Assessing the seismic behavior of steel moment frames equipped by elliptical brace through incremental dynamic analysis(IDA)

Incremental dynamic analysis and nonlinear static pushover analysis are carried out on a performance-based design to determine the seismic demands and capacities of an elliptic braced moment resisting frame(ELBRF).The objective is to assess ductility,overstrength and response modification factors in a modern steel-braced structural system based on incremental dynamic analysis.This integrated system is connected to a beam and column with an appropriate length while providing enough architectural space to allow for an opening without having the common problems associated with architectural spaces in braced systems.Several different classes of buildings are considered on soil type II.Linear dynamic analysis,nonlinear static pushover analysis and incremental nonlinear dynamic analysis related to 12 records from past earthquakes are carried out using OpenSees software.The factors of ductility,overstrength and response modification are calculated for this system.The values of 9.5 and 6.5 are found and suggested only for the response modification factor for ELBRF systems in allowable stress and ultimate limit state methods,respectively.The fragility curves are plotted for the first time for this type of bracing,which contributes to the assessment of building seismic damage.

基于IDA方法的柱承式筒仓结构地震易损性分析

易损性分析是柱承式筒仓结构开展基于性能设计研究的重要基础。为此,选用某钢筋混凝土柱承式筒仓为研究对象,通过有限元软件ABAQUS,分别采用混凝土损伤塑性模型和理想弹塑性模型(Dracker-Prager)模拟筒仓结构及仓内粮食颗粒,建立考虑粮食-仓体相互作用的柱承式筒仓非线性有限元模型。根据增量动力分析法(IDA),按照谱相容性原则选取10条地震动记录,分别以最大层间位移角和地面峰值加速度作为筒仓结构工程需求参数和地震动强度参数,进行空仓、半仓、满仓三种储粮工况的柱承式筒仓结构地震易损性分析以及地震损伤风险评估。结果表明:(1)三种储粮工况下柱承式筒仓结构最大层间位移角均发生在柱顶位置,支承柱进入塑性状态的层间位移角分别为0.015、0.013、0.011 rad;(2)储粮质量大小是决定柱承式筒仓结构损伤刚度退化的重要因素;(3)三种储粮工况下的柱承式筒仓结构均满足“小震不坏、中震可修、大震不倒”的抗震设防目标;(4)满仓工况筒仓50年超越倒塌极限状态的概率为0.45%,小于FEMA P750中定义的50年倒塌风险的限值1%。研究成果可为筒仓结构基于性能的设计研究及抗震性能评估提供依据。

基于IDA方法的带可替换耗能梁段偏心支撑钢框架结构影响系数研究

为研究带可替换双槽钢型剪切耗能梁段偏心支撑钢框架中耗能梁段的截面尺寸、梁段长度、加劲肋个数以及结构层数对于结构影响系数R和位移放大系数C_(d)的影响,通过OpenSees有限元软件对18个不同参数的模型进行增量动力时程分析(IDA),得到各模型的结构影响系数和位移放大系数.结果表明:通过合理设计耗能梁段的构造参数,能够提高带可替换双槽钢型剪切耗能梁段防屈曲偏心支撑钢框架的抗震能力以及变形能力,给出R和C_(d)的建议值,为偏心支撑钢框架结构影响系数的研究提供参考.

基于IDA的钢-混凝土混合风电塔筒地震易损性分析

为研究钢-混凝土混合风电塔筒的抗震性能,基于弹塑性纤维梁柱单元理论建立了某钢-混凝土混合风电塔筒二维数值模型,先依据推覆分析结果确定塔筒的5种损伤状态限值,然后分别以截面曲率和考虑高阶振型的复合地震动强度参数IM 1I&2E作为结构需求参数和地震动强度参数,接着选取20条地震动记录进行塔筒的增量动力分析,建立塔筒的地震易损性曲线,并对塔筒的抗震性能进行评估。结果表明:混合塔筒模型的损伤程度与地震动强度参数呈正相关,其抗震性能可满足Ⅶ度(0.15 g)地震作用下的抗震要求,但在Ⅷ度罕遇地震作用下及处于更高烈度区的风电塔筒应当进行专门的抗震设计。

Incremental dynamic analysis of concrete gravity dams including base and lift joints

