The safety of steel bridges around capital region under severe conditions

本文从疲劳屈曲极限承载能力、风荷载、地震荷载、严重交通活荷载的估算、抗震设计等方面，对恶劣条件下首都圈钢桥进行了综合研究。为确保首都圈钢桥的安全，开展了以下研究工作：(1)疲劳研究；钢桥疲劳开裂数据库的建立。气孔疲劳裂纹扩展的评价。公路桥梁疲劳裂纹扩展的数值模拟。角焊缝疲劳裂纹检测的可行性研究。TIG弧重熔法加固疲劳裂纹节点。(2)极限承载能力；加筋钢板极限强度估算。钢柱受力性能的简化分析与优化。斜拉桥在非均匀支承作用下的分析。(3)严重交通活荷载作用下；移动车辆重量的测量。公路桥梁交通活荷载极值评估的仿真研究。公路桥梁疲劳评估的应力折减系数。车辆多次出现对桥梁疲劳损伤的影响。(4)动力问题；柔性结构在柔性地基上的动力上抬。圆形容器调谐液体阻尼器的试验研究。(5)设计方法；安全系数对桥梁设计的影响分析。粗差对确定安全系数的影响。一种从统计数据中确定分数值的方法。

In the present study we synthesize investigations for steel bridges around capital region under severe condition on different aspects such as ultimate load carrying capacity subjected to fatigue and buckling, estimation of wind load, earthquake load, and severe traffic live load, and anti-earthquake design. With a purpose to ensure the safety of steel bridges around capital region, the following studies are carried out.(1) On fatigue; Establishment of data base for fatigue cracking in steel bridges. The evaluation of fatigue crack growth from blowholes. Simulation of fatigue crack growth in highway bridges. Feasibility study on detection of fatigue crack in fillet welded joint. Retrofitting fatigue-cracked joints by tig arc remelting.(2) On ultimate load carrying capacity; Estimation of ultimate strength of stiffened steel plates. Simplified analysis and optimality on the steel column behavior. Analysis of cable-stayed bridges subjected to nonuniform support.(3) On severe traffic live load; Measurement of weigth of moving vehicles. Simulation for evaluating extremes of traffic live load on highway bridges. Stress reduction factor for fatigue assessment of highway bridges. Effect of multiple presence of vehicles on fatigue damage of bridges.(4) On dynamic problems; Dynamic uplifting of flexible structure on compliant ground. Experimental study on tuned liquid damper using circular containers.(5) On design method; Influence analysis of the factors of safety on the design of bridges. Effects of gross errors for determining the factors of safety. A Method to determine fractile values from statistical data.