可提离式群桩基础桥梁滞回性能模型试验  

Experiment on Hysteretic Properties of Bridges with Pile-group Foundations Allowing Rocking and Uplift of Pile Cap

作　　者：管仲国[1] 杨彬 董凯 李建中[1] 

机构地区：[1]同济大学桥梁工程系,上海200092

出　　处：《中国公路学报》2017年第10期62-68,共7页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(51378384);国家重点基础研究发展计划("九七三"计划)项目(2013CB036302)

摘　　要：为了研究可提离式群桩基础桥梁的抗震性能,设计和制作了大比例尺的可提离式群桩基础和普通群桩基础单墩桥梁试验模型。试验模型采用细砂土箱模拟桩周土体的约束作用,并对可提离节点进行改进设计,以防止局部破坏。采用位移控制分级往复加载,进行拟静力试验研究,对比2种不同基础桥梁的基本抗震性能。试验结果表明:可提离式桩的桩身损伤要远小于普通桩,改进后的可提离桩的节点未见明显损伤;可提离式群桩基础单墩桥梁模型的滞回曲线呈明显的旗帜形,表明结构主要为非线性弹性变形,而普通桩基础桥梁模型的滞回曲线为典型的梭形,表明结构主要为塑性变形;可提离式群桩基础发生提离后,承台位移由平动为主转为以转动为主,表明提离式基础主要依赖承台以上结构的整体转动来适应水平地震作用,进而减小基础的受力和损伤;可提离式桩基础桥梁的残余位移仅为相应普通桩工况的10%,表明其具有较好的自复位性能;基于割线刚度的刚度退化指标不适宜评估自恢复结构的刚度退化,建议采用重新加载至正常使用极限状态下的最不利荷载组合时的刚度指标。To investigate the seismic properties of bridges with pile-group foundations allowing rocking and uplift of the pile cap,typical m odels with a pile-group foundation allowing rocking and uplift of the pile cap and a pile-group foundation with conventional fixed connections in a large scale were designed and fabricated. The effect of surrounding soil was sim ulated with container of fine sand,and m ore considerations were taken for the details in the connections between the pile tops and caps to prevent local dam age. The quasi-static test was conducted under an increasing cyclic displacem ent-controlled loading process. Subsequently,anti-seism ic properties of bridges with different pile-group foundations were com pared. The results show that only m inor dam age is incurred to the piles of the new foundation and there is no obvious dam age in the connections. The m odel with the pile foundation allowing rocking and uplift of the pile cap is adopted, and the hysteretic loops take the shape of the flag. It is indicated that the structure prim arily experiences nonlinear elastic deform ation. W hereas, bridge m odels with com m on pile-foundation take the shape of typical spindle-shaped hysteretic loops, showingplastic deform ation characteristics. The transition-oriented displacem ent turns into rotation-oriented displacem ent, after the uplift of the pile cap. The m odel with the new foundation m ainly accom m odates the lateral seism ic vibration with the rocking and uplift of the pile cap.Therefore,seism ic responses and dam age to the piles are reduced. The residual displacem ent of bridges with pipe foundation is approxim ately 1 0 % of the displacem ent of the conventional foundation. The re-centering capacity of pile-group foundation with the uplift is good. It is pointed out that the traditional m ethod on evaluating the stiffness degradation of ductile reinforced structures by using scant stiffness is not suitable for resilient structures. The stiffness coeffients are adopted by reloading under the ultim a

关 键 词：桥梁工程 滞回性能 拟静力试验 群桩基础 承台提离 

分 类 号：U443.15[建筑科学—桥梁与隧道工程]