| Tunnel segment is the main bearing structure for TBM tunnels, thus the cracking resistance, the security and durability are highly desired. The application of steel fiber reinforced self-consolidating concrete (SFRSCC) in the shield tunnel segment can solve the security and durability problems caused by segment damaged or cracking and the poor bond behavior between concrete matrix and reinforcement. The steel fiber can also be uesd as the shear reinforment for the reducation of stirrup ratio. In order to extend the appliaction of SFRSCC in the shield tunnel segment and other engineering structures, the paper carried out a series of experiments including:workabilty of fresh SFRSCC, mechanical properties of harden SFRSCC and shear behavior of simply supported beams and symmetric inclation beams. Base on the modified compression field theory (MCFT), the methods for predicting the shear capacity of SFRC beams with and without stirrups are proposed.(1) Accroding to the widely used test methods for workabitity of SCC, the flow and filling ability, passing ability, stability and segregation resistance of SFRSCC was tested. At the same time, the compression strength and flexural toughness of hardren SFRSCC was also tested. The test results show that the SFRSCC produced by the proposed mix design meet the requirement for workability and strength of SFRSCC. Steel fiber can abviously improve the flexural toughness.(2) Experiment research on the shear behavior of20simply support SFRSCC beams was carried out. The influences of steel fibers on failure mode, cracking pattern, load-deflection curves, load-bearing capacity, and reinforcement strain are investigated. The influence of steel fiber on shear ductility of SFRCC beams is analyzed quantitatively by two different shear ductility indexes. The results show that steel fiber can improve the failure mode and the distribution of crack in shear span, and aslo enhance the shear capacity and shear ductility. The combination of steel fiber and stirrups shows obvious positive hybrid effect, and the amount of stirrups can be reduced by the addition of steel fiber.(3) A theoretical approach based on modified compression field theory to predict the shear strength of steel fiber-reinforced concrete (SFRC) beams without stirrups is proposed. The contribution of steel fibers on shear capacity is considered in the loacl stresses at crack, in which the stress trasfer of fiber is taken into account. The proposed model is verified by test results form chapter3and139shear failure tests previously conducted on SFRC and RC beams without stirrups. The influences of different parameters on predicted shear strength are also discussed. Comparisons between the predicted and experimental results show that the proposed model estimate shear strength accurately and can be uesd for shear analysis.(4) A propoesd model based on modified compression field theory is presented for estimation shear capacity of steel fiber reinforced concrete beams with stirrups. The tset results form chapter3were veriferied by proposed method and two other methods. Compared with the RILEM TCF162-TDF(2003) and "specification for fiber reinforced concrete structures"(CECS38:2004), the proposed method has a good fit with the test results. In order to verify the reasonability of the proposed method further, other SFRC beams are calcuated. It is also found that the calcuated results are consistent with test results and have a low COV. So it is suitable for shear analysis and design of SFRC beams.(5) The influences of steel fibers on the crack pattern, load-deflection relationship and load-tensile reinforcement strain relationship of symmetric inclination beam are investigated. The main parameters are fiber content, shear span ratio, and stirrup ratio. The results show that the failure modes of symmetric inclination beams are similar with the simply supported beams counterparts. The axial force of symmetric inclination beam can enhance the load-bearing capacity and decrease the longitudinal reinforcement strain. The results also show that steel fiber in inclination beams can improve the failure mode and the distribution of crack in shear span, enhance the shear capacity, and also decrease the longitudinal reinforcement strain and witdth of diagonal crack. The test results of inclination beams are verified by two different methods. And the calculated results show that the two methods are some conservative. |
