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One of the most challenging elements of modeling the behaviour of reinforced concrete (RC) walls is combining realistic material models that can capture the observable behaviour of the physical system. Experiments with realistic loading rates and pressures reveal that steel and concrete display complicated nonlinear behaviour that is challenging to represent in a single constitutive model. To investigate the response of a reinforced concrete structure subjected to dynamic loads, this paper's study is based on many different material models to assess the advantages and disadvantages of the models on 2D and 3D RC walls using the LS-DYNA program. The models consisted of the KCC model and the CDP model, which represented plasticity and distinct tensile/compressive damage models, and the Winfrith model, which represented plasticity and the smeared crack model. Subsequently, the models' performances were assessed by comparing them to experimental data from reinforced concrete structures, in order to validate the accuracy of the overall behaviour prediction. The Winfrith model demonstrated satisfactory results in predicting the behaviour of 2D and 3D walls, including maximum strength, stiffness deterioration, and energy dissipation. The method accurately predicted the maximum strength of the Winfrith concrete model for the 2D wall with an error of 9.24% and for the 3D wall with errors of 3.28% in the X direction and 5.02% in the Y direction. The Winfrith model demonstrated higher precision in predicting dissipation energy for the 3D wall in both the X and Y directions, with errors of 6.84% and 6.62%, correspondingly. Additional parametric analyses were carried out to investigate structural behaviour, taking into account variables such as concrete strength, strain rate, mesh size, and the influence of the element type. [ABSTRACT FROM AUTHOR]

The seismically deficient column details in existing reinforced concrete buildings affect the overall behavior of the building depending on the failure type of the column. The purpose of this study is to develop and validate a machine-learning-based prediction model for the column failure modes (shear, flexure–shear, and flexure failure modes). For this purpose, artificial neural network (ANN), K-nearest neighbor (KNN), decision tree (DT), and random forest (RF) models were used considering previously collected experimental data. Using four machine learning methodologies, we developed a classification learning model that can predict the column failure modes in terms of the input variables using the concrete compressive strength, steel yield strength, axial load ratio, height-to-dept aspect ratio, longitudinal reinforcement ratio, and transverse reinforcement ratio. The performance of each machine learning model was compared and verified by calculating the accuracy, precision, recall, F1-Score, and ROC. Based on the performance measurements of the classification model, the RF model has the highest average value for the classification model performance measurements among the considered learning methods and can conservatively predict the shear failure mode. Thus, the RF model can rapidly predict the column failure modes with the simple column details. Additionally, it was demonstrated that the predicted failure modes from the selected model were exactly same as the failure mode determined from a code-defined equation (traditional method). [ABSTRACT FROM AUTHOR]

Blast loading and seismic excitations are widely recognized as the most detrimental occurrences that a building structure may encounter throughout its lifespan. Therefore, this study investigated the retrofitting capacity of external devices (ENTA damper systems) for reinforced concrete (RC) frames in term of enhancing their resistance under the combined effects of blast and seismic loads. This study presents the establishment of finite element (FE) models for retrofitted RC frames with ENTA damper systems through the utilization of the dynamic analysis software LS-DYNA. The investigation involved the validation for blast performance of RC column in order to identify the most effective method for modeling blasts. Additionally, the study aimed to validate the performance of RC frame models through effects of ENTA damper systems under seismic loading. Subsequently, a performance evaluation of RC frame structures was carried out to examine the impact of the ENTA damper systems when subjected to blast loading. The findings of the study indicate that the use of external ENTA damper systems effectively enhanced the rigidity and structural integrity of RC frames, while maintaining their ability to resist deformation. Finally, the damage assessment of blast and seismic performance is investigated based on various parameters such as ductility, drift and energy-based damage limits. • Finding the suitable model blasts based on the blast performance of RC column. • Validating performance of the RC frame models under seismic loading. • Investigating the blast performance of RC frame and retrofitted RC frame. • Considering the damage performance of RC frames under blast and seismic loadings. [ABSTRACT FROM AUTHOR]

Non-ductile reinforced concrete frames have seismic vulnerabilities due to inadequate reinforcing details. Adequately characterizing the performance of these details is critical to the development of analytical models. This study presents a methodology to simulate the response of such frames with and without fiber-reinforced polymer column jackets. The bond-slip effects between reinforcing bars and surrounding concrete, observed in column lap-splice and beam–column joints, are modeled with one-dimensional slide line models in LS-DYNA. The model is defined from failure modes and bonding conditions observed in full-scale dynamic tests and can predict story displacements, inter-story drifts, and damage mechanisms. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer (FRP) materials continue to demonstrate outstanding performance for strengthening and repairing reinforced concrete structures. However, one of the most significant problems that still has to be tackled is premature failure brought on by the FRP debonding. This research sought to determine how damaged RC columns could be strengthened with aramid (one type of FRP) composites and how that would affect their seismic responses. To further understand the individual effects of each strengthening material on seismic performance, hysteretic responses, such as strength, ductility, and energy dissipation, were examined and compared. Analytical modeling is validated based on the experimental results. Experimental results are validated with comparative study against other solid experimental results within the broader field. Effective bond length (EBL) is crucial for understanding the bonding between aramid fibers and concrete, however various models have different ways of calculating the value of EBL. Therefore, this research examined earlier experimental investigations of EBL and employing finite element (FE) methods established a novel relationship between the EBL and the aramid-to-concrete bond, based on experimental results. • Experimental assessment with various specimens such as RC columns and RC columns with retrofitted aramid sheets. • Developing the FE model to investigate the response of the structural columns. • Considering the effect of the retrofit system on the RC columns. • Proposing the best-fit empirical model between the effective bond length (EBL) and the aramid-to-concrete bond. [ABSTRACT FROM AUTHOR]