新型格构式高墩连续弯梁桥抗震性能分析

以四川雅泸高速公路干海子特大桥为工程背景,采用Midas Civil有限元软件建立三跨一联钢管混凝土格构式高墩连续弯梁桥结构。进行E1弹性地震响应分析,探讨了该类新型梁桥结构的动力特性、内力分布规律,以及地震波激励角度参数对全桥各个指标的影响规律,研究结果表明:钢管混凝土格构式高墩连续弯梁桥结构刚度较柔、周期长,不可忽视弯扭耦合效应。上部主梁弯矩值控制截面位于固定支座位置处,扭矩峰值出现在梁端位置处;下部格构墩弯矩和轴力控制截面均出现在固底墩墩底,墩顶为桥墩位移控制截面。支座中心连线和与之垂直的方向均为最不利激励角度。     

V形墩连续刚构桥0号块空间有限元分析

以某座V形墩连续刚构桥为工程背景,建立V形墩连续刚构桥0号块的ANSYS有限元模型,对拆除支架后V形墩0号块在自重工况下的变形和应力进行分析,同时对V形墩的夹角和厚度在自重工况下的影响进行了研究。研究表明V形墩的下内隅、0号块主梁的跨中截面下缘、箱梁翼板根部截面上缘以及V形墩与主梁的夹角位置可能出现较高拉应力;V形墩的夹角对V形墩0号块的受力影响较为显著,在V形墩夹角较大的情况下,主梁与V形墩之间的夹角建议采用圆弧形,避免应力集中造成节点位置混凝土开裂。     

轻轨高架短线节段法桥梁整体受力性能分析

以澳门轻轨C370标段项目为背景,开展了一联5×60m混凝土节段预制等高度变截面连续箱梁桥有限元计算,以研究该类箱梁在正常使用阶段和施工状态下的结构行为,不同工况组合下梁体应力状况与预应力变化等结构静力性能。研究结果表明：在承载能力极限状态,梁体内力满足规定,整体性较好;体内外预应力增量随跨中弯矩基本呈线性变化,静力增量及预应力损失值相对较小;在施工阶段,梁体下缘压应力储备充足,满足运梁安全性要求。     

预应力混凝土连续箱梁桥静载试验分析与研究

为研究预应力混凝土连续箱梁桥的承载能力及实际工作状况,通过实际桥梁的静载试验,测得桥梁在各个工况下控制截面的应变、挠度随荷载增加能保持良好的线性关系,并判断实测残余变形与实测总变形比值小于0.2,同时采用桥梁专用有限元计算分析软件MIDAS/Civil建立试验跨模型,与静载试验实测数据进行对比分析,得到桥梁的应变校验系数和挠度校验系数,综合判断桥梁的承载能力能满足要求。     

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A flu-id-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, struc-tural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic defor-mation subjected to intensive blast waves, and columns lost carrying capacity, subsequently lead-ing to the collapse of the whole structure. The approach coupling influence between struc-tural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.     

斜拉桥主梁施工底板局部承压安全验算方法

混凝土斜拉桥采用挂篮施工主梁时,挂篮底部行走轮对主梁底板产生巨大的竖向反力.混凝土底板、肋板可能在此反力作用下发生局部承压开裂破坏,需进行安全验算.行走轮与底板的接触区域是未知的,混凝土的受力变形均由接触区域决定.为寻求简单适用的计算方法,采用弹性接触Hertz理论,求解行走轮与混凝土板接触区域大小及应力分布,在此基础上应用规范推荐公式进行底板及肋板的抗裂安全验算.算例表明,该方法是可行的,可以简便地进行主梁底板的局部承压安全验算.     

强震作用下独塔斜拉桥抗震性能分析

以某跨径为110 m的独塔异形斜拉桥为工程背景,通过非线性有限元分析对斜拉桥在强震作用下的地震响应特性及减震措施进行了研究,得出如下结论:相比Lander-amboy波,卓越周期与桥梁固有周期较为接近的Cerro Prieto波能够引起结构较大的地震响应。行波效应能够显著增大工程背景斜拉桥的地震响应,且随着视波速的增大,桥梁的加速度响应明显增大。阻尼系数25 000 kN·s/m为工程背景斜拉桥的最优粘滞阻尼器设计参数,且在塔梁连接处安装该参数粘滞阻尼器后,斜拉桥减震效果显著,尤其能明显减小结构的位移响应。     

Temperature stress analysis of prestressed concrete box girder with corrugated steel webs

To figure out the distribution of temperature gradient along the girder height of steel-concrete composite box girder, combined with the mechanical characteristics of prestressed concrete composed box girder with corrugated steel webs, the calculation formulas of cross-sectional temperature stress along the span in a simply-supported beam bridge with composite section were derived under the conditions of static equilibrium and deformation compatibility of the beam element. The methods of calculating the maximum temperature stress value were discussed when the connectors are assumed rigid or flexible. Theoretical and numerical results indicate that the method proposed shows better precision for the calculation of temperature self-stress in both the top and the bottom surfaces of the box girder. Moreover, the regularity of temperature stress distribution at different locations along the girder span is that the largest axial force of the top or the bottom plate of the box girder is located in the midspan and spreads decreasingly until zero at both supported ends, and that the greatest longitudinal shear density in steel-concrete interface appears at both supported ends and then reduces gradually to zero in the midspan.     

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA.The multi-material Eulerian and Lagrangian coupling algorithm was adopted.A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground,multiple ALE element for simulating air and TNT explosive material.Numerical simulations of the blast pressure wave propagation,structural dynamic responses and deformation,and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed.The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure.The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation.The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves,and columns lost carrying capacity,subsequently leading to the collapse of the whole structure.The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures,and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.     

