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Subject: Roof Design Components and Cladding or MWFRS - ASCE7-02
- To: <seaint(--nospam--at)seaint.org>
- Subject: Subject: Roof Design Components and Cladding or MWFRS - ASCE7-02
- From: "Eric Tompos" <etompos(--nospam--at)ntainc.com>
- Date: Wed, 1 Feb 2006 06:59:32 -0500
My company does
third-party review of truss designs for truss manufacturer's using the
various standard wood truss design programs. To the best of my knowledge
all programs utilize what is called a "hybrid analysis." In this analysis
the truss is designed for MWFRS pressures applied to the ENTIRE truss,
considering various load cases. The resulting uplift reactions shown on
the truss print are taken as the maximum reaction from the MWFRS load
cases. This analysis considers all members and connections under combined
loads (compression/tension and bending).
A secondary analysis is performed to assess C&C loads
on the top chord where the top chord is checked for bending only (not combined
loads). This "hybrid analysis" is described in a article by Charles C.
Hoover, Jr., titled "ASCE 7-93 Wind Load and Its Application in the Design
of Metal Plate Connected Wood Trusses," Wood Design Focus.
procedure for truss is analogous to the design of a wall stud--combined loads
are checked using MWFRS and pure bending is checked for
Eric Tompos, PE
Ph: 574 773-7975
Fx: 574 773-5739