Browsing by Subject "Seismic application"

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Evaluation of concrete modeling in LS-DYNA for seismic application
(2016-12) Coleman, Daniel K., M.S. in Engineering; Williamson, Eric B., 1968-
LS-DYNA is a versatile finite element analysis program that can be used as a highly effective tool for solving a wide range of structural engineering problems. The software’s capabilities are highly desirable for studying the response of structures under earthquakes due to the large number of independent design parameters that can be considered. Because LS-DYNA has been utilized primarily for blast and impact simulations, however, limited effort has been expended to validate the material models used within the software for seismic-resistant design applications. The objective of this study was to evaluate the performance of four commonly used LS-DYNA concrete models (MAT 072R3, MAT 084, MAT 159, and MAT 272) for seismic applications. The first phase of analysis used individual elements to demonstrate the effects of element size, element formulation, hourglass formulation, and strain application rate on each material model’s performance. Additional single-element analyses were conducted to investigate each model’s capability to accurately capture different components of seismic loading, such as shear, cyclic compression, and cyclic load reversal. This single-element study yielded a collection of strengths and weaknesses associated with each material vii model. The second phase of analysis investigated how the strengths and weaknesses identified in the single-element analyses applied to multi-element simulations. This portion of the research was accomplished by replicating two experimental programs and observing and analyzing the differences between the generated numerical results and the documented experimental results. Based on observations from the single-element and multi-element studies, a series of limitations and recommendations pertaining to each material model were developed. MAT 072R3 and MAT 272 were not recommended for use with seismic applications due to damage accumulation limitations and hourglass control restrictions, respectively. Both MAT 084 and MAT 159 demonstrated they include all the necessary capabilities to be used for seismic problems; nonetheless, users should understand that there is some inherent error when applying these models. Additionally, it was observed that both MAT 084 and MAT 159 overpredicted energy dissipation by more than 200%. As a result, the current version of LS-DYNA is not recommended for problems with imposed acceleration histories.