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CONTENTS
Volume 7, Number 2, April 2010
 

Abstract
This paper discusses new capabilities developed for the Virtual Penetration Laboratory (VPL) software package to address the challenges of determining Penetration Resistance (PR) equations for concrete materials. Specifically, the paper introduces a three-invariant concrete constitutive model recently developed by the authors. The Advanced Fundamental Concrete (AFC) model was developed to provide a fast-running predictive model to simulate the behavior of concrete and other high-strength geologic materials. The Continuous Evolutionary Algorithms (CEA) automatic fitting algorithms used to fit the new model are discussed, and then examples are presented to demonstrate the effectiveness of the new AFC model. Finally, the AFC model in conjunction with the VPL software package is used to develop a PR equation for a concrete material.

Key Words
penetration mechanics; constitutive modeling; evolutionary algorithms.

Address
Mark D. Adley, Andreas O. Frank, Kent T. Danielson, Stephen A. Akers and James L. O

Abstract
Penetration of a fragment-like projectile into Fiber Reinforced Concrete (FRC) was simulated using finite element (FE) and particle formulations. Extreme deformations and failure of the material during the penetration event were modeled with multiple approaches to evaluate how well each represented the actual physics of the penetration process and compared to experimental data. A Fragment Simulating Projectile (FSP) normally impacting a flat, square plate of FRC was modeled using two target thicknesses to examine the different levels of damage. The thinner plate was perforated by the FSP, while the thicker plate captured the FSP and only allowed penetration part way through the thickness. Full three dimensional simulations were performed, so the capability was present for non-symmetric FRC behavior and possible projectile rotation in all directions. These calculations assessed the ability of the finite element and particle formulations to calculate penetration response while assessing criteria necessary to perform the computations. The numerical code EPIC contains the element and particle formulations, as well as the explicit methodology and constitutive models, needed to perform these simulations.

Key Words
Fiber Reinforced Concrete; finite element; meshfree; penetration.

Address
James O

Abstract
This paper presents results from a study concerning the capability afforded by the RKPM (reproducing kernel particle method) meshfree analysis formulation to predict responses of concrete and UHPC components resulting from projectile impacts and blasts from nearby charges. In this paper, the basic features offered by the RKPM method are described, especially as they are implemented in the analysis code KC-FEMFRE, which was developed by Karagozian & Case (K&C).

Key Words
ultra high performance concrete; meshfree method; reproductive kernel particle method; penetration; crater analysis.

Address
Hyung-Jin Choi, John Crawford and Youcai Wu: Karagozian & Case, 2550 N. Hollywood Way, Suite 500, Burbank, CA 91505, USA

Abstract
In this work the implementation of a production-level port of the Microplane constitutive model for concrete into the EPIC code is described. The port follows guidelines outlined in the Material Model Module (MMM) standard used in EPIC to insure a seamless interface with the existing code. Certain features of the model were not implemented using the MMM interface due to compatibility reasons; for example, a separate module was developed to initialize, store and update internal state variables. Objective strain and deformation measures for use in the material model were also implemented into the code. Example calculations were performed and illustrate the veracity of this new implementation.

Key Words
microplane model; constitutive model framework; EPIC code.

Address
David Littlefield: Department of Mechanical Engineering, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
Kenneth C. Walls: The University of Alabama at Birmingham, Birmingham, AL 35294, USA
Kent T. Danielson: US Army Engineer Research and Development Center, Vicksburg, MS 39180, USA

Abstract
This paper demonstrates numerical techniques for complex large-scale modeling with microplane constitutive theories for reinforced high strength concrete, which for these applications, is defined to be around the 7000 psi (48 MPa) strength as frequently found in protective structural design. Applications involve highly impulsive loads, such as an explosive detonation or impact-penetration event. These capabilities were implemented into the authors

Key Words
nonlinear finite element analysis; reinforced concrete; microplane constitutive model; parallel computing.

Address
Kent T. Danielson and Mark D. Adley: U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199, USA; Impact & Explosive Effects Branch, Attn: CEERD-GM-I
James L. O\'Daniel: U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199, USA; Structural Mechanics Branch, Attn: CEERD-GS-M

Abstract
The focus of this research effort was characterization of the flexural and tensile properties of a specific ultra-high-strength, fiber-reinforced concrete material. The material exhibited a mean unconfined compressive strength of approximately 140 MPa and was reinforced with short, randomly distributed alkali resistant glass fibers. As a part of the study, coupled experimental, analytical and numerical investigations were performed. Flexural and direct tension tests were first conducted to experimentally characterize material behavior. Following experimentation, a micromechanically-based analytical model was utilized to calculate the material

Key Words
ultra-high-strength concrete; alkali resistant glass fiber; micromechanical model; tensile failure function; finite element analysis; concrete damage plasticity.

Address
M. Jason Roth, Thomas R. Slawson and Omar G. Flores: U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180, USA

Abstract
A laboratory investigation was conducted to characterize the constitutive property behavior of Cor-Tuf, an ultra-high-performance composite concrete. Mechanical property tests (hydrostatic compression, unconfined compression (UC), triaxial compression (TXC), unconfined direct pull (DP), uniaxial strain, and uniaxial-strain-load/constant-volumetric-strain tests) were performed on specimens prepared from concrete mixtures with and without steel fibers. From the UC and TXC test results, compression failure surfaces were developed for both sets of specimens. Both failure surfaces exhibited a continuous increase in maximum principal stress difference with increasing confining stress. The DP tests results determined the unconfined tensile strengths of the two mixtures. The tensile strength of each mixture was less than the generally assumed tensile strength for conventional strength concrete, which is 10 percent of the unconfined compressive strength. Both concretes behaved similarly, but Cor-Tuf with steel fibers exhibited slightly greater strength with increased confining pressure, and Cor-Tuf without steel fibers displayed slightly greater compressibility.

Key Words
ultra-high-performance concrete; steel fibers; mechanical response.

Address
E.M. Williams, S.S. Graham, S.A. Akers, P.A. Reed and T.S. Rushing: U.S. Army Engineer Research and Development Center, Geotechnical and Structures Laboratory, Vicksburg, MS, USA

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