The growth in computer processing power has made it possible to use time-consuming analysis methods such as incremental dynamic analysis（IDA） with higher accuracy in less time.In an IDA study,a series of earthquake records are applied to a structure at successively increasing intensity levels,which causes the structure to shift from the elastic state into the inelastic state and finally into collapse.In this way,the limit-states and capacity of a structure can be determined.In the present research,the IDA of a concrete gravity dam considering a nonlinear concrete behavior,and sliding planes within the dam body and at the dam-foundation interface,is performed.The influence of the friction angle and lift joint slope on the response parameters are investigated and the various limit-states of the dam are recognized.It is observed that by introducing a lift joint,the tensile damage can be avoided for the dam structure.The lift joint sliding is essentially independent of the base joint friction angle and the upper ligament over the inclined lift joint slides into the upstream direction in strong earthquakes.

Equating incremental dynamic analysis with static nonlinear analysis at near-field excitation

In an incremental dynamic analysis(IDA) using a set of ground motion records,nonlinear time history analysis needs to be performed on structures.It is well recognized that IDA calls for high computational efforts and the results are highly sensitive to selected ground motions.As a result,alternative static methods are needed.This study aims to introduce a new double-stage(N1- N2) static method to estimate capacity curves of MR frames.The technique is regulated to resemble IDA results with specific emphasis on near-field ground motions.Using an ensemble of 56 near-field earthquake records,required ID As have been carried out for SAC-Los Angeles 3-,9- and 20-story buildings and an additional 15-story building.The results of the proposed static method are compared with those from IDA,displacement-based adaptive procedure(DAP),and multimodal procedure(MMP).The results indicate that in addition to enhanced accuracy,very little time is required in the case of N1-N2 method.Thus,for the 3-story structure,the time required is less than 1 minute.The proposed N1-N2 method shows the best accuracy in terms of lateral mechanisms for the 15-story frame while for the other cases,the first mode load pattern leads to the best accuracy.

基于IDA方法的综合管廊纵向地震易损性分析研究

为了提出一种基于非线性增量动力分析(incremental dynamic analysis,IDA)的长线型综合管廊纵向地震性能评价的易损性分析方法,以单舱综合管廊为研究对象建立了简化梁-弹簧模型,合理地考虑了管廊接口的力学性能和管廊-土相互作用,将筛选的17组地震动统一调幅至不同强度水平后作为输入开展一维自由场分析以获取管廊底板位置处的地震动时程,最后开展了考虑地震动行波效应的综合管廊地震响应分析。基于IDA分析结果对地震动强度指标进行优选,最终建立了以管廊底板位置处峰值速度和地表峰值速度为地震动强度指标,以管廊接口张开量为损伤指标的易损性曲线,得到了不同地震烈度水平下综合管廊的失效概率。给出的典型II类场地中管廊地震易损性曲线和失效概率可以作为评价该类地下结构抗震性能的有效工具,为长线型综合管廊在不同地震动强度下的损伤预测提供可靠依据。

基于IDA的下弦与撑杆改进构型张弦梁结构的地震易损性分析

采用IDA方法进行地震易损性分析,已成为评估建筑结构抗震性能的常用方法之一。为探究下弦与撑杆改进构型张弦梁结构的抗震性能,使用ATC-63推荐的15组地震动记录数据,选择地震动强度参数结构第一自振周期结构阻尼系数为5%的反应谱加速度S_(a)(T1,5%),并以一阶振型中最大位移点的竖向挠度作为评价指标进行研究。基于有限元软件ANSYS对该结构进行模拟,通过对比时程分析结果,分析不同损伤状态下改进构型的张弦梁结构的抗震性能概率。研究结果表明:在面对大型地震时,此改进构型的张弦梁结构表现出卓越的抗震性能,拥有显著的防震潜力,且结构倒塌的风险较低。

