Ductility Improvement of Pre-cast Concrete Members by Intensive Shear reinforcement

当大量布置主筋，剪应力水平和粘结应力水平增大时，拼接套筒节点集中在铰区的PCa柱的变形能力可能会下降。当拼接区域的键阻不能预期时，纵筋的键长会减小。这样会增加粘接断裂的可能性，使材料的变形性难以保证。刚性接头套筒的销钉作用会加速接头断裂破坏。这将是PCa柱构件设计中的一个严重问题。进行了Pca柱的加载试验，详细测量了纵杆和拼接套的应变。即使在主杆屈服之前，由于接套筒刚度大，最大应变可能出现在套筒的上端而不是下端。最后证明了m的键合长度会减小。强化抗剪加固不仅能提高混凝土的抗剪能力，还能提高混凝土的抗剪能力，提高混凝土的延性。对设计成键裂破坏模式的ISR试件进行了加载试验，探讨了ISR对键裂能力的提高。因此，键容量与ISR的量成比例地增加。ISR对键裂能力的贡献为剪配筋率的0.2 ~ 0.4%。但与常规布置的抗剪钢筋相比较小，相当于ISR的用量。设计了灰浆灌浆套筒缝Pca柱的1 / 2或1 / 3尺度试件。正如预料的那样，需要大量的增援部队。然后用ISR代替所需抗剪钢筋量的25%。试验结果表明，其延性与全剪配筋试件没有明显差异。由于测试设备的能力，主杆的数量，即平均剪应力水平，以及轴向力的大小被限制在一个很小的范围内。今后在改变剪应力水平和轴向荷载水平的情况下，应进行更多的试验验证，并利用ISR与普通抗剪配筋一起赋予PCa柱额外的延性。少

The deformability of PCa columns in which the splicing sleeve joints concentrate in the hinge region possibly degrade, when the large amount of main bar would be arranged and the shear stress level and the bond stress level would increase. When the bond resistance in the splicing region couldn't be expected, the bond length of the longitudinal bars would be reduced. Then, the chance of bond splitting failure would increase and it would become difficult to assure the deformability. The dowel action of the rigid splicing sleeve would accelerate the bond splitting failure. This would be a serious problem in the design of PCa column members.The loading test of Pca columns was carried out where the strain on the longitudinal bar and splicing sleeve was measured in detail. Even before the yielding of main bar, the maximum strain possibly appeared at the top end of the sleeve but the bottom end because of large rigidity of splicing sleeve. Eventually it was proved that the bonding length of m … More ain bar would be reduced. The intensive shear reinforcement (ISR) would improve the bond splitting capacity as well as shear capacity, and it could improve the ductility. The loading test was conducted on the specimens with ISR which were designed to have bond splitting failure mode, and the increase of bond splitting capacity by ISR was discussed. As a result, the bond capacity increased in proportion to the amount of ISR. The contribution of ISR to the bond splitting capacity was 0.2 to 0.4% of shear reinforcement ratio. However, it was smaller than that of the ordinarily arranged shear reinforcement, which was equivalent to the amount of ISR.A half or one-third scaled specimen of Pca column with mortar grouted sleeve joints was designed. As was expected, a heavy reinforcement was required. Then 25% of the amount of required shear reinforcement was replaced by ISR. As a result of experiment, it showed a satisfactory ductility that was not different from the specimen with full ordinary shear reinforcement.The amount of main bar, that mean shear stress level, and the magnitude of axial force ware limited in a small range because of the capacity of testing facility. More experimental verification should be done in future changing the shear stress level and the axial load level, and ISR should be utilized to give the additional ductility to PCa columns together with the ordinary shear reinforcement. Less