Load Test Analysis and Research on Long-Span Concrete Continuous Rigid Frame Bridge

Based on the as-built load test of a large bridge,this paper introduces the procedure of the prestressed concrete continuous rigid frame bridge load test.Numerical analysis of the bridge was carried out by simulating and establishing a finite element model,and comparative analysis was carried out with the measured values.The results show that the calculated values were basically consistent with the measured values,which showed that the establishment method of the model was reasonable,and the mechanical performance of the bridge met the service requirements of the designed live load.

Fatigue Safety Assessment of Concrete Continuous Rigid Frame Bridge Based on Rain Flow Counting Method and Health Monitoring Data

The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.

Field Load Test Based SHM System Safety Standard Determination for Rigid Frame Bridge

The deteriorated continuous rigid frame bridge is strengthened by external prestressing. Static loading tests wereconducted before and after the bridge rehabilitation to verify the effectiveness of the rehabilitation process. Thestiffness of the repaired bridge is improved, and the maximum deflection of the load test is reduced from 37.9 to27.6 mm. A bridge health monitoring system is installed after the bridge is reinforced. To achieve an easy assessmentof the bridge’s safety status by directly using transferred data, a real-time safety warning system is createdbased on a five-level safety standard. The threshold for each safety level will be determined by theoretical calculationsand the outcomes of static loading tests. The highest risk threshold will be set at the ultimate limit statevalue. The remaining levels, namely middle risk, low risk, and very low risk, will be determined usingreduction coefficients of 0.95, 0.9, and 0.8, respectively.

Effect of concrete creep on pre-camber of continuous rigid-frame bridge

The effect of concrete creep on the pre-camber of a long-span pre-stressed concrete continuous rigid-frame bridge constructed by cantilever casting method was investigated.The difference of creep coefficients calculated with two Chinese codes was discussed.Based on the calculations,the pre-camber of a pre-stressed concrete continuous rigid-frame box bridge was computed for construction control purpose.The results show that the short-term creep coefficient and long-term creep coefficient calculated with the CC-1985 are larger than those calculated with the CC-2004,while the medium-term creep coefficient calculated with the CC-1985 is smaller than that calculated with the CC-2004.The difference of creep deformation calculated with these two codes is small,and the influences of concrete creep on the pre-camber for most of the segments are negligible.The deflections and stresses of the box girder measured during the construction stages agree very well with the predictions.

Analytical Research on Deformation Monitoring of Large Span Continuous Rigid Frame Bridge during Operation

Based on a large span continuous rigid frame bridge in Chongqing of China, the main pier vertical displacement and deviation, the bridge deck alignment and the expansion joint deformation are analytically researched during operation. Firstly, the monitoring content and method of the large span continuous rigid frame bridge are clearly stated. Secondly, by finite element software Midas Civil, the relevant deformation values of the bridge are calculated. Thirdly, in practice, the relevant deformation values of the bridge are measured. Finally, the measured values in practice are compared with the calculated ones by the finite element software Midas Civil, finding that the former is less than the latter, and it can be concluded that the bridge is basically in the normal working condition. In this paper, the analytical research on the deformation monitoring can provide the basis for similar bridges, which has good practical significance.

Stability Analysis of Long-Span Continuous Rigid Frame Bridge with Thin-Wall Pier

During cantilever cast in construction of high-pier and large-span continuous rigid frame bridges, structural stability in the longest cantilevered stage is very important. Based on a practical design case of a large-span continuous rigid frame bridge in Wuhan, the longest span stability coefficient is calculated with linear-buckling and nonlinear-buckling methods, respectively. The influences of both geometrical nonlinearity and the dual nonlinearity of material and geometry are considered. Numerical results indicate that the nonlinear solution is necessary to stability analysis because linear buckling loads are much higher than those of nonlinear buckling. Thus, the edge fiber yield criterion is more convenient and faster than ultimate loading criterion when estimating nonlinear stability of structure, and can be used easily in the initial engineering design.

