Calculation methods of elasto-plastic dynamic response of reinforced concrete beams with flexible supports under blast loading were derived based on the theory of Euler-Bernoulli beam. The main factors such as the dynamic loading characteristics, stiffness and damping of supports that have influence on the failure modes were investigated according to the criterion of dynamic ultimate resistance for reinforced concrete beams. Results show that the failure mode of reinforced concrete beam with flexible supports under blast loading not only depends on the loading characteristics, but also on the supporting conditions. The shearing failure times of reinforced concrete beams with flexible supports are delayed greatly, and the shearing failure tends to occur at higher dynamic loading rate, larger blast impulses or blast overpressures. The failure modes of the beams are transferred from flexural failures to shearing failures with the increase in supporting stiffness, and the failure times are delayed with the decrease of supporting stiffness. The peak deflection values, moments or shearing force are attenuated quickly with the increase of supporting damping, but the failure modes and failure times are not changed greatly. The supporting damping seems to have no obvious effects on increasing the ultimate resistance of reinforced concrete beams with flexible supports.%基于Euler-Bernoulli梁理论,推导了柔性边界钢筋混凝土梁在爆炸荷载作用下的弹塑性动力响应计算方法,并结合钢筋混凝土构件的动态极限抗力判别方法,分析了动荷载特征、支座刚度及支座阻尼对柔性边界钢筋混凝土梁破坏模式的影响规律.结果表明:在爆炸荷载作用下,柔性边界钢筋混凝土梁的破坏模式不仅与动载特性有关,还取决于边界条件.柔性边界可使钢筋混凝土梁的破坏时间明显延迟,动荷载加载速率越高、爆炸冲量越大,超压峰值越大,梁就越容易发生剪切破坏；随着支座刚度提高,梁的破坏模式由弯曲破坏转变为剪切破坏,破坏时间随支座刚度减小而延迟；随着支座阻尼增大,梁的挠度、弯矩和剪力幅值衰减越快,但破坏模式和破坏时间变化不大,说明支座阻尼对提高结构极限抗力的贡献很小.
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