Experimental Study On The Mechanical Behavior Of HDC And Shear Performance Of HDC Beams

High ductile fiber reinforced concrete(HDC)is a new material with high strength,high ductility and high energy capacity,which can exhibit typical strain-hardening effect and multiple fractures in tension and bending.HDC is used to instead concrete to improve the shear capacity,deformation ability and failure mode of reinforced beams,and to decrease the damage of component and the repair cost after earthquake.The experimental research,numerical analysis and theoretical research have been done to study the mechanical behavior of HDC and shear performance of HDC beam.The primary contents and achievements are as follows:(1)Experimental Research on the flexural behavior of the HDC.The single factor contrast test method is used to study the influence of the volume and kind of fiber,water-cement ratio,sand binder ratio and the content of fly ash on the mechanical behavior of HDC.It shows that the fiber volume has more lager influence than other factors.And the flexural performance was studied,the relationship between the deflection of beam and sheet was built,and the method to evaluate bending toughness for HDC was suggested.What's more,it is suggested that the bending test can be used to evaluate the tensile behavior of HDC,and the relationships between their indicators were built.(2)Research on the bending-shear behavior of HDC beams without reinforceements.14 HDC beams without stirrups and four reinforced concrete beams were designed.The failure mode and shear mechanism shear behavior were studied through centralized single point load test,and the influence of shear-span ratio,reinforcement ratio and material ductility were analyzed.It can be included that the great tensilestrain-hardening behavior and multiple cracking of HDC can control the incline cracking effectively,prevent the crushing and spalling of concrete,enhace the shear capacity and deformation ability scientifically,and improve the brittle shear behavior of RC beams.(3)The influence of HDC beam's flexural performance on its shear behavior.The bending behavior of HDC beam has great influence on its shear performance,considering the contribution of HDC in tensile region,the strain distribution and flexural capacity of different stages were analyzed,to realize the failure mode that shear failure after bending yield,which give full exerts to component's flexural and shear ductility.Then,ABAQUS has been used to analysis the HDC beams and the influence of steels ratio and mechanical ductility on the flexural behavior.(4)The shear mechanism and model of short HDC beam.It can be found that the shear performance of short HDC beam was effectively improved,and the development and shear failure mode were very different with RC beam.The shear mechanism of short HDC beam was analyzed,and the shear capacity formula considering HDC tension effect was established based on truss-arch model,and it has been simplified according to the code and experiment results.(5)The method to evaluate the shear capacity of HDC beams.In order to verify the rationality of modified method,carrying capacity of HDC beams were calculated according to different specifications of United States,European and Chinese code,which have different indicators,reliability and safety.The tensile strength and ductility coefficient factor have been suggested to modify the codes.The calculations have good agreement with experimental results,showing that the modified unite formula is reasonable.