Dynamic finite element model updating of prestressed concrete continuous box-girder bridge

The dynamic finite element model （FEM） of a prestressed concrete continuous box-girder bridge, called the Tongyang Canal Bridge, is built and updated based on the results of ambient vibration testing （AVT） using a real-coded accelerating genetic algorithm （RAGA）. The objective functions are defined based on natural frequency and modal assurance criterion （MAC） metrics to evaluate the updated FEM. Two objective functions are defined to fully account for the relative errors and standard deviations of the natural frequencies and MAC between the AVT results and the updated FEM predictions. The dynamically updated FEM of the bridge can better represent its structural dynamics and serve as a baseline in long-term health monitoring, condition assessment and damage identification over the service life of the bridge .

Structural Behavior of Continuous Prestressed Steel Fiber Reinforced High Strength Concrete Beam

The flexural behaviors of continuous fully and partially prestressed steel fiber reinforced high strength concrete beams are studied by experiment and nonlinear finite element analysis. Three levels of partial prestress ratio （PPR） are considered, and three pairs of two-span continuous beams with box sections varying in size are designed. The major parameters involved in the study include the PPR and the fiber location. It is concluded that the prestressed high strength concrete beam exhibits satisfactory ductility; the influences of steel fiber on the crack behaviors for partially prestressed beams are not as obvious as those for fully prestressed ones; steel fibers can improve the structural stiffness after cracking for fully prestressed high strength concrete beams; the moment redistribution from mid-span to intermediate support in the first stage should be mainly considered in practical design.

Degradation process assessment of prestressed concrete continuous bridges in life-cycle

To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.

Stiffness Degradation Characteristics Destructive Testing and Finite-Element Analysis of Prestressed Concrete T-Beam

The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis,and the mid-span deflection,girder stiffness and the variation of the cross section strain in the loading process were obtained,and the mechanical properties,mechanical behavior,elastic and plastic behavior and ultimate bearing capacity of T girder with large span were revealed.Furthermore,the relationship between the beam stiffness degradation,the neutral axis in cross-section,steel yielding and concrete cracking are investigated and analyzed.A method was proposed to predict the residual bearing capacity of a bridge based on the variation of the position of the cross section strain distribution and the section neutral axis,which provided a theoretical basis for predicting the stiffness detection and carrying capacity assessment of prestressed concrete beam.

Analysis and calculation of factors on curvature ductility of unbonded prestressed concrete beams

In consideration that behavior of curvature ductility of interior support directly influences the degree of moment modification of unbonded prestressed concrete (UPC) continuous structures, constitutive relationships of concrete, non-prestressed reinforcement and prestressed reinforcement used for nonlinear analysis are given. Through simulation analysis on simple beams subjected to single loading at the middle of the span, the law of factors influencing curvature ductility, such as global reinforcing index, prestressing degree, effective prestress, strength of concrete and grade of non-prestressed reinforcement are explored. Based on these researches, calculating formula of curvature ductility coefficient of UPC beams is established, which provides basic data for further research on plastic design of UPC indeterminate structures.

Bridge Falsework in Staged Construction of a Prestressed Concrete Beam Bridge

The formwork and falsework in the construction of twin ribbed slab decks on a multi-span ecological bridge for a dual carriageway are presented. The bridge is situated in a valley plain which is crossed by small rivers and was designed principally with the environment in mind. The bridge length is over 356 m, and the width of the decks is 11.5 m. For the bridge works, a simple conventional falsework system was chosen with steel frames for the supports and steel rolled beams for the decks. The formwork was constructed in solid timber and plywood as multiple-use panels. The falsework was designed in order to build the two 10-span bridge decks in stages. The decks are continuous cast-in-situ prestressed concrete twin rib with spans of 30 m, 34 m and 45 m. An individual falsework system was designed, which was easy to move transversally following completion of each stage for one deck. After finishing each stage, for the second deck, the falsework was dismantled and used again in the next construction fronts. An individual arrangement for the falsework along with timber pilings was used to cross the biggest river. The formwork timber panels were used several times in the multistage bridge construction. The adopted falsework system is very simple, but it allowed the speedy construction of the two decks where there were severe time constraints.

大跨径预应力混凝土连续梁桥加固研究进展

基于我国危旧桥改造需求多、病害情况复杂给桥梁加固提出的挑战,需把握桥梁加固国内外的研究现状,为未来深入研究和工程应用提供参考。结合大跨径预应力混凝土连续梁桥主要加固手段的基本原理,对各加固手段的优点、局限性及适用对象进行分析,系统梳理近两年来的最新研究成果,并对未来发展进行了展望。

