Abstract
The purpose of this study is to devise empirical formulae for predicting the ultimate strength of tubular joints under static loads. The joints investigated herein are simple tubular joints that include the tubular X, T, Y and Kjoints and joints having gusset plates welded on tubular members. Most of the existing ultimate strength formulae for tubular joints^<(1)〜(5), (18)〜(20)> were mainly based on those empirical relationships between the strength and the geometrical parameters of the joints which were inferred from various series of test results. The ultimate strength formulae in this report were derived by the multiple regression anlysis on the majority of test data that have been obtain since 1963. In the process of building a mathematical model for a prediction equation, it was assumed that the joint was able to be replaced by a simple and fictious structure. There are two important differences between the formulae for T, Y and K-joints proposed in this report and existing formulae. The one of the differences is that these formulae give fairly reasonable estimates of ultimate strength when D/T-ratio is greater than 21 and less than 90, whereas all existing formulae tend to overestimate the ultimate strength as D/T becomes greater than about 50 (see Fig. 7 and Fig. 13). The other difference is due to the fact that the formula takes account of such behavior of the K-joint that the strength of the joint increases as two braces intersect and then overlap with each other (see Fig. 13). It was also found that these ultimate strength formulae were able to be extended to explain the carring capacities of various tubular joints with gusset plates.
