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为了研究强震区桥梁跨活动断层时,桩基在地震中的动力响应,以海文大桥为工程背景,利用Midas GTS有限元软件建立其强震区桩-海床岩土体-断层耦合作用的数值模型,研究不同强度(0.20g～0.60g)的50年超越概率为10%的地震波(后文简称5010地震波)作用下,桥梁桩基加速度、位移、弯矩及剪力的动力时程响应特性。结果表明：上部大厚度松散土体对桩身加速度有放大及滤波作用,而基岩对桩身加速度几乎不产生作用;断层上、下盘桩基础的桩顶水平位移随输入地震动强度的增大而增大,但达到振幅的时刻一致;上、下盘桩基础桩顶竖向位移时程响应都在50 s以后产生永久沉降;桩身最大弯矩截面处时程响应均在40 s以后产生永久弯矩;应重点考虑上部覆盖层软硬土体界面和基岩界面的抗弯承载力设计,及桩顶和基岩面附近的抗剪承载力设计;上盘桩基础按桩身加速度、弯矩、桩顶水平位移等动参数控制设计,下盘桩基础按动剪应力控制设计。 相似文献
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近海复杂环境下的H-M-T受荷桩内力位移分析 总被引：2，自引：0，他引：2
为探讨近海复杂恶劣环境（台风超强风力、车辆冲击力或地震产生的复杂力等）下水平力H、弯矩M及扭矩T共同作用时的基桩桩身内力变形特性,基于传统有限杆单元法思想,获得了H-M-T受荷桩的基本单元刚度矩阵。然后,基于m法考虑桩周地基土的侧向约束作用,并计入H-M-T耦合效应,采用凝聚方法导得了具有简洁统一形式的桩身杆单元刚度矩阵,由此建立水平力、弯矩和扭矩组合作用下的桩身内力位移有限杆单元法计算模型,进而采用MATLAB编制出相应的分析计算程序。最后,结合近海工程算例进行了分析。结果表明：1文中提出的改进有限杆单元法能考虑桩周地基土的分层特性、不同边界条件及H-M-T的耦合效应;2相比单一考虑水平受荷,扭矩的存在加大了桩身的位移和内力;3H-M-T复杂受荷模式下,荷载传递存在有效传递深度,当相对深度z/L超过0.5后,桩身弯矩和剪力趋近于零,而扭矩显著减小。 相似文献
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为研究地震荷载作用下桩基-土-核电结构的抗震性能及土结动力反应规律,对拟开展的地震模拟振动试验模型进行数值计算分析。核电工程结构上部质量大和刚度大,试验模型不同于一般的工程结构,为检验振动台试验模型设计、传感器布设方案,对试验模型进行了数值模拟。数值模拟以单端承桩为研究对象,计算了上部结构质量和刚度变化时,在脉冲荷载及基于RG1.60谱人工合成地震动作用下桩身的地震反应规律。数值模拟表明:在水平地震动作用下,桩身剪力和弯矩包络线呈"X"状分布,桩底和顶处剪力弯矩较大;上部结构质量越大,桩身的剪力与弯矩越大;上部结构的刚度越大,桩身的剪力与弯矩越小;随着上部结构质量的增大和刚度的减小,反弯点逐渐向桩顶移动。桩顶发生最大位移时所对应的桩身挠度随着上部结构质量的增加而增大并且随着上部结构刚度的增大而减小。土层分界面处,桩身内力发生突变。此外,在脉冲荷载输入下,桩身反弯点位置与输入荷载的周期有关。计算结果为振动台试验模型设计提供了理论依据。 相似文献
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为研究斜腿夹角对V形墩连续刚构桥地震响应的影响及合理斜腿夹角角度,以一座典型V形墩预应力混凝土连续刚构桥为研究对象,采用有限元分析方法研究了斜腿夹角θ对桥梁内力及位移的影响,得出了θ对结构地震响应的影响规律和变化曲线。研究结果表明:随着斜腿夹角的增加,在纵向地震力作用下,墩底纵向弯矩逐渐减小,墩顶和主梁墩顶支撑处纵向弯矩逐渐增大;在横向地震力作用下,跨中横向弯矩逐渐减小,墩底横向弯矩逐渐增大,墩顶横向弯矩基本不变;在竖向地震力作用下,墩底和墩顶竖向弯矩逐渐增大,主梁支撑处竖向弯矩逐渐减小;斜腿夹角对纵向或横向地震力作用下结构位移影响不大,对竖向地震力作用下的位移影响较大。在满足静力设计的前提下,当两斜腿夹角为90°时,结构地震响应相对较小,受力合理性最优。研究成果可为该类桥梁的抗震设计与斜腿夹角角度选取提供参考和依据。 相似文献
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依托于某大直径盾构隧道工程项目，建立了基于黏弹性边界的地层-结构时程分析有限元模型。首先，基于振动台试验结果，验证了有限元数值模拟方法的有效性；进而，从软硬土层剪切波速比、软硬土层与隧道的相对位置、隧道埋深等三个方面，系统开展了上软下硬场地对大直径盾构隧道地震响应的影响研究。研究表明：上软下硬场地中的大直径盾构隧道弯矩最大值始终出现在软硬土层分界线附近。随着软硬土层剪切波速差异的增大，隧道的弯矩、剪力和接头张开量都有明显的增大，而隧道轴力和直径变形率的增大幅度较小。软硬土层与隧道的相对位置对隧道内力的影响具有不确定性。随着隧道埋深的增大，隧道弯矩、轴力和直径变形率逐渐增大。 相似文献
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盾构超近距离上穿既有运营隧道时,由于施工引起的土体扰动较大,控制地层沉降和扰动变形的难度也随之增大.基于宁波轨道交通5号线上穿运营的宁波轨道交通2号线区间隧道建立Flac3D模型,研究了掘进过程中既有隧道的变形规律,并探究了不同推进速度对隧道变形的影响.结果表明,当隧道开挖时,在掌子面还未达到既有隧道范围、位于既有隧道中心附近、超出既有隧道范围的过程中,既有隧道的纵向沉降与水平位移均出现明显的上升与回落现象;隧道超近距离上穿既有隧道将诱发双线隧道上行线和下行线相似的竖向沉降以及不同的水平变形规律,且水平变形数值沿盾构掘进方向有所增大;在保障隧道施工过程稳定性的前提下,考虑工程特点与施工效率,试验段推进12环/d,穿越段推进10环/d为该工程的最佳推进速度. 相似文献
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利用地震波斜入射下水下地基场地地震动分析的一维化时域算法,推导了平面P波入射下,水下地基场地的位移、加速度和应力表达式,重点分析了水深变化对位移峰值、加速度峰值、剪应力峰值和孔隙水压力峰值沿土层深度的分布规律。数值结果表明:同一土层深度处,当水深不超过1倍的土厚时,竖向位移峰值随水深的增大而增大;当水深超过1倍的土厚时,竖向位移峰值随水深的增大而减小。水平位移峰值与水深的关系基本上与竖向位移峰值相反。同一水深下,竖向位移峰值沿土深不断减小,水平位移峰值呈先减小后增加的趋势。同一水深下,竖向加速度峰值沿土深是一个不断减小的过程,水平位移峰值是一个反复增大和减小的过程。在0.75倍的土厚到基岩的范围外,水深对剪应力峰值的影响均较小。孔隙水压力峰值沿土深的分布大致是先减小再增加最后减小。 相似文献
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为了研究近断层地震动速度脉冲及强竖向地震动对风机塔地震响应的影响,以某陆上风电场1.5 MW风机塔为研究对象开展了结构在水平向脉冲型地震动、水平向非脉冲型地震动、水平与竖向地震动组合3种地震输入工况的时程分析。通过3种工况下塔顶位移时程、加速度时程、塔底剪力、弯矩及轴力的对比分析发现:近断层速度脉冲对结构塔顶水平位移、塔顶水平加速度、塔底剪力与弯矩均影响显著;竖向地震动会加大结构的塔顶竖向加速度响应及塔底轴力响应;随着竖向与水平加速度峰值比增大,塔顶竖向加速度响应增大,最大轴力随着峰值比增大而增大,最小轴力随着峰值比增大而减小。此外,增量动力分析表明,采用自接触的有限元模型可以更真实地预测风机塔的失稳破坏机制。 相似文献
