Towards probabilistic seismic performance of vehicle-bridge interaction systems: From stochastic dynamic model to fragility analysis

This paper aims to assess the seismic fragility of vehicle-bridge-interaction (VBI) systems considering the effects of vehicle types, traffic conditions, and road surface qualities. A stochastic nonlinear mechanical model for the earthquake-VBI system is developed, and the fragility functions for the proposed VBI model are derived by considering the relevant probabilistic seismic demand parameters. On the basis of a typical four-span continuous prestressed concrete highway bridge in China, a complete numerical model for the VBI system is built considering multiple uncertainties from bridge and vehicle parameters, as well as the road surface qualities. A total of 120 real ground motion records with different combinations of magnitude-source-to-site distance (M-R) and earthquake intensity characteristics are selected. Meanwhile, 80 scenarios in terms of different combinations of vehicle types, vehicle speeds, and road surface irregularities are defined. In this context, 96,000 nonlinear time-history analyses are performed, and the developed fragility models are applied to the VBI system at both component and system levels. Results indicate that the fragilities of pier drift, bearing shear strain, and the overall VBI system increase with the increase of the vehicle weight or the decrease of the vehicle speed, while the vertical deck displacement is dominated by the vehicle weight. It is also found that the road surface quality has a negligible effect on both component and system fragilities.     

高桩码头锈蚀破损面板残余承载力评估方法

高桩码头长期工作在具有腐蚀介质的潮湿环境中，因钢筋的锈蚀会使构件表面砼胀裂而破损，目前我国大部分的高桩码头进入了锈蚀破损的高峰期。通过研究指出：以往国内外用构件蚀破损表面积大小或顺筋裂缝大小的标准来确定维修方案的方法是不正确的。根据一般构件为等截面，而沿跨度分布的弯矩不均匀的事实，指出构件在控制断面以外的部位强度有富裕，允许钢筋适当的锈蚀仍能满足设计强度的新见解。提出了锈蚀破损面板的强度安全性评估准则、强度因子新概念及其具体计算式，可以量化评估犭蚀破损面板的残余承载力，为科学制定锈蚀破损面板的维修方案提供参考，在保证码头结构安全的同时，大大节省维修费用。     

Dynamic Analysis of a Single-Column Platform

In this paper, a single-column structure used as well-head platform is studied. The loads of wave and current exerted on the single-column will be greatly reduced, therefore the cost of the structure will be decreased. The advantages of the single-column structure compared with ordinary jacket structure are explained. A dynamic analysis of this type of structure is made and some problems related to dynamic analysis are solved. In order to check the reliability of computation theory and programme, model tests have been carried out. However, as space is limited, the conclusion of tests will be introduced in another paper. Therefore, this type of structure is applicable for proctical engineering.     

Developing empirical formulas for assessing the scour of vertical and inclined piers

Abstract

Because scour is one of the main reasons for bridge failure, this study focuses on accurately predicting the maximum scour depth around different vertical and inclined piers. Scouring is an issue of concern in the bridge design process, as most existing equations for predicting local scour near bridge piers suffer from over- or underprediction issues, resulting in higher foundation costs or bridge failure and inaccurate predictions of the scour around piers. The dimensionless maximum scour depths (y_s/D) of vertical and inclined piers were investigated for seven pier shapes with different L/D ratios and four inclination angles (θ) under shallow flow conditions. The inclined pier configuration reduced the y_s/D of the piers. The maximum y_s/D was observed for a rectangular pier with an L/D of 4.5 in both vertical and inclined configurations (θ of 10, 15 and 21°, respectively). The y_s/D was significantly decreased by increasing the angle of the pier from 10 to 30°. The y_s/D of the inclined rectangular piers decreased as θ decreased from 30 to 10° and the L/D ratio increased from 1 to 4.5. The best y_s/D results were obtained for inclined rectangular piers at a θ value of 30° and an L/D ratio of 7.5 compared to other shapes and inclination angles. New equations were developed to predict the local scour depth for circular, square and rectangular bridge piers. The equations yielded excellent results for predicting the maximum clear water scour depth around vertical and inclined piers with inclination angles of 10, 15, 21 and 30°, respectively.     

