Research On Traffic Load Of Steel Structure Bridges And Fatigue Mechanism Of Orthotropic Steel Deck

Orthotropic steel deck is an integral structure composed of bridge deck,longitudinal stiffener rib and diaphragm plate. Owing to advantages like saving material,light weight, high ultimate bearing capacity, short construction period and so on,orthotropic steel deck is widely applied to long-span bridges at domestic and foreigncountries. However, orthotropic steel deck’s complex structure leads to prominentfatigue cracking phenomenon under axle cyclic load, especially at the intersection oflongitudinal ribs and diaphragm plate, where fatigue cracks of varying degrees arefound in bridge instances around the world. In this paper, by integrating Haihe Bridgeinspection report, in-situ testing and finite element analysis, fatigue performance andstress state of orthotropic steel deck were studied, fatigue life of connection details wereestimated. The main research contents are as follows:（1） Stress response of diaphragm plate of Haihe Bridge was measured whilerecording the traffic. Simplified vehicle load spectrum was obtained through dataprocessing.（2） Finite element model of steel box girder of Haihe Bridge were built usingABAQUS. Applying simplified vehicle load spectrum, stress history of diaphragmplate of Haihe Bridge were calculated.The measured and calculated stress history werecompared using rain-flow count method to verify the simplified vehicle load spectrum.（3） With the verified load spectrum, stress and strain history of connectiondetails of Haihe Bridge（with and without brace） were calculated and fatigue life ofthese connection details was estimated. Fatigue performance of connection details ofHaihe Bridge was compared before and after setting up the brace.（4） After cuttingResidualstresswas importedinto submodelofdiaphragmplate,fatigue life of arc-shape cutout was recalculated. Taking average stress into account,fatigue life of arc-shape cutout was estimated again.（5） Stressstate variationofconnectiondetailsunder axlecyclic loadwasstudied,Direction of tensile principal stress was compared with crack orientation. Variation ofprincipal stress amplitude and internal force also was compared to find internal relations.