Time-Dependent Deformations of Prestressed and Prestressed Reinforced High Strength Concrete Members

点击翻译按钮获取中文摘要

This study presents the experimental investigation on creep and shrinkage of concrete with compressive strength of more than 100N/mm2 and the research on mechanics and numerical analysis of long-term deformations of prestressed concrete (PC) and prestressed reinforced concrete (PRC) members under sustained load after prestressing. The results obtained from the study executed in 1996 and 1997 are summarized as followings :(1) Based on the principle of superposition, drying, shrinkage strain increases in approximate proportion as 70% of autogenous shrinkage strain increment after drying start, and the proportion is independent of drying start time.(2) The empirical equations of CEB Model Code 1990 (MC90) were modified to predict creep and autogenous shrinkage strain of high strength concrete in accordance with the experimental results in which loading was carried out at various ages of concrete.(3) Based on the principle of superposition taking into account the effect of age concrete at … More loading and modeling the mechanical properties of high strength concrete, time-dependent strain of reinforcing bar due to autogenous shrinkage can be estimated with satisfactory accuracy.(4) When the maximum value of strain of reinforcing bar is 650-1000 (*10^<-6>), the tension stiffness of high strength concrete (105N/mm^2) members is 14-18% larger than that of normal strength concrete (45N/mm^2) members in case of steel ratio of 0.37-0.64%, which is defined as difference between maximum value and average value in strain of reinforcing bar.(5) Average curvature of high strength concrete members at 400 days after loading was 63% of normal strength concrete members. For evaluating curvature, MC90 for tension stiffening overestimats average curvature as the reinforcement stress becomes large.(6) The design equation of effective flexural stiffness in JSCE Standard Specification was valid for high strength concrete members.(7) Based on the principle of superposition for not only concrete but also bond, basic bond equations were formulated for analysis of time-dependent deformations of RC and PRC members subjected to bending moment. Less