Structural Behavior And Design Methology Study For High Performance Steel Bridge

Compared with conventional structural steels used in bridges, high performance steel(HPS) has superior characters in strength, weld ability, fracture toughness and weatheringcharacteristics. These material characters realize both economic and low carbon releasing ofHPS bridges, which shows HPS is a new type of structure steel. To date, many developedcountries have devoted much effect to the developed of HPS and construction of HPSbridges. These HPS bridges in-service now have demonstrated advantage in structuralbehavior and economical in whole life cycle. Nowadays, China has devoted effect to exploitHPS and series of HPS has developed nowadays. However, high performance steel withnominal yield strength beyond420MPa has not included in Chinese steel bridge designspecification. To promote HPS bridge construction and establishment of high performancesteel bridge design specification in China, high performance steel HPS485W, with nominalyield strength of485MPa, is focused in this thesis. According to typical failure modes ofsteel bridge (yielding, fatigue and fracture, and buckling), researches for HPS bridge areconducted in aspect of frature control, fatigue resistance design, fabrication technology,structural strength and stability. The studies in this paper are shown below:(1) With aspect of fracture control, series of fracture test were conducted, includingimpact toughness (CVN) test, ductile fracture toughness (JIC) test, and crack tip openingdisplacement (CTOD) test. Research result shows HPS485W has high toughness and lowerductile to brittle transation temperature compared with tranditional bridge steel Q345, whichmeans HPS485W can used in lower temperature region. Test result of HPS485W crack tipopening displacement result belongs to the acceptable field of failure assessment curve inBS7910metal structure defect acceptability evaluation methods guide.(2) With aspect of fatigue resistance design and remaining life prediction for HPSbridges, fatigue behavior test study are conducted for HPS base material and typical HPSwelding connector in steel bridges. Fatigue crack growth rate (da/dN) tests were conductedfor7.5mm,12.5mm and19.5mm specimens under load ratio of R=0.1,0.5and0.8, andthreshold value for19.5mm specimen was also tested and calaculted for HPS485W basemateral. Paris equation was used to determine the fatigue crack growth rate and the test result shows that fatigue crack growth resistance is much better than traditional steel.Fatigue test was conducted for typical butt welding HPS connection. The high cycle fatiguedamage and failure characters for HPS485welding members are analyzed, and its faitugeresistance grade is determined.(3) With aspect of HPS bridge fabrication, welding procedure qualification isconducted for HPS485W welding craft, including X ray flaw diction, tension test for buttwelding specimen, side bending test for butt welding specimen, bending test for T jointspecimen, and toughness test for both welding and heat affection zone. HPS485W weldingquality is evaluated and welding procedure is determined, which supplies reference for highperformance steel bridge frabrication.(4) Bending behavior for high performance steel beam is studies based on test, finiteelement calculation and theortical analysis. Bending test is conducted for12highperformance steel simple supported I beams. After test, it is captured the bending capacity,elastic and plastic deformation, failure mode, local buckling, and bending behaviorcharacters of HPS beams in elastic and plastic stage. Considering material stress and strainbehavior, lateral bracing condiction, residual stress, mesh dimension, initial imperfectionand so on, effective finite element model simulating bending behavior and failure mode oftest beams was established and parameter analysis was conducted to get design suggestionsfor high performance steel beam. Local bucking of cmpressive flange and web, and lateralbuckling are analyzied. Strength design index and deformation control factor are proposedfor high performance steel beam. Suggestions are proposed for cross section design limitformular and lateral bracing.(5) Theortical study, finite element analysis and preliminary test study are conductedfor shear behavior of high performance steel beam. The shear ultimate capacity calculationmethod is analyzied. Finite element analysis identifie affecting rules for web shear bucklingand shear ultimate capacity from parameter study. Suggestions are proposed for sheardesign of high performance steel beam.(6) Based on research result above, high performance steel bridge design sggestionsare summarized and proposed. High performance steel plate girder bridges and traditionalsteel plate girder bridges are designed under the same background. The advantages of high performance steel bridge are summarized from comparison. Research in this paper serves asreference for engineering application.