European Prequalification of joint solutions for steel structures subjected to seismic actions - bolted unstiffened extended end-plate beam-o-column joints

Abstract: According to EN 1998-1, the seismic design of steel structures is based on the concept of dissipative structures, in which specific zones of the structures are identified and designed to develop plastic deformations in order to dissipate the seismic energy. In steel moment resisting frames, the beam extremities are generally used as dissipative zones, and the beam-to-column joints are designed in order to resist to the internal forces associated to the development of plastic hinges at the beam extremities. However, such an approach may lead to quite expensive joint solutions, mainly due to the fact that the possible overstrength and strain hardening effects developing in the dissipative zones have to be taken into account when designing the non-dissipative zones. EN 1998-1 allows the use of partial-strength joints as dissipative zones but, in this case, the ductility and the dissipation capacity of the joints should be demonstrated by means of experimental tests, which is not realistic for practical projects. For this reason, a European RFCS project named EQUALJOINTS was developed with the objective of developing and prequalifying three types of bolted joints that are commonly used in European practice. Within the present paper, the main design issues and the relevant findings obtained for bolted unstiffened extended end-plate beam-to-column joint are described and discussed.