Study On Dynamic Response Of Reinforced Concrete Slab Based On Meso-model Under Explosive Load

Concrete/reinforced concrete is widely used in civil and military engineering,and is an important component material of Engineering structure.At present,regional conflicts,terrorist attacks,negligence of gas in daily life and aging of chemical facilities in production all lead to frequent explosion accidents.The damage of structure caused by explosive impact load causes serious loss of life and property.Therefore,the study of the response of concrete and reinforced concrete structural members under explosive load has attracted many scholars' attention.The existing research on the response of concrete slabs under explosive loading is basically from a macro perspective,which regards concrete as a continuous homogeneous medium,but ignores the complex meso-structure inside concrete materials.Under the action of strong dynamic load,the propagation law of stress wave is very complicated.The interaction between stress wave and meso-structure should be fully considered,including the interaction between stress wave and steel bar,aggregate,ITZ and other components,cracks,and the impact on the overall failure mode.In this paper,a Meso-Random aggregate model of plain/reinforced concrete slab is established by considering the aggregate-mortar interface and steel-mortar interface.LS-DYNA was used for numerical simulation of reinforced concrete slabs based on meso-modeling under explosive loading.The accuracy of the meso-modeling method was verified by comparing with the experimental and homogeneous modeling methods.Furthermore,the structural dynamic response of plain/reinforced concrete slabs based on meso-modeling under different explosive loads was studied,and the response process and failure mode of plain/reinforced concrete slabs were obtained.The results show that:(1)Under low explosive loading(1kg,2kg),the influence of meso-structure on plain/reinforced concrete slab is less,and there is no significant difference compared with homogeneous model.The failure modes of meso-plain/reinforced concrete slabs are mainly longitudinal and transverse plastic hinge lines,and plain concrete slabs have more cracks than reinforced concrete slabs due to the absence of reinforcement.The central section of plain/reinforced concrete is V-shaped.The more dosage,the more plastic hinge lines.(2)Under high explosive loading(5kg,10 kg and 15kg),the meso-structure has a great influence on plain/reinforced concrete slabs,which is quite different from the homogeneous model.The meso-modeled plain/reinforced concrete slabs have craters in the center of the front blasting face.Due to the action of strong tensile wave,spallation and collapse of the concrete on the back of the slabs occur.The slabs change from a single longitudinal and transverse plastic hinge line to circular and radial cracks ce ntered on the plate blasting pit.With the increase of explosive charge,the bigger the explosion pit on the front side and the more serious the concrete cracking on the back side.The larger the charge is,the more radial cracks and annular cracks develop around the center of the slab,the more bare the steel bar(reinforced concrete slab)is,and the more serious the bending is.With the increase of the dosage,the central section develops from V-shaped to funnel-shaped,and the local damage in the middle of the plate becomes more serious.Under heavy loads,plain concrete often breaks into larger blocks,and reinforced concrete only appears in the middle of the slab through the upper and lower blasting pits,other positions are relatively complete.