Flexural and Shear Behavior of Prestressed Reinforced Continuous Beams and Analysis

点击翻译按钮获取中文摘要

Flexural and shear behavior of two-span continuous prestressed reinforced concrete (PRC) beams with mean prestress of about 3N/mmィイD12ィエD1 and mechanical prestressing degree of about 0.5 was studied in comparison with that of comparable reinforced concrete (RC) beams, and then those test results were compared with calculations obtained from a nonlinear analysis and design equations.Conclusions obtained from this study are summarized as follows.1) Width of flexural crack was considerably smaller in PRC beam than RC beam, and was somewhat larger in unbonded beam than bonded one. Those could be estimated relatively well using steel stress by nonlinear analysis and crack width equation by the JSCE Code.2) Ultimate flexural strength of PRC beam was higher by about 8% on the average than that of comparable RC beam, and then that of unbonded beam was lower by maximum 10% than that of bonded one. Those could be estimated well by applying the limit analysis.3) Ridity of PRC beam after flexural cracking was higher than that of RC beam, and use of high strength concrete of f'ィイD2cィエD2=80N/mmィイD12ィエD1 was very effective for improving member rigidity.4) Moment redistribution initiated after flexural cracking, but no significant difference could be recognized in load-moment relations at loading point or intermediate support between PRC and RC beams and between two types beams of f'ィイD2cィエD2=40 and 80N/mmィイD12ィエD1. Flexural behavior up to the ultimate state after cracking of PRC beams could be estimated well by a nonlinear analysis applied in this study.5) Ultimate shear strength of PRC beam without web reinforcement was larger by about 55% on the average than that of comparable RC beam.6) Measured ultimate shear strength was fairly in excess of calculation obtained by setting all of safety factors in design equation of the JSCE Code to be 1.0.7) Stirrup strains in PRC beam could be estimated well by the modified compression field theory.