结构性能退化的评估和贝叶斯动态预测

结构性能的退化影响因素复杂、时间跨度长、不确定性大,其预测不可避免地要考虑具体结构的实际情况,即在一般规律认识的基础上,不断利用在具体结构生命周期中得到的新信息,更新对结构未来性能退化的预测,进而得到更确切合理的可靠度分析和决策。基于这一思路,引入贝叶斯动态模型理论,设计模型结构,用于结构性能退化的预测。同时,根据结构性能退化的多阶段特点和目前工程实践可获取的结构检测信息的实际情况,提出状态指标的概念,用于描述结构性能退化。计算实例验证贝叶斯动态预测的优越性及信息更新对结构性能退化预测和寿命评估的影响,同时说明状态指标具有简便实用的特点。     

锈蚀钢筋混凝土梁的结构性能退化模型

通过对锈蚀钢筋混凝土梁的试验,研究了结构性能退化机理.根据退化机理分析,锈蚀钢筋的力学性能退化以及锈蚀钢筋与混凝土粘结性能退化是导致钢筋混凝土锈蚀梁的结构性能退化的主要因素.通过锈蚀钢筋力学性能及其与混凝土的粘结性能的试验研究,建立了锈蚀钢筋的应力-应变关系和锈蚀钢筋与混凝土的粘结应力-滑移关系的退化模型.在基本力学性能研究基础上,建立锈蚀梁有限元模型,实现了锈蚀梁的有限元分析.     

结构性能退化的评估和贝叶斯动态预测

 结构性能的退化影响因素复杂、时间跨度长、不确定性大，其预测不可避免地要考虑具体结构的实际情况，即在一般规律认识的基础上，不断利用在具体结构生命周期中得到的新信息，更新对结构未来性能退化的预测，进而得到更确切合理的可靠度分析和决策。基于这一思路，引入贝叶斯动态模型理论，设计模型结构，用于结构性能退化的预测。同时，根据结构性能退化的多阶段特点和目前工程实践可获取的结构检测信息的实际情况，提出状态指标的概念，用于描述结构性能退化。计算实例验证贝叶斯动态预测的优越性及信息更新对结构性能退化预测和寿命评估的影响，同时说明状态指标具有简便实用的特点。     

锈蚀钢筋混凝土梁的结构性能退化

本文对锈蚀钢筋混凝土简支架进行了试验研究，其试验结果表明梁的承载能力和延性有明显退化现象，其破坏形态向脆性破坏转化。利用钢筋混凝土结构有限元方法和钢筋与粘结性能的退化数学模型，对不同锈蚀量的钢筋混凝土梁进行了分析，并对锈蚀钢筋混凝土梁的结构性能退化机理进行了研究。     

氯离子侵蚀盾构隧道衬砌结构性能退化试验

在近海或海洋环境下,氯离子侵蚀是引起隧道衬砌结构钢筋锈蚀的主要因素.根据电化学方法加快钢筋锈蚀的基本原理,以上海长江隧道工程为研究背景,在室内进行盾构隧道管片结构钢筋加速锈蚀试验,得到了一组不同锈蚀程度的试验构件;对锈蚀后构件的承载力、变形、延性及破坏特征等进行试验测试,得出了氯离子侵蚀下隧道衬砌结构性能的退化规律.试验结果对隧道衬砌结构服务寿命预测和耐久性设计具有重要参考价值.     

混凝土构件结构性能检验要点

介绍了混凝土构件试验准备工作,根据试验构件的要求,从支承装置、荷载、变形量测等方面,介绍了混凝土构件结构性能试验中的注意事项,以确保试验结果的准确性。     

超高层钢结构中的施工偏差对结构性能影响分析

超高层钢结构安装过程中的柱身垂偏等施工偏差对结构性能的影响程度是工程中经常遇到的问题.本文结合实际工程,利用SATWE和ETABS两种不同的软件就施工偏差对高层钢结构结构性能的影响进行了深入的分析和总结,为类似工程问题的解决提供思路和参考.     

轻骨料混凝土桥跨车辆运营时的结构性能

通过对轻骨料混凝土双孔空心板梁桥跨结构进行静、动载试验,验证整桥结构在车辆运营时的工作性能,判定其承载能力和刚度是否满足设计和规范要求,并与普通混凝土预应力空心板梁桥跨结构比较。     

基于修正邓肯-张模型的低胶结砂石坝结构性能研究

借助Abaqus有限元软件,研发低胶结砂石料应变预测模型的Umat子程序,进行竣工期与蓄水期低胶结砂石坝结构工作性态分析,研究结果表明,基于该新模型得出的低胶结砂石坝应力变形分布规律与其他学者得出的相应规律基本相同。研究成果可为低胶结砂石坝这一新坝型的结构设计提供一种新方法。     

预制钢筋混凝土楼梯水平放置结构性能检验分析

文章通过对预制钢筋混凝土楼梯的实际受力分析,依据国家相关规范提出一套便捷的水平放置加载方案,并对1块预制楼梯进行加载试验,通过与常规倾斜放置试验结果对比,分析该加载方案可行性及预制楼梯的安全可靠性。     

装配式小箱梁荷载横向分布分析

以25m跨径的小箱梁为例,分别采用横向分布系数实用算法和空间梁格法进行了荷载横向分布的分析比较,得到荷载作用位置和连续梁对横向分布系数的影响,从而为装配式小箱梁的设计积累一些经验。     

