Flexural and Shear Behaviors of Unbonded Prestressed Continuous Beams and Analysis

本文首先对无粘结预应力两跨无粘结连续梁和有粘结连续梁的受弯性能进行了对比试验，并与非线性分析的理论结果进行了比较。其次，研究了无粘结梁和有粘结梁在剪切作用下的受力性能。试验结果表明：1)无粘结梁的极限抗弯强度比有粘结梁的极限抗弯强度低10~20%，采用合适的无粘结预应力钢筋协调系数值并进行极限分析，可以较好地估算出有粘结梁的极限抗弯强度；2)无粘结梁受弯开裂后构件的挠度和预应力钢筋的应力增量比有粘结梁小得多，并采用高强混凝土(f‘c=85N/mm^2)或横向c…。进一步细化加固对提高无粘结梁的受力性能是非常有效的。3)弯矩重分布发生在开裂后，但无粘结梁和粘结梁在加载点或中间支承处的荷载-弯矩关系没有显著差异；4)采用非线性分析方法可以很好地估计预应力混凝土连续梁开裂后的弯矩重分布、预应力钢筋应力和挠度等抗弯行为，其中有粘结梁和无粘结梁的预应力筋协调系数分别为1.0和0.2。在抗剪性能方面，研究表明：1)有粘结梁和有粘结梁的受弯裂缝沿梁跨的分布有很大差异，粘结梁比无粘结梁更容易发生剪切破坏；2)无粘结梁和有粘结梁的实测强度都远远超过了按日本土木工程师学会标准将设计公式中的所有安全系数设为1.0所估算的抗剪强度。较少

In this study, firstly the flexural behavior of unbonded prestressed two-span continuous beams without bond of prestressing steel was examined in comparison with that of bonded beams, and then the results of those tests were compared with theoretical ones obtained from the nonlinear analysis. Secondly, the load carrying behavior of unbonded and bonded beams under shear were studied. And the recent trends on externally prestressing similar to unbonded prestressing were also investigated.It was shown on flexural behavior that 1)ultimate flexural strength of unbonded beam was lower by 10-20% than that of comparable bonded beam, and that of former beam could be estimated well by using appropriate value of compatibility factor for unbonded prestressing steel and applying limit analysis, 2)member ridity and stress increase in prestresing steel after flexural cracking were considerably small in unbonded beam than bonded one, and application of high strength concrete (f'c=85N/mm^2)or lateral c … More onfining reinforcenment was very efective for improving of unbonded beam. 3)moment redistribution initiated after flexural cracking, but no significant difference could be recongnized in load-moment relations at loading point or intermediate support between unbonded beam and bonded beam, and 4)flexural behavior up to the ultimate state after cracking of prestressed concrete continuous beams such as moment redistribution, prestressing steel stress and deflection could be estimated well applying nonlinear analysis, in which compatibility factor for prestressng steel was set to be 1.0 and 0.2 for bonded beam and unbonded beam, respectively. As for the shear behavior, it was indicated that 1)distribution of flexural cracks along beam span differed markedly between unbonded and bonded beams, and shear failure was liable to occur due to extensive flexural shear cracking in bonded beam rather than unbonded one, and 2)measured strength of unbonded beam as well as bonded beam was fairly in excess of calculated shear strength which was estimated by setting all of safety factors in design equations by Japan Society of Civil Engineers Standards to be 1.0. Less