基于IDA的基础隔震站房结构地震易损性分析

为研究铁路站房隔震结构的地震易损性,以某典型铁路站房为研究对象,对其进行基础隔震设计,分别建立铁路站房的隔震和非隔震数值模型,定义铁路站房结构中混凝土框架、钢结构屋架、非结构构件和基础隔震支座的损伤指标和极限状态,对铁路站房结构进行增量动力分析,并针对铁路站房的隔震和非隔震结构进行局部和整体地震易损性分析。研究结果表明,铁路站房各局部结构构件的损伤程度由大到小依次为:非结构构件、基础隔震支座、钢结构屋架、混凝土框架,这与铁路站房非隔震结构的损伤程度基本一致。在8度(0.3g)罕遇地震作用下,铁路站房隔震结构中各局部结构构件的损伤程度较非隔震结构均有所减小,其中非结构构件出现毁坏的超越概率降低幅度最大为86.38%,整体结构出现毁坏的概率上界和下界分别减小了97.02%和98.39%。这表明基础隔震技术能够显著降低铁路站房在地震时损坏的概率,提高铁路站房结构的抗震性能。因此,在铁路站房设计中,建议采用隔震技术降低站房的地震易损性,提高铁路站房的抗震性能。

基于IDA的“站桥合一”式高铁车站结构地震易损性分析

“站桥合一”式车站结构体系是大型交通枢纽车站的重要型式,具有结构形式复杂、质量刚度不均匀等特点,目前缺乏统一的抗震设计规范。本文以典型工程场地下的“站桥合一”式高铁车站结构为研究基础,采用基于IDA的地震易损性分析法,对该结构进行抗震能力评估,得到不同设防烈度地震下结构的失效概率。结果表明:不同地震动记录下结构的IDA曲线变化趋势大致相似,存在明显的“应力硬化”和“波动”特性;结构在强震作用下,不易出现倒塌破坏,在X、Y方向上对应超越概率为50%严重破坏性能水准的PGA值分别为5.4g与5.1g。本文能为此类结构的抗震设计研究提供理论参考。

基于IDA方法的地铁车辆基地TOD开发全框支剪力墙结构抗震性能评估

全框支剪力墙结构因上部塔楼剪力墙完全不落地而存在竖向构件不连续、刚度突变、大底盘多塔等不规则项,为综合有效评估此种超限结构的抗震性能,基于增量动力分析(IDA)方法得到不同地震烈度下结构最大层间位移角分布情况,并将结构性能水准划分5个等级,最终分析其地震易损性和损伤风险性。研究结果表明,结构随地震动峰值加速度(PGA)增大逐渐屈服并最终倒塌,不同地震记录时结构IDA曲线具有明显离散性;结构在7度多遇地震作用下处于正常使用性能水准的概率为97.914%,罕遇地震作用下结构倒塌的概率仅为0.053%;生命安全和接近倒塌性能水准对应的PGA中位数分别为1.287g和1.411g,远高于预估罕遇地震PGA;结构正常使用、基本可用、修复可用和接近倒塌性能水准50年超越概率分别为4.89%、1.74%、0.112%和0.046%。综上所述,结构满足预设抗震性能目标,具有良好的抗震性能及抗倒塌能力。

Comparison of seismic fragility analysis methods for arch dams

This study focuses on the seismic fragility analysis of arch dams.The multiple stripe analysis(MSA),cloud analysis(CLA),and incremental dynamic analysis(IDA)methods are compared.A comprehensive dam-reservoir-foundation rock system,which considers the opening of contraction joints,the nonlinearity of dam concrete and foundation rock,the radiation damping effect of semi-unbounded foundation,and the compressibility of reservoir water,is used as a numerical example.225,80,and 15 earthquake records are selected for MSA,CLA,and IDA,respectively.The results show that MSA provides satisfactory fragility analysis,while both CLA and IDA have assumptions that may lead to deviations.Therefore,MSA is the most reliable method among the three methods and is recommended for the fragility analysis of arch dams.It is also shown that the choice of demand level affects the reliability of fragility curves and the effect of the material uncertainty on the fragility of the dam is not significant.

