FATIGUE PERFORMANCE OF CRACKED WELDED CRUCIFORM JOINTS STRENGTHENED BY CFRP
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摘要: 疲劳破坏是焊接钢桥在循环荷载下失效的常见形式,为了延长其寿命,需要对开裂结构进行加固修复。碳纤维复材(CFRP)由于优良的性能,广泛应用于混凝土结构加固中,而很少用于焊接钢结构。通过试验和有限元方法研究循环荷载作用下不同初始裂纹深度、CFRP布厚度和弹性模量对疲劳性能的影响。采用有限元软件ABAQUS分析加固和未加固焊接十字接头应力强度因子的变化规律,并与解析结果相比较。分析发现:未加固试件数值模拟解和理论解得到的应力强度因子误差很小,验证了数值模拟的准确性。当胶层分别采用CPE8和黏结单元(cohesive element)来模拟时,最大偏差为-3.4%。CFRP能够有效降低裂纹尖端处强度因子,延长其疲劳寿命,最大增幅达到67%。当CFRP布弹性模量和厚度越大,对裂纹尖端处应力强度因子的降低幅度越明显。基于Paris公式估算十字接头的剩余疲劳寿命,并将预测寿命与试验结果进行对比,发现吻合较好。Abstract: Fatigue failure is a common form of failure of welded steel bridges under cyclic loading. In order to extend its life, the cracked structure needs to be strengthened and repaired. Due to its excellent performance, CFRP has been widely used in the reinforcement of concrete structures, but rarely used in welding steel structures. In the paper, the effects of different initial crack depths, CFRP fabric thickness and elastic modulus on fatigue performance under cyclic loading were studied through experiments and finite element methods. The finite element software ABAQUS was used to analyze the change laws of stress intensity factors of reinforced or unreinforced welded cruciform joints, and compared with the analytical results. It was found that the error of the stress intensity factor obtained by the numerical simulation solution and the theoretical solution of the unreinforced specimen was very small, which verified the accuracy of the numerical simulation. The adhesive layer was simulated by using CPE8 and cohesive element, and the maximum deviation was found to be -3.4%. CFRP could effectively reduce the strength factor at the cracking tip and extend its fatigue life, with a maximum increase of 67%. When the elastic modulus and thickness of the CFRP cloth were larger, the decrease of the stress intensity factor at the cracking tip was more obvious. The remaining fatigue life of the cruciform joints was estimated based on the Paris formula, and the predicted life was compared with the test results, and it was found that the agreement was good.
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Key words:
- CFRP /
- welded cruciform joint /
- fatigue life /
- numerical simulation /
- stress intensity factor
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