Fundamental Research on High Seismic Performance RC Piers with Unbonded Bars

本研究提出UBRC结构为下一代高抗震性能结构。并进行了低周反复荷载试验和拟动力试验，以了解其基本性能。在此基础上，提出了UBRC结构的分析方法，并进行了参数化研究。研究结果表明：（1）通过设置无粘结钢筋，可以较容易地实现具有稳定屈服后刚度的钢筋混凝土结构。与普通钢筋混凝土结构相比，由于杆件效应，UBRC结构具有较小的残余位移。(2)结构的耗能能力仅取决于纵向钢筋的数量，并不因纵向钢筋的设置而发生变化。也就是说，UBRC结构的最佳纵向钢筋用量与RC结构的最佳纵向钢筋用量相当，以达到预期的耗能效果。(3)从反复荷载试验结果来看，可以得到与在钢筋混凝土结构中设置弹性构件的原理等效的结果。这种结构只需在钢筋混凝土结构中设置无粘结钢筋即可实现。因此，这种结构可以以简单和容易的施工工程和低成本来建造。(4)为了提高结构的屈服后刚度，本文提出了三种方法：增加配筋率、外放配筋和缩短配筋长度。通过在锚处设置差距，屈服后刚度不会改变。通过改变这些参数，可以实现各种形式的载荷-位移滞后. (5)在拟动力试验中，还认识到杆的影响（稳定的屈服后刚度和小的残余变形）。考虑到施工方便、造价低廉，UBRC结构具有较高的抗震性能。

In this study, the UBRC structure was proposed as the high seismic performance structure in the next generation. And, the cyclic loading tests and the pseudodynamic tests were carried out in order to obtain the fundamental performance. Furthermore the analytical method for the UBRC structure was developed, and we carried out the parametric studies. From this study, the following results are obtained:(1) By installing unbonded bars, it is possible to easily realize the RC structure with the stable post-yield stiffness. And the UBRC structure has small residual displacement in comparison with the conventional RC structure by the bar effect.(2) The capacity of the energy dissipation is only depend on the amount of longitudinal reinforcement, and never change due to the installation of bars. That is to say, the optimal amount of longitudinal reinforcement for the UBRC structure is the equivalent to that of RC structure in order to expect the energy dissipation.(3) From the results of the cyclic loading tests, it can be obtained the equivalent results to the principle got by installing the elastic member into RC structures. This structure can be realized only by installing unbonded bars into RC structure. Therefore this structure can be constructed with simple and easy construction works and low cost.(4) In order to increase the post-yield stiffness, we have three method; Increase the bar ratio, Place bars outside and Shorten the bar length. By installing the gap at the anchor, the post-yield stiffness doesn't change. Changing these parameters, the various kind of the load -displacement hysteresis can be realized.(5) In the pseudo dynamic tests it is also recognized the bars' effect (stable post-yield stiffness and the small residual deformation). Considering with the easy construction and the low construction cost, the UBRC structure has the high seismic performance.