古建筑木结构构架加固试验研究

通过对未加固构架和加同构架低周反复荷载试验,研究碳纤维布加固效果和构架的抗震性能.试验得出构架水平力和水平位移的滞同曲线及骨架曲线,根据滞回曲线和骨架曲线的特征,得出了水平力和位移的关系方程和构架恢复力模型,从强度、刚度、变形能力几个方面说明加固效果较好.研究结果为古建筑的抗震性能研究和修缮加周提供了有用的参考.     

高性能混凝土剪力墙恢复力模型研究

高性能混凝土剪力墙的侧向刚度较大,变形能力较差。为了增强其侧向变形能力,通常在剪力墙截面两端设置约束边缘构件。根据15个设置边缘约束构件的高性能混凝土剪力墙弯曲(弯曲剪切)破坏的试验结果,以屈服点、峰值点和极限点将此种剪力墙的力-位移骨架曲线简化为三线型模型;基于平截面假定,分别推导了屈服荷载、峰值荷载及极限荷载的表达式;公式推导中考虑了边缘约束构件的影响。根据理论分析和试验数据,建立了骨架曲线各阶段的刚度计算公式。从理论值与试验值的比较可以看出,基于平截面假定所得到的屈服荷载和峰值荷载的计算值均与试验值接近。考虑了卸载时的刚度退化,并建立了适合高性能混凝土剪力墙的恢复力模型。     

侧向刚度对高位拱式转换层结构抗震性能的影响

通过分析指出了等效刚度比对高位拱式转换层结构抗震性能的影响.等效侧向刚度比对结构的自振周期及上部结构的振型曲线影响不大,而对结构的绝对位移和层间位移角影响较大;等效侧向刚度比为0.8～1.2较合适.除此之外,还应使转换层本层的侧向刚度与转换层相邻上一层的侧向刚度比大于0.6.     

古建筑木结构直榫和燕尾榫节点试验研究

通过对典型透榫和燕尾榫榫卯连接的模型低周反复荷载试验,研究了榫卯半刚性连接特性和刚度退化规律.试验得出榫卯连接的弯矩-转角滞回曲线及骨架曲线,并拟合出了弯矩-转角的关系方程和榫卯连接节点恢复力模型,由试验结果给出了两种榫卯连接刚度的非线性变化.研究结果为古建筑的抗震性能研究和修缮加固提供了理论基础.     

饱和砂土地基中群桩侧向动力响应试验与数值模拟对比研究

可液化场地中桩基尤其是群桩的横向动力响应特性的研究,一直是国内外岩土地震工程领域关注的热点问题。由于桩-土-承台结构动力相互作用过程的复杂性,基于砂土-群桩-承台结构模型振动台试验,对饱和砂土中群桩侧向动力响应特性进行了分析。在此基础上,通过大型有限元软件OpenSees建立了三维模型,展开了数值模拟研究,并将数值模拟结果与试验结果进行了对比研究。结果表明:在正弦波输入下,无论是干砂还是饱和砂土试验,群桩承台加速度和位移时程与模拟承台加速度和位移时程在曲线趋势和峰值上基本吻合;在El-Centro地震波输入下,干砂和饱和砂土的模拟承台加速度时程曲线峰值和趋势与试验的比较吻合,而承台位移时程曲线频率比试验要高,但承台位移峰值基本一致。     

新型弹塑性软碰撞防护装置试验研究

为限制隔震层位移,研发了同时提供刚度和阻尼力的新型弹塑性软碰撞防护装置,该装置主要由铅芯橡胶支座、剪力键及中空连接钢板组成。首先对铅芯橡胶支座进行了设计压应力12MPa下基本性能试验及压应力0 MPa下剪切试验;然后进行了弹塑性软碰撞防护装置的水平力学性能测试试验,测定装置的屈服后刚度、屈服力及支座顶端转角,探讨了剪力键外圆面罩橡胶套对试验结果的影响,对比分析了装置的水平力学性能指标与支座在0MPa下剪切试验结果的差异;最后,对弹塑性软碰撞防护装置进行了数值模拟,对比了数值模拟与试验的水平力-位移滞回曲线。结果表明:弹塑性软碰撞防护装置可提供刚度及阻尼力,在剪力键外圆面罩上橡胶套后对试验结果基本无影响;与0MPa下支座测试结果相比较,装置的屈服后刚度及屈服力有所降低;支座顶端转角随支座剪应变的增大而增大;数值模拟与试验的滞回曲线吻合良好,该装置具有良好的滞回耗能能力。     

