Study on the application of high strength concrete to RC and PC structures and its design method

In this study, fundamental behaviors of concrete members with high strength concrete are investigated in order to establish a rational design method for concrete members using high strength concrete. The main results obtained are as follows. 1.By using high strength concrete with compressive strength of fc*80N/mm^2, the ultimate flexural capacity of prestressed concrete (PC) simple and continuous beams as well as the stress of prestressing steel at the ultimate state can be increased, especially in unbonded PC members. Even in the case of unbonded PC members with high strength concrete, flexural behaviors up to the ultimate state can be evaluated by ordinary flexural analysis using the deformation compatibility factor of beta=0.20-0.25. 2.Shear cracking load increases with increasing the introduced prestressing stress and compressive strength of concrete scarcely affects its increasing ratio. Shear capacity is also increased with increasing the prestress. However, its increasing ratio in the PC beams with high strength concrete becomes smaller compared with that with normal strength concrete. 3.As for the fatigue behaviors of reinforced concrete (RC) beams under water, shear force carried by concrete decreases with increasing the repeated cycles and its decreasing ratio becomes larger in case of the beams with high strength concrete. However, fatigue strength of RC beams is larger in the beams with high strength concrete than the beams with normal strength concrete. 4.Long term deflection of prestressed reinforced concrete (PRC) beams with high strength concrete can be reasonably estimated by the method proposed by JSCE Standard Specification for Design and Construction of Concrete Structures. 5.Compressive ductility of high strength concrete as well as flexural ductility of RC beams with high strength concrete can be effectively improved by lateral confinement using continuous fiber sheets.