Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels.This paper is divided into two parts.The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity(CDP)model,while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2(JH-2)damage model and their ability to describe the behavior of concrete panel under impact loads.The first and second concrete panels have dimensions of 1500 mm1500 mm150 mm and 675 mm675 mm200 mm,respectively,and are meshed using 8-node hexahedron solid elements.The impact object used in the first part is a spherical projectile of 150 mm diameter,while in the second part steel projectile of a length of 152 mm is modeled as rigid element.Failure and scabbing characteristics are studied in the first part.In the second part,the comparison results are presented as damage contours,kinetic energy of projectile and internal energy of the concrete.The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model.In addition,the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.

Perforation studies of concrete panel under high velocity projectile impact based on an improved dynamic constitutive model

The finite-depth concrete panels have been widely applied in the protective structures,and its impact resistance and dynamic fracture failures,especially the scabbing/perforation limits,under high velocity projectile impact,are mainly concerned by protective engineers,which are numerically studied based on an improved dynamic concrete model in this study.Firstly,based on the framework of the KCC(Karagozian&Case concrete)model,a dynamic concrete model is proposed which considers an independent tensile damage model and a continued transition between dynamic tensile and compressive properties.Secondly,the strength surface,equation of state and damage parameters of the proposed model are comprehensively calibrated by a triaxial compressive test with high confinement pressure,the rationality of which is further verified based on the single element tests,e.g.,uniaxial and triaxial compression as well as uniaxial,biaxial and triaxial tension.Thirdly,a series of projectile high velocity impact tests on thin and thick concrete panels are simulated,which indicates that the projectile residual velocity and dynamic fracture failures are reproduced satisfactorily,while the KCC model underestimates both the spalling and scabbing dimensions severely.Finally,based on the validated concrete model and finite element analyses approach,the validations of the existing five empirical formulae are evaluated,in terms of the depth of penetration(DOP)and scabbing/perforation limits of concrete panel.Both the Army corps of engineers(ACE)and modified National Defense Research Committee(NDRC)formulae are recommended in the design of the protective structure to avoid scabbing failure.

Numerical modeling of high velocity impact applied to reinforced concrete panel

A numerical simulation of a high-velocity impact of reinforced concrete structures is a complex problem for which robust numerical models are required to predict the behavior of the experimental tests.This paper presents the implementation of a numerical model to predict the impact behavior of a reinforced concrete panel penetrated by a rigid ogive-nosed steel projectile.The concrete panel has dimensions of 675 mm675 mm200 mm,and is meshed using 8-node hexahedron solid elements.The behavior of the concrete panel is modeled using a Johnson-Holmquist damage model incorporating both the damage and residual material strength.The steel projectile has a small mass and a length of 152 mm,and is modeled as a rigid element.Damage and pressure contours are applied,and the kinetic and internal energies of the concrete and projectile are evaluated.We also evaluate the velocity at different points of the steel projectile and the concrete panel under an impact velocity of 540 m/s.

Theoretical Calculation and Analysis of Slip and Deformation for Concrete Sandwich Panels

Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.

Flexural behavior of textile reinforced mortar-autoclaved lightweight aerated concrete composite panels

To improve the deficiencies of prefabricated autoclaved lightweight aerated concrete(ALC)panel such as susceptibility to cracking and low load-bearing capacity,a textile-reinforced mortar-autoclaved lightweight aerated concrete(TRM-ALC)composite panel was developed in this study.One group of reference ALC panels and five groups of TRM-ALC panels were fabricated and subjected to four-point flexural tests.TRM was applied on the tensile side of the ALC panels to create TRM-ALC.The variable parameters were the plies of textile(one or two),type of textile(basalt or carbon),and whether the matrix(without textile)was applied on the compression side of panel.The results showed that a bonding only 8-mm-thick TRM layer on the surface of the ALC panel could increase the cracking load by 180%−520%.The flexural capacity of the TRM-ALC panel increased as the number of textile layers increased.Additional reinforcement of the matrix on the compressive side could further enhance the stiffness and ultimate loadbearing capacity of the TRM-ALC panel.Such panels with basalt textile failed in flexural mode,with the rupture of fabric mesh.Those with carbon textile failed in shear mode due to the ultra-high tensile strength of carbon.In addition,analytical models related to the different failure modes were presented to estimate the ultimate load-carrying capacity of the TRM-ALC panels.