Seismic analysis of long-span continuous rigid frame bridges in cold regions:a case study of Bridge 1 in north of international tourism resort in Changbai Mountain

It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain international tourism resort as an example,the authors studied it in shutdown phase and the cantilever construction process,established the simulation model by using Midas / civil,and analyzed time-history of each construction stage for the bridge.The study shows that long-span bridge cantilever construction in northeastern China can be divided into two-year tasks for construction(suspending in winter).It is needed to think about seismic stability of the cantilever position in shut-down phase of winter.The effect of longitudinal vibration is the most disadvantageous influence to bridge,and its calculation results can provide reference for seismic design of similar bridges in the future.

Time-varying Reliability Analysis of Long-span Continuous Rigid Frame bridge under Cantilever Construction Stage based on the Monitored Strain Data

In general,the material properties,loads,resistance of the prestressed concrete continuous rigid frame bridge in different construction stages are time-varying.So,it is essential to monitor the internal force state when the bridge is in construction.Among them,how to assess the safety is one of the challenges.As the continuous monitoring over a long-term period can increase the reliability of the assessment,so,based on a large number of monitored strain data collected from the structural health monitoring system(SHMS)during construction,a calculation method of the punctiform time-varying reliability is proposed in this paper to evaluate the stress state of this type bridge in cantilever construction stage by using the basic reliability theory.At the same time,the optimal stress distribution function in the bridge mid-span base plate is determined when the bridge is closed.This method can provide basis and direction for the internal force control of this type bridge in construction process.So,it can reduce the bridge safety and quality accidents in construction stages.

Maintenance Management Research of a Large-span Continuous Rigid Frame Bridge Based on Reliability Assessment by Using Strain Monitored Data

When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very help­ful tool for solving this problem.In this paper,a large number of strain data acquired from the structural health monitoring system(SHMS)installed on a continuous rigid frame bridge are adopted to do reliability assessment.Firstly,a calculation method of punctiform time-dependent reliability is proposed based on the basic reliability theory,and introduced how to cal­culate reliability of the bridge by using the stress data transformed from the strain data.Secondly,combined with“Three Sigma”principle and the basic pressure safety reserve requirement,the critical load effects distribu­tion function of the bridge is defined,and then the maintenance reliability threshold for controlling the unfavorable load state which appears in the early operation stage of this type bridge is suggested,and then the combi­nation of bridge maintenance management and health monitoring system is realized.Finally,the transformed stress distribution certifies that the load effects of concrete bridges practically have a normal distribution;as for the concrete continuous rigid frame bridge with C50 strength grade concrete,the retrofit reliability threshold should be valued at 6.13.The methodology suggested in this article can help bridge engineers do effective maintenance of bridges,which can effectively extend the service life of the bridge and bring better economic and social benefits.

体外预应力加固曲线PC连续刚构桥受力性能分析

越来越多的桥梁随着使用年限的增长出现跨中下挠和裂缝等病害,其中,曲线PC连续刚构桥较为严重,需对其进行加固设计。为了准确反映病害桥梁的现状,本文提出基于Midas/Civil的4种损伤工况模型,根据挠度确定损伤工况并以此作为计算模型分析病害产生的原因。根据体外索下弯的次数提出3种加固方案并建立模型,依据加固思路对加固前后的抗弯承载力、截面上下缘应力以及挠度进行对比分析。结果表明:体外预应力张拉后,桥梁极限承载力、结构刚度以及压应力储备都得到提升,且抑制了主梁下挠,改善结构线形。

PC连续刚构桥长期下挠参数敏感性分析

随着交通强国建设的不断推进,PC连续刚构桥以其出色的跨越能力和耐久性,广泛用于多样化的桥梁建设中。然而,这种桥梁结构在长期使用过程中可能出现的下挠问题,对其稳定性和使用寿命产生了重大影响。基于全桥有限元仿真模型,分别选取了自重、徐变、预应力损失以及刚度折减四个主要参数,对其下挠表现的敏感性展开研究。结果表明:混凝土的超重增幅、初始加载龄期过短、成桥时间、预应力的损失以及刚度的折减均会对桥梁长期下挠产生不利影响,有针对性的采取相应措施可以有效避免长期下挠的持续发展。以便在设计、施工和运营中科学决策,为同类桥梁建设提供理论支持和技术指导。

