Fe-SMA主动加固钢桥面横隔板弧形切口疲劳裂纹实桥应用研究

Research on Using Fe-SMA Material to Actively Strengthen FatigueCracks of Arc-Cutouts in Diaphragms

为确定铁基形状记忆合金(Fe-SMA)主动加固正交异性钢桥面板横隔板弧形切口疲劳裂纹的可行性,以某在役钢箱梁斜拉桥为背景进行实桥加固研究。根据现场横隔板弧形切口的开裂特征,在对裂纹钻孔止裂的基础上,提出利用Fe-SMA材料对横隔板弧形切口裂纹进行粘贴加固的方案,并进行加固施工。通过现场测试得到Fe-SMA板条热激活过程的应变和温度变化,分析Fe-SMA板条和钢板之间的相互作用及加固机理。结果表明:粘贴Fe-SMA板利用Fe-SMA热驱动形状记忆效应可有效便捷地为结构施加预压应力,实现对受损部位的主动加固;经过Fe-SMA联合止裂孔修复后,热驱动作用下的Fe-SMA可以产生200~240 MPa的预拉应力,并在钢板止裂孔边缘施加43~90 MPa的压应力,可有效阻止裂纹进一步扩展;加固体系在加热激活过程完好可靠,当控制一侧加热区域中部温度为200℃时,热传导作用下非加热区域中部的温度为60℃以下,而背面总体温度基本在90℃以下。

This study investigates the feasibility of using the iron-based shape memory alloy(Fe-SMA)to actively strengthen fatigue cracks of arc-cutouts in diaphragms of the orthotropic steel deck.An in-service cable-stayed bridge with superstructure consisting of steel box girders was used as a case.Given the cracking characteristics of the arc-cutouts in the diaphragms,it was proposed to drill crack stop holes first,then to bond Fe-SMA plates to repair the cracks.Tests were performed to observe the strain responses and temperature variation of the Fe-SMA plates during the thermal activation process,and the interaction between the Fe-SMA material and steel diaphragm and the strengthening mechanism were analyzed.It is shown that bonding Fe-SMA plates is an effective and convenient way to apply pre-compressive stresses to the diaphragm,which takes good use of the thermal-driven shape memory effects of Fe-SMA material to achieve active strengthening of damaged locations.Combined with crack stop holes,the Fe-SMA plate can generate a pretensile stress of 200 to 240 MPa under the thermal drive,and impose a compressive stress of 43 to 90 MPa circling the crack stop hole,leading to effective hindrance of the further propagation of cracks.The Fe-SMA plate remained intact during the thermal activation process,when the temperature at the center of the heating zone reached 200℃,the temperatures at the center and back of the non-heating zone were below 60℃and 90℃,respectively,due to the heat conduction effect.