Numerical Investigations of the In-Plane Behavior of Reinforced-Concrete (RC) Walls: Cyclic and Accident Thermal Loadings
Abstract
This study aims at the development, and experimental validation of 3D finite element models to investigate the seismic response of reinforced concrete (RC) squat shear walls subjected to postulated high energy thermal accident. Behavior is simulated using commercially available robust finite element modeling software LS-DYNA, employing explicit time stepping algorithm for calculating nodal forces and displacements. The basic performance of four constituent material models in capturing the seismic response is examined via material and component level simulations. Comparisons between the theoretical knowledge and analytical results presented herein will help in making the users cognizant of the inherent strengths and limitations associated with these material models. Performance validation of the nonlinear analysis is carried out with the help of experimental program executed in the BOWEN laboratory at PURDUE university. Tests are conducted on four specimens, under force and displacement controlled loading conditions, each having an aspect ratio of 0.6. Design parameters include reinforcement ratio, concrete and steel material strength, duration, and the maximum amplitude of thermal loading obtained from initial findings of the project. Two heating protocols: continuous and cyclic are used to depict accident thermal loads at 300F and 450F. The results include global force-displacement and thermal responses as well as damage progression during explicitly accounted material and geometric nonlinearities. Predicted responses are in a reasonable agreement with measured values. Based on the numerical and experimental studies, walls are found out to be flexural shear and shear critical. Numerical simulations also confirm the measured response that accident thermal loads during the first 15 to 30 minutes cause a reduction of around 10 to 35% in the overall secant stiffness depending upon the pre-heated cracking, and as the non-linear temperature gradient reduces with the passage of time, the subsequent reduction in stiffness is mainly due to mechanical damage. Additionally, the studies reveal no significant impact of the duration and exposure to abnormal loading conditions on the peak shear strength of the walls.
Degree
M.S.C.E.
Advisors
Varma, Purdue University.
Subject Area
Civil engineering|Engineering
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