Analysis of Capacity Decay, Impedance, and Heat Generation of Lithium-ionBatteries Experiencing Multiple Simultaneous Abuse Conditions

Abuse of Lithium-ion batteries,both physical and electrochemical,can lead to significantly reduced operational capabilities.In some instances,abuse can cause catastrophic failure,including thermal runaway,combustion,and explosion.Many different test standards that include abuse conditions have been developed,but these generally consider only one condition at a time and only provide go/no-go criteria.In this work,different types of cell abuse are implemented concurrently to determine the extent to which simultaneous abuse conditions aggravate cell degradation and failure.Vibrational loading is chosen to be the consistent type of physical abuse,and the first group of cells is cycled at different vibrational frequencies.The next group of cells is cycled at the same frequencies,with multiple charge pulses occurring during each discharge.The final group of cells is cycled at the same frequencies,with a partial nail puncture occurring near the beginning of cycling.The results show that abusing cells with vibrational loading or vibrational loading with current pulses does not cause a significant decrease in operational capabilities while abusing cells with vibrational loading and a nail puncture drastically reduces operational capabilities.The cells with vibration only experience an increase in internal resistance by a factor of 1.09–1.26,the cells with vibration and current pulses experience an increase in internal resistance by a factor of 1.16–1.23,and all cells from each group reach their rated lifetime of 500 cycles without reaching their end-of-life capacity.However,the cells with vibration and nail puncture experience an increase in internal resistance by a factor of 6.83–22.1,and each cell reaches its end-of-life capacity within 50 cycles.Overall,the results show that testing multiple abuse conditions simultaneously provides a better representation of the extreme limitations of cell operation and should be considered for inclusion in reference test standards.

Exceeding probability analysis for rail of high-speed railway under seismic excitations

Purpose–The smoothness of the high-speed railway(HSR)on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges,which may threaten the safety of running trains.Indeed,few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard.The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approach–In order to investigate the exceeding probability of the rail displacement under different seismic excitations,the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis(IDA)is proposed,and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined.Then a finite element model(FEM)of an assumed HSR track-bridge system is constructed,which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track.Under different seismic excitations,the seismic displacement response of the rail is calculated;the character of the rail displacement is analyzed;and the exceeding probability of the rail vertical displacement exceeding the allowable standard(2mm)is investigated.Findings–The results show that:(1)The bridge-abutment joint position may form a step-like under seismic excitation,threatening the running safety of high-speed trains under seismic excitations,and the rail displacements at mid-span positions are bigger than that at other positions on the bridge.(2)The exceeding probability of rail displacement is up to about 44%when PGA 50.01g,which is the level-five risk probability and can be described as’very likely to happen’.(3)The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge,and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/value–The work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.

设有叠合柱的局部错层RC框架结构地震易损性分析

为研究某一设有叠合柱的局部错层钢筋混凝土(reinforced concrete,RC)框架结构在近断层和远场地震作用下的破坏概率,自定义钢管混凝土叠合柱塑性铰参数,并与试验对比验证塑性铰参数的有效性。采用SAP2000建立非线性分析模型,选取近断层和远场地震波共22条,分别以地震峰值加速度(peak ground acceleration,PGA)和最大层间位移角作为地震动强度指标和结构性能指标,基于增量动力分析(incremental dynamic analysis,IDA)结果和点估计函数对错层框架结构进行易损性分析。结果表明:对于远场地震动,结构满足“三水准”抗震设防要求,在罕遇地震下超越防止倒塌极限状态的概率仅为0.24%;结构在近断层多遇地震下仍能满足“小震不坏”的设计要求,设防地震下结构超越修复后使用极限状态的概率为53.63%,发生中等破坏的概率较大,罕遇地震下结构达到倒塌极限状态的概率为5.37%,较远场地震作用破坏更为严重。研究结果可为错层框架结构的设计和地震风险评估提供参考。

寒区环境温度对板式橡胶支座连续梁桥地震易损性影响研究

针对现行规范对寒区桥梁减隔震设计中仅考虑橡胶支座力学特性受环境温度作用影响,而忽略桥墩混凝土材料特性受温度影响的不足,以高寒地区一座两联3×30 m混凝土连续梁桥为背景,开展不同环境温度下桥墩混凝土材料抗压性能试验,确定温度对其力学参数的影响,基于试验结果对不同环境温度下的桥墩混凝土力学参数进行修正,从而建立不同环境温度下的全桥精细化非线性有限元模型,并基于增量动力分析(IDA)法探究不同环境温度下该桥的地震易损性。结果表明:极端温度引起桥墩混凝土材料参数和支座刚度的改变,使得该桥自振频率随着温度的升高而降低;地震作用下,极端低温时桥墩墩顶位移较常温增大了26.8%,而极端高温时支座位移增大了19.4%;根据现行规范计算的极端低温时支座和桥梁系统的损伤概率偏小,极端高温时结构和构件的损伤概率偏大,在设计中应予以重视;极端低温下桥墩、支座及桥梁系统的损伤概率,较常温分别增大45.0%、35.2%和27.5%,对于高寒地区该类桥梁设计时需考虑低温对其抗震性能的影响。

