# Assessment of a Substandard Reinforced Concrete Frame's Beam-Column Joint Using Shake Table Testing
## 1 Introduction
This correlation indicates that revising existing seismic assessment standards in light of this model could improve both the precision and cost-effectiveness of performance-based seismic design for ductile concrete frames. Collectively, these validated analytical methodologies from the recent literature provide robust and precise tools for evaluating seismic vulnerabilities, facilitating targeted and effective retrofitting solutions to enhance structural resilience. [PERSON] et al. [12] underscore the essential function of beam-column joints in evaluating the seismic safety of RC frames. It particularly draws attention to the unforeseen damage mechanisms  
Figure 1: Failure of cyclic seismic action: (**a**) corner joint, (**b**) exterior joint, and (**c**) interior joint. that have emerged during previous seismic occurrences, which significantly impacted these joints. To investigate this further, the authors formulated a finite element model introducing an additional element positioned between the beam and column members. This model effectively replicates the nonlinear behavior of beam-column joints, thereby illustrating the importance of incorporating these joints in the seismic analysis of RC frames through numerical simulations. [PERSON] and [PERSON] [13] discussed improvements in analytical modeling achieved by creating a feed-forward artificial neural network (FFNN) designed to estimate the shear strengths of beam-column joints made of RC. The proposed methodology improves the precision and dependability of forecasting seismic responses, effectively mitigating the shortcomings associated with conventional rigid-end offsets in joint modeling. Complementing these analytical studies, experimental investigations remain indispensable for validating theoretical models and capturing complex seismic phenomena empirically. Fundamental experimental methodologies, such as shake table and cyclic load testing, enable researchers to simulate realistic earthquake scenarios, facilitating detailed analyses of structural responses within controlled laboratory settings. Studies consistently underscore the susceptibility of beam-column joints, highlighting prevalent damage patterns like severe shear cracking, concrete spalling, bar slip, and a loss of joint confinement. [PERSON] and [PERSON] [14] were pioneers in experimentally demonstrating that beam-column joints, which are confined to all four sides by beams, show enhanced performance under reversed cyclic loading. Their findings led to the conclusion that such joints do not need additional shear reinforcement. On the other hand, joints that lack confinement necessitate both shear and transverse reinforcements to mitigate damage from shear cracking and to prevent the buckling of the longitudinal column reinforcement. The seminal work by [PERSON] and [PERSON] [14] is recognized within the ACI 318-19 [15] seismic provisions as foundational research significantly influencing modern seismic design codes. Their experimental findings demonstrated that RC beam-column joints confined by beams on all four sides exhibited substantially improved seismic performance under cyclic loading, even without additional shear reinforcement. This crucial observation has led to current seismic design standards to prioritize enhanced detailing requirements for joints lacking such beneficial confinement. Specifically, their work underpins the mandate for explicit shear and transverse reinforcement in joints not adequately confined by beams, highlighting a critical vulnerability previously underestimated in earlier design codes. Consequently, the contemporary seismic design codes extensively incorporate insights from [PERSON] and [PERSON] [14] by emphasizing rigorous beam-column joint detailing, proper confinement, and reinforcement practices. Subsequent experimental findings revealed that extensions of beams and columns, when adequately sized and reinforced with both longitudinal and transverse bars, effectively confine the joint faces. For instance, [PERSON] et al.