Bridge design with reserve and residual reliability constraints

System reliability is evolving as an important design method for selecting components and topology. It should be used to investigate the original intact structure behavior as well as providing sufficient reserve capacity under likely accident and damage scenarios. Highway bridges are an area of special concern since effort to optimize the cost of construction may not provide adequate redundant capacity. The paper describes an example in which a typical girder bridge structure is optimized (both size and girder spacing) to achieve target system performance. System reliability constraints are imposed on the behavior of the intact structure under highway loads. Also, residual system reliability constraints are imposed to control safety under specified accident scenarios corresponding to damage and “lost” members due to corrosion, fatigue, fire or accidental collisions. An optimal design framework for controlling safety under all these life cycle situations is thus provided.     

混凝土桥及其高性能材料2020年度研究进展

为了解2020年混凝土桥及其高性能材料研究方向的发展动态,并在总结其研究内容、方法和成果的基础上更好地开展后续研究,从混凝土桥、高性能混凝土材料及高性能加劲筋材3方面着手,查阅近期文献,并进行分类、总结和评述。研究发现：目前,混凝土桥方向较为关注运维阶段的耐久性能、极端环境下的工作性能及混凝土桥运营事故等问题;高性能混凝土材料的研究进展在高性能、绿色环保以及智能化3个方面表现突出;高性能筋材则主要围绕强度更高、更耐久的FRP筋展开研究,其在梁、板、柱等构件上的应用得到积极的探索。对现有研究的不足和有待深化的问题提出初步建议,期待与相关学者共同努力,为该方向的进一步发展做出贡献。     

公路桥梁抗震设计细则分析

《公路桥梁抗震设计细则》(JTG/T B02-01—2008)已于2008年10月1日开始正式实施。本文分别从桥梁抗震设防标准、桥梁延性抗震设计和能力保护设计、桥梁减隔震设计等几个主要方面将之与原《公路工程抗震设计规范》(JTJ 004-89)进行比较,得出两者之间的不同之处,以利于对新规范的理解和掌握。     

转体施工法连续刚构桥设计

转体法施工以其投入施工设备少、适用范围广、操作简单安全、施工速度快、造价低等优点成为较优的施工方法.上海市松江工业区文翔路-联阳路跨沪杭高速公路大桥主桥采用42 m+70 m+42 m转体施工连续刚构方案,减少了对既有线运营的影响.介绍桥型构思及总体布置,上部结构设计、转盘、承台、墩身、桩基础设计、结构分析方法、主桥施工方法.经计算,在各种荷载的不利组合下,结构处于良好的受力状态,满足规范设计要求.     

Field measurement on wind characteristic and buffeting response of the Runyang Suspension Bridge during typhoon Matsa

Field measurement on wind characteristic and buffeting response of existing bridge is of great value to the development of bridge wind engineering, and the structural health monitoring system (SHMS) employed in many long-span bridges provide a research basis for the field measurement. In order to provide reliable basis for wind resistant evaluation of Runyang Suspension Bridge (RSB), two anemometers and 85 accelerometers were installed in the SHMS of RSB. In August 2005, Typhoon Matsa crossed over Jiangsu, the SHMS timely recorded the typhoon and structural vibration responses. In this paper by using the time-frequency technique and statistical theory, the recorded data were analyzed to obtain the strong wind characteristics, the buffeting response characteristics of the cable and deck, and the variation of buffeting response RMS versus wind speed. Results obtained in this study can be employed to validate the credibility of current buffeting response analysis theory techniques, and provide reference values for wind resistant evaluation of other long-span bridges. Supported by the National Hi-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA04Z416), the Key Project of the National Natural Science Foundation of China (Grant No. 50538020) and the Outstanding Youth Fund of the National Natural Science Foundation of China (Grant No. 50725828)     

