Wave propagation and band gap analysis in metaconcrete for vibration control

Concrete is regarded as the main infrastructure material due to its high compressive strength, durability, and economical cost for large-scale structural members. However, standard concrete does not have much intrinsic ability to modulate elastic wave propagation or attenuate vibrations, especially at low frequencies, most detrimental for many structural systems (human-induced vibrations, machines, and traffic, as well as some seismic sources). Vibration and dynamic loads result in enhanced stresses, accelerate the fatigue behavior, and may introduce serviceability or safety problems in structures. Hence, new material adaptations for controlling undesired elastic waves are of considerable practical as well as scientific interest. In this thesis, the design and study of a new concrete material is introduced to attenuate the waves generated by the dynamic excitation. Recent advances in metamaterials science have enabled the development of new classes of composite media showing extraordinary properties in their interaction with elastic waves. We introduce a novel structural metamaterial, a metaconcrete, with significantly improved material properties for dynamic loading. In this composite material, ordinary stone and bourgeon aggregates in common concrete are replaced by engineered spherical inclusions. A metaconcrete aggregate consists of a composite structure with a dense core surrounded by a thin, compliant outer sheath. This configuration enables resonance to occur at or near the eigenfrequencies of the inclusions. To this purpose, the characteristics of the aggregates can be tuned so that specific frequencies of dynamic external loading excite resonant oscillations. When activated, these resonant aggregates counteract the incoming wave motion, thereby reducing the transmitted energy at selected frequencies and producing an effective negative mass for the overall system due to the generation of an energy band gap.