Failure Mode Control and Seismic Response of Dissipative Truss Moment Frames

AbstractIn this paper, a new design approach for dissipative truss moment frames (DTMFs) able to guarantee, under seismic forces, the development of a yield mechanism of global type is presented and applied. In particular, DTMFs consist of a truss moment frame where the energy dissipation is provided by means of special devices located at the ends of the truss girders at the bottom chord level. The proposed design methodology is based on the kinematic theorem of plastic collapse. The method is based on the assumption that sections of truss elements and the yield threshold of dissipative parts (i.e., special devices) are known, and therefore the column sections are the unknowns of the design problem, which are obtained by imposing that the equilibrium curve corresponding to the global mechanism has to lie below those corresponding to all the possible mechanisms within a displacement range compatible with local ductility supply of dissipative elements. The design methodology has been implemented in a computer program and applied to the design of some DTMFs. Aiming to demonstrate the effectiveness of the proposed approach, several push-over analyses have been carried out to compare the obtained pattern of yielding with the design goal, that is, the development of a collapse mechanism of global type. In addition, the validation of the design procedure is further supported by the results of nonlinear dynamic analyses, carried out by the OpenSees computer program, which are herein reported and discussed.