体外预应力筋加固不同初始状态箱梁受力性能的试验研究

Experimental analysis on mechanical property of externally prestressed box beams based on different original status

设计和制作5片普通钢筋混凝土小箱梁,基于被加固构件不同的初始受力状态,采用构件预裂、不同张拉控制应力、不同配筋率等方式,进行体外预应力加固箱梁受力性能的试验研究,并与理论计算结果进行比较。研究表明:体外预应力加固可以明显提高结构刚度和承载力,预裂梁加固和完整梁加固没有明显区别;箱梁存在剪力滞现象,开裂后较开裂前明显;预应力筋张拉控制应力越小,应力增量增长越快。原构件配筋率越小,应力增量会有适当增加;在试验中,体外预应力筋极限应力增量实测值与挠度法的计算值较为吻合,在正常使用状态下应力增量用结构力学方法计算最为适合。

Five reinforced concrete box beams were designed in the test.According to different original status,such as crack,different controlled stretching stress and reinforcement ratio,mechanical property of the box beams strengthened with external prestressed tendons were analysed in the test and comprared with the calcucalted results.The study shows that the rigidity and bearing capacity of strengthened beam can be improved with external prestressing tendons,and there is no clear difference between the beam with original crack and that without crack.The shear lag effect after cracking is more obvious than before.The less the controlled stretching stress is,the more rapidly the prestressed stress increment increases.The reinforment ratio shows a certain influence on the stress increase.In the test,the measured ultimate stress of external prestressed tendon agrees with the calculated result based on energy method,and the stress in serviceability stage agees with the result based on structural mechanics method.