深中通道泄洪区非通航孔桥主梁设计

深中通道泄洪区非通航孔桥总长6.05 km,分布于伶仃洋大桥及中山大桥2座通航孔桥两侧。泄洪区非通航孔桥采用等跨连续梁布置,4~6跨一联。主梁设计过程中,首先进行110、120、130 m三种跨径方案比选,确定采用最经济的110 m跨径方案。然后针对结构形式,提出预应力混凝土梁、钢-混组合梁和钢箱梁3种方案,从力学性能、经济性和施工风险等方面综合考虑,最终推荐采用钢箱梁方案。钢箱梁采用外形简洁流畅的封闭式断面,有利于后期维养;考虑全线景观效果,主梁高度取4 m,高跨比为1/27.5;横隔板间距取2.5 m,采用实腹式横隔板和框架式横肋的组合式设计,使箱室内部通透性更好;钢箱梁采用Q420qD钢和Q345qD钢2种材料。钢箱梁施工采用适合海上长大桥梁的大节段预制+现场拼装的施工方案。

大跨度预应力混凝土连续梁悬臂浇筑施工技术

本文探究了悬臂浇筑施工技术在某大跨度预应力混凝土连续梁中的应用。采用悬臂平衡浇筑法进行施工,在悬臂端设计了三角形挂篮,利用挂篮做吊架进行悬臂浇筑、完成合拢段施工,降低了施工难度,提高了施工质量。在本工程中,贯彻全过程、精细化管理理念,分别从支架搭设与预压、挂篮制作与安装、钢筋绑扎、混凝土浇筑预养护、孔道压浆与封锚等方面采取了控制措施,确保了预应力混凝土连续梁悬臂施工的顺利完成。

PC连续箱梁桥的日照温度效应及合龙温度研究

以云南省某大跨径预应力混凝土连续箱梁桥为工程背景,研究其日照温度效应以及合龙温度的确定。使用ANSYS数值模拟混凝土箱梁的温度场,结合实测值验证其可靠性,并拟合相应的指数型温度梯度曲线;使用Midas研究日照温度模式对混凝土箱梁桥施工中和成桥下的内力和位移影响;基于年温差效应对合理合龙温度进行研究,并针对非设计合龙温度下的合理施工提出相应的改善措施。结果表明,温度场计算理论得出的数据同实测值吻合较好;拟合出指数型的升温和降温模式下的温度效应公式,尤其是对最大悬臂状态的下挠影响显著,最大下挠值达21.6 mm;结构因整体升温或降温产生的横向位移值比竖向位移值大,升温22℃时,最大纵向位移值为-31.2 mm;合龙温度为10℃时,对主梁结构的受力最好,同时升温带来的结构上挠值对结构长期变形有利。

基于LS-DYNA的船-桥墩碰撞分析

基于ANSYS/LS-DYNA及Hypermesh建立了船舶-桥墩碰撞有限元模型,着重针对一典型工况对桥墩遭受撞击作用后的动力响应进行分析并确定其失效模式。然后通过模拟一系列的船舶撞击桥墩的工况为船撞力简化计算公式的拟合提供大量的数据样本并对得到的数据进行统计分析拟合出船撞力的简化计算公式,并与国内外相关规范的规定进行对比分析,相关结果表明,我国规范中规定的船舶撞击力相对偏小。

预应力混凝土梁桥关键施工技术分析

为保证预应力混凝土梁桥的施工质量,文章总结了连续梁桥的形式、受力特点等,分析了悬臂浇筑法的施工流程和特点。同时,以某公路连续箱梁桥为研究对象,从0#块支架计算和墩梁临时固结、挂篮预压、合龙等方面分析了施工要点,最后从线形控制和应力控制两方面阐述了连续梁桥的施工控制方法,研究成果可供类似桥梁结构施工借鉴。

高速铁路预应力混凝土连续梁桥施工BIM技术研究与应用

文章介绍了应用BIM技术开展高速铁路预应力混凝土连续梁桥施工的重要环节,分析了高速铁路预应力混凝土连续梁桥施工特点,在明确技术适用性的基础上,针对BIM模型建立、预应力筋碰撞检查、有限元仿真分析、施工过程监测管理等方面内容进行了强调,能够缓解以往设计与施工存在的衔接困难问题,提高施工过程监控水平。

桥梁顶升施工有限元分析

山东省青岛市辽阳路桥是一座预应力混凝土连续箱梁桥。为实现与新建桥梁的衔接,现需该桥的46#桥梁顶升655~1218mm。利用ANSYS软件建立46#桥梁有限元计算模型,分析其在同步顶升工况、千斤顶失效工况下,顶升至最高点时所需的最大顶升力以及箱梁桥和分配梁的受力和变形情况,以确保桥梁顶升过程中的安全性。结果表明桥梁在两类工况下,均具有较大的安全储备,可保障桥梁顶升过程中的安全可行性。研究成果可为其他同类型桥梁顶升施工工程提供案例参考。

