Study On Shear Resistance Of PVA Fiber Ultra-high Strength Concrete Without Web Reinforcement Under Diagonal Tension Failure

With the emergence of high-rise buildings,high strength concrete is more and more widely used in modern engineering.The high-strength concrete has been used widely in construction industry,which can not only reduce the structural weight and speed up the construction progress,but also bear more loads on the unit area,comparing with normal strength concrete.It's possible that the high-strength concrete members can be with a smaller cross-section area under the same load and it can provide larger space and flexible spatial arrangement.High-strength concrete has the good character of denser micro structure,forst resistance,impermeability,corrosion resistance and better durability.However,with increase of concrete strength,its brittle characteristics becomes more obvious.In order to overcome in various unfavorable factors in the application of high strength concrete,the article using PVA fiber's bridging effect to the concrete substrate,made from a new kind of material: PVA fiber high strength concrete.And experimental studies of PVA fiber reinforced high strength concrete without stirrups has been conducted.In order to quantitatively study the shear behavior of high-strength concrete without web reinforcement,the artificial neural network(ANN)calculation method is used to analyze the main influencing factors affecting shear stress.Based on the experimental data,the data of the research group and the collected data,the shear calculation model suitable for PVA fiber high-strength coagulation without web reinforcement was discussed.And based on the suggestion,the safety factor is discussed by using the reliability calculation method.In summary,this paper carried out the following research:1)The shear test study of PVA fiber high strength concrete beams under concentrated load is carried out.Through the test of 9 PVA fiber high-strength concrete without web reinforcement,the concrete strength,the effective depth of the beam section and the the longitudinal reinforcement ratio on the shear capacity were studied.The migration law of beam failure mode is discussed.It is found that the effective depth of beam section and the reinforcement ratio of longitudinal reinforcement have great influence on the shear capacity of concrete beams.2)Based on experimental data,data of the research group and collected data,a total of249 groups,Using the ANN calculation method,10 sets of ANN models were established.Through the statistical analysis of the calculation results,it is found that the model of 6-12-1 is the most suitable.The calculation results of the model are compared with the calculation results of national codes.Through statistical analysis,it is found that the calculation results obtained by using the calculation model are obviously better than the calculation results of national codes.3)Through the calculation method of ANN,the shear capacity of beam without web reinforcement basis of GB2010 was revised.The individual influence factors such as concrete strength,beam section effective height,longitudinal reinforcement ratio and PVA fiber volume were analyzed.The longitudinal reinforcement ratio and the effective depth of the beam section are taken into account in the proposed formula,and the obtained results are in good agreement with the experimental values.Simultaneously,based on the proposed formula,based on the reliability calculation method,the corresponding safety factor is obtained given the failure probability.