Bending Stiffness of Concrete-Filled Steel Tube and Its Influence on Concrete Placement Timing of Composite Beam-String Structure

When the upper chord beam of the beam-string structure(BSS)is made of concrete-filled steel tube(CFST),its overall stiffness will change greatly with the construction of concrete placement,which will have an impact on the design of the tensioning plans and selection of control measures for the BSS.In order to accurately obtain the bending stiffness of CFST beam and clarify its impact on the mechanical properties of composite BSS during construction,the influence of some factors such as height-width ratio,wall thickness of steel tube,elasticity modulus of concrete,and friction coefficient on the bending stiffness are analyzed parametrically by the numerical simulation technology based on an actual project.The calculation formula of the equivalent bending stiffness of CFST is also established through mathematical statistical simulation.Then,the equivalent bending stiffness is introduced into the construction and use stages of the composite BSS,respectively,and the mechanical properties such as prestress-tensioning control value,structural deformation,and internal force of key members are comparatively analyzed when adopting two different construction plans.Moreover,the optimal construction plan of concrete placement first and then prestress-tensioning is proposed.

Structural performance of a façade precast concrete sandwich panel enabled by a bar-type basalt fiber-reinforced polymer connector

In this study,a novel diagonally inserted bar-type basalt fiber reinforced polymer(BFRP)connector was proposed,aiming to achieve both construction convenience and partially composite behavior in precast concrete sandwich panels(PCSPs).First,pull-out tests were conducted to evaluate the anchoring performance of the connector in concrete after exposure to different temperatures.Thereafter,direct shear tests were conducted to investigate the shear performance of the connector.After the test on the individual performance of the connector,five façade PCSP specimens with the bar-type BFRP connector were fabricated,and the out-of-plane flexural performance was tested under a uniformly distributed load.The investigating parameters included the panel length,opening condition,and boundary condition.The results obtained in this study primarily indicated that 1)the bar-type BFRP connector can achieve a reliable anchorage system in concrete;2)the bar-type BFRP connector can offer sufficient stiffness and capacity to achieve a partially composite PCSP;3)the boundary condition of the panel considerably influenced the out-of-plane flexural performance and composite action of the investigated façade PCSP.

Simplified theoretical analysis and numerical study on the dynamic behavior of FCP under blast loads

Precast concrete structures have developed rapidly in the last decades due to the advantages of better quality,non-pollution and fast construction with respect to conventional cast-in-place structures.In the present study,a theoretical model and nonlinear 3D model are developed and established to assess the dynamic behavior of precast concrete slabs under blast load.At first,the 3D model is validated by an experiment performed by other researchers.The verified model is adopted to investigate the blast performance of fabricated concrete panels(FCPs)in terms of parameters of the explosive charge,panel thickness,and reinforcement ratio.Finally,a simplified theoretical model of the FCP under blast load is developed to predict the maximum deflection.It is indicated that the theoretical model can precisely predict the maximum displacement of FCP under blast loads.The results show that the failure modes of the panels varied from bending failure to shear failure with the mass of TNT increasing.The thickness of the panel,reinforcement ratio,and explosive charges have significant effects on the anti-blast capacity of the FCPs.

Effect of earth reinforcement,soil properties and wall properties on bridge MSE walls

Mechanically stabilized earth(MSE)retaining walls are popular for highway bridge structures.They have precast concrete panels attached to earth reinforcement.The panels are designed to have some lateral movement.However,in some cases,excessive movement and even complete dislocation of the panels have been observed.In this study,3-D numerical modeling involving an existing MSE wall was undertaken to investigate various wall parameters.The effects of pore pressure,soil cohesion,earth reinforcement type and length,breakage/slippage of reinforcement and concrete strength,were examined.Results showed that the wall movement is affected by soil pore pressure and reinforcement integrity and length,and unaffected by concrete strength.Soil cohesion has a minor effect,while the movement increased by 13–20 mm for flexible geogrid reinforced walls compared with the steel grid walls.The steel grid stresses were below yielding,while the geogrid experienced significant stresses without rupture.Geogrid reinforcement may be used taking account of slippage resistance and wall movement.If steel grid is used,non-cohesive soil is recommended to minimize corrosion.Proper soil drainage is important for control of pore pressure.