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The study presents the dynamic structural response of steel member subjected to a localized impact from falling rock blocks in rockfall areas. A novel compliance contact model is derived for the interaction between the elastic-plastic member (the target) and an impacting rock block. Unlike other existing models, the proposed compliance contact model accurately evaluates the material properties of the rock block (considered as a deformable indenter) and of the steel target (considered as an elastic-plastic target of finite thickness). A simplified two degrees of freedom (2-DOF) lumped masses model accounting for nonlinear contact interaction and material nonlinearities is used to describe the dynamics of the phenomenon. The proposed contact law and the 2-DOF model are validated with detailed static and dynamic analyses conducted with finite element software ANSYS. The results are compared and commented in order to be implemented in future civil engineering applications. [ABSTRACT FROM AUTHOR]

Linear energy harvesters have a narrow frequency bandwidth and hence operate efficiently only when the excitation frequency is very close to the fundamental frequency of the harvester. Consequently, small variations of the excitation frequency around the harvester's fundamental frequency drop the energy output making the harvesting process inefficient. To extend the harvester's bandwidth, some recent solutions call for using electromechanical devices with stiffness-type nonlinearities. This work deals with the optimisation of the performance of a single degree-of-freedom electromagnetic energy harvester whose mechanical behaviour has a Duffing-type nonlinearity, as for suspended masses, to reduce the size of energy harvesting devices without affecting their power output. The vibration input is assumed as a broadband Gaussian white noise base acceleration. It is analytically shown that the optimum load resistance of the device is different to that which is dictated by the principle of impedance matching. [ABSTRACT FROM AUTHOR]