Fundamental Research on High Seismic Performance RC Piers with Unbonded Bars

在本研究中，UBRC结构被认为是下一代高抗震性能结构。为获得其基本性能，进行了循环加载试验和拟动力试验。进一步建立了UBRC结构的分析方法，并进行了参数化研究。研究结果表明：(1)通过安装无粘结杆，可以很容易地实现RC结构屈服后刚度稳定。与常规钢筋混凝土结构相比，UBRC结构受杆效应的残余位移较小。(2)消能能力仅与纵向配筋量有关，不因加装筋而发生变化。也就是说，UBRC结构的最佳纵向配筋量与RC结构等效，以期望耗能。(3)通过循环加载试验的结果，可以得到在钢筋混凝土结构中安装弹性构件原理的等效结果。这种结构只需在钢筋混凝土结构中安装无粘结钢筋即可实现。因此这种结构施工简单，施工方便，造价低。(4)为了提高屈服后刚度，我们有三种方法；增加杠比，将杠放在外面，缩短杠长。通过在锚处安装间隙，屈服后刚度不会改变。改变这些参数，就可以实现各种载荷-位移滞回。(5)在拟动力试验中也确认了杆的作用（屈服后刚度稳定，残余变形小）。UBRC结构施工简单，造价低，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.