Design of Fire Rated Wood Beams Exposed three sides based on “Lie Method”

There are several methods have been developed since early 70’s when T. T. Lie developed a simplistic method to design heavy timber beams exposed on three sides for fire resistance at NRCC [1].

I have performed several design examples for calculating endurance time for beams exposed to three sides for various sizes based on the equations provided in technical literature provided by AF&PA [2] and below are my calculated results*. The sizes which has endurance time of 1 hour or more are highlighted in green.

 

Fire_Resistance_Exposed_Wood_Beams

Design Results for Fire Resistance of Wood Beams Exposed on Three Sides

References:

1. “Calculating Fire Resistance of Exposed Wood Members” By AF&PA – Technical Report 10.

2. “Design for Code Acceptance” by AF&PA.

*”These results shall not be used directly for any design without performing a design and analysis by a structural engineer and confirmed by a professional engineer. This blog is for educational purposes only and are based upon calculations done based on formulas provided in technical literature by AFPA [2]”

100% 75% <=50%
b d t
1.5 9.25 14.62 16.45 19.01
3 9.25 28.01 31.51 36.41
4.5 9.25 40.16 45.18 52.21
1.5 11.25 14.73 16.57 19.15
3 11.25 28.45 32.00 36.98
4.5 11.25 41.15 46.29 53.49
1.75 9.5 16.96 19.08 22.05
3.5 9.5 32.28 36.32 41.97
5.25 9.5 45.97 51.72 59.76
7 9.5 58.02 65.27 75.42
1.75 11.875 17.12 19.27 22.26
3.5 11.875 32.94 37.06 42.82
5.25 11.875 47.44 53.38 61.68
7 11.875 60.64 68.22 78.83
1.75 14 17.22 19.38 22.39
3.5 14 33.34 37.50 43.34
5.25 14 48.34 54.38 62.84
7 14 62.23 70.01 80.90
1.75 16 17.29 19.46 22.48
3.5 16 33.62 37.82 43.70
5.25 16 48.96 55.09 63.65
7 16 63.34 71.26 82.34
1.75 18 17.35 19.52 22.55
3.5 18 33.83 38.06 43.98
5.25 18 49.45 55.63 64.29
7 18 64.21 72.23 83.47
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