Computer-Aided Design of Prestressed Concrete Cellular Bridge Decks

Abstract: This paper illustrates the application of an effective optimization procedure for the design of prestressed concrete cellular bridge decks consisting of single- and two-cell box girders or voided slab systems. An approximate live load moment analysis using the finite-strip method and finite-difference techniques that determines moment sensitivities to changes in the deck depth and flange thickness is proposed for box girder decks. The optimization process is much simplified by eliminating the need of finite-strip reanalysis at each iteration. The optimal design is formulated as a nonlinear programming problem and solved by the projected lagrangian method. The resulting solutions may be used as preliminary designs for short- and medium-span highway bridges, for which cellular decks represent competitive solutions. Optimization results show that voided slab decks are more economical than box girder decks for the short span range and wide decks, and single-cell box girders are a cost-effective alternative for medium span range and narrow decks.     

波形或桁架式钢腹板的预应力钢混组合桥主梁的安全性能和使用性能评估

在许多国家,预应力混凝土箱梁被认为是中等跨径(30～50m)混凝土梁最有效的结构形式。但是当混凝土梁的单跨长度超过50m时,相对钢梁,混凝土箱梁自重问题成为其最大约束。因此,在韩国,中等跨径桥梁主要采用钢箱梁。在20世纪,研究者们多次尝试提高预应力混凝土箱梁结构的有效性,最终采用混凝土-钢混合梁以减轻结构自重。但是,混合桥采用不同类型钢腹板及不同连接形式,会引起结构安全性能和使用性能的变化。为了全面了解钢腹板梁及钢腹板连接形式的性能,对5根带腹板的预应力混凝土梁进行静力荷载试验。这5根试件中,有2根混合梁采用波形钢腹板,而另3根采用桁架式钢腹板。结果显示:通过加强钢腹板与预应力筋的连接节点,可以改善使用性能相关问题(开裂荷载和挠度)及安全性能相关问题(刚度和极限承载力)。     

预应力混凝土斜交连续箱梁的非线性分析

基于CB壳单元,采用层状模型模拟预应力混凝土结构,考虑材料和几何双重非线性效应,有效地模拟了三跨连续斜交箱梁的开裂、屈服和失效的全过程。结果表明,CB壳单元模型对于预应力混凝土箱梁的非线性分析有良好的适应性,对箱梁开裂后的使用性能评估有实际应用价值。基于非线性计算分析了箱梁在开裂后的刚度及裂缝的位置和发展情况,探讨了混凝土和预应力钢筋在斜交箱梁开裂后的应力发展规律,得出了若干有益的结论。     

公路悬索桥正交异性板钢箱梁桥面局部应力简化计算方法初步研究

选取公路悬索桥正交异性板钢箱梁典型结构,根据顶板厚度、主梁高度、横隔板间距以及吊杆纵向间距内横隔板节间数等4个参数对结构进行研究。用有限元法试算确定最不利荷载位置后,分别对各结构的节段模型进行加载计算,研究钢箱梁桥面的顶板纵向最大拉应力与最大压应力、顶板横向最大拉应力与最大压应力、纵肋纵向最大拉应力与最大压应力,并由计算结果推导出公路悬索桥正交异性板钢箱梁桥面局部应力简化计算公式,初步验证该公式具有一定的计算精度与简便性。     

小跨高比混凝土简支箱梁静力性能试验研究

山地城市排水干管埋地箱涵由于滑坡导致地基塌陷而成为简支箱涵,支承方式的改变导致管道结构存在破坏风险.为此,文章对简支下小跨高比埋地箱梁进行了模型静力加载试验,分析了小跨高比埋地箱涵在简支条件下的破坏形式、抗剪性能以及剪力滞效应,讨论了现行有关设计规范对于箱涵抗剪承载力计算之不足.研究表明,竖向均布荷载作用下,小跨高比箱...     

