Effects of Brace Configuration and Structure Height on Seismic Performance of BRBFs Based on the Collapse Fragility Analysis

The brace configuration and structure height are two factors that have a significant effect on the seismic behavior of braced frame buildings. In the present study, the buckling-restrained braced (BRB) frames were considered to estimate the effect of these two parameters using probabilistic seismic assessment methods. The uncertainty in the different parameters involved in the seismic design of the structural system was also considered. Four, six, and ten-story buildings with the Chevron and inverted Chevron bracing configurations were designed, and their responses due to various ground motions were estimated using incremental nonlinear dynamic analyses. Fragility curves, mean annual frequency of exceeding immediate occupancy (IO), and collapse prevention (CP) states were generated using probabilistic seismic analysis, fragility curves concept, and drift hazard curves. The results demonstrate that the inverted Chevron type BRBFs has better structural performance than Chevron bracing types. Furthermore, an increase of the height of structures, despite lower drift’s hazards, increases the fragility probability.

Simplified probabilistic seismic assessment of dampers in tall and braced structures in buildings

Purpose The paper aims to focus on adjacent buildings response, equipped with damper, to analyze the vibration reduction in the nearby buildings. The nearby buildings were also equipped with dampers. The occurrence of adjacent buildings with adequate or inadequate space in between is a common phenomenon. However, many a times not much attention is paid to provide or check gap adequacy or to connect the two buildings suitably to avoid pounding of two structures on each other. This study emphasizes the utility of providing a damper in between two adjacent buildings for better performance. Design/methodology/approach The two steel structures taken for study are prototype of two structures normally found in industrial structure such as power plant, where in one of boiler structure is often tall and braced and short structure of turbine building which is moment resistant, modeled in SAP. There could be similar such structures which are often connected to a platform or a walkway with a sliding end, so as not to transfer horizontal force to other structures. If the advantage of stiffness of tall braced structure is taken into account, shorter structure can be suitably connected to braced structure to transfer forces during seismic cases under nonlinear conditions, thereby avoiding pounding (incase gap is too less), reducing response and thus optimizing the section sizes. The structures were subjected to El Centro earthquake, to simulate MCE (which could be the other site TH scaled up as desired for real site PGA), and damper location and parameters were varied to find optimum value which offers reduced base shear, reduced top floor displacement and minimum inter story drift and highest energy absorption by fluid viscous dampers. Findings The findings show that taller structures, which are braced, have more stiffness; the effect of damper is more pronounced in reducing displacement of shorter moment resistant structure to the tune of 60%, with suitably defined Cd value which is found to be 600 KNs/m for the present study. Thus, advantage of stiffener structure is taken to leverage and reduce the displacement of shorter moment resistant structure in reducing its displacement under nonlinear conditions of seismic case. Originality/value This work shows the original findings, of the adjacent buildings response, equipped with damper, to analyze the vibration reduction on other buildings which were planned to be constructed nearby.