Stress Wave Mitigation And Performance Optimization Of Metaconcrete

Metaconcrete is a new type of concrete made by embedding engineered aggregate into normal concrete.The engineered aggregate is made by wraping soft coating outside heavy core.The density of heavy core is higher than that of natural coarse aggregate,and the elastic modulus of soft coating is lower than those of natural coarse aggregate and mortar matrix.Due to the unique composition of engineered aggregate,there is relative movement between the heavy core and the mortar matrix of metaconcrete under the action of external load,which leads to the engineered aggregate can absorb wave energy,and mitigate stress wave herein.When the frequency of stress wave propagating in metaconcrete is around the resonant frequency of engineered aggregate,engineered aggregate can effectively attenuate the stress wave,which means the stress wave with the frequency close to the resonant frequency of engineered aggregate cannot propagate in metaconcrete.The region of frequency for which the stress wave is attenuated is called bandgap.Under strong dynamic loads such as explosion and impact,spall damage of concrete caused by stress wave will occur.In this work,the attenuation mechanism of stress wave of metaconcrete,the optimal design of engineered aggregate and the application of metaconcrete in blast-resistance are studied through numerical simulation.The main research contents and results are as follows:(1)The mechanism of metaconcrete to mitigate stress wave and the feasibility of using metaconcrete to resist blast load is studied.The response of metaconcrete subjected to blast load is studied by using LS-DYNA,and the coupled effect between the nonlinear response of material and the local resonance of engineered aggregate is analysed.The results show that engineered aggregate can absorb the energy in metaconcrete subjected to blast load,and attenuate the stress wave herein;Stress concentration appears in the matrix around engineered aggregate,resulting in the material strength of metaconcrete is lower than that of normal concrete.(2)The design method of engineered aggregate is proposed based on the bandgap characteristics of engineered aggregate.The effects of soft coating,heavy core material and the design of engineered aggregate on the bandgap characteristics of engineered aggregate and the mitigation of stress wave of metaconcrete are studied via the software LS-DYNA.The results show that soft coating plays a decisive role in the generation of bandgap;Using engineered aggregates with multiple bandgaps to make metaconcrete can improve the energy absorption capacity and the stress wave mitigation capacity of engineered aggregate.(3)The concept of enhanced engineered aggregate is proposed.The effect of enhanced coating layer on the bandgap characteristics of engineered aggregate,the stress wave mitigation and spall strength of metaconcrete is studied.The effect of mixed using of engineered aggregates with multiple bandgaps on the spall strength of metaconcrete is studied.The results show that enhanced coating has little effect on the bandgap characteristics and energy absorption capacity of engineered aggregate;The enhanced coating improves the material strength of metaconcrete.(4)The blast-resistcance performance of metaconcrete subjected to blast load is studied.The feasibility of using metaconcrete to reduce spall damage of concrete beam is investigated.The results show that enhanced metaconcrete can effectively reduce the spall damage of concrete beam subjected to blast load.