柔性约束边界对板抗爆动力响应的影响分析

EFFECTS OF FLEXIBLE BOUNDARY RESTRAINTS ON DYNAMIC RESPONSE OF A SLAB UNDER EXPLOSION LOADINGS

约束边界的形式和刚度的差异会直接影响结构在爆炸荷载作用下的动力响应及其承载能力,现有防护结构的计算理论未能考虑柔性边界的影响,已不再适用,因此有必要建立考虑边界效应的结构抗爆计算方法。该文建立了具有周边分布柔性约束板的计算模型,推导出结构的振型函数,并计算分析了竖向弹性与阻尼约束、抗弯约束和荷载作用时间对结构位移和内力的影响。计算表明:竖向弹性与阻尼约束使板的整体位移增加,由此引起的附加惯性力会消耗部分能量,从而降低了结构的挠曲变形(相对位移)和弯矩值;周边的抗弯约束能限制结构的转动,也有效降低板的最大位移值,因此可通过调节周边柔性约束的形式和刚度提高结构的抗爆潜力。荷载作用时间主要通过参数d?t影响结构的响应,d?t较小时,随着d?t的增加,弯矩值显著增大。

The differences of the form and stiffness of boundary restraints do directly affect the dynamic responses and bearing capacity of structures under explosion loadings, and the existing theories are not suitable for its failure to take account of effects of flexible boundary conditions. Therefore, it is necessary to establish a new method. The model for a plate under explosion loadings with flexible edge restraints is established, and the mode functions are conducted to analyze the effects of a vertically elastic support and a damping support, the rotational constraint and the duration time of loads on displacement and internal force. The results show that the vertically elastic support and damping support can make the total displacement increase, and that the inertia force induced by the increase consumes energy, making the flexural deformations and bending moments decreased. The rotational restraints confine the rotation of the plate and decrease the maximum deformation. Therefore, the anti-explosion potential can be relatively improved by adjusting the form or stiffness of flexible edge constraints. Loading time gives its influence on the dynamic response mainly by the parameter ωtd. With the increase of ωtd, the bending moment will significantly increase when the parameter is smaller.