AWC Completes CLT Connections Testing


The American Wood Council recently completed testing of connections used in cross-laminated timber diaphragm. The latest tests results showed that the connections performed better than expected in higher-than-expected shear capacities.

“In order to fully understand the full-scale CLT diaphragm test results done last year, we needed to better understand some of the connections that were used in the full-scale tests. The results of these latest tests could lead to changes allowing more efficient CLT diaphragm designs in the future,” said AWC Vice President of Engineering Bradford Douglas, P.E.

The tests were conducted in support of new criteria for design of the CLT diaphragm design approach included in the 2021 Special Design Provisions for Wind and Seismic. They focused on the structural performance of the individual connections of the diaphragm, designed in accordance with the National Design Specification for Wood Construction.

The connection testing was conducted at Weyerhaeuser’s ISO 17025 accredited test facility in Federal Way, Washington, and included lateral, withdrawal and bearing strength per standard methods. The 2021 SDPWS is referenced in the 2021 International Building Code.

Past AWC Updates

Last August, AWC, along with the International Code Council, released a joint publication: Mass Timber Buildings and the IBC, which aims to provide an overview of requirements for mass timber construction as found in the 2015, 2018 and 2021 International Building Code.

The document highlights changes beginning with the 2015 International Building Code that allow for construction of mass timber buildings with larger heights and areas than was permitted for buildings of wood construction types (Types III, IV and V) prior to the 2015 IBC.

The document also reviews the 2015 IBC recognition of cross-laminated timber, the reorganization of heavy timber provisions in the 2018 IBC, followed by the changes in the 2021 IBC and International Fire Code for tall mass timber construction.

Earlier that summer, the American Wood Council released an updated “Technical Report 10 (TR10), Calculating the Fire Resistance of Wood Members and Assemblies."

The revised 2020 guidelines are in accordance with the 2018 National Design Specification for Wood Construction.

Three primary revisions were included in the TR10, which are:

  • The expansion of design provisions for calculating the contribution of gypsum board protection in Chapter 4, “Design Procedures for Exposed and Protected Wood Members.” The revised provisions provide information for calculating both the increased structural fire resistance and thermal resistance provided by various types of protection.
  • The alculation of thermal separation times were updated in Example 5 (Exposed Cross-Laminated Timber floor design) and Example 6 (Exposed Cross-Laminated Timber wall design) to more closely estimate the benefits of protection.
  • Example 8 (Protection of Steel Ledger Connection) and Example 9 (Protection of Beam-Column Connection) were also updated to include information on use of gypsum board as required to protect connections of mass timber members in the new Type IV-A and IV-B buildings permitted in the 2021 International Building Code; and a new Example 10 (Protection of Tension Splice Connection) was added at the request of designers seeking an example of a completely concealed mass timber connection.

Tagged categories: American Wood Council (AWC); cross-laminated timber; Good Technical Practice; NA; North America; timber; Wood

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