A knowledge-based system for maintenance planning of highway concrete bridges

This paper presents a knowledge-based system that is used for maintenance planning of highway concrete bridges. The system includes functions for maintenance priority setting among bridges, feasible treatment assessment in each case, and maintenance planning for a bridge stock. Maintenance priorities are set using a scoring model with decision parameters appropriately weighted. Feasible treatments are determined based on bridge condition and other factors that accelerate deterioration. Decisions for maintenance planning result from a linear programming model and are based on priority ranking, cost and effectiveness characteristics of feasible treatments, and existing budget constraints. The system has been successfully evaluated with actual and simulated data.     

Damage analysis and numerical simulation for failure process of a reinforced concrete arch structure

This work focuses on the implementation of damage mechanics model to explain and understand failure mechanisms of the concrete structures. A tensorial damage theory and an isotropic application to the arch ribs of a real bridge are presented. Two reinforced concrete arch ribs of a 28 year old bridge has been removed from the field to the laboratory. They were loaded up to failure in order to study the remaining strength of the structure. The damage model involves three independent parameters for simulating the damage behaviors of the concrete material. The damage theory—additional load—finite element method is developed to simulate numerically the failure process of the RC structures based on the proposed damage model. The predicted displacements, strains and failure mode of the RC arch are good agreement with the experimental results. The values of the three material parameters that describe the damage characteristics of concrete were obtained. The numerical calculations revealed the interested behaviors of concrete in a damaging process. The proposed damage model can be used effectively to describe the damage and fracture behaviors of concrete.     

苏通长江公路大桥南塔墩钢吊箱设计

苏通大桥为主跨双塔双索面七跨连续钢箱梁斜拉桥,居世界第一.南塔墩钢吊箱作为承台施工围水结构,规模空前,受长江口恶劣的水文条件影响,其工况复杂,设计难度大.重点介绍南主塔墩钢吊箱的结构设计、计算、强度及稳定性分析.     

Durability of FRP Composite Bridge Deck Materials under Freeze-Thaw and Low Temperature Conditions

Fiber-reinforced polymer (FRP) composites, especially lightweight sandwich structures, are rapidly finding their way into civil infrastructure application. FRP composite panels are particularly attractive as bridge deck systems due to their high strength, low density, and durability, which are of importance to the bridge industry. Most of the vast amount of durability data for FRP has been generated for aerospace and automotive applications, which involve very different service conditions than civil infrastructure. For civil engineering applications, it is essential to examine the durability performance of FRP materials under weathering conditions. The ultimate goal of this research is to develop a reliable framework for durability assessment of FRP decks, including laboratory testing procedure and finite-element simulation capability. Such a framework should be applicable to all types of FRP deck construction. In this paper, specimens of typical FRP bridge deck skin materials are subjected to freeze-thaw cycling between 4.4 and ?17.8°C in media of dry air, distilled water, and saltwater, and constant freeze at ?17.8°C . The selected deck is used as an example for demonstration purposes. In addition, selected specimens are subjected to simultaneous environmental exposure conditions and sustained loading of 25% ultimate strain. It should be emphasized that most of the environmental conditions reported in the literature produce minor deterioration of a single composite property, and the assessment of such effect on this single property becomes unreliable because of a large property variation. Therefore, in this paper we use multiple mechanical properties as performance indices for damage evaluation. Based on findings from this work, it is concluded that freeze-thaw cycling between 4.4 and ?17.8°C alone and up to 1,250 h and 625 cycles caused very insignificant or no change in the flexural strength, storage modulus, and loss factor of the FRP specimens conditioned in dry air, distilled water, and saltwater. Small reductions in storage modulus (about 1% or less) were observed when specimens were prestrained and subjected to 250 freeze-thaw cycles in distilled water and saltwater. Changes in flexural strength were statistically insignificant, since they were within the data scatter.     

Safety Analysis of Moving Road Vehicles on a Long Bridge under Crosswind

This paper presents a safety analysis of high-sided road vehicles running on a long span cable-stayed bridge when the road vehicle enters a sharp-edged crosswind gust while the bridge is oscillating under fluctuating winds. Road vehicle accidents, including overturning, excessive sideslip, and exaggerated rotation, are defined first. The mathematical model and the equation of motion of coupled road vehicle–bridge systems under crosswind are then established, which include road surface roughness, vehicle suspension, and the sideslip of the vehicle tire relative to the bridge deck in the lateral direction. A case study using a real long cable-stayed bridge and a high-sided road vehicle is finally conducted, and an extensive computational work is performed to obtain a series of accident vehicle speed against mean crosswind speed, by which the decision on the threshold of mean wind speed above which the bridge should be closed to the road vehicle can be made. The obtained accident vehicle speeds are also compared with those for the same vehicles running on the ground. It is shown that the oscillation of the cable-stayed bridge will lower the accident vehicle speed when wind speed reaches a certain level.     

跑车试验测定桥梁结构冲击系数的理论及应用

从理论上对匀速车辆在桥梁结构上引起的动力响应进行了分析，揭示了桥梁结构在汽车车辆荷载作用下的变形实质，并据此探讨了跑车试验测定桥梁冲击系数的方法。     

芜湖长江大桥

芜湖长江大桥,是一座公路、铁路两用桥,在极其恶劣的环境条件下,采用了跨径为(180 312 180)m的斜拉桥,其特点为塔矮,塔高与中跨跨径之比为0.11,边跨跨径大,边跨与中跨的比值0.577,铁路荷载很大,动力作用大,提高梁的刚度,采取了三点措施,以满足铁路运行的需要.     

电流控制技术在移相全桥变换器中的应用

本文介绍了开关电源的电流型PWM控制技术的原理及特点，并和传统的电压型控制作了比较。针对移相全桥变换器，采用UC3875设计了电流控制电路。     

铰接斜板桥的一种实用计算方法

本文根据横向铰接料板桥结构力学性能的特点，认为跨内径向弯矩是斜板桥结构设计计算的关键之所在．采用与等跨简支架跨中弯矩相比拟的方法，求出将斜板桥离散为单块板（粱）时的等效荷载横向分配系数．从而将斜板跨内径向弯矩的求解简化为单跨简支架跨中弯矩的计算，解决了由斜板间相互铰接而给计算带来的困难，较其它实用计算法更加简捷、实用．文中给出了一个抖板桥算例，并通过与经典的有限元法、有限条法及其它实用计算方法的计算结果的比较，证实了本文方法的正确性和实用性．