Philosophy and educational policy: possibilities,tensions and tasks

In this study, we investigate two principals’ learning in a progressive district in the southern United States. Both principals talked about ‘ownership’ and ‘continuous progress'as key to education reform, yet their words carried different meanings for learning. Principals’ use of reform terminology was embedded within two distinctly different communities of principal's practice ‐‐ Total Quality Management and ‘whole language’. We conclude by discussing ways to bridge such gaps in understanding among principals and communities by creating opportunities for learning and discourse. Educational administrators might thereby talk about and explore the different nuances of meaning they bring to their practice.

     

大跨度连续刚构桥墩梁固结区受力分析

大跨预应力混凝土连续刚构桥墩梁结合部位受力复杂,且布置数量较多的预应力钢束,是刚构桥中的关键部位。结合昆明市城市三环路东段工程预应力混凝土连续刚构桥的设计方案,利用有限元分析软件ANSYS对墩梁固接区进行精细有限元局部分析,得到施工阶段及运营阶段墩梁固结区的应力分布。结果表明该结构预应力配束合理,施工阶段及运营阶段应力均满足设计规范要求。     

钢-混凝土组合箱梁日照温差的实测和理论分析(英文)

为了探讨和验证钢-混凝土组合截面日照温度场的计算方法, 依托某大跨径三跨变截面连续箱梁桥, 对钢-混凝土组合箱梁的日照温度场进行了现场实测. 通过实测发现, 由于各腹板接受太阳漫散射的程度不同, 外侧钢梁温度普遍高于内侧箱梁, 且钢箱的整体平均温度数值与箱内空气基本吻合. 在此基础上借助ANSYS有限元计算软件, 根据不同位置钢腹板所处环境条件确定了各自的太阳辐射和对流换热情况, 进行了综合边界条件的瞬态热分析. 各测点理论计算结果与实测数据能较好地吻合, 温度差值在2℃以内, 说明了理论计算方法的可靠性, 为后续深入研究钢-混凝土组合截面日照温度场奠定了基础.     

基于响应面法的钢拱桥可靠度分析

大型复杂桥梁结构的极限状态函数都是隐式的非线性函数,采用传统的可靠性分析方法可能无法实现,但利用响应面有限元法可以很好地解决这类问题。利用响应面法对一下承式钢拱桥拱肋、主梁在正常使用极限状态下的轴向应力、竖向位移的可靠度进行了分析,并根据拟合出的各极限状态函数显式表达式得出了相应的可靠度指标,说明响应面有限元法是计算下承式钢拱桥构件可靠度的有效方法。     

Transient response of piles-bridge under horizontal excitation

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城市单柱式点支承曲线桥的分析

本文以线性支承曲线梁理论为基础,对城市立交桥和高架桥中正在研究的单柱式点支承曲线桥提出解析方法。通过与曲线格子梁理论对比分析,验证了本方法的可靠性。作为实际应用,本文对天津市市政工程勘测设计院正在设计的一座单柱式点支承曲线桥做了计算分析,两种方法所得结果吻合很好。     

85m主跨预应力混凝土连续刚构桥设计

简要对预应力混凝土连续刚构桥桥型和结构尺寸的选择、设计以及结构受力分析进行了介绍.大桥采用主跨为85 m的预应力混凝土连续刚构桥,主梁采用单箱单室变截面箱型梁,配置三项预应力体系,下部结构采用矩形薄壁空心墩,钻孔桩基础.通过对该桥进行结构分析,桥梁各部分均满足规范要求,具有较好的安全性能.总结该桥的设计要点,为其他同类桥梁设计提供参考.     

岔口河特大桥连续梁现浇支架设计技术

介绍了岔口河特大桥连续梁现浇支架的地基处理技术,以及现浇支架全部的设计计算过程,采用大型通用有限元软件ANSYS对重点部位进行了数值模拟,并详细阐述了岔口河特大桥连续梁支架设计计算方法,和支架预压方案,为类似的相关支架工程做参考。     

部分斜拉桥的施工控制

针对银川北二环一号桥的具体特点,在主梁标高控制、斜拉索索力测试和控制、主梁截面应力监测等方面作了详细的陈述,为同类型桥梁的施工控制提供技术参考。     

蒙特卡罗数值模拟及其在大跨桥梁可靠度分析中的应用

为了定量地研究大跨桥梁在多种随机因素下的可靠度,采用了蒙特卡罗法中的拉丁超立方体抽样法,对润扬悬索桥(中国跨度最大的悬索桥)在温度、风、车辆荷载、车辆冲击等随机变量作用下的结构可靠度进行了计算.通过对大桥在正常运营和损伤状态下的可靠度分析,获得了大桥主缆应力、吊索应力、桥塔位移以及钢箱梁线形等重要指标的可靠度和累积分布函数,分析结果形象直观,提高了评估的效率,使维护决策的制定更加客观准确.     

钢梁与钢筋混凝土桥墩的新型刚节点联结形式及其静载反复试验

提出了一种新型的桥梁钢梁与钢筋混凝土桥墩的刚节点联结形式．刚节点内部构件间的连接全部采用高强度螺栓连接方式且施工方便，能够较理想地将上部结构弯矩传递到下部结构，剪力传递钢板承受了大部分的水平剪力．通过静荷载反复试验获得了有关这种新型结构性能方面的有效数据，试验结果表明该结构内部应力传递路径明确，并具有良好的抗震性能．有关结构的强度和塑性变形的计算及试验结果均表明，这种结构即使在发生很大变形的情况下，也能保持良好的能量吸收功能且没有出现因应力集中而发生的局部曲屈现象．由于避免使用了价格昂贵的支座，采用这种新型组合结构形式不但具有良好的抗震性能，同时可以降低桥梁的建设成本．