Narrow Results

A steel arch bridge originally designed against moderate earthquakes is retrofitted by installation of buckling-restrained braces (BRBs) to sustain severe earthquakes. Two retrofitting methods are considered to obtain good seismic performance of this arch bridge. The original model and retrofitted models subjected to the major earthquakes are investigated by dynamic analyses using 12 patterns of severe (level 2) earthquakes as input ground motions. It is found that the retrofitted models using BRBs can greatly improve seismic performance (displacement, section force, strain, reaction force, etc.) of the steel arch bridge. In addition, to investigate the influence of repeated earthquakes on the seismic responses of the main structure and the demands of BRBs, 12 patterns of earthquake ground motions are repeated by three times. Based on the analytical results, the seismic demands of BRBs against repeated earthquakes are obtained, and the required capacity of BRBs is recommended using a safety factor concluded by comparing the demands under the earthquake applied one and three times. Finally, the influence of the different yield stress on the demand of BRBs is examined by changing the steel grade of BRBs.

Quantifying the higher-mode effects on the seismic demands of buildings may benefit not only the awareness of characteristics of the seismic responses of buildings, but also the development of rapid/simplified methods for the seismic assessment of buildings. This study proposes an approach that is applicable for quantifying the aforementioned effects, covering the full range of building heights and deformation types. The vehicle used in this proposed approach is the generalized building model, which has been modified from the conventional cantilever beam model. In addition to building height and deformation type, the strength ratio of each vibration mode and the site class of buildings are the parameters considered in this study. The higher-mode effects on floor displacements, inter-story drift ratios, floor accelerations, and base shears with relation to the aforementioned parameters are investigated. Finally, the proposed approach is verified via the investigation of the higher-mode effects of a 20-story exemplar building.