钢吊车梁上部区域裂缝的现场调查及其加固方法研究

根据现有资料，分析了内蒙古包头钢铁公司出轧厂某车间钢吊车梁裂缝发生的原因，找出了偏心荷载是产生裂缝的主要原因。在此基础上，提出了以增加吊车梁截面的方法，在梁的两侧用角钢和高强度螺栓进行加固，并在裂缝尖端处钻孔，防止裂缝的继续发展及其他措施。为了解加固效果，现场实测了吊车梁在垂直荷载作用下角钢中的应力大小和相应措施位置腹板中的应力大小。结果表明，加固效果良好，并得出一些对吊车梁后期工作性能显著改善的结论。

Study on the Investigating and Strengthening of Crack of the Upper Part of Welded Steel Crane-Girder

Based on the investigating data on-site available the reasons why the cracks of crane-girder of the workshop of Baogang blooming plant created are analyzed. It is found that the eccentric load is a major crack reason, and the stress concentration is linear increased along with the eccentricity adding. Different chemical composition between steel and welding rod make very small cracks, it can lead to fatigue crack of the upper part of steel crane-girder. Circulatory stress and very small cracks are two necessary conditions of cracks. Macroscopic cracks make stress concentration seriously, and cracks develop continuously. . The contents of carbon and manganeses make steel force properties to reduce. Then some strengthening methods are used. First, angle steel and high strength bolts are used to increase the crane-girder's section. Second, boring holes at the end of cracks cut off the developing of cracks. Third, setting up cushion courses transmit stress. The angle steel stress and the web stress are monitored. The angle steel stress increases quickly along with the load added. The web stress of crane-girder is reduced whether load is big or small. So the fatigue cracks are created by the stress concentration. Weld position is very important for the mechanic properties of crane-girder. This method makes the later stage working properties of crane-girder are improved obviously. The crane-girder's rigiding and steadiness, especially the part steadiness, are increasing greatly. The results show that the strengthening method is well.