To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based sim...To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.展开更多
In this study,a finite element(FE)analysis of shallow tunnels exposed to a blast inside the tunnel,with soil as surrounding medium and a structure at ground level,was performed.The ConWep program,developed by the US A...In this study,a finite element(FE)analysis of shallow tunnels exposed to a blast inside the tunnel,with soil as surrounding medium and a structure at ground level,was performed.The ConWep program,developed by the US Army,was used to simulate blast loading using ABAQUS/Explicit■.Drucker-Prager(D-P)plasticity model,concrete damage plasticity(CDP),and Johnson-Cook(J-C)plasticity models were used to define the behavior of the soil,concrete,and reinforcement,respectively.FE analysis was carried out to compare the damages to the superstructure with variation in the cross-sectional shapes of the tunnel under internal blast loading.Three tunnel shapes(circular,rectangular,and horseshoe cross-sections)were considered in the FE analysis.An explosive of 100 kg TNT was located at the center of the cross-section of the tunnel.The response of the tunnel in terms of displacement and stress at critical locations was computed.The results showed that changes in the cross-section of the tunnel affect the stability of the tunnel,even when keeping all other factors constant.It was observed that the intensity of the stresses was the highest for a rectangular tunnel and lowest for a circular tunnel.Furthermore,it was also determined that the tunnel with a rectangular cross-section experienced the maximum displacement in the reinforced concrete(RC)lining compared with the horseshoe and circular tunnels.The displacement measured at critical structural members of the superstructure was found to be the highest for the tunnel with a rectangular cross-section and lowest for the tunnel with a circular cross-section.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271317 and 52071149)the Fundamental Research Funds for the Central Universities(HUST:2019kfy XJJS007)。
文摘To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.
文摘In this study,a finite element(FE)analysis of shallow tunnels exposed to a blast inside the tunnel,with soil as surrounding medium and a structure at ground level,was performed.The ConWep program,developed by the US Army,was used to simulate blast loading using ABAQUS/Explicit■.Drucker-Prager(D-P)plasticity model,concrete damage plasticity(CDP),and Johnson-Cook(J-C)plasticity models were used to define the behavior of the soil,concrete,and reinforcement,respectively.FE analysis was carried out to compare the damages to the superstructure with variation in the cross-sectional shapes of the tunnel under internal blast loading.Three tunnel shapes(circular,rectangular,and horseshoe cross-sections)were considered in the FE analysis.An explosive of 100 kg TNT was located at the center of the cross-section of the tunnel.The response of the tunnel in terms of displacement and stress at critical locations was computed.The results showed that changes in the cross-section of the tunnel affect the stability of the tunnel,even when keeping all other factors constant.It was observed that the intensity of the stresses was the highest for a rectangular tunnel and lowest for a circular tunnel.Furthermore,it was also determined that the tunnel with a rectangular cross-section experienced the maximum displacement in the reinforced concrete(RC)lining compared with the horseshoe and circular tunnels.The displacement measured at critical structural members of the superstructure was found to be the highest for the tunnel with a rectangular cross-section and lowest for the tunnel with a circular cross-section.
