爆炸荷载作用下RC单向简支板的优化设计

Optimal design of RC panels against blast loads using energy-based approach

目前,对爆炸荷载作用下的钢筋混凝土(RC)结构和构件的设计主要采用控制其动力响应最大位移的方法,例如TM-5和ASCE的试算法,类似于静力作用下的极限状态设计法,虽然过程简单,却无法获得最优化的设计。由RC板的抗力—挠度(R-y)曲线分析可知,曲线下方面积代表板在爆炸荷载作用下可能吸收的能量,直接体现RC板抵抗爆炸荷载的能力。采用TM-5和ASCE推荐的单自由度体系简化RC简支单向板,选用双折线模型计算RC板的R-y曲线,分析不同配筋率的R-y曲线下方面积,面积最大时的配筋率即为该设计的最佳配筋率,改变板的几何尺寸,按上述方法分别得出不同设计方案的最佳配筋率。爆炸荷载作用下必须考虑应变率对混凝土和钢筋的应力影响和材料非线性,不能直接应用静力计算中的矩形等效原则简化计算,研究采用分层法迭代求解R-y双折线的特征值。研究成果和分析方法对爆炸荷载作用下的RC板的结构设计和加固设计具有较高的指导价值。

Displacement-controlled approach is now being used by current guidelines such as TM5 and ASCE to design RC structures against blast loads. Although this method is easy to use, it may not obtain an optimal design. Actually the area under the resistance-deflection curve of a RC member represents its energy-absorption and thus a slab with different reinforcement ratios absorbs energy differently. The optimal reinforcement ratio for a slab corresponds to its maximum energy absorption capacity. A layered analytical model which allows for the varying strain rates over the cross-section was used to calculate a bilinear resistance-deflection relationship for a simply supported slab with different ratios so that the maximum energy absorption capacity of the slab as well as its optimal reinforcement ratio could be determined. Geometric size of the slab on the influence of the optimal reinforcement ratio was also investigated. The developed method is very useful to facilitate an optimal design to resist air-blast loads.