Cyclic loading testing of repaired SMA and steel reinforced concrete shear walls

This paper presents the results of reverse cyclic load testing of a repaired slender concrete shear wall reinforced internally with superelastic Shape Memory Alloys (SMAs) in the boundary zones within the plastic hinge region. In addition, a companion-repaired wall reinforced with deformed mild steel was also tested. Provided herein is an assessment of the performance of the repaired walls against the same set of walls previously tested in their original condition. The repair strategy included removing heavily damaged concrete within the plastic hinge region, replacing ruptured and buckled reinforcing steel, and shortening of the SMA bars in the boundary zones. High-strength, self-consolidating concrete replaced the removed concrete. The concrete above the plastic hinge region remained intact given the negligible damage (hairline cracking) of the original walls in this zone. The test results demonstrated that SMA-reinforced concrete structural components are self-centering, permitting repair of damaged areas. Furthermore, the SMA bars were re-usable for the repair application due to their capacity to reset to their original state within the range of inelastic strains of up to 6%. The repaired walls were capable of restoring the yield and ultimate lateral load capacities, but sustained lower drift capacities. The repaired SMA wall was capable of recovering the imposed lateral drifts up to 2%, after which residual displacements accumulated due to rupturing of the SMA bars in the boundary zone. The repaired walls dissipated up to 7.8% more energy than their original walls for a significant portion of the loading range. The length of the SMA bars and the presence of starter bars in the original walls were influencing factors in the location of failure of the SMA- and steel-reinforced walls.

本文介绍了对在塑性铰区域内边界区域采用超弹性形状记忆合金（SMA）内部加固的修复细长混凝土剪力墙进行反向循环荷载试验的结果。此外，还对一根采用变形低碳钢加固的对比修复墙进行了试验。在此对修复后的墙体与先前在原始状态下进行试验的同一组墙体的性能进行了评估。修复策略包括去除塑性铰区域内严重受损的混凝土，更换断裂和屈曲的钢筋，以及缩短边界区域内的SMA筋。高强度自密实混凝土替代了被去除的混凝土。鉴于原始墙体在塑性铰区域上方该区域的损伤（发丝裂缝）可忽略不计，该区域上方的混凝土保持完好。试验结果表明，SMA加固的混凝土结构构件具有自复位能力，允许对受损区域进行修复。此外，由于SMA筋在高达6%的非弹性应变范围内能够恢复到其原始状态，因此可用于修复应用。修复后的墙体能够恢复屈服和极限侧向荷载能力，但承受的侧移能力较低。修复后的SMA墙能够恢复施加的高达2%的侧向侧移，之后由于边界区域内SMA筋的断裂而累积残余位移。在大部分加载范围内，修复后的墙体比原始墙体多耗散7.8%的能量。SMA筋的长度以及原始墙体中起始筋的存在是影响SMA和钢筋加固墙体破坏位置的因素。