Residue Fatigue Life Evaluation Of In Service Highway Steel Truss Continuous Girder Bridges

A lot of steel truss Bridges in service in China operate for more than50years. The increase of traffic load, accelerated the inside fatigue damage of bridge truss structure. These Bridges prone to fatigue damage for what it often leads to the fracture of the structure of the bridge collapsed, with a sudden. In order to eliminate the fatigue of the steel truss Bridges in service security, scientific judging bridge maintenance and replacement, the residual fatigue life assessment of the existing steel truss bridge approach process is vital.The paper collected the literature and research results for residual fatigue life of steel structure from many countries. Combined with the Niujiaotuo bridge on the jialing river safety assessment project, the structure stress state of the continuous steel truss girder bridge which is in service, the fatigue performance of truss components, the stress spectrum simulation method of urban road bridge, has carried on the certain research, set up suitable method for residue life assessment of highway steel truss continuous girder bridge which is in service.Thesis mainly carried out the following research work:①Established steel truss space finite element model by using beam element, according to the design drawings of Niujiaotuo bridge on the jialing river and on-site inspection, the reasonable release beam end constraint.②Through the analysis of the bridge structure model, selected the control bar of truss girder bridge for assessing Fatigue.③Cut and replaced the typical bar of truss girder bridge structure.④Fabricated the specimen in order to test material performance and test fatigue performance.⑤On the basis of investigated bridge traffic load, control the space between vehicles by the statistical bridge vehicle numbers within a period of time.⑥Evaluate the residual life of Niujiaotuo bridge on the jialing river with nominal stress method.The residual fatigue life evaluation process of Niujiaotuo bridge on jialing river has certain reference significance of residual fatigue life assessment of similar steel bridge. This paper evaluated of stress fatigue property of steel bridge mainly through the whole section loading fatigue test and measurement of typical members and simulation of key members of the time history. The key bar selection, consider two main factors, namely the rod of the live load stress amplitude bigger, the average stress smaller. Because the project is riveted bridge, typical members and selected consists of four non equilateral angle steel composition, component at the upper and lower ends of the rivets and steel truss gusset plate connection, angle steel are connected by a batten plate, batten plate and angle was found among the rivet. Angle and node plate element for hot riveting process, should not be removed, so choose a limb intercepted some typical component angle test.By the fatigue assessment of typical members and the whole bridge control the residual fatigue life of bar calculation, the structure of the Jialing River Niujiaotuo bridge bar shortest remaining fatigue life of46.82years.