大跨度波形钢腹板PC连续刚构桥内衬混凝土参数优化设计研究

波形钢腹板组合梁桥因具有“手风琴效应”逐渐成为大跨度桥梁发展的新方向,为研究内衬混凝土参数对波形钢腹板预应力混凝土(Prestressed Concrete,PC)连续刚构桥抗剪性能的影响规律,采用ANSYS软件建立波形钢腹板PC连续刚构桥有限元模型,通过对比实测数据与数值模拟数据验证了该有限元模型的准确性,并分析了内衬混凝土参数对波形钢腹板剪力及承剪比的影响规律,通过研究可知,内衬混凝土长度、厚度、厚度变化率3个参数的适宜取值分别为9.5 m、0.5 m和0.3。相关结论可为大跨度波形钢腹板PC连续刚构桥的设计和施工提供一定参考。

大跨度曲线UHPC连续刚构箱梁桥的设计研究与实践

以上海市松江区外下洋路油墩港桥为研究对象,研究基于UHPC的大跨度曲线连续刚构桥的总体设计和构造设计;结合体内及体外预应力布置方式,研究节段箱梁及下部桥墩的装配化施工方案。分别建立空间梁单元模型和整梁空间实体单元模型进行计算分析,并对计算结果进行对比分析。分析结果表明空间实体单元模型的应力分布与空间梁单元相比趋于均匀,采用空间梁单元模型的计算结果进行分析验证偏于安全,结构受力完全满足要求。该工程首次提出采用钢结构横隔板代替传统混凝土横隔板,钢结构横隔板构造简单,便于节段箱梁的预制施工。从空间实体单元模型计算结果来看,钢横隔板与UHPC横隔板的作用效果基本一致,满足结构整体受力性能的需求。

基于底板束预张拉的大跨PC连续刚构桥新型合龙技术

文中以萍莲高速某预应力混凝土连续刚构特大桥为研究对象,基于等效荷载法,将中跨预应力底板束预张力分解为钢束沿程竖向荷载及锚固点水平力,提出不施加配重,浇筑合龙段混凝土同时预张拉底板束消除湿重下挠效应的合龙技术.采用Midas/Civil建立有限元模型,完全模拟全桥施工阶段,将新型合龙技术与等位移配重法合龙进行对比,分析两种合龙方法成桥后全桥线形与应力差异.结果表明:新型合龙技术在不使用配重的前提下,能有效消除合龙过程中合龙口附近截面扰动,成桥累计变形值最大提升17 mm,底板压应力储备为6.31 MPa,10年收缩徐变后底板压应力为5.32 MPa,与传统方法相比压应力储备未明显减少,满足设计要求.

大跨PC连续刚构桥抗震研究进展综述

我国已建设大量的大跨PC (prestressed concrete)连续刚构桥,其墩高可达百米及以上,存在遭受强震的可能,尤其是在西部高地震风险区,连续刚构桥主墩与主梁是刚性连接,主梁与桥墩共同承担地震力.为促进刚构桥的抗震研究,首先,梳理了国内外近期经受地震考验的几座刚构桥的震害表现;然后,从抗震理论及模型试验、减隔震(耗能)设计和震后修复等方面,对连续刚构桥桥墩、上部结构、基础等主要构件以及全桥整体抗震性能等热点问题进行了评述,刚构桥具有良好的抗震性能,高阶效应及墩梁固结处纵桥向弯矩对桥墩地震反映影响较大,模型试验及理论分析中主梁开裂及损伤问题易被忽视,低墩或双柱墩刚构桥已展开墩底及基础隔震研究;最后,对未来可开展研究方向进行了探讨,强震下箱梁的开裂机理及损伤控制,基于新型材料及耗能构件组成的高墩,基础隔震及高墩底部隔震的实用技术,箱梁及空心墩的地震损伤识别及震后修复,(近)跨断层地震作用下刚构桥的渐进倒塌机理与防止.

