Study On Mechanical Properties Of Steel Bridge Deck Pavement Repaired Interface Under Coupling Of Load And Seepage

Steel bridge deck pavement(SBDP)is paved on orthotropic plate directly.Damage of deck pavement is increasing under various negative environmental conditions.For the common diseases of SBDP,the repaired interface is still seriously damaged,even if it is repaired through excavating and resurfacing.Especially when there is water in the pore of asphalt concrete near the repaired interface,the coupling effect of load and seepage aggravates the failure of the repaired interface.The recurring failure behavior of interface has complex mechanism,which is a difficult problem for SBDP maintenance work.On the basis of summarizing the present situation of load-seepage coupling and the research on the failure of repaired interface of SBDP at home and abroad,using multiscale numerical simulation and laboratory test,mechanical property of steel bridge deck new-old asphalt pavement structure with repaired interface under load-seepage coupling was analyzed.First of all,modified asphalt concrete frequently-used in SBDP was prepared.Old asphalt concrete of different aging degrees was finished through aging test.Excellent interfacial binder was selected to compose new-old asphalt concrete composite specimens with new asphalt concrete which was without long-term aging test.Repaired interface failure mechanism was explored from the tensile properties of the composite structure.Composite beam specimens were prepared and tested through bending test.It was found that the fracture of composite beams on the side of old asphalt concrete with higher rebound modulus from experiment.The selection of repair materials shall meet the resilience modulus similar to that of the original asphalt pavement,to make the whole composite structure in a state of balanced stress and coordinated deformation.Composite Marshall specimens were prepared and scoured using selfmade hydrodynamic pressure test device to simulate load-seepage coupling action of composite structure with repaired interface.It was found that the water continuously filled the gap and makes the composite specimen almost saturated while the hydrodynamic pressure acting.After hydrodynamic pressure acting,splitting tensile strength of water saturated composite specimen reduced and toughness increased.Also,failure state of specimen was changed.The long-time hydrodynamic action not only reduced the tensile strength of composite specimen,but also made the interfacial bonding failure.Secondly,orthotropic steel bridge deck pavement with repaired interface macroscopic model by finite element software was built.Most unfavorable pothole patching position,where the repaired interface was directly above the diaphragm,was determined.Then mechanical analysis of repaired interface under dynamic load-seepage coupling was finished.Mechanical response of severely stressed area was researched.The reasons that probably cause repaired interface damaged were determined: transverse tensile stress on the surface of repair interface above U-rib,longitudinal tensile stress on the surface and pore water pressure at the bottom of the repaired interface at the center of the load wheel trace.From the perspective of repair materials and external loads,the influence of different internal causes and external causes to mechanical behavior of repaired interface was analyzed by control variable method and orthogonal test.It is clear that material modulus was unfavorable to the transverse tensile stress of the repaired interface,tire pressure was unfavorable to the longitudinal tensile stress,tire pressure and speed was unfavorable to the pore water pressure.Thirdly,new-old asphalt concrete composite structure model considering practical micromaterial characteristic was built using digital image processing technology.Macroscopic displacement boundary condition was transmitted to mesoscopic structure through submodel method.From the perspective of original asphalt pavement and external load,mechanical responses of composite structure and influencing factors in meso-scale were analyzed.The increasing of load and old asphalt mortar modulus was very unfavorable to the stress of original asphalt pavement materials on the side of repaired interface.The damage characteristics of composite structures with preset cracks were analyzed by the extended finite element method.Because of bottom constraint under the unfavorable pothole patching position,and attenuation of mechanical properties on original asphalt pavement in the adverse water environment,preset crack would extend under the dynamic vehicle load.Also,it was easy to produce cracks near repaired interface.If some areas of the repaired interface were not firmly bonded due to improper construction and other reasons,resulting in the formation of preset cracks,the closer the crack was to the surface interface,the greater the stress difference between the new and old materials on both sides of the interface would increase.Finally,based on research of test and numerical simulation.Failure mechanism of repaired interface was summarized and analyzed.And according to the internal causes and external causes of repaired interface failure and damage,suggestions of SBDP repairing work were put forward from the selection of materials and the improvement of construction technology.Finite element analysis and mechanical test were combined to study tensile properties of repaired interface under coupling load and seepage in different scales.The failure behavior of new and old asphalt concrete composite structure with repaired interface was explored.And reasonable suggestions were put forward for the repair works of SBDP.