高速铁路长大桥梁救援定点的选址决策模型

为提高高速铁路的防灾能力,确保救援定点布局经济合理,采用约束最优化法进行长大桥梁救援定点的选址决策.研究分析救援定点选址决策的3个约束条件:设置间距、风险等级和救援时程.以各地方救援部门至救援定点的时程总和最小为目标,建立长大桥梁救援定点的选址决策模型,并对模型进行实例验证.结果表明:当区间桥梁长度大于10 km时,应该沿线路方向每隔约6~10 km设置一处救援定点;应用贝叶斯网络理论评价救援定点备选位置的风险等级和采用Dijkstra算法求解地方救援部门至救援定点之间的最优时程是合理有效的.该模型计算过程简单,评价结果可靠,能够较好地解决长大桥梁救援定点的选址决策问题.     

近距多座并行桥梁墩前壅水研究

为了研究近距多座并行桥梁的壅水规律,在分析了单座桥梁的壅水规律后,类比应用到两座并行桥梁壅水的研究中且得到相应的规律,然后基于这些成果可达到研究目的。研究结果表明,如果被动影响桥梁位于主动影响桥梁的下游,则主动影响桥梁的壅水除了受自身阻水影响外,还要附加上被动影响桥梁的壅水对其带来的正影响作用;反之,则会受到被动影响桥梁的壅水对其带来的负影响,且影响系数都会随着两桥的桥间距增大而减小。假设并行桥梁的壅水仅仅两两影响时会形成修正壅水,且该修正壅水对其它桥梁产生重复的二次影响后会无限接近真实壅水。在这个前提下,总结出多桥并行时各桥壅水的经验公式。     

公路减隔震桥梁的地震反应简化分析

采用单自由度反应谱方法对满足一定条件的减隔震桥梁进行地震反应分析可以简化计算过程,但需要解决精度问题。针对规范反应谱阻尼修正方法对计算精度的影响进行了分析并提出了改进方法。为了验证改进方法的合理性,对一座常规减隔震桥梁分别采用不同计算方法进行了比较分析,结果表明采用改进的阻尼修正公式后,简化反应谱方法的计算精度得到很大提高,且结果偏于安全。     

Evaluation and testing of a fracture critical bridge

The I-40 bridges over the Rio Grande in Albuquerque, New Mexico were due to be razed in the fall of 1993 due to geometry and traffic safety considerations, thus providing a unique opportunity for testing them. These medium span steel bridges represent a common design in the US and are classified by AASHTO as non-redundant ‘fracture critical’ two girder steel bridges (fracture critical classification means that failure of a primary member would probably cause collapse of the bridge). The subject bridge, built in 1963, is a 1275 foot (600m) bridge, and consists of three medium span continuous units with spans of 131′-163'−131′ each. The bridge was field tested to determine the impact of a near full depth girder fracture on the redistribution of loads, the load capacity, and the potential for collapse. Four levels of damage were introduced in the middle span of the north plate girder by making various cuts in the web and the flange of the girder. The final cut resulted in a six foot deep crack in the 10ft deep girder, extending from the bottom flange to the floor beam to girder connection. Data was taken under dead load and under a static live load consisting of an 82 000 lb truck. The after fracture response and the load redistribution in the fractured bridge were evaluated. The contribution of the different members to the redundancy of the structure was assessed.     

青海省公路桥涵水文分区方法与指标研究

介绍了青海省公路桥涵水文分区的现状,通过分析河流的水情变化,论证了修正现行水文分区的必要性,并结合青海省河流的特殊性,对比了省内外一些典型的水文区划方法及水文因子。结果表明:①应根据流域水系、内外流区、沙漠面积等定性指标,以原水文分区为一级区划,在其基础上进行修正并确定二级分区;②利用河川径流强度指标法进行分区划分时,分区指标为年平均降水量、岩土类型、河网密度和沟谷比重;③利用模糊聚类法进行分区划分时,分区指标为年平均径流深、年平均降水量、气候带、河流补给形式及单位面积上50 a一遇设计流量,但只有黄河上游区、湟水大通河区可使用该方法;④青海省内沙漠面积较大,在分区时可将其划分为非产流区。