不同竖向荷载下带“昂”柱头铺作抗震性能试验研究

EXPERIMENTAL STUDY OF SEISMIC PERFORMANCE OF ZHUTOU PUZUO WITH“ANG”UNDER DIFFERENT VERTICAL LOADS

带昂柱头铺作的抗震性能研究是应县木塔抗震性能研究的重要基础。为揭示不同竖向荷载下该类铺作的变形模式和抗震性能,该研究以应县木塔二层明层外槽带昂柱头铺作为原型,制作了2个1∶3.7的缩尺试件,进行了拟静力抗震性能试验。通过分析该铺作的水平力-位移滞回曲线、骨架曲线和等效粘滞阻尼系数等,明确了竖向荷载对该铺作抗震性能指标的影响。结果表明:竖向荷载的变化基本不影响该铺作的变形特征,但竖向荷载的增大会加剧滞回曲线的不对称性,且会显著提高该类铺作的水平承载力、初始刚度和耗能能力。竖向荷载增大3.7倍,水平承载力在正向和负向分别提高了2.2倍和2.9倍,初始刚度提高了2.4倍,耗散能量增加了3.0倍;增大竖向荷载虽然会改变铺作初始滑移出现的位置,但不改变该试验铺作的滑移累积方式和薄弱位置,最终两个铺作的滑移模式都表现为两跳华栱间的相对滑移。提出了该铺作节点的位移-承载力骨架曲线简化模型,得到了不同竖向荷载对抗侧刚度和水平承载力的影响系数β_(k)和β_(F),用以修正骨架曲线简化模型在不同竖向荷载下的刚度k。

Study of seismic behavior of Zhutou Puzuo with“Ang”lays critical foundations for insight into the seismic performance of Yingxian Wood Pagoda.To explore deforming behavior and seismic performance of Zhutou Puzuo with“Ang”,two scaled models derived from Yingxian Wood Pagoda at 1∶3.7 were designed and manufactured.Low cyclic-reversed loading experiments under different vertical loads were carried out.Based on the analysis of hysteretic curve,of skeleton curve,and of equivalent viscous damping coefficient,the effects of different loads on the above relevant seismic behavior indexes were clarified as following:Increasing vertical load hardly to change deformation features of this kind of Puzuo,but it would result in much more asymmetric performance in hysteretic curve and remarkable improvement on all Puzuo's relative properties.The vertical load increased 3.7 times,the horizontal bearing capacity increased 2.2 times and 2.9 times in positive and negative directions,the initial stiffness increased 2.4 times,and the dissipated energy increased 3.0 times.In addition,raising vertical load changed the position where the initial slip occurred at early stage of test.But it changed neither mode of accumulating slip nor the weaken positions.However,the Puzuo's finial slip pattern remained similar,which mainly performed as slipping between two Huagongs.A simplified model for the displacementbearing capacity of the Puzuo was proposed.The influence coefficients β_(k) and β_(F) of different vertical loads were obtained according to fit the data of these two tests,and the coefficients were able to modify the initial stiffness k of the simplified skeleton curve model under different loads.