PP-ECC用于墩底塑性铰区域的抗震性能试验

为增强桥墩的抗震能力，探讨塑性铰区域采用聚丙烯纤维水泥基复合材料（PP-ECC）桥墩的抗震性能和损伤容限，设计并制作3个剪跨比为7的钢筋混凝土高墩试件，其中2个桥墩试件的塑性铰区域采用不同高度的PP-ECC材料，1个普通混凝土桥墩为对比试件。基于低周反复荷载试验获得桥墩试件开裂过程、破坏形态和水平力-位移滞回曲线等试验结果，对比分析墩底潜在塑性铰区采用不同PP-ECC高度对桥墩延性、承载力、耗能以及刚度等抗震性能指标的影响，并与普通混凝土桥墩的抗震性能指标进行对比分析。研究结果表明：与普通混凝土桥墩相比，采用PP-ECC材料可以明显改善桥墩的破坏形态，控制裂缝的宽度和发展，提高桥墩的损伤容限；局部使用PP-ECC材料可以提高桥墩的位移延性系数，该构件具有良好的变形能力和抗倒塌能力；相对普通混凝土桥墩，PP-ECC桥墩的滞回曲线面积更大且滞回环更加饱满，骨架曲线下降段较为平缓，承载能力和刚度退化缓慢，耗能能力提高了20%；PP-ECC材料高度增加1倍，桥墩位移延性系数提高了15.2%，能量耗散系数变化不大，试件的侧移刚度有一定的提高，刚度退化变缓；墩底PP-ECC材料与普通混凝土相交的界面未出现剪切滑移现象，可见PP-ECC材料的黏结性较好，可以保证2种材料协同受力，共同工作。

Experimental Investigation on Seismic Behavior of Bridge Piers with Polypropylene-engineered Cementitious Composite in Plastic Hinge Regions

In this study, the strengthening of the seismic capacity, seismic performance, and damage tolerance of bridge piers were investigated. This was performed by partially using polypropylene-engineered cementitious composite (PP-ECC) in three 7-shear span ratio RC high pier specimens. The PP-ECC was used in the plastic hinge region of two specimens, with normal concrete in the third for comparison. The bridge piers were designed, fabricated, and tested under low-cycle repeated loadings. The cracking process and failure modes were observed, and the horizontal force-displacement hysteretic curves were obtained. Based on these experimental results, the influence of the PP-ECC, with different heights for the potential plastic hinge region at the bottom of the pier, on the seismic performance (such as the ductility of piers, bearing capacity, energy dissipation, and stiffness) was compared and analyzed. The seismic performance indexes were compared and analyzed with the normal concrete pier. The use of PP-ECC significantly controlled the development and width of the cracks, and improves the failure modes of the piers compared with those of the normal concrete pier. PP-ECC had a good deformability and anti-collapse ability, and the partial use of PP-ECC improved the displacement ductility ratio of the piers. Compared with the normal concrete pier, the areas of the hysteretic curves for the PP-ECC piers were larger, the hysteretic loops were more complete, and the descending sections of the skeleton curves had lower gradients. Furthermore, slow degradations were observed in the bearing capacity and stiffness, and the energy dissipation capacity increased by 20%. When the height of the PP-ECC region was doubled, the displacement ductility ratio increased by 15.2%, the energy dissipation coefficient did not change significantly, the lateral stiffness of the specimen improves slightly, and the stiffness degradation slowed down. There was no shear slip at the interface between the PP-ECC material and ordinary concrete at the bottom of the pier. The PP-ECC material had good cohesiveness, and allowed that the two materials work together under synergistic forces.