Are you aware of the new additions to the 2021 Special Design Provisions for Wind and Seismic (SDPWS)?  Several changes have been incorporated in the 2021 edition, which is the first revision since 2015 for this IBC-referenced document.  The provisions were developed by AWC’s Wood Design Standards Committee, and new sections have been added to Chapter 4 to include more guidance when using cross-laminated timber (CLT).

In the July 2022 SEU session, Lori Koch, PE, from American Wood Council, presented Special Design Provisions for Wind and Seismic (SDPWS) 2021 Updates.  Lori identified the major changes between the 2021 SDPWS and previous editions.  She highlighted the new format for the shear wall and diaphragm capacity tables and described the new table for out-of-plane wind resistance for OSB and plywood wall and roof sheathing.  Also, she introduced the new shear wall and diaphragm provisions for cross-laminated timber (CLT).

Lori noted that Chapter 4 of SDPWS now contains sections 4.5 Cross-Laminated Timber (CLT) Diaphragms and 4.6 Cross-Laminated (CLT) Shear Walls.  Section 4.5 is a one-page standard whose requirements are largely an engineered approach which references the National Design Specification (NDS) for the design of CLT diaphragms. 

Section 4.6 references the newly added Appendix B for design provisions applicable for wind and seismic.  Appendix B includes the mandatory requirements for CLT shear walls and defines two systems: CLT shear wall and CLT shear wall with shear resistance provided by high aspect ratio panels only.  The requirements mandate platform construction where CLT floor panels bear on CLT walls below.  There are limits to the aspect ratio of the panels and which connectors may be used, and uplift due to overturning must be resisted by hold-downs.  There is an exception to the requirements in Appendix B for buildings in low seismic hazard areas which do not exceed 65 feet in height.

Lori noted that extensive testing to CLT shear walls was conducted in accordance with FEMA P-695 in order to identify seismic performance factors of CLT shear walls as a new seismic force resisting system (SFRS).  The methodology used is consistent with the primary “life safety” performance objective of seismic regulations in model building codes.  To view the results of this FEMA  P-695 report, click here.

With the addition of the CLT sections to the 2021 SDPWS, engineers now have a codified standard for use in their wood structures.  To download the new updates to the 2021 SDPWS or to purchase your own copy, click visit the AWC website.