RESEARCH INTO THE EFFECT OF SIZE AND SHAPE IN PERFORATED GUSSET PLATES ON SEISMIC BEHAVIOR OF CBFS

Concentrically braced frames, CBFs, are among common lateral load carrying systems and their relative advantages, such as ease of implementation and lower cost compared to moment resisting frames, has led to their widespread usage. Experiences of past earthquakes indicate that the inherent defects and brittle behavior due to the buckling of compressive braces are the cause of the main damage in structures. In this paper, by making a hole in the gusset plates of diagonal bracing samples, it was endeavored to provide more ductility and improve the seismic performance of CBF through nonlinear static and dynamic analyses using ABAQUS software. For this purpose, holes were designed to have less axial capacity than the brace critical buckling load to help earthquake energy dissipation. The eects of hole shape and dimension and, also, the eect of near and far eld earthquakes, were studied. Concentration of inelastic response in the hole neighborhood, results in high energy dissipation and prevents nonlinear behavior in other elements. The hysteresis curves show ductile behavior, enhancing energy dissipation during cyclic loading of the nal specimens and postponing the occurrence of buckling in the brace members until lateral displacement at about 2cm. Normal braces buckle in 1cm displacement, leading to brittle behavior. The increase of the frame nal displacement between 13-43% and base shear reduction between 19-37% demonstrate the superior seismic behavior of the proposed system. Moreover, equivalent damping ratios in the proposed samples are signicant by about 20% The proposed model is relatively easy to implement in a variety of braces, such as X-braces, chevron and diagonal congurations, without too much cost. In this research, by a slight change in the common system and without using complicated devices, energy dissipation is provided. This is one of its distinctive features compared to other research projects. It should be noted that due to the appropriate results obtained in numerical analysis, specimen fabrication and experimental work should be on the agenda to verify the results in the next stage of research.