Seismic rehabilitation of bolted end plate connections using post-tensioned tendons

摘要

Rehabilitation of existing steel structures is an inevitable work in the cases of contractor shortcoming in construction, adding new stories or change of construction code requirements. Bolted steel connections have been frequently used after Northridge earthquake. Rehabilitation of these connections without the need for changing or replacing their components is a problem that has been recently considered by engineers, since it is difficult to change or replace their components. In this paper, the use of post-tensioned tendons as a way to rehabilitate end plate bolted connections with weak end plate or bolts is studied constructing 6 experimental specimens of corner connections under SAC cyclic loading protocol. The results of the study show that this rehabilitation method improves the cyclic behavior of the weak connections. In addition, it provides specimens with better performance than that of the reference connection designed according to AISC. The moment capacity, initial rotational stiffness of the rehabilitated connections are averagely higher than those of the reference connection by 5 and 45 percent respectively. Furthermore, rehabilitation with post tension tendons adds the self-centering ability to the rehabilitated connection that in turn plays an important role in preventing permanent deformations in frame and thus, providing the potential 'for using frictional dampers in self-centering frames to increase energy dissipation. It should be noted that this rehabilitation method is more efficient for cyclic behavior of a bolted connections with weak end plate than a bolted connection with weak bolts, due to the participation of end plate in energy absorption and higher energy absorption capacity.