Statistical Evaluation of Strength of Steel Beam Columns

A data base is developed for examining the behavior of steel beam columns. This data base, made in the format of a relational data base, contains the results of 237 tests carried out previously in Japan. By using the data base, the strength characteristics of steel beam columns are investigated statistically, and the following observations are made. The experimental strength is 16% larger on the average than the strength predicted by the load and resistance factor design (LRFD) specification with the coefficient of variation as 0.10. Variation in the yield stress, with respect to the nominal yield stress, makes the experimental strength larger than the predicted strength by 7% but does not change the coefficient of variation. The experimental strength is 40% larger on the average than the design strength stipulated in the LRFD specification. The experimental strength is larger by 10-15% for beam columns with steep moment gradient than for those with uniform moment, and also for beam columns whose yield ratio is below 0.7 than for those with a larger yield ratio. The aforementioned observation demonstrates that the effect of strain hardening on the strength of beam columns is conspicuous.