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

本文对高强混凝土构件的基本性能进行了研究，以期建立合理的高强混凝土构件设计方法。得到的主要结果如下：1。采用抗压强度为fc*80N/mm^2的高强混凝土，可提高预应力混凝土简支梁和连续梁的极限抗弯承载力和预应力钢的极限受力，特别是无粘结预应力混凝土构件。即使是未粘结的高强度混凝土PC构件，其极限状态下的抗弯性能也可以通过普通的抗弯分析来评估，其变形协调系数为β =0.20-0.25.2。剪切开裂荷载随引入预应力的增大而增大，混凝土抗压强度对其增大比影响不大。抗剪能力随预应力的增大而增大。然而，与普通强度混凝土相比，高强混凝土PC梁中其增加比例变小。对于钢筋混凝土梁的水下疲劳性能，混凝土所承受的剪力随循环次数的增加而减小，且在混凝土强度较高的情况下，混凝土所承受的剪力减小的幅度更大。然而，高强度混凝土梁的疲劳强度大于普通强度混凝土梁。采用JSCE《混凝土结构设计与施工标准规范》提出的方法，可以合理估算高强混凝土预应力钢筋混凝土梁的长期挠度。采用连续纤维板横向约束可以有效地提高高强混凝土的抗压延性和高强混凝土RC梁的抗弯延性。

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.