边界约束对梁抗爆动力响应的影响(Ⅰ)–理论研究及分析

Effects of boundary restraints on dynamic responses of a beam under blast loadings(Ⅰ)-theoretical study and analysis

边界约束的差异会直接影响结构的抗爆动力响应及承载能力,建立了复杂约束条件下抗爆梁在弹性阶段和塑性阶段的解析计算方法,并计算分析了竖向弹性与阻尼约束、水平约束刚度、抗弯约束、荷载形式以及屈服弯矩动力强化系数对动力响应的影响。计算表明:竖向弹性与阻尼约束会引起附加惯性力,能够明显降低结构在弹塑性阶段的位移动力系数。水平约束和抗弯约束影响结构的动态响应主要在塑性阶段,水平约束使梁截面在变形过程中产生横向压力,抗弯约束直接限制刚体转动,均有效降低了梁位移动力系数,相对提高结构的承载力。相同约束刚度和荷载峰值条件下,平台荷载下结构的位移动力函数均高于三角形荷载下位移动力函数,说明动荷载的作用时间越长,对结构承载越不利。另外考虑屈服弯矩的动力增强系数时,可提高结构的抗爆潜力。

Dynamic responses and bearing capacity of members under blast loadings are directly affected by different boundary restraints.Both elastic and plastic analytical methods for a beam with general flexible supports and restraints under blast loadings were proposed,and the effects of vertical elastic and damping support,horizontal supporting stiffness,rotational constraint,loading characteristics and dynamically intensified coefficient of yielding bending moment on responses were analyzed.The results showed that the inertia forces owing to vertical elastic and damping support can decrease the dynamic coefficient of the beam deflection markedly in elastic-plastic stages;horizontal supports exerting a transverse pressure on beam cross-section in deformation process and rotational restraints confining rotation of rigid body directly both have great effects on the dynamic responses of the beam mainly in plastic stage to reduce the dynamic coefficient of the beam displacement and to increase the load-carrying capacity of the beam;under on the condition of the same constraints and peak load,the dynamic coefficient of the beam displacement with rectangular pulse loads is always higher than that with triangular pulse loads,it means that longer duration of pulse loads is negative to the load-bearing capacity of the beam;in addition,the potential anti-explosion ability of a beam can be improved by taking intensified coefficient of yielding bending moment into account.