As we migrate from ANSI/TPI 1-2014 to ANSI/TPI 1-2022, it is important to discuss and be aware of Chapter 3 updates. These changes impact QC inspections and should be understood by your in-house QC inspector and your truss builders.
The changes are in two categories in Chapter 3 — a general aspects category and a group that addresses top chord bearing components, as follows.
General Aspects
Changes to 3.8 Repressing: This section was reworded to make it clear that if a plate has not been fully pressed, it can be repressed to reach full connector plate grip strength. Keep in mind that plates that have been removed are still governed by 3.9.2, which states that plate removal resulting in damaged wood is considered ineffective, and requirement 3.9.3, which allows for a 50% reduction when the lumber is not damaged.
Changes to 3.7.2.1 Plate Placement: This section was reformatted for clarification.
Top Chord Bearing Components
New 3.4.8 Lumber Wane: This new section was added to alert inspectors that lumber wane could be prohibited in the bearing area of some extended chord bearing applications.
Changes to 3.7.2.2 Alternative Positioning Procedure: Due to concerns with how this method determines suitability, extended chord bearing joints have been excluded from use with the alternative positioning procedure.
Changes to 3.7.3 Plate Rotation: Extended chord bearing joints have also been excluded from the 10-degree plate rotation tolerance. The new exception states that there is no plate rotation permitted.
What Focusing on Top Chord Bearing Components Means
Why is understanding this change important? These changes will have an impact on how your QC inspector analyzes conformance. The change also impacts truss builders because certain tolerances that were available to them previously are not necessarily allowed now.
Different software providers have addressed this in different ways, but in general, notes will be provided on the engineering drawing to indicate the controlled conditions that are not normal. For example, rotation is typically ±10 degrees, and the software designer can control this with a setting in the software. The new requirements stipulate that both zero angulation and zero wane conditions need to be maintained.
Thank you to these plate suppliers for providing the following information.
MiTek
Here is an example of how the MiTek software handles this situation by stating that “Wane is prohibited in the bearing area.” [For image, See PDF or View in Full Issue.]
Alpine
Alpine has taken a different approach. From their engineering department:
“[We do not have a note] to TPI 1-2022 section 3.4.8 because we design extending chord bearings considering the reduced compression-perpendicular-to-grain design value (meaning we use the 1/3rd reduction specified for cperp in top-chord-bearing joints per section 7.3.13.1 rather than specifying no wane at such bearings and using the full cperp design value).”
Simpson Strong-Tie
Simpson’s approach has been to address the situation in this manner.
“On the truss design drawing, we print the following note any time the analytical method has been used in analysis on a top chord bearing truss: TC bearing joint plate lateral resistance value has been reduced by 20% on the top chord as required by the Extended Chord Analytical Method analysis."
“In addition, the Cq factor/angle on an extended top chord plate using the analytical method is forced to be 1.0 and 0 degrees respectively (as required by ANSI/TPI 1-22), so an additional note will also appear stating the following:
" * = Plate designed with modified Cq Factor and/or Rotational Tolerance." (The values of which are then clearly stated in the QC reports.)” [For image, See PDF or View in Full Issue.]
Eagle Metal
Eagle has addressed it by adding a note to their drawings stating that lumber wane is not allowed at the top chord bearing. [For image, See PDF or View in Full Issue.]
The Bottom Line
It is imperative for all component manufacturers to ensure that your team understands how ANSI/TPI 1 changes affect plant procedures, and this will be directly related to the way the changes are handled by your software provider.
Regardless of how wane is addressed, rotation of the connector must be deliberately positioned correctly, and any rotation needs to be evaluated. Also, wane impacts bearing and should always be limited in situations at the bearing.
When you have questions about your specific situation, please contact your plate supplier. They are your number one resource in successfully transitioning to the new version of ANSI/TPI 1.