小半径曲线梁桥地震响应分析

以某高速公路立交匝道桥梁为例,建立曲线梁桥的空间梁单元有限元模型,研究地震动输入、结构动力特性、地震动输入方向及组合方法,分析结果表明,曲线梁桥结构复杂,相对直线桥,其振型参与质量分布离散,桥墩内力对地震输入方向比较敏感,宜采用多个方向进行地震动输入,并对结果进行组合。     

Simplified site-specific traffic load models for bridge assessment

Traffic load is identified as one of the greatest sources of uncertainty in the assessment of bridges. In recent years, simulation techniques, using measured traffic data, have been used to predict the characteristic traffic load effects on bridges. However, the techniques are complex, sensitive to the assumptions adopted and require specialist statistical expertise. This work presents a simplified site-specific traffic load model that generates comparable load effects to the corresponding results from a full simulation. While the simplified model is still sensitive to the underlying assumptions, these can be carefully reviewed prior to the method being approved. Further, the simplified method can be employed by practising engineers for bridge assessment.     

装配式小箱梁桥的荷载横向分布计算

以某一装配式小箱梁桥为例,利用刚性横梁法、刚接梁法分别对其进行荷载横向分布计算,并给出计算过程,同时根据梁格理论建立空间有限元模型进行验算,通过比较分析空间与平面分析结果吻合较好。     

Bridge performance indicators based on traffic load monitoring

The assessment of the existing road bridges as a part of bridge management networks has been a subject of several European research projects and actions in the last few decades. Bridge management includes a series of activities, interconnected in order to achieve optimal balancing of required costs, potential risks and overall bridge performance. This paper discusses a valuable link between a specific indicator (traffic load information calculated using Bridge Weigh-in-Motion measurement data) and the corresponding structural performance (reliability of existing bridge). It is shown that implementation of weigh-in-motion measurements in the probabilistic assessment of existing road bridges can reveal hidden bridge reserves and predict bridge reliability development over the required lifetime. Consequently, such approach can yield an unrestricted use of the bridge over a much longer remaining service life. Broader advantages lie in an improved road network management, road bridges in particular, and in a more sustainable development of infrastructure network and greater satisfaction of road users and owners.     

A comprehensive traffic load model for bridge safety checking

In this paper a new model for the global analysis of traffic actions on roadway bridges will be presented. It has been developed in the frame of Crespo-Minguillón, C., Reliability based methodology for the definition of the limit state of decompression in prestressed concrete bridges. Ph.D. thesis, Department of Civil Engineering, Technical University of Catalunya, Barcelona, 1996. In order to make it feasible for use in the verification of most important limit states, the model includes an algorithm for the simulation of a continuous flow of traffic and another for the extrapolation of maximum results in short periods to long return periods. The model for traffic flow simulation includes a statistical treatment of most significant variables involved, and some original techniques to account for the most important correlations found in actual traffic. At the end, an example of application is shown.     

基于静荷载试验的预应力混凝土连续梁桥承载力分析

桥梁在使用过程中,不可避免受雨雪、地震、冰冻等自然因素的影响、人为因素的冲击破坏以及在有害物质的侵蚀下产生的混凝土碳化、钢筋锈蚀等病害,随着时间的增长,这类病害将进一步发展,甚至危及桥梁的结构使用安全。为探究桥梁服役一定年限后的承载能力,以两联六孔预应力混凝土连续梁为工程实例,通过桥梁荷载试验,对其承载力展开分析和研究,掌握桥梁结构实际工作状态了解,评定桥梁结构的工作性能和状态,确保后续加固和维修方案切实可行、有据可依。     

C50高性能混凝土在箱梁施工中的应用

从主要原材料选取与配合比设计两方面介绍了高性能混凝土制备的要点,并结合工程实例,阐述了C50高性能混凝土在箱梁施工中的技术要求,指出高性能混凝土减少了水泥用量,降低了生产成本,非常适合钢筋密集位置混凝土的施工。     

变截面波形钢腹板组合箱梁桥荷载试验分析

以南水北调大桥工程为例,通过建立该桥的结构有限元计算模型,对该桥荷载试验数据进行了分析,结果表明:该桥强度、刚度和动力特性满足规范要求,设计、施工安全可靠,相关数据可为同类桥梁的建设提供参考。     

A numerical investigation on the fire response of a steel girder bridge

The response of bridges subject to fire is an under researched topic despite the number of bridge failures caused by fire. Since available data shows that steel girder bridges are especially vulnerable to fire, this paper delves into their fire response by analyzing with a 3D numerical model the response of a typical bridge of 12.20 m span length. A parametric study is performed considering: (1) two possibilities for the axial restraint of the bridge deck, (2) four types of structural steel for the girders (carbon steel and stainless steel grades 1.4301, 1.4401, and 1.4462), (3) three different constitutive models for carbon steel, (4) four live loads, and (5) two alternative fire loads (the hydrocarbon fire defined by Eurocode 1 and a fire corresponding to a real fire event). Results show that restraint to deck expansion coming from an adjacent span or abutment should be considered in the numerical model. In addition, times to collapse are very small when the bridge girders are built with carbon steel (between 8.5 and 18 min) but they can almost double if stainless steel is used for the girders. Therefore, stainless steel is a material to consider for steel girder bridges in a high fire risk situation, especially if the bridge is located in a corrosive environment and its aesthetics deserves special attention. The methodology developed in this paper and the results obtained are useful for researchers and practitioners interested in developing and applying a performance-based approach for the design of bridges against fire.