TR 10 - Calculating the Fire Resistance of Wood Members and Assemblies

UPDATED with New Connection Protection Designs!

131 pages (3.31 MB PDF) October 2018

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 2018 in accordance with the 2018 NDS, major revisions include the following:

  • Addition of new Chapter 3, "Protection of Structural Members and Connections," which summarizes the evaluation of test data and determination of the added fire resistance provided by wood, gypsum board, and insulation used to protect wood members and connections.
  • Addition of design provisions for calculating the contribution of protection to the existing chapter on Design Procedures for Exposed Wood Members. The revised chapter, titled Chapter 4, "Design Procedures for Exposed and Protected Wood Members," offers provisions for calculating both the increased structural fire resistance provided by various types of protection and the thermal separation provided by protective membranes. Connection design and details were modified to provide more guidance on how to address char contraction in connections at ends of members.
  • Design examples were moved to a new Chapter 5. Calculation of thermal separation times were added to Example 5 (Exposed Cross-Laminated Timber floor design) and Example 6 (Exposed Cross-Laminated Timber wall design); a new Example 7 (Protected 2x10 joist floor) was added to provide example calculations of structural fire resistance and thermal separation times of gypsum-wallboard-protected floor assemblies; and new protected connection designs were added in Example 8 (Protection of Steel Ledger Connection) and Example 9 (Protection of Beam-Column Connection).
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