Del Zoppo Marta, Di Ludovico Marco, Balsamo Alberto, Prota Andrea
Department of Engineering, University of Naples Parthenope, 80143 Naples, Italy.
Department of Structures for Engineering and Architecture, University of Naples Federico II, 80125 Naples, Italy.
Polymers (Basel). 2018 Mar 24;10(4):361. doi: 10.3390/polym10040361.
Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The Fiber Reinforced Polymers (FRP) externally bonded reinforcement is known to be a valid technique to improve the shear capacity or the ductility of existing RC columns. However, few experimental tests have proven its effectiveness in the case of columns affected by shear interaction mechanisms. In this work, the behavior of existing RC columns with border line behavior between flexure and shear have been investigated in the case of poor quality concrete and light FRP strengthening with local jacketing and medium quality concrete and strong FRP strengthening with local jacketing, in order to highlight the effect of concrete strength on the effectiveness of the retrofit intervention. As an alternative to FRP jacketing; the effectiveness of the Fiber Reinforced Cementitious Composite (FRCC) jacketing for the seismic strengthening of columns with highly deteriorated concrete cover or columns already damaged by an earthquake is also evaluated. Six full-scale RC columns have been tested under cyclic loading: one was used as a control specimen; four were strengthened in the potential plastic hinge region with carbon FRP (CFRP); and one was fully jacketed with FRCC. The comparison between poor and medium quality concrete columns showed that the CFRP local jacketing is more effective in the case of poor quality concrete. The FRCC jacketing appears to be a sound repair strategy and a suitable alternative to the FRP jacketing in case of poor quality; however, more experimental research is needed for improving this retrofit technique.
现有结构中典型的钢筋混凝土（RC）柱在地震事件中常常会过早失效（即纵向钢筋屈曲和剪切相互作用机制），这是由于混凝土质量差以及潜在塑性铰区域缺乏适当的抗震细节。众所周知，外部粘贴纤维增强聚合物（FRP）加固是提高现有RC柱抗剪承载力或延性的有效技术。然而，很少有试验测试证明其在受剪切相互作用机制影响的柱中的有效性。在这项工作中，研究了在混凝土质量差且采用局部包裹轻质FRP加固以及混凝土质量中等且采用局部包裹强力FRP加固的情况下，具有弯曲和剪切临界状态的现有RC柱的性能，以突出混凝土强度对加固干预有效性的影响。作为FRP包裹的替代方案，还评估了纤维增强水泥基复合材料（FRCC）包裹对混凝土保护层严重劣化的柱或已被地震损坏的柱进行抗震加固的有效性。六根足尺RC柱在循环加载下进行了测试：一根用作对照试件；四根在潜在塑性铰区域用碳纤维增强塑料（CFRP）加固；一根用FRCC进行全包裹。质量差和质量中等的混凝土柱之间的比较表明，在混凝土质量差的情况下，CFRP局部包裹更有效。FRCC包裹似乎是一种合理的修复策略，在质量差的情况下是FRP包裹的合适替代方案；然而，需要更多的试验研究来改进这种加固技术。
