The Composite Behavior Of Steel And Hybrid-fiber Engineered Cementitious Composites And Its Application In Bridge

The application of Engineered Cementitious Composites(ECC)in orthotropic steel deck or composite bridge could effectively solve the cracking problem in hogging moment region.Meanwhile,ECC could also reduce strutural stress level,and enhance the load-bearing capacity and long-term performance of bridge deck by synergizing with the steel structure.Experimental research,theoretical analysis and numerical simulation were conducted in this dissertation,focusing on the composite behavior of steel and hybrid-fiber Engineered Cementitious Composites(Hy ECC)with outstanding mechanical properties.The main results and findings are as follows:(1)With the help of Digital Speckle Correlation Method,an optimized dog-bone tensile test was established to measure the axial tensile behavior and cracking development of high-ductile cementitious composites accurately.Further,through axial compression and flexural tests,the ke y mechanical parameters of Hy ECC were calibrated.Its uniaxial constitutive relationship and bridging stress-crack width model were developed,laying a foundation for the study of composite behavior at the member and structure level.(2)Six groups of steel rebar-Hy ECC composite tensile tests were accomplished,exploring the influence of reinforcement raio,diameter of rebar and the type of cementitious material on the composite tensile behavior.Combined with steel rebar,Hy ECC could exhibit excellent capability in crack control,and high ductility with rational reinforcement ratio.Four basic modes of steel rebar-ECC composite tensile behaviors were summarized,and an effective model was established based on the constitutive of bond-slip and bridging stress-crack width,which could accurately delineate the macroscopic mechanical behavior and crack development law.(3)By conducting eight groups of steel plate-Hy ECC pushout tests,this dissertation analyzed the influence of the height and diameter of stud connector,reinforcement situation,and the type of cementitious material.Stud shearing failure mainly appeared in Hy ECC with relatively high stiffness and poor post-peak ductility.The design methods to calculate the ultimate resistance capacity and initial stiffness of stud connectors were discussed,and applicable shear resistance-slip model was built.(4)A theoretical calculation method of interfacial slip distribution and flexural bearing capacity of steel-ECC composite beam,considering the influence of ECC,was derived.Parameter analysis was carried out based on fine finite element model.The rationality and accuracy of both theoretical and numerical methods were verified via experimental tests,and design suggestions for practical projects were proposed.(5)On the basis of aforementioned theories and methods of steel-ECC composite mechanical behavior,fiber beam element considering the composite effects was developed on the ABAQUS platform.It could effectively and precisely simulate the tensile and flexural behaviors of reinforced ECC members and steel-ECC composite beams with arbitrary cross sections,and has been verified by comparison with various experiments of ECC structures.This model could be further applied into calculation,simulation and design of composite bridges.