弯曲型BRB在某中学综合楼消能减震设计中的应用

Application of Buckling Restrained Bending-plate Brace in the Design of Energy Dissipation and Vibration Reduction of a Middle School Complex Building

屈曲约束支撑BRB刚度大、耗能能力强、性能稳定、价格便宜,是抗震设计中最常用的阻尼器之一。但由于屈曲约束支撑是通过轴向拉伸及压缩产生塑性变形而耗能的,故其变形能力小,易发生应力集中,一旦发生较大变形就面临更换。在可能经常发生较大变形的部位设置弯曲型BRB是一种更好的选择,本文以某中学综合楼为例,采用普通BRB减小综合楼部分楼层偏心率和扭转位移偏大的问题,在地震作用下变形大的第二层中增设弯曲型屈曲约束支撑,改善第二、三层刚度差异较大的问题,使结构从底部往上形成刚度呈阶梯型降低。分析结果表明小震下屈曲约束支撑均处于弹性状态,其偏心率和扭转位移比得到明显改善,层间位移角明显变小,中震下弯曲型屈曲约束支撑先于普通屈曲约束支撑进入弹塑性阶段,层间位移角减震率两个方向均略大于20%。大震作用下,所有BRB均进入了弹塑性阶段,结构层间位移角满足预定的性能水准要求。

Buckling Restrained Brace BRB is one of the most commonly used dampers in seismic design due to its large stiffness strong energy dissipation capacity stable performance and low cost.However since the ordinary BRB consumes energy through plastic deformation caused by axial tension and compression its deformation capacity is small and stress concentration is prone to occur.Once large deformation occurs it must be replaced.Thus it is a better choice to set up a buckling restrained bending-plate brace where large deformation may occur frequently.A middle school complex building is used as an example in this paper.Ordinary BRB is used to reduce the eccentricity and torsional displacement of some floors.On the second floor where large deformation occurs under the earthquake buckling restrained bending-plate braces are added to solve the problem of large stiffness difference between the second and the third floors.Thus the stiffnesses of the structure decrease in a stepped manner from bottom to top.The analysis results show that under frequent earthquakes BRBs are in an elastic state the eccentricity and torsional displacement ratio are significantly improved and the inter-story displacement angle is significantly reduced.Under the design earthquake the buckling restrained bending-plate braces enter the elastic-plastic stage earlier than the ordinary BRBs and the damping rate of inter-story displacement angles in both directions are slightly greater than 20%.Under the rare earthquake all BRBs enter the elastic-plastic stage and the inter-story displacement angles meet the predetermined performance level requirements.