Feasibility Research on Strengthening Damaged Steel Structure with Self-Stress SMA
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摘要: 为提高钢结构疲劳裂纹的加固效率,将形状记忆合金(SMA)作为预应力的载体引入加固方案。首先,分别对两种不同材质的形状记忆合金(NiTiNb-SMA和Fe-SMA)的力学性能和热力学性能进行试验研究,确定材料的弹性模量、抗拉强度等力学参数,研究其加热恢复性能,并确定其应用于试件加固时的最佳尺寸参数和激活温度。然后通过有限元方法分析了止裂孔法、CFRP布粘贴加固止裂孔法、NiTiNb-SMA及CFRP粘贴加固止裂孔法和Fe-SMA粘贴加固止裂孔法对损伤钢板加固的修复效率,最后通过静载试验验证数值模型的可靠性。研究结果表明:NiTiNb-SMA和Fe-SMA材料的本构关系存在较大差异,NiTiNb-SMA的力学性能参数高于Fe-SMA。NiTiNb-SMA材料在室温和高温条件下的应力应变历程有较大差别,但弹性模量和抗拉强度接近;在激活温度为170℃下,NiTiNb-SMA的恢复应力为274 MPa,高出Fe-SMA约96 MPa。对比止裂孔法,有限元结果表明CFRP、NiTiNb-SMA及CFRP复合贴片和Fe-SMA的加入能使孔边应力集中处的应力分别降低58.8%、87.0%和122.4%,静载试验结果表明实测结果与有限元结果总体上线性吻合较好,因此通过形状记忆合金引入预应力对加固损伤钢结构具有广阔的应用前景。Abstract: In order to improve the reinforcement efficiency of fatigue cracks in steel structures, shape memory alloy (SMA) was introduced as a prestressed carrier into the strengthening scheme. First, the mechanical properties and thermodynamic properties of two different shape memory alloys (NiTiNb-SMA and Fe-SMA) were tested to determine the material’s elastic modulus, tensile strength and other mechanical parameters, the heating recovery performance was also investigated, and its optimal size parameters and activation temperature when applied to repair were determined. Then, the finite element method was used to analyze the repair efficiency of the stop-hole method, CFRP patched stop-hole method, NiTiNb-SMA and CFRP patched stop-hole method to strengthen damaged steel plates. Finally, the reliability of the model was verified by static load test. Research results showed that there was a large difference in the constitutive relations between NiTiNb-SMA and Fe-SMA materials, and the mechanical properties of NiTiNb-SMA were higher than those of Fe-SMA.The stress-strain behavior of NiTiNb-SMA material at room temperature and high temperature was quite different, but the elastic modulus and tensile strength were nearly close.At an activation temperature of 170 ℃, the recovery stress of NiTiNb-SMA was 274 MPa, which was about 96 MPa higher than that of Fe-SMA. Compared with the stop-hole method, the finite element results showed that the addition of CFRP, NiTiNb-SMA and CFRP composite patches, and Fe-SMA could reduce the stress at the edge of the hole by 58.8%, 87.0% and 122.4%, respectively. The test results and FEM results were generally in good agreement with the linearity. It is indicated that the shape memory alloy has broad application prospects for strengthening damaged steel structures by introducing prestressing force.
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Key words:
- shape memory alloy /
- self-stress /
- test /
- mechanical properties /
- strengthening
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