Study Design And Flexural Behavior Of 30m Prestressed UHPC Tee Beam

In recent years,Ultra-high performance concrete(UHPC)has attracted more and more attention from engineering professionals due to its high mechanical properties.It has been found that bridges made based on UHPC can solve the problems of long-term difficulties in engineering,such as self-importance,easy cracking,and severe downward deflection,with broadly application foreground.Based on the approach bridge of Chongqing Taihong Yangtze River Bridge,the structural design and finite element model optimization analysis of prestressed UHPC-T beam are carried out.The force characteristics of UHPC-T beam are summarized by finite element analysis.The main work of this paper is as follows:(1)According to the relevant UHPC specifications and design theory,combined with UHPC material characteristics,the 30m prestressed UHPC-T beam is designed to determine the section size,local stability analysis and local force analysis under vehicle load to ensure the size meets the requirements.The configuration of prestressed steel bars and the calculation and analysis of deformation,stress and crack resistance of prestressed UHPC-T beams should be compared with the finite element software.(2)According to the design parameters,the model was established by ABAQUS,and the nonlinear analysis was carried out to study the ultimate bearing capacity of the UHPC beam.The whole process dynamic behavior of the UHPC beam from the loading state to the failure state of the real bridge concrete material is analyzed,and the damage law of UHPC-T beam is mastered.It is found that the ultimate load of the UHPC beam under the same parameters is 1.53 times and 1.24 times that of the ordinary concrete beam,and the ductility index is larger than that of the ordinary concrete beam.(3)The effects of changing parameters on the bending stiffness of UHPC beams were studied in detail by changing the parameters of UHPC beam height ratio and reinforcement ratio.The results show:The high-span ratio is from 1/15 to 1/21.43,the main beam’s cracking load is reduced by 46%,the ultimate load is reduced by 49%,and the area is reduced by 32%;When the reinforcement ratio is constant,the strength grade of the steel bar is replaced by HRB400 to HRB500,which has little effect on the stiffness of the elastic phase,and the ultimate load capacity is only increased by 9%;For the prestressed tendon beam only,the area of the prestressed tendon increases by 560 mm2,the ultimate load increases by 17.82%,and the cracking load increases by 15.38%.When the parameters are the same,the beam without ordinary steel bars is reduced by 18%compared with the beam with ordinary steel bars,and the ultimate deflection is reduced very little.(4)Based on the existing UHPC constitutive relationship research results,considering the tensile properties of UHPC materials,the calculation formula for the UHPC beam cracking load is obtained.By comparing the finite element analysis results with the calculated values of the formula,the two agree well.The derivation process and the correctness of the selected parameters.