冲击下箱型梁弯曲失效临界载荷的评估方法研究

An evaluation method of the critical load of box girders under impact load

箱型梁作为工程应用最广泛结构之一,其结构安全裕度需得到清晰表达。箱型梁通常具有纵横加筋结构,冲击载荷下容易发生局部结构屈曲,但是箱型梁后屈曲失稳路径相对稳定,难以采用现有方法确定其失效对应的临界载荷。以简支钢质箱型梁为研究对象,首先研究了非线性有限元建模方法因素的影响,分析不同冲击载荷下箱型梁动态响应的变化规律;其次,根据不同冲击载荷工况计算结果,绘制冲击载荷与箱型梁位移曲线,提出了振幅极值准则和曲率极值准则两种新准则用于箱型梁动态失效临界载荷下限值与上限值的评估;最后,将该准则推广应用于三角形、矩形冲击载荷与落锤冲击作用下箱型梁弯曲失效的临界载荷评估,以及不同梁截面、边界条件和载荷工况下箱型梁弯曲失效临界载荷的评估。该研究结论可为冲击载荷下箱型梁结构安全评估提供基础支撑。

Box girder is one of the most widely used structures in engineering.The safety margin of box girder needs to be clearly expressed.As box girders usually have longitudinal and transverse reinforcement structures,they are prone to buckling under impact loads.However,the buckling path of box girders are relatively stable,making it difficult to determine the critical load corresponding to its failure with existing methods.Firstly,the structural dimensions and material parameters of the box girder are introduced.Secondly,based on the calculation results under different impact loads,a vertical displacement-impact load curve of the girder is formed.And a new criterion for evaluating the lower and upper limit of the box girder’s critical load under impact is proposed.Then,the criterion is applied to evaluate the critical failure conditions of box girder under the triangular,rectangular impact load,and drop load.Also,this criterion can be used to evaluate the critical bending load of box girders with different sections and under different boundary conditions.The results of this article may provide basic support for the safety assessment of box girders under impact load.