装配式T梁翼板后张法预应力交叉连续梁柱节点施工关键技术

公开了一种装配式T梁翼板后张法预应力交叉连续梁柱节点建造新技术,在装配式混凝土梁柱节点处采用板下一体化叠合T梁翼板端预应力张拉技术,有效改善了梁柱节点受力特性,节点抗负弯矩效果好,预应力梁柱增强节点抗震能力强。采用有限元软件ABAQUS对“低标准,提前张拉”“超标准,控制张拉”两种工况下节点进行优化施工模拟。由分析结果可知:当梁侧加腋板底张拉节点只有柱侧双边张拉时,在保障结构安全的前提下,可在混凝土凝结硬化达到混凝土设计强度的75%时进行张拉;当梁侧加腋板底张拉节点为三边或四边张拉时,在混凝土凝结硬化达到混凝土设计强度的85%时进行张拉;整体技术方案较常规技术可节省45%左右的吊装工期,节点抗震效果更好,成本降低20%左右,有效简化了施工工艺,整体装配建造新技术符合“绿色建造”规范要求。

高速铁路大跨度低高度预应力混凝土连续梁设计研究

为降低铁路大跨度预应力混凝土连续梁高度,扩大其适用范围,提出主跨100 m低高度连续梁合理跨度配比及构造尺寸,计算结果均满足规范要求。通过与常用高速铁路主跨100 m连续梁对比分析,系统研究了跨度配合比、构造参数等对结构的影响,总结出大跨度低高度连续梁的优缺点及构造建议值。研究结果表明:(1)低高度连续梁在同等跨度下混凝土用量更省,每延米混凝土用量降低约20%,较传统连续梁更经济;(2)低高度连续梁由于梁高降低,主梁刚度略有降低,但工后徐变上拱值降低明显,减幅约60%;(3)对于主跨100 m低高度连续梁,建议配跨长度在70~80 m之间,且不宜小于60 m;(4)主跨100 m低高度连续梁墩顶梁高不宜小于6 m,建议取值范围6.0~6.5 m,跨中梁高不宜小于3.0 m,建议取值范围3.0~3.5 m。

预应力混凝土连续梁桥悬臂施工与监控技术

随着桥梁建设工程的迅速发展,预应力混凝土连续桥梁凭借其优势获得快速发展。在预应力混凝土连续桥梁建设过程中,必须进行施工监控以实现工程设计目标。因此,研究以衡阳市耒水特大桥工程为背景,对该工程的施工与监控技术进行相应的研究。研究考虑到桥梁结构等影响因素,计算其立模标高,并与实测值进行对比。研究采用midas土木工程分析软件,对预应力混凝土连续桥梁进行建模、分析与处理。结果表明,测点标高的理论值与实测值保持基本一致,施工质量高,测量和控制方法有效。在3Y测点出现最大差值,高差为0.005 m,理论高度为14.021 m,实际测得的高度为14.016 m。桥梁右幅8号块混凝土浇筑前最大弯矩与挠度数值分别为1.261×10^(11) N·m和2.868 mm;混凝土浇筑后最大弯矩与挠度数值分别为1.672×10^(11) N·m和1.411 mm。浇筑混凝土后,桥梁的刚度增加,变形减小。研究能够较为准确监控桥梁施工中各项数据,及时纠正施工过程中的偏差,确保桥梁施工质量。

预应力混凝土桥梁挂篮施工安全技术应用研究

以某高速公路特大桥预应力混凝土箱梁挂篮施工为背景,对连续箱梁挂篮施工流程进行了分析;在合理采用挂篮施工工艺基础上,提出了挂篮行走的安全保证措施和专门的挂篮防倾覆措施,并对挂篮施工高空作业和已完梁段邻边做了安全设置,确保了预应力混凝土连续箱梁挂篮施工质量和安全稳定性。

现浇预应力混凝土连续箱梁施工技术研究

研究了现浇预应力混凝土连续箱梁施工技术,指出了在模板搭设方面,通过合理的模板搭设能够确保工程的顺利进行;在预应力筋布设阶段,科学合理地安排预应力筋的布设对于工程的质量至关重要;在混凝土浇筑阶段,遵循严格的浇筑工艺,可以保障混凝土的质量;对于预应力杆的处理与调整,精准的处理和调整可以保证预应力结构的稳定和安全。论文还针对混凝土的养护以及安全与质量管理进行了详细分析,并提出了一系列可行的技术方案。

大跨径单箱双室连续梁桥0号块空间受力分析

以佛山南沙涌特大桥为工程实例,对施工阶段过程中不利工况以及长期运营阶段中的墩顶最不利弯矩和剪力组合应力状况进行分析,得出单箱双室0号块在三向预应力情况下的应力结果和分布规律。结果表明最大单悬臂施工阶段、成桥阶段无活载以及成桥后长期荷载作用下,支座附近、顶底板与腹板连接处、横隔板与顶板连接处产生较大的拉应力,且单箱双室的顶板的倒角汇合区域产生了集中拉应力。建议在单箱双室的设计中适当加厚顶板,施工中注意顶板压浆密实性。