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Coupling behavior of shear deformation and end rotation of elastomeric seismic isolation bearings 
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下载免费PDF全文 This paper presents a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to combined end rotations and shear deformation. The mechanical model consists of a series of axial springs at the top, mid‐height and bottom of the bearing to vertically reproduce asymmetric bending moment distribution in the bearings. The model can take into account end rotations of the bearing, and the overall rotational stiffness includes the effect of the variation of vertical load on the bearing and the imposed shear deformation. Static bending tests under various combinations of vertical load and shear deformation were performed to identify the mechanical characteristics of bearings. The test results indicate that bearing rotational stiffness increases with increasing vertical load but decreases with increasing shear deformation. Simulation analyses were conducted to validate the new mechanical model. The results of analyses using the new model show very good agreement with experimental observations. A series of seismic response analyses were performed to demonstrate the dynamic behavior of top‐of‐column isolated structures, a configuration where the end rotations of isolation bearings are typically expected to be larger. The results suggest that the end rotations of elastomeric bearings used in practical top‐of‐column isolated structures do not reduce the stability limit of isolation system. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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采用三维弹塑性有限元方法,研究了PCC桩群桩在水平荷载作用下的工作性状。比较了PCC桩群桩和等截面实心圆形桩群桩的水平承载力和群桩效率,得到了PCC桩纵、横向群桩效应的临界桩距;分析了桩距、桩数、桩顶约束条件对PCC桩群桩效率的影响。研究表明,PCC单桩和群桩的水平承载力都较等截面实心圆桩大;PCC桩纵、横向群桩效应的临界桩距分别约为外径的7.4倍和2.8倍;桩距愈小、桩数愈多,PCC桩群桩效率愈小,当设计桩距小于临界桩距时,应考虑群桩效应;PCC桩桩顶固接或铰接时,弯矩分布和承载力差异较大,设计中可以通过改变桩顶的约束条件来协调桩身受力性状。 相似文献
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本文以一座三跨总长60 m的整体桥为案例桥,分别试设计了同跨径的半整体桥、延伸桥面板桥和常规连续梁桥。通过Midas/Civil软件建立四种桥型的有限元模型,并对其进行了E1和E2反应谱分析和时程分析,对比了四种桥型的结构反应峰值（墩顶位移、桥墩及桩基剪力与弯矩、台底位移、桥台桩基剪力与弯矩）。计算结果表明:当桥梁存在15°的斜交角,整体桥、半整体桥在地震动沿平行于桥台长边方向及其垂直方向输入时更不利,而延伸桥面板桥和常规连续梁桥在地震动沿顺桥向和横桥向输入时更不利。四种桥型在地震作用下:整体桥抗震性能最优异,但其台底位移、桥台桩基的剪力和弯矩最大;半整体桥台底位移、桥台桩基的剪力和弯矩最小,其墩顶位移、桥墩及桩基的剪力和弯矩仅比整体桥大;延伸桥面板桥和常规连续梁桥的墩-梁相对位移远大于整体桥和半整体桥,不适用于地震基本烈度高的区域。 相似文献
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This paper presents an engineering approach for analysing the longitudinal behaviour of tunnels subjected to earthquakes. The tunnel is modelled as a Timoshenko beam connected to the far soil by means of continuous elastic support (Winkler model). Seismic free-field inputs, such as those caused by surface waves travelling parallel to the tunnel axis, were imposed at the base of the springs of the Winkler model, generating bending moments and shear forces on the cross-sections of the tunnel. Closed-form expressions of the tunnel displacements, shear forces, and bending moments were determined at any tunnel section in terms of the seismic excitation, tunnel geometry and material properties, and subgrade reaction modulus of the soil. A dimensional analysis was carried out to ascertain directly the maximum tunnel displacement, bending moment, and shear force. 相似文献
