Assessment Of Remaining Fatigue Life For Existing Continuous Steel Truss Bridges

In China, the situation of many existing steel bridges, especially the remaining fatigue life is a topic of considerable importance. In order to make their continued safe use possible while at the same time avoiding unnecessary repairs or replacements, methods for estimation of the actual fatigue life of such structures are urgently required.On the basis of documentation collection from many countries and the analysis of the predecessors' experiences of fatigue problems, a suitable approach to evaluate the remaining fatigue life of exiting continuous steel truss bridges is development in the paper, in which mechanic behaviors of existing continuous steel truss bridges, fatigue load simulation of highway bridges, method for fatigue life evaluation, S-N curve for rivet and bolt detail, etc. are included. In details, the following aspects are investigated:1. Combined with the characteristics of existing bridges, finite-element model (FEM) of actual continuous steel truss bridge is established. In the way of mechanic behaviors simulation, the appropriate working model is developed, which can be employed to evaluate the remaining fatigue life of the existing bridges.2. For the present problem of no traffic load simulation specifications in Chinese highway bridges design codes, the stress spectrum is calculated through the simulation of highway traffic load with Monte-Carlo method.3. An applicable S-N curve for bolt details of existing steel bridges is presented through contrast between fatigue test data for bolt details and S-N curves of design codes from reference documents.4. Based on investigation of the appropriate fatigue strength category for a bolted and riveted bridge member, linear fatigue-damage accumulation approach, commonly known as Miner's rule, is applied to calculate the fatigue life of existing continuous steel truss bridge members.5. The evaluation method is applied to assess the remaining fatigue life of highway existing continuous steel truss bridge which includes primary and strengthening structure.