Special Truss Moment Frames (STMF) under combined gravity and lateral loads.

Abstract

The Special Truss Moment Frame (STMF) is a framing system with inelastic deformation confined to a special segment when subjected to earthquake loading. This study had two phases; (1) slab effects on the STMF response under lateral loading alone, and; (2) STMF response under combined gravity and lateral loads. In Phase I, an experimental and analytical study was performed. The experimental program consisted of two tests. The first test examined the behavior of the STMF with a corrugated metal deck-concrete floor and compared its response to that of the STMF without the floor deck. The results indicate that the floor deck can be neglected for calculating the design strength of the STMF, but should be included in the design of the structure outside the special segment. The second test examined the reparability of the STMF by testing the repaired specimen of Test 1 under the same loading. The results confirmed that the STMF can be retrofitted to the original strength and stability with minimum cost. The analytical program of Phase I provided the best model for correlation study. It was found that due to cyclic composite action it was not possible to accurately model the complete hysteretic loops. However, a good correlation was obtained once proper parameter values were used in combination with the expected yield mechanism under monotonic loading. In Phase II, first a design procedure was developed for the design of STMF under combined gravity and lateral loads. Next, a structure was designed based on the proposed design procedure. Then a complete experimental and analytical program was carried out to verify the design procedure and to study the behavior of the STMF system for this loading condition. The experimental program consisted of two tests on a subassembly of the same structure with two different loading conditions. The analytical program in this part was aimed at providing information for analytical modeling of the STMF system by correlating with the test results. The results showed that STMF system can be designed under combined gravity and lateral loads and can perform satisfactorily in the event of a severe ground motion.