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Previous quasi-static cyclic tests of shear walls, which routinely used an incremental lateral displacement test protocol with a constant axial load, failed to reflect the character of moment-shear force interaction of prototype buildings. To study the effect of the moment-shear force interaction on the seismic performance of shear walls, three identical 2-story shear wall specimens with different loading patterns were constructed at 1/2 scale, to represent the lower portion of an 11-story high-rise building, and were tested under reversed cyclic loads. The axial force, shear force and bending moment were simultaneously applied to simulate the effects of gravity loads and earthquake excitations on the prototype. The axial force and bending moment delivered from the upper structure were applied to the top of the specimens by two vertical actuators, and the shear force was applied to the specimens by two horizontal actuators. A mixed force-displacement control test program was adopted to ensure that the bending moment and the lateral shear were increased proportionally. The experimental results show that the moment-shear force interaction had a significant effect on the failure pattern, hysteretic characteristics, ductility and energy dissipation of the specimens. It is recommended that moment-shear force interaction should be considered in the loading condition of RC shear wall substructures cyclic tests. 相似文献
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Elastomeric isolation bearings consist of multiple rubber layers with their top and bottom surfaces bonded to steel plates to restrict compressive deformation. Deformation constraints result in a variation of elastic modulus over the cross section of the rubber layers. In this paper, we describe a normalized compression modulus distribution on a circular rubber pad. The compressive and bending moduli of the rubber pad can be reproduced by applying the distribution to a series of axial springs. We also present a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to large shear deformation and high compressive load. The mechanical model consists of a series of multiple shear springs at midheight and a series of axial springs at the top and bottom interfaces of the bearing. Simulation analyses of bearing tests were conducted to validate the proposed model. The analyses demonstrated that a model for circular lead-rubber bearings can successfully capture the influence of the axial load magnitude on the bearing shear behavior. The new model can simulate much more realistic behavior than prior models based on a uniform modulus assumption. 相似文献
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在Rayleigh能量法和Southwell＇s频率合成法的基础上,将结构的振动基频表示为由各变形元和惯性元组成的子系统频率的合成,其中变形元为结构的弯曲变形和剪切变形,惯性元为结构的分布质量和塔顶附加质量。通过选取满足边界条件的挠度函数,建立了底部固定、顶端带有附加质量的塔式结构基频与刚度的关系,因此可通过测量结构的振动基频识别出塔式结构的抗弯刚度和抗剪刚度。以某钢塔为计算实例,采用该算法推导出了结构振动基频与弹性模量的关系,只要知道截面的几何尺寸和材料性质,便可快速识别出各截面的刚度。有限元空间建模计算结果证明了本文提出的算法具有较高精度。该方法适合底部固定的塔式结构,可为复杂空间塔式结构使用状态的监测与评估提供参考。 相似文献