基于Fe-SMA的钢桥面板疲劳裂纹装配式主动加固方法

为实现对钢桥面板的快速加固，提出了基于铁基形状记忆合金(Fe-SMA)的钢桥面板疲劳裂纹新型装配式主动加固的方法；通过精细化双面加固有限元模型计算结果及对初步激活与加载试验的观察，验证了加固系统安全性与可靠性；在此基础上以U肋对接焊缝的疲劳裂纹为研究对象，根据线弹性断裂力学，结合该疲劳细节受力与开裂特征，采用循环荷载作用下表面裂纹和中裂纹尖端的Ⅰ型裂纹应力强度因子幅值对加固系统的加固效果进行评价，确定了针对不同长度裂纹的具体加固方案。研究结果表明:基于Fe-SMA的钢桥面板疲劳裂纹主动加固方法可将裂纹尖端应力强因子幅值降低至扩展阈值以下，能有效遏制疲劳裂纹的进一步扩展；对于长度在50 mm以下的未贯穿型疲劳裂纹可采用宽度为60 mm的Fe-SMA进行加固，裂纹前缘关注点应力强度因子降幅达90%以上；当贯穿型疲劳裂纹长度为50~120 mm时，可采用宽度为120 mm的Fe-SMA进行加固；当疲劳裂纹长度为120~350 mm时，需采用底板、腹板同时加固的方法来对疲劳裂纹进行加固，均能达到理想的止裂状态。 

A Fe-SMA-based fabricated active reinforcement method for fatigue cracks in steel bridge decks

A new fabricated active reinforcement method for fatigue cracks in steel bridge decks based on iron-based shape memory alloy (Fe-SMA) was proposed to achieve the rapid reinforcement of the steel bridge decks. The safety and reliability of the reinforcement system were verified by the calculation results of the finite-element refined double-sided reinforcement model and the observation of the preliminary activating and loading test. On this basis, the fatigue cracks in the U-rib butt weld were taken as the research object, the linear elastic fracture mechanics was involved, the stress and cracking characteristics of the fatigue details were considered, the amplitude of the stress intensity factor of mode-Ⅰ cracks at the tips of surface and internal cracks under cyclic loading was used to evaluate the reinforcement effect of the reinforcement system, and the specific reinforcement schemes for cracks with different lengths were determined. Analysis research results show that the amplitude of the stress intensity factor of the crack tips can be reduced to below the propagation threshold by the Fe-SMA-based active reinforcement method for fatigue cracks in steel bridge decks, and can effectively restrain the further propagation of fatigue cracks. The non-penetrating fatigue cracks shorter than 50 mm can be reinforced by the Fe-SMA with a width of 60 mm, and the stress intensity factor of the points of concern at the crack tips reduces by more than 90%. The 50-120 mm long penetrating fatigue cracks can be reinforced by the Fe-SMA with a width of 120 mm. The fatigue cracks with a length of 120-350 mm need to be reinforced simultaneously by bottom plates and webs. The desired crack-arresting state is achieved invariably. 2 tabs, 19 figs, 30 refs.