小箱梁桥横向减震体系及其耗能特性

Transverse Seismic System of Multi-box Girder Bridges and Its Energy Dissipation Characteristics

为改善小箱梁桥的横向抗震性能,以三角形钢板为基本耗能构件,提出板式橡胶支座与钢阻尼器组合、板式橡胶支座与钢挡块组合2种横向减震体系,详细阐述了2种减震装置的构造特点和力学特性。钢挡块体系的挡块间隙取板式橡胶支座发生滑动时的位移,以充分发挥支座的柔性减震作用。以一座简支小箱梁桥为例,在成本相同的前提下,研究2种减震装置屈服力变化对减震效果的影响,阐明了减震体系主要力学参数的确定方法,并采用非线性时程反应分析方法,对2种减震体系的耗能特性进行深入分析。选取2条典型的地震动输入,分析了2种减震体系对墩梁相对位移、最大墩底弯矩的影响和各自减震装置的耗能机制。结果表明:地震下钢阻尼器耗能大,通过提供耗能及较大的恢复力能有效控制墩梁相对位移,而钢挡块耗能小,主要通过提供恢复力来控制墩梁相对位移,因而阻尼器体系的限位效果要显著优于挡块体系;在一定范围内,增大钢阻尼器(挡块)屈服力可以显著减小最大墩梁相对位移,但不会明显增大下部结构地震力;当地震动输入在正负方向能量分布不均时,钢挡块体系中梁体频繁撞击一侧挡块,挡块的滞回圈数会显著减少,支座较易遭受地震损伤;而钢阻尼器体系更能适应不同的地震动输入。

In order to improve the transverse seismic performance of multi-box girder bridges, two transverse seismic systems taking triangular steel plates as energy dissipation elements were proposed. One is a combination of the laminated rubber bearings （LRBs） with steel dampers （denoted by L-D system）, whilst the other is a combination of the LRBs with steel blocks （denoted by L-B system）. The structural characteristics and mechanical characteristics of the two kinds of shock absorbers were described in detail. The gap between girder and steel blocks of L- B system is the displacement when the girder begins to slide on the laminated rubber bearing, so as to make full use of bearings＇ shock absorption capacity. Taking simplified multi-box girder bridges as an example, the influence of the yield force of two kinds of shock absorbers on shock absorption effect was investigated by dint of the same costs. Besides, a method for determining the key parameters of the seismic systems was proposed, and an in-depth nonlinear time-history analysis was performed to investigate characteristics of energy dissipation. Two typical ground motions were input to suspect the effect of the maximum relative displacement of pier and beam, the maximum pier bottom moment and the respective energy dissipation mechanism. The results indicate the L-D system provides an excellent energy dissipation capacity as well as a relatively large restoring force, so L-D system can control the pier-deck relative displacement by both energy dissipation and resilience. Whereas the L-B system consumes much less energy and restrains the pier-deck relative displacement, simply by providing a normal restoring force. The limit effect of L-D system is better than that of L-B system. The increase of yield forces for the steel dampers or blocks （at a certain range） can significantly reduce the maximum pier-deck relative displacement while the seismic force which is transmitted to the substructure slightly increases. When the ground motion input is not evenly distributed in both directions, the girder in L-B system will hit one side of blocks more frequently and the number of hysteresis loops in the block will be significantly reduced, resulting in the potential damage of bearings. However, the L-D system can better adapt to the different seismic inputs.