| Orthotropic steel-composite bridge decks are formed by laying reinforced concrete structure layer on the orthotropic steel decks(OSDs),which connected by stud shear connector.Orthotropic steel-concrete composite bridge decks have better fatigue resistance and flexural and torsional resistance than ordinary OSDs,which effectively solved the problems that the pavement of OSDs is easy to damage and the structure has poor fatigue resistance.Under the action of wheel load,the cracking of the concrete layer of the composite bridge deck is inevitable,which will affect the mechanical behavior and fatigue resistance of the composite bridge deck structure.This thesis conducted the bending static test of orthotropic steelconcrete composite bridge deck with single U-rib after the concrete layer is cracked and the full-scale fatigue test of SFRC(steel fiber-reinforced concrete)-steel orthotropic composite deck.By combining with the calculation of the composite deck FEM(finite element model),it studied the structural flexural rigidity,local deformation and fatigue resistance of the composite bridge deck before and after the concrete layer cracked.The main work of this thesis is as follows:(1)In view of the increase in bending deformation of the orthotropic steel-concrete composite bridge deck after the concrete layer cracking,an experiment of an orthotropic steelconcrete composite deck with a single large U-rib was conducted,which concrete layer exists a precast transverse crack.Meanwhile,a composite bridge deck FEM was established.The changes in the bending deformation of the composite bridge deck before and after the concrete layer cracked were found,it is revealed that the bending deformation increases with the increase of the length and depth of the transverse crack,the maximum increase in the bending deformation of the structure is 19.7%.As well,bending deformation of the structure increase is more obviously affected by the variation of the crack depth.(2)In order to explore the effect of concrete layer cracking on the local deformation of the orthotropic steel-concrete composite bridge deck structure with multiple U-ribs.By combining the full-scale fatigue test with FEM of the SFRC-steel orthotropic composite bridge deck calculation,chapter Ⅲ studied the deformation behavior of the composite bridge deck before and after the cracking of the concrete layer under the U-rib loading mode,determined that the structural deformation performs the local deformation under the combined action of bending and torsion.The influence degree of concrete horizontal and vertical cracking on the local deformation of the structure is analyzed,and it is concluded that the local deformation of the composite bridge deck increases with the increase of the size of the horizontal and vertical cracks,the maximum local deformation increase reaches 16.2%.When the sizes are the same,the longitudinal cracking of the concrete layer causes the increase of the local deformation of the structure is more obvious.(3)In allusion to the increase of the stress amplitude of the fatigue-prone details of the steel structure of the orthotropic steel-concrete composite bridge deck caused by the cracking of the concrete layer,the FEM was used to analyze the stress amplitude distribution of the fatigue-prone details of the steel structure,and the calculation results were compared to the full-scale fatigue test results,by which it confirmed the accuracy of the FEM.Based on the FEM of the composite bridge deck,the fatigue-prone stress amplitudes of the composite bridge deck steel structure with different sizes of transverse and longitudinal cracks in the concrete layer were studied.Here are the conclutions,the fatigue stress amplitudes of the steel structure fatigue-prone details increased with the increase of the cracks’ sizes,among them,the ribdiaphragm fatigue-prone detail fatigue stress amplitude value is the highest,which is 29.8%.The fatigue detail that affected by the cracking of the concrete layer most markedly is the longitudinal ribs-diaphragms fatigue-prone detail.This paper studied the effect of concrete layer cracking on the local deformation and stress amplitudes of the key steel structure fatigue details of the orthotropic steel-concrete composite bridge deck.It provides a basic direction for controlling the concrete layer cracking of the composite bridge deck and has engineering practical significance and engineering economic value. |