基于振动台试验的鱼线固定梅瓶文物响应规律性研究

为了探索鱼线固定梅瓶文物在实际博物馆的地震响应以及抗震效果,首先选取了典型梅瓶文物,并在三层钢筋混凝土框架结构中开展了24种地震工况的振动台试验,然后建立了上述试验所用梅瓶文物的有限元模型,验证了有限元模型的准确性,最后采用增量动力分析法分析了该文物在两种常见直径鱼线保护措施下的运动响应。结果表明:鱼线固定梅瓶文物在地震作用下会产生滑移、摇摆、倾覆以及鱼线断裂等现象;不同楼层下的文物响应差别较大,尤其在大震作用下,高楼层的鱼线固定梅瓶文物易发生倾覆和鱼线断裂破坏,要重视高楼层文物的震前保护措施;在较强的地震作用下,仅依靠增大鱼线直径有时对控制文物的倾覆情况起不到关键性决定作用,需要进一步采取其它措施对文物进行保护。

基于向量式有限元的网壳结构地震易损性分析

为解决网壳结构地震易损性研究中,增量动力分析(incremental dynamic analysis,IDA)所面临的结构非线性分析耗时长且求解困难的问题,提出了一种基于向量式有限元的IDA方法。首先,以一个Kiewitt-8型单层球面网壳为例,验证了向量式有限元方法求解结构地震响应的准确性,其次选取12个不同参数的Kiewitt-8型单层球面网壳为研究对象,并考虑材料不确定性进行IDA分析,以地震峰值加速度与结构最大节点位移比为参数,绘制了结构在地震作用下的IDA曲线和轻微破坏、严重破坏及倒塌这三种性态下的易损性曲线。结果表明:向量式有限元能高效且准确的求解网壳结构的地震响应,屋面质量和矢跨比的增加均会增加三种性态点的超越概率;对于本文的网壳结构算例,求解时间仅为传统有限元方法的1/15,误差在3%以内,屋面质量和矢跨比的改变导致地震危险性最大增加了75%。

考虑氯离子侵蚀的深层隧道地震易损性分析

氯离子侵蚀对隧道的抗震性能产生不利影响,研究隧道在侵蚀环境下的地震易损性对全寿命周期的抗震评估至关重要.为了量化分析隧道长期在氯离子侵蚀作用下抗震性能的退化趋势,基于地震易损性理论,结合考虑氯离子侵蚀影响的混凝土和钢筋强度时变模型,分别选取峰值地面加速度和隧道直径变形率作为地震动强度指标和结构损伤指标,通过采用增量动力分析(incremental dynamic analysis,IDA)方法进行时程分析,深入探讨了深层隧道的地震易损性,得到了不同服役时间及不同损伤状态下的地震易损性曲线.结果表明:在相同的服役时间和地震动强度下,轻微损伤的发生概率最高,其次是中等和严重损伤;在相同的损伤状态和地震动强度下,随着服役时间的延长,氯离子侵蚀导致隧道抗震性能下降,损伤概率上升;在轻微损伤状态下,当峰值地面加速度为0.30g且服役达100 a时,损伤概率是服役初期的2.39倍.研究结果可为深层隧道的抗震设计提供科学依据.

基于小波函数的IDA分析在RC框架结构中的应用

针对某实际框架结构的抗震性能评估问题,利用OpenSees建立结构有限元模型,以谱加速度为地震动强度指标,层间位移角最大值为结构损伤指标,通过基于小波函数的拟合方法合成目标反应谱的地震动加速度时程,并对结构进行增量动力分析。结果表明,在相同条件下,基于小波函数所仿真出来的IDA曲线离散性显著降低,随着拟合精度的提高,三个分位数曲线更加集中,结构的IDA分析也更为有效。研究结果为提高框架结构的抗震性能提供了有效途径。