钢结构加层混凝土框架结构Pushover分析侧向力分布研究

针对钢结构加层混凝土框架结构,考虑地震作用下其层间刚度变化的影响,提出了一种计算侧向力分布的方法——层间刚度侧向力分布法。通过对一钢结构加层混凝土框架结构进行推覆分析,得到各楼层侧移、层间位移角和塑性铰分布情况,并与时程分析结果进行了比较分析。结果表明,文中方法推覆分析得到的楼层侧移和层间位移角与时程分析结果吻合较好,塑性铰分布情况也较一致,并且本方法得到的推覆曲线是推覆计算结果的下限,用于结构的抗震评估更安全。     

群桩-土-墩柱相互作用体系抗震性能试验及数值模拟研究

为进一步研究土-结构相互作用(SSI)体系的抗震性能,以1∶4比例尺桥梁墩柱模型为试验对象,考虑土-结构相互作用,通过拟静力试验观察了试验现象,得到了模型滞回曲线、耗能能力等数据。通过有限元软件ABAQUS建立了与试验情况相同的有限元模型,并分析计算。建模分析结果与试验结果一致,在此基础上,以本模型为对象进行了地震反应时程分析,得到了不同地基条件下的位移时程曲线及桩身应力、桩身位移响应曲线,并用m法对比计算桩的位移响应曲线。分析结果表明:不同地基条件下群桩-土-刚度较大墩柱结构体系破坏形式不同;在地震作用下,短桩基础在桩的中段处应力达到最大值,有必要在此处予以加强;在地震作用较大时,m法计算的桩顶位移偏小,且m法无法计入群桩效应,可能导致群桩基础内力的计算偏于不安全,建议予以重视。     

斜向荷载作用下锈蚀RC矩形墩抗震性能拟静力试验及易损性分析

为探究锈蚀钢筋混凝土(RC)桥墩在非正交水平荷载下的抗震性能,设计制作了4个不同加载角度构件进行拟静力实验,并利用OpenSees软件构建非线性有限元纤维模型,分析不同地震动入射角对其地震易损性的影响。结果发现：拟静力实验中,加载角度偏近弱轴,最大侧向力和屈服强度降低,达到最大侧向力的位移和屈服位移减小,极限强度降低,刚度和耗能能力下降,抗震性能减弱,但对位移延性系数影响较小;易损性分析发现：RC桥墩不同破坏状态对应的失效概率随PGA增大而增大。在PGA不变时,相同破坏状态下的失效概率随地震动入射角度由强轴趋向弱轴而增大。所做工作能为锈蚀RC桥墩的地震风险评估提供试验基础。     

新型编织式金属阻尼器减震性能研究

本文提出一种编织式金属阻尼器,并通过数值模拟和试验研究相结合的方法展开系统的研究。本文首先进行了有限元模拟和拟静力试验,得到了该阻尼器的力-位移曲线,结果表明本阻尼器的疲劳性能好,但滞回曲线有一定的捏缩现象。然后运用ANSYS对其设计参数进行了优化,结果发现改用梭形截面杆后,阻尼器出力和滞回性能大幅提高。最后采用Bouc-Wen模型建立了阻尼器的恢复力模型,运用SAP2000软件对安装此阻尼器前后10层平面框架进行弹塑性时程分析,结果表明,安装该阻尼器后结构的层间位移、层剪力和顶点位移大幅降低,从而验证了其耗能性能。     

组合橡胶支座及橡胶支座与柱串联系统的水平刚度计算方法

目前基础隔震建筑中应用的叠层橡胶支座都是等截面的,其水平刚度是以遭遇强烈地震为依据设计的,当遭遇中小地震时水平刚度将偏大,致使上部结构的减震效果比遭遇设计地震时明显减小,而由两个不同截面橡胶支座组成的组合橡胶支座在不同强度地震时均能发挥较好设计的隔震效果。     

2D numerical investigation of segmental tunnel lining under seismic loading

Segmental tunnel linings are now often used for seismic areas. However, the influence of segment joints on the segmental lining behavior under seismic loading has not been thoroughly considered in the literature. This paper presents a numerical study, which has been performed under seismic circumstance, to investigate the factors that affect segmental tunnel lining behavior. Analyses have been carried out using a two-dimensional finite difference element model. The proposed model allows studying the effect of the rotational joint stiffness, radial stiffness and the axial stiffness of the longitudinal joints. The numerical results show that a segmental lining can perform better than a continuous lining during earthquake. It has been seen that the influence of the joint distribution, the joint rotational stiffness, the joint axial stiffness, Young׳s modulus of the ground surrounding the tunnel, the lateral earth pressure factor and the maximum shear strain should not be neglected. Some important differences of the segmental tunnel lining behavior under static and seismic conditions have been highlighted.     

