钢筋混凝土柱在侧向撞击作用下破坏模式研究

Investigation into Failure Mode of RC Column Subjected to Impulsive Load

近似地分析了结构构件在侧向冲击荷载作用下的动力反应模式。得出了钢筋混凝土柱在冲击荷载作用下弯曲型变形与直剪型变形2种单自由度模型动力反应计算公式,并尝试将构件几何尺寸、材料力学性能以及冲击荷载都作为随机变量,考虑荷载不同持时及不同峰值,用打靶法计算了一个实例构件在瞬时冲击荷载作用下的破坏概率,为初步判断构件的破坏模式提供依据。计算结果表明荷载持时与峰值是决定结构构件破坏模式的重要因素。从构件破坏模式的变化过程来看,将构件在侧向撞击荷载作用下的动力反应分解成弯曲型与直剪型是合理的,失效概率的计算结果与定性分析的趋势是一致的。直剪型动力反应的振动频率远大于弯曲型动力反应的振动频率,反映了结构构件2种不同的破坏机制有很大的差别。当荷载峰值增加、持时缩短时,构件的动力反应趋向于直剪型,当荷载峰值减小、持时增加时,构件的动力反应趋向于弯曲型。

An approximate analysis approach about dynamic response of structure member subjected to impulsive load was made from the second class of Lagrange Equation.Furthermore,a solution for computation of two kinds of SDOF system models,in flexural response mode and in direct shear response mode was derived.Attempt was also made to investigate the failure probability of RC members with random properties,such as impulsive load,geometrical and material properties being treated as random variables.An example is demonstrated where a structural column is exposed to various combinations of peak pressure and loading duration,with targeting practice to evaluate its failure probability as a primary estimation of the failure mode.The results show that the pressure peak value and its loading duration are the two significant factors in dictating the failure mode.It could be seen from the development of failure mode that it is quite reasonable to divide failure modes into flexural type and direct type,which corresponds to the qualitative analysis.The frequency of direct shear is greatly larger than that of flexural vibration,indicating the notable difference between two failure modes.A larger peak value and shorter lasting time is accompanied likely by direct shear mode and the vice versa.