UPDATED with New Connection Protection Designs!
137 pages (3.6 MB PDF) February 2021
The superior fire performance of timbers can be attributed to the charring effect of wood. As wood members are exposed to fire and the wood begins to burn, a char layer is formed. The char layer acts as an insulator and protects the core of the wood section. Thus, wood members can be designed so that a sufficient cross section of wood remains to sustain the design loads for the required duration of fire exposure. A standard fire exposure is used to calculate the fire resistance. Revised in 2020, in accordance with the 2018 NDS, major revisions include the following:
- 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.
- Calculation 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 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.