of Type S mortar) is out for final ballot
with the expectation that it will be ready for use in late 2008
or early 2009. Contact TMS
for additional details.
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