| A large-scale new single L in the mid-span of the hollow slabs(main structure)appeared in the Yangsi viaduct of Taijin Expressway in Zhejiang Province,as a result of the concrete railings(attachment structure),which is different from the traditional longitudinal cracks of hollow slabs.This kind of attachment structure parting participates in the stress,and has which influence whole structure,which attracts more and more attention of scholars around the world.This dissertation is based on the existing research results of the research group,based on the stress characteristics of the hollow slabs,an equivalent rectangular concrete beam with a mid-span compression parting is designed and tested,the impact of the concrete beam compression parting on the stress concentration effect and bearing capacity of the tensile and compression zones of the structure,and combined with the results of experiments and finite element analysis,the space structural analysis of the full bridge finite element model of the case bridge was carried out,in order to get the internal mechanism of the main structure failure caused by the parting of this kind of attachment structure.The following work has been carried out in this dissertation:(1)A total of 24 equivalent rectangular concrete beams in 8 working conditions were designed,to explore the stress concentration effect and the bending capacity of the normal section due to the compression cracks in the mid-span,based on domestic and international research on stress concentration and bearing capacity of the system,and the effects of factors such as the depths of parting,the width of parting,and the span on the stress concentration effect and bearing capacity of the split beam are analyzed.(2)ABAQUS elastic and plastic damage model of the test have been established,finite element analysis of the test beam and parametric analysis is carried out on the mechanical properties of the parting concrete beam by compared the result of test and the result of FEM.(3)Based on the test and finite element analysis results,the spatial finite element analysis of the case bridge is carried out,and the rigidity and stress concentration of the concrete railing parting on the side plate are considered and superimposed,and the spatial mechanical performance analysis of the hollow slab is carried out.The results show that:(1)The compression parting in the middle of the concrete will cause obvious stress concentration effect on the concrete in the compression zone at the parting and the corresponding tension zone at the bottom;(2)The failure mode of the parting beam in the mid-span compression zone of the normal cross-section changes,oblique cracks appear in the pure bend of the mid-span and develop along the shortest path;(3)ABAQUS calculations show that the plastic damage model could more accurately simulate the mechanical properties of parting beam under mid-span compression.(4)Establish a finite element full bridge model to analyze the stress of the case bridge under the spatial effect,after comprehensively considering the contribution of the stiffness of the railing,the stress on the side plate increases significantly,so the design and calculation of the specific full bridge model should consider the stiffness of the cast-in-situ railing impact;(5)Due to the contribution of the stiffness of the railing,the overall load of the integral member formed by the side panel and the railing is relatively large,which is superimposed on the cross-section weakening caused by parting of the mid-rail,resulting in the stress concentration effect of the hollow slab side panel cracking main reason.The research results of this dissertation have certain engineering guiding significance for the design and construction of cast-in-place railings on smallsection beam bridges such as hollow slab and short T-beam. |
