Abstract
Regarding the application of the LRFD to structural design, an important issue would be to evaluate ultimate strength of structures. The plastic design method or the limit design method may play a vital role in working out ultimate strength of structures. The following three issues in relation to T-stub joints, which are widely utilized in construction of steel structures as tension joints, are presented.
(1) Collapse loads and prying forces at the load to plastic collapse of symmetrical T-stub joints corresponding to each collapse mode are worked out theoretically and illustrated by numerical calculation with about one thousand seven hundred examples. In western countries, the pre-tensile force being subjected to bolts for T-stub joints are generally disregarded. In this paper, however, effects of the pre-tensile force, which behaves important role in classification of collapse modes, are duly evaluated. Disregarding the pre-tensile bolt force has negative effects to the collapse loads from the point of structural design. The numerical collapse loads and collapse modes are illustrated relating to structural dimension of T-stub joints. The figures clarify characteristics of relations between collapse loads and modes to dimensions of T-stub joints comprehensively.
(2) The numerical results of the collapse loads are converted to the maximum loads per bolt adopting the measured strength of materials of the tested joints. The converted numerical results of the collapse loads show good agreement with the experimental results reported by Swanson J.A.
(3) The design method by the author is applied to the examples designed by the allowable stress method shown on the reference11). The dimensions assessed by the allowable stress methods are not so conservative when the bolt force is at critical, while the structural dimensions assessed by the allowable stress methods are conservative when the dimensions of tee-stubs are determined by the fiber stress in flange.