考虑残损的古建木结构地震易损性分析

现役古建木结构普遍存在残损现象,这将影响结构的抗震性能。本文以北京故宫的咸福宫西配殿为研究对象,通过简化其屋顶、斗拱、榫卯和柱脚节点建立结构的理想模型,并在此基础上考虑材料老化和节点性能降低等因素建立其残损现状模型。通过地震易损性分析,得到古建木结构的地震易损性曲线并进行理想和残损结构的震害等级及其发生概率对比。研究结果表明:残损现象降低了咸福宫西配殿的刚度和自振频率;相比于理想结构,咸福宫西配殿残损结构在小震作用下发生轻微损坏的概率增大21.1%,在中震作用下发生中等破坏的概率增大3.7%,大震作用下发生严重破坏的概率增大10.6%;咸福宫西配殿在大震作用下发生倒塌的概率很小,体现了木结构具有良好的抗震性能。     

大空间地下结构地震响应混合试验研究

基于OpenSees-OpenFresco-MTS混合试验系统,选取关键构件底层中柱,进行大空间地下结构地震响应混合试验研究。在混合试验过程中,取结构底层中柱为试验子结构,取结构剩余部分与土体为数值子结构。为了满足试验要求,开发了一种专用于混合试验的可变刚度钢构件。通过更换柱脚螺杆改变试验装置侧向刚度。在混合试验前,根据数值模型中对应单元侧向刚度确定钢构件侧向刚度;根据幅值比和相位差等频域指标评价混合试验结果。试验结果显示:在上海人工波工况、El Centro波工况和Kobe波工况中,理论结果与试验结果匹配良好。在以大空间地下结构地震响应为研究对象时,基于OpenSees-OpenFresco-MTS的混合试验系统具有良好的稳定性与精确性。     

整体式桥梁动力特性及抗震性能研究

为深入了解整体式桥梁的动力特性和抗震性能,建立台-土有限元模型,并提出合理的台-土相互作用数学模型,然后利用Midas Civil整体模型研究台-土相互作用、桩-土相互作用、桥墩构造等因素对整体式桥梁抗震性能的影响。结果表明：与简支梁相比,同等跨度下整体式桥梁的纵向刚度明显提高,但横向刚度差距不大;台后土的约束刚度大小对桥梁的静动力特性不产生明显影响,整体式桥梁根据我国现有规范计算台后地震力相对保守;改变桩-土约束刚度对整体式桥梁的抗震性能影响不大;提高桥墩的横向刚度,将独柱墩改为双柱墩能大幅提高结构抗震性能。研究结论及台后土压力系数的计算方式,可供整体式桥梁抗震计算提供参考。     

盾构施工对不同刚度桩体影响的数值分析

针对苏州轻轨一号线盾构隧道的施工情况,采用三维有限元数值模型,研究了盾构施工对不同刚度桩体的影响。计算结果表明：当盾构施工时,不同刚度桩体均偏向隧道移动,在隧道轴线处的横向位移均为最大。桩身横向位移最大值、竖向位移随桩体刚度增大而变小,桩身轴力、弯矩则随桩体刚度增大而逐渐增大,桩身最大负弯矩均出现在隧道轴线位置处。在盾构正下方穿越单桩过程中,桩身沿隧道轴向位移近似为一条直线。当桩体弹性模量为0.5 GPa时,柱顶和桩底处竖向位移相差较大;当桩体弹性模量大于0.5 GPa时,桩身竖向位移急剧增大。桩身轴力沿桩身两端大、中间小。桩身弯矩随桩体弹性模量增大而明显增大。     

