| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1997: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1996: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
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
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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
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