U形肋加劲板局部稳定性试验研究

Experimental study on local stability of U-rib stiffened plate

U形肋加劲板是构成钢箱梁顶板、底板的主要板件,U形肋腹板与被加劲板局部失稳是其两种主要失稳破坏模式。为研究U形肋加劲板的局部稳定性能,分别设计并制作了U形肋腹板与被加劲板壁板两组局部稳定试件,并考虑U形肋腹板宽厚比、被加劲板宽厚比以及U形肋翼缘与腹板间弯曲半径变化。通过轴压试验得到了U形肋加劲板的局部失稳破坏模式、稳定承载力、应力-位移曲线以及局部稳定折减系数。试验研究表明:随着局部板件宽厚比的增大,试件由强度破坏转变为失稳破坏,且失稳破坏特征表现得越明显。当板件宽厚比不小于22.5时,宽厚比较大的板件先于其他板件失稳。U形肋腹板与翼缘之间弯曲半径增大时,U形肋腹板宽度及宽厚比变大,导致U形肋腹板稳定承载力降低。将试验结果与公路钢桥规范中的稳定系数曲线对比发现,对于钢桥规范中的稳定曲线,采用钢材屈服强度计算得到的板件稳定承载力明显小于试验值,而采用抗拉强度计算得到的板件稳定承载力接近试验值,说明采用钢桥规范计算U形肋加劲板稳定承载力,其安全系数和钢材的抗拉强度与屈服强度比值相当。

U-rib stiffened plate is the main bearing members of the top and bottom flanges of a steel box girder. The local buckling of U-fib web and the stiffened plate are the two main failure modes. To study the local stability performance of U-rib stiffened plate, two specimens of U-rib web and stiffened plate were designed and manufactured, where ratio of width to thickness of U-rib web and stiffened plate as well as the bending radius between U-rib flange and web are the main parameters. Through the compression test, local buckling failure mode, the stability bearing capacity, stress-displacement curve and local stability reduction factor of the specimens were obtained. Experimental results show that ： with the increase of ratio of width to thickness of local plate member, the failure mode of specimen will be changed from strength failure into buckling, and the buckling failure characteristics turn to be more and more obvious. When the ratio of width to thickness of plate member is greater than 22.5, the plate member would be instability earlier than other members. With the increase of the bending radius between U-rib flange and web, the width of the web and its ratio of width to thickness will be larger, which will result in the decrease of U-rib＇ s stability bearing capacity. Comparing the test results with the stability coefficient curve of the China design specification on highway steel bridges, it can be seen that using yield strength to calculate the local stability reduction factor, the calculated plate＇ s stability bearing capacity is obviously less than the experimental value ; while using ultimate strength to calculate the local stability reduction factor, the calculated plate＇ s stability bearing capacity is close to the experimental value. It is shown that the safety factor will be equal to the ratio of ultimate strength to yield strength, when using the steel bridge specification to calculate the stability bearing capacity of the U-rib stiffened plate.