Calibration of the reliability levels for allowable stress design of wood structures
2004
Nakamura, N. (Niigata Univ. (Japan). Faculty of Agriculture) | Horie, K.
The objective of this research was to obtain a reliability level for the present Allowable Stress Design (ASD). We calculated the reliability index 0, or, in other words, failure probability, for ASD using the Advanced First Order Second Moment method. The 2P Weibull and log-normal distributions were assumed for the ultimate limit state and the serviceability limit state for stress, and the normal distribution was assumed for the serviceability limit state for deformation. The results are as follows: (1) The relationship between the ratio (r) of the mean main and dead loads and beta is different for the 2P Weibull and log-normal distributions for the ultimate limit state and the serviceability limit state of stress. (2) beta converged to a certain value according to the increase of r regardless of the distribution of resistance, the limit state and for coefficients of variation ranging from 0.1 to 0.4. (3) The convergence value of beta (betaC) is 1.8 for D(deadload) +L(live load),between 2.1 and 2.3 for D + L+S(snow load),and between 2.4 and 2.5 for D + L+W(wind load), D + L + S+W,D+L+E(earthquake load) and D + L + S + E for the ultimate limit state. betaC is 2.7 for D+L and D + L + S, between 3.2 and 3.3 for D + L+W and D + L + S + W, and 3.6 for D + L + E and D + L + S + E for the serviceability limit state of stress. Further, betaC is 1.7 for D + L, 1.1 for D+L + Sh (heavy snow area), between 2.0 and 2.1 for D + L + So (ordinary snow area), D + L + W and D + L + S + W,and 2.7 for D + L+E and D + L + S + E.
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