Mitigation of Earthquake Damage of Reinforced Concrete Structures

众所周知，大量的抗剪钢筋提高了钢筋混凝土构件的抗剪能力和延性。然而，过度使用钢筋在可施工性和经济性方面都可能适得其反。本研究的主要目的是研究控制纵向钢筋的粘结如何改善钢筋混凝土结构的抗震性能，如抗剪强度和延性。本研究进行了广泛的实验和分析研究。试验研究采用了15根300×300 mm方形钢筋混凝土柱在反复荷载作用下进行试验。柱子有六种不同的粘合条件，从使用普通变形棒的完美粘合到完美的松开粘合。其他试验变量包括剪跨比、抗剪强度比和未粘结区域的长度。试验结果表明，通过降低纵向钢筋的粘结强度，可以将极限状态下的破坏模式由剪切破坏转变为弯曲破坏。试验结果还表明，粘结控制筋加固的钢筋混凝土柱的抗剪强度和延性明显好于普通钢筋加固的钢筋混凝土柱。通过三维非线性有限元分析，验证了纵向钢筋粘结控制对提高钢筋混凝土桥墩抗震性能的作用。提出的分析方法可以模拟无粘结钢筋混凝土桥墩的整体滞回性能和破坏模式，与试验结果具有很好的相关性。

It is well known that a large amount of shear reinforcement enhances the shear capacity and ductility of RC members. Excessive use of reinforcements, however, can become counterproductive in terms of both constructability and economy. The main objective of this study is to examine how controlling the bond of the longitudinal reinforcements can improve seismic performance, such as shear strength and ductility of RC structures. An extensive experimental and analytical investigation was carried out in this study. The experimental study employed fifteen 300 x 300 mm square RC columns tested under reversed cyclic loading. The columns were of six different bond conditions, varying from the perfect bond with the use of ordinary deformed bars, to the perfect unbond. The other test variables included the shear span to depth ratio, the shear to flexural strength ratio, and the length of unbonded region. The results of the experiment revealed that the failure mode at the ultimate state could be changed from shear to flexure by reducing the bond strength of the longitudinal bars. The test results also showed that RC columns reinforced with bond controlled bars had significantly better shear strength and ductility than RC columns reinforced with ordinary bars. Three Dimensional nonlinear finite element analysis was also carried out to verify the enhancement of seismic performance of reinforced concrete bridge piers by controlling bond of longitudinal reinforcement. Proposed analytical method was found to model the global hysteretic behavior and failure mode of unbonded RC piers producing an excellent correlation with that of the experimental results.