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[SEAOC] Truss discussion.[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: [SEAOC] Truss discussion.
- From: Frank Woeste <fwoeste(--nospam--at)vt.edu>
- Date: Sun, 04 Aug 1996 17:31:07 +0600
At 09:39 PM 8/3/96 -0700, you wrote: > >Question: Have you ever been provided loads of the lateral bracing so that >you could provide connections and resisting members by your local truss >supplier? Tom and Neil: This is a good question and it has been fixed at least "on paper." If you will refer to WTCA 1-1995 (Standard Responsibilities in the Design Process Involving Metal Plate Connected Wood Trusses), Section 6.0 Truss Designer Responsibilities, paragraph 6.2 states "For each Truss Design Drawing, set forth as a minimum the following:....................................... 6.2.11 Maximum axial compression forces in the Truss members to enable the Building Designer to design the size, connections and anchorage of permanent continous lateral bracing. Forces may be shown on the Truss Design Drawing or on supplemental Documents; and 6.2.12 Required permenent truss member bracing location. So to calculate the lateral bracing loads, you need the information from 6.2.11 from the Truss Designer and a factor to convert from truss member force to a required lateral restraining force. TPI literature has given a 2% rule for many years; ie, "The force required to restrain the top chord against buckling in the lateral directiom is assumed to be two percent of the maximum axial force, per lateral brace, per truss braced."(Paragraph H-188.8.131.52, HIB-91 Handling, Installing & Bracing Metal Plate Connected Wood Trusses, Truss Plate Institute) The TPI telephone number is 608-833-5900 if you would like to purchse HIB-91, a 109 page pocket size manual. The word "Maximum" in 6.2.11 is very important because trusses are now analyzed under 3 or 4 load cases. So--to design the lateral bracing, you need the maximum compression in each member for ALL load cases used in the truss design. Sincerely, Frank Woeste Frank E. Woeste, Ph. D., P. E. Biological Systems Engineering Virginia Tech Blacksburg, VA 24061-0303 Home:(540)951-0469 Office:(540)231-6093 FAX:(540)231-3199 ...
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