Modeling the Reliability of Wood Tension Members Exposed to Elevated Temperatures

Authors

  • Peter W. Lau
  • J. Dave Barrett

Keywords:

Modeling, reliability, wood, lumber, tension member, elevated temperature, fire

Abstract

The merit of approaching fire safety design from the standpoint of reliability is the impetus of this paper. Reliability, a direct function of time to failure, is a measure of performance that falls naturally under a performance-based code. The objectives of this study focus on advancing our understanding of the structural behavior of light-frame wood members subject to tension and elevated temperatures, and on the time to failure under a given stress and temperature history. A model based on linear damage accumulation theory was developed to predict the time to failure. This model is based on a kinetic theory for strength as a function of temperature and stress, coupled with a kinetic term, to express the pyrolytic process as a form of damage. The model, which requires the short-term strength as an input, fits well to experimental data on nominal 2X4 structural lumber tested at three different rates of tension loading, and at 150, 200, and 250°C, and room temperature. The model also predicts, with reasonable accuracy, the behavior of lumber under constant-load at 250°C. It predicts that lower-grade material generally has a lower reliability index; however, those differences are insignificant as far as current design practices are concerned. The reliability is sensitive to variability in temperature but not to variability in stress.

References

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Published

2007-06-19

Issue

Number 3 / July 1998

Section

Research Contributions

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