Study On The Structural Performance And Design Method Of UHPFRC Slabs

As a new type of building material,Ultra-high performance fiber-reinforced concrete(UHPFRC)has obvious improvement in durability and mechanical properties,which can improve the problem that the ordinary concrete bridge deck has large weight and poor durability.Based on this,the following work was completed through test and simulation method:Under the premise of ensuring the strength and liquidity of the UHPFRC,the cooperate with 3.5%steel fiber content was obtained by adjusting the amount of cement and water reducer.The test results showed that such UHPFRC had good mechanical properties and obvious strain strengthening effect.Comments on the design specifications of Japan,Germany,Australia and France were made,and the characteristics of the design specifications were analyzed.The test study of 10 UHPFRC slabs was completed,from which the load-deflection curves,the moment-curvature curve,the load-strain of steel bar curve and structural failure modes were obtained.The influences of shear span ratio,reinforcement and loading mode on the bending performance of slabs was studied.According to the test result and the strain strengthening effect and strain softening effect of UHPFRC,the bending process of the slabs was divided into four stages:elastic stage,microcrack propagation stage,macrocrack development stage and decline stage.The influence of strain strengthening effect on the flexural capacity was studied.Through the ABAQUS,the nonlinear finite element simulation of the test was carried out.The simulation results agreed with the test results.Further the influence of thickness on the bending performance of slabs was studied.The maximum thickness of UHPFRC slabs without considering strain softening effect was suggested.According to the research on the tensile and compressive properties of UHPFRC,a reasonable constitutive model of UHPFRC slabs was selected.Using the selected constitutive model,the bending process of the UHPFRC slabs was analyzed,and the moment-curvature curve was obtained.By comparing the selection method of constitutive parameters in the design code of Japan,Germany,Australia,France and the code of reinforced concrete design in China,combined with the UHPFRC performance obtained in this test,the parameters of UHPFRC constitutive model for slabs were obtained.According to the model parameters,the simplified calculation method of the section bearing capacity and the calculation method of bending stiffness in the elastic stage were proposed.According to the test results,the simplified calculation method was verified.The results showed that the simplified calculation method was safe and could be used in practical engineering.