跨座式单轨独柱大悬挑钢-混组合框架高架车站抗震设计探讨

Discussion on Seismic Design of Straddle Monorail Elevated Station with Single Column Large Cantilever Steel-concrete Composite Frame

针对跨座式单轨独柱大悬挑钢-混组合框架高架车站结构抗震冗余度低,在高烈度地区应用较少,为更好地分析高架车站抗震受力全过程,以某跨座式单轨独柱大悬挑钢-混组合框架高架车站工程实例为背景,根据建筑规范和城市轨道交通规范要求设定合理的抗震性能目标,并研究构件抗震受力历时过程中的受力情况。采用大型有限元Midas作为主要计算软件,选取合理的地震波,进行多遇地震和设防地震有限元计算时采用弹性时程分析方法,且对振型分解反应谱法地震作用进行相应的放大,结果分析构件满足抗震性能目标要求。进行罕遇地震计算时,为更好地模拟工程实际情况,计算模型考虑桩土共同作用,采用结构-承台-桩基整体计算建模方法,进行弹塑性时程分析,关键构件采用截面纤维模型进行计算,能够反映关键构件在大震作用下进入破损阶段之后的行为,可以查看关键构件截面混凝土的开裂和压碎历史,钢材或钢筋的屈服和硬化过程。研究结果表明结构构件均满足抗震性能目标:(1)关键构件的钢材纤维受拉受压均未超过屈服强度,保持弹性工作状态,混凝土纤维受拉开裂,受压未达到屈服强度,同时延性系数D/D1小于1,均说明关键构件满足抗震性能为压弯、抗剪不屈服的目标;(2)桩基的钢筋纤维受拉、受压均未超过屈服强度,混凝土纤维受拉开裂,受压未达到屈服强度,满足抗震性能为压弯、抗剪不屈服的目标;(3)地震作用下,带有桩模型与无桩模型的基底剪力有一定差距,表现为带有桩基模型的地震剪力较大,设计时应考虑桩土共同作用。

Targeting the low seismic redundancy of the single-column large cantilever steel-concrete composite frame in straddle-type monorail elevated station structures,which is rarely applied in high-intensity seismic regions,an engineering case of a straddle-type monorail single-column large cantilever steel-concrete composite frame elevated station is used as the background.to better analyze the entire process of seismic resistance at elevated stations.Rational seismic performance goals are set up according to building codes and urban rail transit standards,and the stress situation during the seismic resistance of components is studied.The finite element analysis software Midas is used for calculation and suitable seismic waves are selected.The elastic time-history analysis method is adopted for frequent earthquakes and medium earthquakes,and the response spectrum analysis of structures for the earthquake effect is amplified.The results show the components meet the seismic performance goals.For rare earthquake calculations,to better simulate actual engineering situations,the calculation model takes into account of the pile-soil interaction by using an integrated superstructure-bearing platform-pile foundation calculation modeling method and performing an elastic-plastic time-history analysis.Key components are calculated with a fiber cross-section model,reflecting the behaviors of key components after entering the damage stage under rare earthquake effect.The cracking and crushing history of the concrete sections,and the yielding and hardening process of steel or rebars can be reviewed.The results show all structural components meet the seismic performance goals:(1)Steel fibers in key components,whether under tension or compression,do not exceed the yield strength,maintaining an elastic state.Concrete fibers crack under tension but do not reach yield strength under compression.Meanwhile,the ductility coefficient D/D1 is less than 1,indicating that key components meet the seismic performance goal of not yielding under compression bending and shear;(2)Rebar fibers in the pile foundation,whether under tension or compression,do not exceed yield strength,and concrete fibers crack under tension but do not reach yield strength under compression,meeting the seismic performance goal of not yielding under compression bending and shear;(3)Under earthquake effect,there is a noticeable difference in base shear between models with piles and models without piles,and models with pile foundations exhibit larger earthquake shear forces.Pile-soil interaction should be considered in the design.