预应力活性粉末混凝土箱梁抗弯性能试验

为研究预应力活性粉末混凝土(RPC)箱梁的正截面受力性能,进行了2片预应力RPC箱梁的抗弯性能试验,研究了RPC箱梁的受力变形特征以及顶板横向预应力对其抗弯性能的影响。结果表明:预应力RPC箱梁具有良好的变形能力,其极限变形可超过跨径的1/50;RPC箱梁正常使用阶段的裂缝宽度和短期刚度可参照《纤维混凝土结构技术规程》（CECS 38:2004）的相应公式计算,其中的钢纤维影响系数可分别取为0.4和0.2;RPC箱梁顶板内的横向预应力对截面抗弯承载力的影响较小,但会使受压区混凝土的应变分布更加均匀,从而减弱箱梁顶板受压的剪力滞效应并增加构件的延性;试验中对顶板内施加2.95 MPa的横向预压应力（仅为RPC棱柱体抗压强度94 MPa的3.1%）后,可使箱梁受压翼缘的有效分布宽度增加约10%,构件延性指标增加约3%。试验结果验证了提出的预应力RPC箱梁正截面抗裂和抗弯承载力的计算公式。     

Bending strength of concrete-filled narrow-width steel box girder

A new type of partially concrete filled steel box girder is proposed. The distance between the two webs is narrower than that of a conventional steel box girder, and concrete is filled inside the box girder at the intermediate supports of the continuous girder. Static bending loading tests were conducted with these new type girders, showing that the ultimate bending strength of the concrete filled steel box girder model was 40% larger than that of the steel box girder model. The ductility also increased about 8 times. The tests with the half concrete filled steel box girder model showed that the ultimate bending strength was 25% larger than the steel box girder model and the ductility was about 6.5 times larger. The half concrete filled steel box girder model without vertical stiffeners had the same ultimate bending strength of that of the girder with vertical stiffeners but the ductility was about half. The simple calculation method was developed using fibre models. The calculated results agreed with the test results and the calculation method has been verified.     

Experimental investigation on inelastic behavior of composite box girder under negative moment

The mechanical behavior of negative bending moment zone in composite girder is very complex. The nonlinear characteristics due to the cracking of concrete slab need careful studies. In this experimental research, two specimens of steel-concrete composite box girder with inclined webs under hogging moment were cautiously conducted and tested. The relative slips between the steel and concrete, load-displacement relationship, the strain distribution of the steel girder, the reinforcements and the concrete slab, and the cracking behavior of the concrete slab were measured during the tests. The relatively small slips on the surfaces between the concrete slab and the top flange of the steel girder showed the full shear connection composite behavior of the girders. The initial cracking load was compared with the calculation results from linear analysis and nonlinear analysis based maximum strain. The strain of the steel web measured at different positions along the vertical direction showed the establishment of plane section assumption and the variation of neutral axis in the loading process. Moreover, shear lag effect was found in the strain distribution of the bottom flanges. The strain of concrete slab and the crack spacing showed the effect of the longitudinal reinforcement ratio on the cracking behavior of the concrete. The maximum crack width was observed in the loading process and compared with the calculation results according the design codes. The influence of reinforcement ratio on the strain of reinforcement and on the load capacity in serviceability limit state was studied in the context and it was found that the reinforcement ratio play an important role on the crack control of composite girder under hogging moment.     

Investigation on the Collapse Behavior of Diagonal Stiffened Composite Plate Girders Subjected to Shear Loading

In this study, a new analytical method is presented to estimate the shear capacity of diagonally stiffened steel–concrete composite plate girders. This method is formulated based on tension field action in steel girder web and failure mechanism of concrete slab deck. To validate the accuracy of the proposed method, the obtained results are compared with three-dimensional finite element analysis of composite plate girders with different configuration of stiffeners. The results of analytical and numerical investigations indicate that the proposed method can accurately estimate the ultimate shear capacity of composite plate girders. In addition, it is shown that the diagonal stiffeners on one hand can reduce the buckling effects of shear panel of girders and on the other hand can increase the strength of elastic shear buckling and ultimate shear capacity of girders well in comparison with the unstiffened thin steel plate girders.     