海岸浮式活动码头架设区域选取的多属性决策模型研究

海岸浮式活动码头架设区域的选取是方案设计与研究的重点.文中分析了影响海岸浮式活动码头架设区域选取的主客观因素,建立架设区域多属性决策模型,运用综合赋权的方法对各评价指标赋权,采用综合评分的方法对各备选方案进行评分和排序.实例分析表明,运用多属性决策模型解决海岸浮式活动码头架设区域选取问题是可行的、有效的.     

免棱镜全站仪和AutoCAD在桥墩围堰定位中的应用

在桥墩围堰定位测量中,考虑到在水面无法架设反光镜,结合工程实例,探讨了将免棱镜全站仪与AutoCAD绘图软件相结合用于桥墩围堰施工测量的方法。首先利用免棱镜全站仪直接测量出桥墩外沿的坐标,然后根据外沿坐标在AutoCAD中定出桥墩中心,再通过作图得到围堰坐标,从而精确确定围堰的位置。实际应用表明,该方法既满足精度要求,又快捷方便,应用效果良好。     

考虑桩土相互作用的变截面高墩自振频率计算分析

针对变截面群桩基础高墩的几何特性,将桥墩与群桩基础简化为空间整体,在考虑桥墩变截面特性及桩土相互作用的基础上,提出群桩基础变截面桥墩分析模型;将分析模型分解成群桩基础的刚体变形与桥墩的弹性变形两个部分,分别基于能量法与有限单元法求解相应的自振频率,并采用Southwell频率合成法,将整体计算模型表示成两个部分的合成,从而导出变截面桥墩的自振频率,通过算例证明该方法的实用性,并分析了桥墩参数对自振频率的影响,获及了一些定性的结论。结果表明,变截面高墩自振频率的计算分析中,桩-土相互作用的影响不容忽视,考虑桩土相互作用和桥墩本身的非线性更符合工程实际。     

带耗能腋撑竖向不规则短肢剪力墙结构减震性能分析

在不影响建筑使用空间前提下,提出在抗侧构件不连续处设置耗能腋撑以改善竖向不规则结构抗震性能。以底部大空间短肢剪力墙结构为研究对象,利用大型通用有限元程序ETABS研究耗能器类型与场地土对耗能腋撑工作性能和竖向不规则结构受力性能的影响。研究表明,黏滞型耗能腋撑对文中分析模型各楼层地震反应有较好的控制效果,对转换层处层间位移角与层剪力最大值减幅最大,分别为40.14%和15.66%,对顶层加速度与基底剪力峰值的最大减幅分别为16.06%和23.57%,黏滞型耗能腋撑最大能耗散输入结构能量的42%,而黏弹型耗能腋撑对结构的控制效果不理想;当地震震级较大、震中距较小时,耗能腋撑对坚硬与软弱场地土的模型结构控制作用相差不大,减震位移比在转换层处达到最小值0.76;随着震级减小或震中距增大,耗能腋撑对该模型结构的控制作用随场地土变硬而逐渐增强,其减震位移比介于0.68～0.74之间。     

钢管混凝土桥墩抗震性能试验研究

为研究钢管混凝土桥墩的抗震性能,对钢管混凝土桥墩和钢筋混凝土桥墩进行了拟静力对比试验研究。根据试件的破坏发展过程以及各试件的滞回曲线和骨架曲线,分析了其滞回性能、耗能能力、延性、强度退化及刚度退化等抗震性能。试验结果表明,钢管混凝土桥墩的抗震性能明显好于钢筋混凝土桥墩。在含钢率和轴力相同的情况下,钢管混凝土桥墩的滞回曲线比钢筋混凝土桥墩丰满得多,前者的耗能能力约为后者的4.46倍,钢管混凝土桥墩的延性大于钢筋混凝土桥墩;随着轴压比的增大,钢管混凝土桥墩延性有所下降,强度退化加快,但对其刚度退化的影响不大。     

USE OF SURFACE GUIDE PANELS AS PIER SCOUR COUNTERMEASURES

1 INTRODUCTION Protection of bridge piers against local scour is of major importance to bridge maintenance. The safety of bridges is seriously threatened by the river flood during typhoons or thunderstorms. In Taiwan typhoon’s floods are often so strong in possession of high energy to transport a large amount of bed sediment in river. The average velocity in a flood river can go typically over 3 m/s even up to 5 m/s, several times of the regular flow speed. The peak discharge of flood i…