A Study on Life-Prediction and Life-Expansion of Existing Steel Bridge

近年来，许多公铁两用钢桥发生疲劳破坏的报道屡见不鲜。在这样的背景下，如何估计桥梁的寿命，制定有效的维修计划就显得尤为重要。为了建立钢桥寿命预测和延寿的方法，本文针对钢桥的疲劳问题开展了以下研究：1)为了预测既有桥梁的寿命，了解既有桥梁疲劳裂缝的位置、类型和原因是非常重要的。首先，为了建立数据库，对日本和美国公铁两用钢桥的疲劳失效情况进行了重新整理。2)为了探讨疲劳失效的发生机理，进行了应力测量和有限元分析。3)最后，以延长钢桥使用寿命为目标，采用小型焊接接头试件(面外节点板、面内节点板和十字形焊接节点)和包括部分焊接节点(腹板、翼缘节点板和竖向加劲肋)的梁试件，研究了钢桥疲劳性能的改善方法。作为提高疲劳强度的方法，研究了欠匹配焊条和焊趾处的TIG熔修、毛刺磨削、锤击等焊后处理方法。

Recently, it has been often reported that fatigue failure occurred in many steel highway and railway bridges. From this background, now it becomes much important to estimate the way to predict of life of bridge and to make an efficient plan of maintenance work. In this study, aiming to establish the way of life prediction and life-expansion of steel bridges, the following studies were carried out considering fatigue.1) In order to predict life of existing bridges, it is very important to know location, type, and reason of fatigue crack in Existing bridge. First, in this study, to establish the data-base, fatigue failure occurred in steel highway and railway bridge in Japan and U. S. A were rearranged2) Next, in order to discuss the mechanism of occurrence of fatigue failure, stress measurement and FEM analysis were carried out. Here, scallop detail and cross-connection detail were studied in testing laboratory and also actual bridges considering secondary stress and deformation mode.3) Finally, aiming life-expansion of steel bridges, some fatigue improvement methods were studied with using small welded joint specimens (such as out-of-plane gusset welded joint, in-plane gusset welded joint and cruciform welded joint) and girder specimen including some welded joints (such as web gusset, flange gusset and vertical stiffener). As fatigue strength improvement method, under-matching weld electrode and post-welding processing at welded toe such as TIG-dressing, burr-grinding and hammer peening were dealt with in this study.