Cladding influence on dynamics response of tall buildings

Precast concrete panels form attractive facades for steel frame buildings and are generally regarded as non-structural by structural engineers. However, panels have been found to add lateral stiffness until their capacity or that of their connections is exceeded. Consequently, the computed dynamic response based on a model of the structural framing alone may be quite different from that experienced by the actual structure. As a case study, the influence of precast concrete panels on lateral and torsional stiffness of a 25-storey building was investigated. The effect of cladding on dynamic properties and linear seismic response was explored by varying panel stiffness. Cladding stiffness was added to the bare frame model until analytical frequency values matched vibration test results. Then, using the cladding stiffness values obtained, an accidental eccentricity between centres of mass and rigidity at each floor level was imposed and linear seismic response computed. Torsional response effects were increased substantially. Finally, a modified cladding panel connection was developed based on previously-reported studies for panelized construction. The influence of the proposed connection on overall structural response was determined for different ground motion inputs.     

带窗洞加强肋复合墙体抗震性能及抗侧刚度影响因素研究

进行了1榀开窗洞1:2比例的加强肋复合墙体模型的伪静力试验,通过对墙体中钢筋应变进行分析,研究墙体的受力性能和破坏模式,探究在低周反复荷载作用下带窗洞加强肋复合墙体的承载力、滞回及耗能能力、延性和刚度退化等抗震性能,并与不开洞墙体的抗震性能进行对比。在试验研究的基础上,建立具有不同窗洞参数的有限元数值模型,探究窗洞位置、大小、肋柱截面及肋柱配筋率的改变对加强肋复合墙体抗侧刚度的影响。结果表明:带窗洞加强肋复合墙体按照砌块-外框-肋梁的顺序依次破坏,破坏模式以弯剪型破坏为主;相比不开洞加强肋复合墙体,带窗洞墙体的抗侧刚度等抗震性能明显较差;相同窗洞尺寸情况下,窗洞居中时加强肋复合墙体的抗侧刚度相对较大;窗洞开洞率小于12.9%的墙体洞边可不设肋柱;洞边加强肋柱对开窗洞墙体的抗侧刚度提升作用显著,但其提升作用随着窗洞肋柱截面的增大而逐渐减弱;增大加强肋柱配筋率对墙体抗侧刚度的提高不明显。     

Behavior of braced excavation in sand under a seismic condition: experimental and numerical studies

The behavior of braced excavation in dry sand under a seismic condition is investigated in this paper. A series of shake table tests on a reduced scale model of a retaining wall with one level of bracing were conducted to study the effect of different design parameters such as excavation depth, acceleration amplitude and wall stiffness. Numerical analyses using FLAC 2D were also performed considering one level of bracing. The strut forces, lateral displacements and bending moments in the wall at the end of earthquake motion were compared with experimental results. The study showed that in a post-seismic condition, when other factors were constant, lateral displacement, bending moment, strut forces and maximum ground surface displacement increased with excavation depth and the amplitude of base acceleration. The study also showed that as wall stiffness decreased, the lateral displacement of the wall and ground surface displacement increased, but the bending moment of the wall and strut forces decreased. The net earth pressure behind the walls was influenced by excavation depth and the peak acceleration amplitude, but did not change significantly with wall stiffness. Strut force was the least affected parameter when compared with others under a seismic condition.     

Lateral stiffness estimation in frames and its implementation to continuum models for linear and nonlinear static analysis

Continuum model is a useful tool for approximate analysis of tall structures including moment-resisting frames and shear wall-frame systems. In continuum model, discrete buildings are simplified such that their overall behavior is described through the contributions of flexural and shear stiffnesses at the story levels. Therefore, accurate determination of these lateral stiffness components constitutes one of the major issues in establishing reliable continuum models even if the proposed solution is an approximation to actual structural behavior. This study first examines the previous literature on the calculation of lateral stiffness components (i.e. flexural and shear stiffnesses) through comparisons with exact results obtained from discrete models. A new methodology for adapting the heightwise variation of lateral stiffness to continuum model is presented based on these comparisons. The proposed methodology is then extended for estimating the nonlinear global capacity of moment resisting frames. The verifications that compare the nonlinear behavior of real systems with those estimated from the proposed procedure suggest its effective use for the performance assessment of large building stocks that exhibit similar structural features. This conclusion is further justified by comparing nonlinear response history analyses of single-degree-of-freedom (sdof) systems that are obtained from the global capacity curves of actual systems and their approximations computed by the proposed procedure.