混凝土连续箱梁长期受力性能试验研究

目前混凝土连续箱梁普遍存在开裂等病害现象,研究表明混凝土连续箱梁设计理论的不完善是引起结构开裂的重要原因之一.对钢筋混凝土连续箱梁模型均布荷载作用下的长期受力性能进行1006 d的试验观测表明:受拉钢筋的应变增长相对较小,受压钢筋和受压混凝土的应变增长相对较大,且跨中截面的压应变增长较中间支座截面显著,中间支座截面受压翼缘有效分布宽度系数较跨中截面增加更显著.对试验模型持荷1006 d的内力重分布规律进行试验观测,与理论预测结果吻合较好.对现行设计规范进行参数修正后能较好地预测连续箱梁各控制截面的裂缝宽度,跨中长期挠曲变形实测值较理论计算值偏大约11.4%.     

Effect of secondary elements on bridge structural system reliability considering moment capacity

Secondary elements such as barriers, sidewalks, and diaphragms may increase the load carrying capacity of girder bridges. This in turn affects reliability. The objective of this study is to evaluate the potential benefit of secondary elements on the system reliability of girder bridges, if these elements are designed with the structural system to participate resisting vehicular live loads. Simple span, two lane structures are considered, with composite steel girders supporting a reinforced concrete deck. For structural analysis, a finite element procedure is developed that combines a grillage model of the bridge deck with solid elements for edge-stiffening effects. Random variables considered are composite girder, barrier, and sidewalk flexural strengths (each in turn composed of many random variables), load magnitude (dead load and truck traffic live load), and live load position. System resistance parameters are estimated with a point integration method. System resistance is evaluated in terms of maximum load carried at ultimate capacity. It was found that the interaction of typical secondary element combinations has a varying effect on system reliability, depending on element stiffness, bridge span, and girder spacing.     

九江长江大桥钢箱梁制作创新工艺设计及应用

本桥设计为双塔双索面斜拉桥,主桥结构为六跨不对称混合梁,其中钢梁为单箱三室结构的扁平钢箱梁。结合主桥钢箱梁的结构特点,进行了26项重点工艺方案设计,有多项工艺进行了创新设计,本文列举几项,例如梁段间预留间隙设置尺寸的加大,保证了梁段端口焊缝的焊接质量;对横隔板上、下接板的对中及变形控制采用一些列的工艺措施,保证了横隔板与顶板、横隔板上下接板间的焊接质量及尺寸精度;对桥面衔接构造无过焊孔的工艺处理进行改进,并提出组焊顺序,提高了钢箱梁的使用寿命。     

钢箱梁正交异性板受力性能分析

针对钢箱梁正交异性板结构,建立有限元模型,并进行计算分析和实测对比。结果表明,相对于传统解析法,有限元法能较好地模拟钢箱梁正交异性板的实际受力状态;在钢箱梁正交异性板局部加载中,横向最不利荷载位置为加载在U肋之上,且轮位中心处应力值最大;纵向最不利荷载位置为横隔板中间处,最大应力值在中间轮外侧;钢箱梁正交异性板整体刚度较大,横向车辆增加时对应的应力增加并不明显。     

ANSYS软件在无粘结预应力混凝土箱型梁承载力分析中的应用

为了对工程中存在的无粘结预应力混凝土箱型梁的承载力做出正确评价，提出了无粘结预应力混凝土箱型梁的非线性有限元计算模型，利用非线性有限元软件ANSYS对2个工程实例梁的承载性能分别进行了分析，并将计算结果与现场静载试验的结果进行对比，两者吻合较好，可供设计参考。     

Response of a continuous, skewed, steel bridge during deck placement

An investigation was conducted to study environmental, material and deck placement effects on the behavior of a continuous, skewed, High Performance Steel (HPS), integral abutment bridge during construction using field data and three-dimensional finite element models. The finite element models were calibrated against girder strain measurements recorded during deck placement. During calibration, the effects of temperature changes during deck placement were clearly evident and were shown to have a significant effect on the accuracy of the finite element results. Effects from hardening of the concrete deck as the pour progressed were shown to be less evident. A calibrated model was used to compare stress variations and deflections of the two outer girders when concrete was placed (1) perpendicular to the girders and (2) parallel to the skew. The influence of various parameters on numerical model results was postulated and a deck placement method was recommended.     

