Date of this Version
Winkelbauer, B.J., "Phase I Evaluation of Selected Concrete Material Models in LS-DYNA," Master's Thesis submitted to the University of Nebraska-Lincoln, December 2015.
Numerous roadside safety systems are configured with reinforced concrete materials, such as bridge railings, median barriers, and roadside parapets. These protective barrier systems are intended to safely contain and redirect errant vehicles as well as prevent impacts into hazardous fixed objects or other geometric features. The analysis and design of these structures may involve impact simulation with finite element software, like LS-DYNA, which includes multiple concrete material models. For such investigations, limited guidance is available for selecting preferred concrete material models and determining appropriate values for specific parameters. This Phase I study investigated the viability and performance of existing concrete material models to simulate unreinforced components subjected to common loading conditions, such as compression, tension, shear, and bending. For this study, five material models were evaluated – CSCM, K&C, RHT, Winfrith, and CDPM.
Initially, single-element simulations were conducted in order to gain a basic understanding of material model performance. Next, small components with multiple elements were simulated to evaluate different loading conditions. Physical test data was obtained from several external experimental testing programs with unreinforced concrete in three basic load cases - compression, tension, and shear. Following the initial investigation on unreinforced concrete components, it was found that two out of the five concrete material models (CSCM and K&C) provided adequate simulation results when compared to the experimental test results. Among the other three models, the RHT model provided overestimation of peak forces, the Winfrith model performed poorly in tension and shear, and the plastic solver of the CDPM prevented simulations from completing. Both the CSCM and K&C concrete material models were further investigated and compared to internal component tests.
Additional component simulations were completed to validate models against new experimental tests under four basic load cases - compression, tension, shear, and flexure. For the compression scenario, seven tests were completed on standard 4-in. diameter x 8 in. (102-mm diameter x 203-mm) cylinders. For the tension scenario, six 4-in. x 3-in. x 12-in. long (102-mm x 76-mm x 305-mm long) dog-bone specimens were loaded in direct tension. For the flexure and shear scenario, six four-point bend tests were completed on 6-in. x 6-in. (152-mm x 152-mm) beam specimens. For the follow-on simulation effort and noted specimen geometries, the CSCM and K&C models showed promise in predicting peak forces and damage patterns for loading conditions using element sizes of ¼-in. (6.4-mm), ½-in. (13-mm), and ½-in. (13-mm) for compression, tension, and shear/flexure, respectively. The default parameters for both material models provided a reasonable comparison of results between experimental and simulated tests. Further investigation is recommended for the five selected concrete material models when used in combination with steel reinforcement.
Advisor: Ronald K. Faller