Pseudo static test for pre-cast segmental bridge columns with dry joints

为了比较节段拼装桥墩与整体现浇桥墩之间抗震性能的差异,以是否存在预应力钢筋、不同施工方法、预应力筋的位置和粘结状态、是否存在耗能钢筋等为试验参数,设计了一个包含五种不同构造类型混凝土桥墩的试验方案。采用拟静力试验方法比较分析了这五种不同构造类型混凝土桥墩的破坏形态、易损部位、荷载位移滞回曲线、节段拼装桥墩接缝的开展、拟静力残余位移、曲率分布、耗能能力、粘滞阻尼比等,得到了三种节段拼装桥墩、整体现浇钢筋混凝土桥墩和预应力混凝土桥墩之间拟静力行为的异同。试验结果表明:节段拼装桥墩在循环荷载作用下发生接缝的交替开闭,曲率变化集中在接缝附近,没有发生整体现浇混凝土桥墩通常出现的塑性铰现象。耗能钢筋的存在可以延缓接缝的张开,增加构件的极限弯矩和耗能能力,从而有利于增加抗震能力;采用无粘结预应力钢筋和有粘结预应力钢筋连接的节段拼装桥墩的拟静力残余位移比较小,而采用耗能钢筋的节段拼装桥墩的拟静力残余位移较大,基本上与整体现浇桥墩的拟静力残余位移相近。The similarities and differences of a seismic performance between a pre-cast segmental bridge column and a cast-in-place bridge column were investigated with a test project including five kinds of concrete bridge columns.Prestressed tendon,construction methods,arrangement and bonded state of prestressed tendons,and additional energy-dissipating bar were selected as test variables.Through the pseudo static test of the five kinds of concrete bridge columns,the development rules of failure mode,failure area,load-displacement hysteretic loops,opening of segmental joints,residual displacement,distribution of curvature,energy dissipation ability,and viscous damping ratio were gained.The experimental results showed that the segmental column experiences opening-closing between segmental interfaces under cyclic loading;the change of curvature focuse on the area of the segmental interfaces;the segmental bridge column has no plastic hinge mechanism at the bottom of the column,as commonly seen in conventional reinforced concrete bridge columns;the addition of energy dissipating bars crossing the joint can delay the gap opening,increase the strength and the hysteretic energy dissipation of the column,it certainly helps anti-earthquake;the residual displacement of the segmental bridge column with bonded or unbonded prestressed tendons is less,and the segmental bridge column with energy-dissipating bars has bigger residual displacement,it is close to that of a cast-in-place bridge column.国家自然科学基金项目资助(50508032);上海市优青专项科研基金(YYY09007

自组织生长InAs量子点发光的温度特性

报道了InAs/GaAs自组织生长量子点结构中发光的温度特性.在12～150K温度范围内,实验测得的InAs激子发光能量随温度增加明显红移,其红移速率远大于InAs带隙的温度关系,而光谱宽度则明显减小.这些结果表明InAs量子点结构是一种强耦合系统,局域在InAs量子点中的载流子波函数会相互交迭、相互贯穿,从而增强了载流子的弛豫过程