Control of droplet transfer in consumable electrode welding with short circuiting of the arcing gap

We present the results of an experimental programme of fatigue tests carried out on two types of butt joints with thicknesses of 20 and 40 mm respectively, characterized by a significant gap between weld edges, not compliant with the requirements of construction specifications. The tests were conducted on specimens taken from the weld beads of joints typical of those produced at the site (butt joints between web and flanges) and made with the same procedures (welding process, welding position, welding filler, etc.). The test results were elaborated statistically to determine the fatigue resistance category in accordance with the requirements of standard EN 1993-1-9 and IIW recommendations. Calculations took into account both the thickness of the specimens (tests were carried out on both to-scale and true-thickness specimens for the purposes of validation) and also flexural stress components induced by the non-planarity of the specimens.     

Optimization of management strategies applied to the national reinforced concrete bridge stock in France

The increasing age of national highway bridge stocks demands novel management policies that can maintain or increase safety levels in the light of reducing and budgets from the government. The French Highways Agency uses its Image Qualité Ouvrages d'Art – Structural Quality Imaging (IQOA) inspection programme to determine the conditions of its bridges. The present paper principally describes the development of a model to predict different trends in bridge condition rating in the light of different management strategies. Whilst the approach described is intended to be a general method for managing bridges, it will be demonstrated by particular reference to the stock of reinforced concrete bridges managed by the French Highways Agency. The prediction model utilises Markov chains, which were chosen because they allow a non-parametric discrete model to be built, to evaluate the varying condition of the whole bridge stock over time. The development of the model is described in detail, together with how the hypotheses for applying the Markov chains were validated to accurately predict the transition matrices between different IQOA states. The paper then goes on to describe how the model is used to differentiate between different management strategies, and to predict how future costs can be optimised to give the most efficient management actions across the whole bridge stock under different constraints.     

桥面平整度的极大熵分析

本文针对实测的桥面平整度的特点，提出一种桥面平整度谱分析的分析方法－极大熵法。对在２０座桥上实测的７４条不同结构类型的桥面平整度特性曲线，利用极大熵法进行了谱分析，提出了用于分析行进车辆荷载作用下桥梁动力响应的桥面平整度的功率谱密度表达式。     

桥梁健康监测系统中时钟同步的应用研究

基于桥梁健康实时监测系统的总体框架和现状,重点分析了该系统中存在的时钟不同步的问题。介绍了几种主要的时钟同步技术和方法。根据监测系统的实际情况、结合常用的时钟同步技术,设计提出了一种适用于小范围局域网内的高速实时数据采集系统的时钟同步模型,阐述了该模型的时钟同步过程。最后,讨论了该模型的时钟同步过程的误差来源及其系统的扩展性问题。     

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.     

桥面板连续简支T型组合梁桥典型病害及力学机理分析

以京珠高速公路某特大桥为例,通过理论分析与有限元模拟,总结了桥面板连续简支T型组合梁桥普遍存在的典型病害特征,研究了病害产生的力学机理,并提出了相应的加固处治措施,为该类桥梁的管理养护提供参考.     

斜拉桥塔柱索导管施工技术在重庆蔡家嘉陵江大桥中的应用

结合蔡家嘉陵江大桥高塔柱索导管安装工程,详细介绍了索导管安装方法,包括索导管安装方式比选,索套管下料问题,以及大套管在混凝土浇筑状态下的抗上浮验算.深入总结了索导管定位及安装技术,包括定位标准和原理,索导管的定位计算,索导管测量定位及安装施工,人员及辅助设施以及索导管安装注意事项.     

A continuous vibration analysis model for cables with sag and bending stiffness

The paper reports an investigation on a continuous model for dynamics of large-diameter sagged cables, taking bending stiffness and sag extensibility into account. Following the classical guidelines of cable dynamics, and by making some simplifications, a continuous model is found in this work; frequency and mode shape equations have been obtained in non-dimensional form. Comparison with Finite Element (FE) and Finite Difference (FD) models has been made to validate the proposed method. Moreover, it allows us to represent local effects at the end zones of cable correctly, if clamped boundary conditions are assumed. To obtain comparable results, the FE model would require a large subdivision, with consequently, a large number of elements. The proposed eigenfunctions allow us to solve the dynamic problem without a large computational effort compared to FE or FD approaches. Finally, in order to show the usefulness of the developed continuous model, an application on the main cables of the designed Messina Strait Bridge has been made.     

钢混组合梁桥的新技术

钢板具有高的抗拉强度,但是相对于由压应力引起的屈曲来说相对脆弱.然而,当钢板与混凝土结合,屈曲增加的抵抗力和重型加劲肋的阻力是没有必要的,这样使钢桥对混凝土桥更具有经济效益和竞争力.钢混组合的新型结构形式已经在日本几个实际的桥梁中积极提出和发展了.利用钢管混凝土梁桥的新思路设计的钢-混凝土复合材料,也被分析和证明是经济可行的.