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This reduced cross-section would then be checked under fire conditions, with allowable design stresses increased by the factors given in NDS
Table 16.2.2. For example, a 2.85 increase factor could be applied to allowable bending stresses. AWC's TR 10 provides design examples for a
number of exposed timber applications under fire conditions.
The stress adjustment factor, K, to increase
the reference design stress is for use when
performing a structural capacity check
under the fire load condition with allow-
able stress design (ASD) load combinations
(e.g., D + L, etc.). This stress adjustment
factor is not intended to be used with load
and resistance factor design (LRFD) load
combinations, including those intended for
extraordinary events such as in ASCE 7-16
Section 2.5.
Appendix A of TR 10 provides design tools
for beams and columns of solid sawn,
glulam or SCL materials under fire design
scenarios using the char calculation provi-
sions of NDS Chapter 16. Table A1 provides
a method to quickly check if a beam ex-
posed on three sides passes the structural
fire condition check provided the designer
knows the beam's size and maximum de-
mand to capacity ratio (Rs) under the required non-fire condition using ASD load combinations. Table A2 provides a similar design table for
columns exposed on all four sides.
For more information, the complete paper can be downloaded from the WoodWorks website, along with an Inventory of Fire Resistance-
Tested Mass Timber Assemblies and Penetrations.
WoodWorks – Wood Products Council provides free technical support as well as education and resources related to the code-compliant de-
sign of commercial and multi-family wood buildings. A non-profit organization staffed with architects, structural engineers and construction
experts, WoodWorks has the expertise to assist with all aspects of wood building. For assistance with a project, visit
www.woodworks.org/project-assistance or email help@woodworks.org.