Ultimate load behaviour of webs in steel–concrete composite plate girders

The paper is concerned with the tension field action in webs of steel–concrete composite plate girders. A three-dimensional finite element model has been used to carry out nonlinear analyses on composite plate girders. The results obtained from the finite element analyses are compared with those from experiments. It is observed from the comparative study that the proposed nonlinear finite element model is capable of predicting the ultimate load behaviour of steel–concrete composite plate girders to an acceptable accuracy. Results are presented to explain the development of the tension field action in the webs and to illustrate a measure of the contribution by the concrete slab acting compositely with the girder to the changes in tension field compared to a plain steel girder.     

采用斜撑加固钢吊车梁的设计分析与现场动测试验研究

本文结合太钢(集团)有限公司第二炼钢厂主厂房由于生产工艺改造要求,加大多台重型吊车吨位后,对钢吊车梁系统进行检测鉴定与加固设计的实际工程,介绍了一种在不停产情况下采用钢斜撑方案加固在用钢吊车梁的方案设计与可行性分析;并结合对已经加固施工并投产使用的三榀钢吊车梁的现场实际动测结果,按考虑下部钢斜撑与钢吊车梁二者协同工作的原理对钢吊车梁与下部斜撑之间的荷载分配比例以及加固后钢吊车梁的承载能力进行了进一步的计算验证和对比分析,论证了采用钢斜撑方案加固已有钢吊车梁的可行性。计算分析及试验研究结果表明,采用钢斜撑加固钢吊车梁以满足吊车吨位增加要求的方案设计是经济合理、切实可行的。本文提出的按协同工作方法对钢吊车梁采用钢斜撑方案进行加固的设计与计算方法可行,可以在今后的工业厂房吊车梁系统改造工程中推广应用。     

Reliability-based condition assessment of deteriorating concrete bridges considering load redistribution

A wide variety of models have been proposed for estimating the reliability of highway bridges. For reinforced concrete bridges subjected to environmental attack, time-variant reliability methods have to be used. In this study, the condition of reinforced concrete girder bridges is assessed using a time-variant system reliability approach in which both load and resistance are time-variant quantities. Several system models are considered, including failure of any girder (series system) and failure of a specified number of adjacent girders (series-parallel system). Adaptive importance sampling is used to determine the cumulative-time system failure probability. An existing reinforced concrete T-beam bridge located near Pueblo, Colorado, is investigated. The influence of resistance degradation and post-failure load redistribution is included. A comparison of reliability estimates for several system models is given, including the influence of correlation among initial girder strengths. The results can be used as a guide for the selection of system models for bridge reliability analysis, identification of critical girders in a bridge system, and for the development of optimal reliability-based maintenance strategies for reinforced concrete highway bridges.     

钢箱—混凝土组合梁正截面承载力的初步研究

基于方钢管混凝构件和箱形梁的特性 ,提出了钢箱—混凝土组合截面梁 ,并给出了正截面极限承载力计算方法 ,根据使用条件 ,提出了可能的截面形式。完成了一根梁的初步试验研究 ,并与某特大桥的主梁进行了综合比较 ,综合分析表明钢箱—混凝土组合截面梁具有良好的应用前景。     

城轨钢箱梁U肋正交异性钢桥面板疲劳应力的 正交化计算方法

针对城轨钢箱梁正交异性桥面板关键构造疲劳应力问题,基于有限元方法提出正交化计算方法。首先计算典型正交异性钢桥面构造疲劳应力在城轨A型车和B型车作用下的纵向影响范围及最不利加载位置,并分析减振垫、吊点横隔板、轨下纵梁和道床板等参数的影响。然后根据大量工程实桥设计参数统计提出轨道交通桥梁正交异性板钢箱梁基准计算模型,并建立基准计算模型的空间有限元模型,通过数值计算得到顶板厚度、横隔板高度、横隔板间距、轨下纵梁高度及2种常见开孔形式等关键设计参数的影响系数,基于正交化方法提出不同设计参数条件下正交异性桥面板结构细节的疲劳应力计算公式。最后通过算例验证了正交化计算方法的可靠性和适用性。结果表明:城轨A型车在疲劳荷载作用下结构受力最不利; 轨下纵梁刚度对疲劳应力有显著影响。