Esra Mete Güneyisi

Seismic Upgrading of Steel Moment-Resisting Frames by Means of Friction Devices

In recent decades, several passive energy dissipation systems have been conceived in order to minimize the damage in structural and non-structural components of either new or existing buildings. In this study, the use of friction damped tension-compression diagonal braces for seismic upgrading of a steel moment resisting frames is investigated. To this aim, nonlinear time history analyses have been carried out on a set of representative frames with and without friction damped braces. In the nonlinear time history analyses, two sets of natural accelerograms compatible with seismic hazard levels of 10% and 2% probability of exceedance in 50 years have been considered. Under these records, the structural re- sponse has been comparatively investigated in terms of the maximum inter-storey drift ratio, maximum storey accelera- tion, residual drift ratio and displacement demand for the friction device. The results clearly highlighted that the applica- tion of friction damped braces allows reducing the damages to the main structural elements, thus significantly improving the seismic behaviour of the frame.

Nonlinear Behaviour of Mid-rise Steel Buildings with Gate Braced Frames

Abstract: Off-center or gate braced frames are a special configuration of inverted V bracing with non-straight diagonal members that are made of two elements connected to the corner of the frame by another member. This arrangement is characterized by an eccentricity of the intercepted bracing as respect to the straightness of the theoretical working length of the diagonal members in chevron configuration. These types of braced frames permit larger openings with significant advantages in terms of architectural functionality. The seismic performance of gate braced frames differs from that of traditional chevron braced frames, because of the out-of-straightness eccentricity of bracing members and the position of the corner-to-brace connecting element. Therefore, in this paper, a numerical parametric study based on both nonlinear static pushover and dynamic time-history analyses is presented and discussed in order to examine the influence of brace-to-brace detailing on seismic response of this structural typology. The results showed that the initial stiffness, the strength and the interstorey drift demand are very sensitive to the out-of-straightness eccentricity of bracing.