This work investigates intermodal targeted energy transfers (IMTET) for passive mitigation of a large-scale nine-story structure subjected to blast excitation. This is achieved by inducing extreme, fast time scale energy transfers from lower-frequency structural modes which are mainly excited by the blast to higher-frequency ones. These targeted (directed) energy transfers are governed by a non-resonant nonlinear dynamical mechanism induced by inelastic Hertzian vibro-impacts between the nine-story structure (referred to “primary structure”) and an internal secondary “core structure” assumed to be rigid. The clearance distribution between the primary structure and the core structure is optimized using a multi-objective genetic algorithm by minimizing both the characteristic damping time of the transient response of the primary structure, and the energy redistributed from the lowest-frequency (fundamental) structural mode to higher modes. The results show that the IMTET mechanism enables extremely rapid and nearly irreversible low-to-high frequency scattering of the blast energy in the primary structure. In turn, this nonlinear energy scattering rapidly reduces the overall amplitude of the transient structural response, even in the case of purely elastic Hertzian contacts. The mitigation performance is substantially enhanced when more realistic inelastic vibro-impact nonlinearities are considered. In the studied example with the realistic model of a nine-story structure, the synergy between extremely rapid low-to-high frequency energy redistribution and dissipation due to inelastic vibro-impacts yields a reduction of the characteristic damping time by a factor of 20 compared to the linear case. We envision that the proposed concept of rapid nonlinear IMTET is of broad applicability to general classes of dynamical and acoustical systems.

这项工作研究了多式联运目标能量转移(IMTET)，用于被动缓解受到爆炸激发的大型九层结构。这是通过诱导从主要由爆炸激发的低频结构模式到高频结构模式的极端、快速的时间尺度能量转移来实现的。这些有针对性的（定向）能量转移是由一个非共振的由九层结构（称为“初级结构”）和内部二级“核心结构”之间的非弹性赫兹振动冲击引起的非线性动力机制，假设为刚性。通过最小化主结构瞬态响应的特征阻尼时间和从最低频率（基本）结构模式重新分配的能量，使用多目标遗传算法优化主结构和核心结构之间的间隙分布到更高的模式。结果表明，IMTET 机制能够在主结构中实现爆炸能量极快速且几乎不可逆的低频到高频散射。反过来，这种非线性能量散射会迅速降低瞬态结构响应的整体幅度，即使在纯弹性赫兹接触的情况下。当考虑更现实的非弹性振动冲击非线性时，缓解性能得到显着提高。在具有九层结构真实模型的研究示例中，由于非弹性振动冲击引起的极快的低频到高频能量重新分配和耗散之间的协同作用使特征阻尼时间减少了 20 倍到线性情况。我们设想所提出的快速非线性 IMTET 概念对一般类别的动力和声学系统具有广泛的适用性。由于非弹性振动影响，极快的低频到高频能量重新分配和耗散之间的协同作用使特征阻尼时间与线性情况相比减少了 20 倍。我们设想所提出的快速非线性 IMTET 概念对一般类别的动力和声学系统具有广泛的适用性。由于非弹性振动影响，极快的低频到高频能量重新分配和耗散之间的协同作用使特征阻尼时间与线性情况相比减少了 20 倍。我们设想所提出的快速非线性 IMTET 概念对一般类别的动力和声学系统具有广泛的适用性。