A reliable concrete constitutive material model is critical for an accurate numerical analysis simulation of reinforced concrete structures under extreme dynamic loadings including impact or blast. However, the formulation of concrete material model is challenging and entails numerous input parameters that must be obtained through experimentation. This paper presents a damage scale analytical model to characterize concrete material for its pre-and post-peak behavior. To formulate the damage scale model, statistical regression and finite element analysis models were developed leveraging twenty existing experimental data sets on concrete compressive strength. Subsequently, the proposed damage scale analytical model was implemented in the finite element analysis simulation of a reinforced concrete pier subjected to vehicle impact loading and the response were compared to available field test data to validate its accuracy. Field test and FEA results were in good agreement. The proposed analytical model was able to reliably predict the concrete behavior including its post-peak softening in the descending branch of the stress-strain curve. The proposed model also resulted in drastic reduction of number of input parameters required for LS-DYNA concrete material models.

The need for assessing and retrofitting structures increased with time as terrorism-induced explosion trends rose with time. This paper presents a numerical investigation on performance assessment of a two-story, one-bay seismic resistant reinforced concrete framed building under close-in blast loading. ANSYS AUTODYN, an explicit nonlinear finite element software program, was used for 3D model development and analysis. The experimental results reported in the literature were used to validate proposed FE models. Furthermore, parametric studies on close-in explosive story-to-story locations and charge masses were performed on both conventional and seismically detailed RC framed structures. FEA results showed that a decrease in scaled distance raised effective plastic strain and damage index values. Furthermore, simultaneous use of close-spaced transverse steel reinforcement spacing in mid-height and ends of reinforced concrete columns is found to be effective in reducing both effective plastic strains and damage index values.

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It is not uncommon to provide openings in beams due to utility needs such as mechanical, electrical and sewerage passages. However, no clear guidelines are available in code of practice to handle beam web openings and presence of openings in beams changes behavior of Reinforced Concrete beam into a more complicated one. This research work investigates response of RC beam with openings under impact loading and proposes application of carbon fiber reinforced polymer (CFRP) composites to restore lost beam performance due to the presence of web openings. 3D nonlinear finite element software LS-DYNA is used for model development, validation and parametric finite element analysis work. The accuracy of the nonlinear finite element models are verified using experimental results from literature. Further parametric studies are performed to optimize beam web openings on opening location, size and CFRP no. of layers and fiber orientation. Numerical results showed as compared to control, large opening cutouts in RC beam decreased impact resistance of a beam by 54%. Also, RC beam exhibited poor impact loading resistance close to loading point (mid span) and performed good near shear zone. As compared to control as-built RC beam, Carbon Fiber Reinforced Polymer (CFRP) composites strengthening reduced mid span deflection by 74% and improved beams brittle failure mode. Also, 900 fiber orientation complete wrapping resulted in reduction of shear cracking around opening however exhibited low overall impact resistance as compared with 0º fiber orientation.

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