A
Component Manufacturing dverti$ dverti $ er
A
LL T
Don’t Forget! You Saw it in the
OD
Th e
HINGS WO
Adverti$$er
September 2023 #15290 Page #94
“Person Loading” of Chords Without Structural Wood Sheathing
By Frank Woeste The National Design Standard for Metal Plate Connected Wood Truss Construction, ANSI/TPI 1-2022 has been updated to require a design load check that accounts for a Person Loading of a roof truss chord without structural wood sheathing. As discussed in the ANSI/TPI 1 Commentary, this loading requirement is “intended to represent the occurrence of a person on the bottom Chord of a truss,” not the roof man-load in ASCE 7. The Person Loading requirement language from ANSI/TPI 1-2022 is given in Section 6.2.2.5: “6.2.2.5 Person Loading In addition to any load cases required for the applicable end use, each roof Truss spanning 18 feet (549 cm) or more shall be designed for a single concentrated load at the mid-point of any Chord panel that is not sheathed with structural wood sheathing. This concentrated load shall be 300 lbs. (1335 N) and shall be applied concurrently with dead load. It shall not be applied concurrently with any other load. The load duration factor for this load case shall be 1.6 or less.”
Consensus Process for Updating ANSI Standards ANSI has specific requirements to create or update a standard. The committee must be balanced, meaning certain percentages are required to be Producers, Users, and General Interest members. Specifically, no one interest group can outnumber the other two interest groups. Revisions to an ANSI design standard is an evolutionary process that involves consensus of a committee, with public input, that deems the change is needed for various justifiable reasons, such as product performance and safety. The Person Loading revision is an example of the evolutionary nature of ANSI design standards. In the mid-1990s, I used the Purdue PPSA2 program to analyze a 4/12 W-Truss, 2 ft. on-center with a maximum span of 30-5-0 using 2x4 No.2 Southern Pine chords. A man-load, which at that time was 250 lbs., was placed at the center of one of the bottom chord panels in addition to the truss design dead load. The analysis revealed that the 10-ft. lower chord panel was overstressed.
Continued next page
PHONE: 800-289-5627
Read/Subscribe online at www.componentadvertiser.com
FAX: 800-524-4982