预应力损失对大跨宽幅PC连续刚构桥挠度影响研究

近年来随着预应力混凝土技术以及悬臂施工技术的迅速发展,大跨宽幅PC连续刚构桥得到了较快的发展。但是研究分析发现,在时间的流逝中会出现预应力损失的现象,同时发现桥梁的挠度与预应力损失之间的联系密不可分。以重庆首座高速公路、市政道路合建连续刚构桥--龙溪嘉陵江特大桥为研究对象,运用有限元软件建立有限元模型,对钢筋管道摩阻以及混凝土截面的各类预应力钢束损失造成的桥梁下挠问题进行研究,发现钢筋管道的摩擦阻力与桥梁下挠问题之间的联系较小,但钢束预应力损失对桥梁下挠造成的影响较大,在桥梁下挠的问题中应重视此类问题。研究结果对大跨连续刚构桥的挠度控制方面有着积极的意义。

波形钢腹板PC连续刚构桥施工中自动化焊接技术的应用

对波形钢腹板PC连续刚构桥悬臂施工中自动化焊接工艺进行研究,依托具体工程探讨波形钢腹板PC连续刚构桥施工阶段自动化焊接与传统焊接工艺在效率、质量、安全性等方面的比较,并且在恶劣环境条件下调节焊接作业小车相关参数,对关联应用效果进行分析。

大跨宽幅PC连续刚构桥箱梁底板混凝土防崩裂技术研究

大跨宽幅预应力混凝土(PC)连续刚构桥广泛应用于跨越水域、山谷等地形,但随着其应用的普及,该桥型在施工运营过程中箱梁出现裂纹的情况也日益凸显,严重时甚至会发生大面积崩裂,威胁桥梁质量和寿命,底板崩裂就是其中一种病害。龙溪嘉陵江特大桥主桥为三跨(108m+200m+108m)PC连续刚构桥,研究依托该工程,在参考大量文献和现场施工分析的基础上,进行了箱梁底板混凝土崩裂理论研究,并提出了对应的防崩措施,在解决该桥问题的同时给同类工程提供参考借鉴。经研究表明,在采取正确的施工工艺和防崩措施的情况下,可有效避免箱梁底板混凝土出现崩裂。

桥梁预拱度对行车舒适性的影响及桥面线形调整

为研究成桥预拱度对连续刚构桥行车舒适性的影响,以多座主跨跨径为110~200 m的连续刚构桥为研究对象,首先,采用滤波白噪声法建立桥面时域模型,并与按余弦曲线设置的成桥线形叠加模拟成桥后的桥面不平度;其次,采用MATLAB/Simlink搭建车辆-桥面系统模型,以加速度均方根值(RMS)作为桥梁边跨、中跨桥面的行车舒适性评价指标,以最大瞬态振动值(MTVV)作为边跨峰值处短时内的行车舒适性评价指标;最后,分析采取经验法按照余弦曲线设置成桥预拱度的桥梁其跨径和设计时速对边、中跨RMS值的影响,以及成桥预拱度取值对边跨3L/8处MTVV值的影响。研究结果表明:在边跨、中跨处RMS值均小于0.315 m/s^(2),说明采取经验法按照余弦曲线设置成桥预拱度并不影响中跨处的行车舒适性;在边跨3L/8处MTVV值在短时内存在大于0.345 m/s^(2)的情况,说明在边跨峰值处短时内会产生一定不舒适感。提出了一种基于桥面铺装层施工优化边跨3L/8处和边墩墩顶桥面线形的方法,改善了边跨的行车舒适性。

风屏障透风率对强风作用下重载铁路刚构-连续梁车桥耦合振动响应的影响

为探究风屏障透风率对强风作用下重载铁路刚构-连续梁车桥耦合振动的影响,先通过节段模型风洞试验获取桥上设置0%,20%,40%,60%和无风屏障5种不同透风率风屏障时车桥系统的三分力系数,再根据弹性系统动力学总势能不变原理建立风-车-桥耦合振动仿真计算分析模型,对不同车速下重载货运列车通过设置不同透风率风屏障刚构-连续梁桥开展风-车-桥系统动力学仿真计算与分析研究。结果表明:在列车上桥初期,桥梁横向位移峰值随透风率的增大而明显减小,而当列车运行趋于满布桥梁时,桥梁的横向位移峰值随透风率的增大变化不明显;列车的动力响应峰值随风屏障透风率的增大而增大,相比于满载编组列车,空载和轻重混编编组列车的动力响应对风屏障透风率的变化更加敏感。综合桥梁动力响应和列车走行安全性评价指标(脱轨系数和轮重减载率),该桥梁应设置40%透风率的风屏障。