Sustainable RC Beam-Column Connections with Headed Bars: A Formula for Shear Strength Evaluation

Abstract

Beam-column joints are critical regions for reinforced concrete (RC) frames subjected to earthquakes. The steel reinforcement is, in general, highly concentrated in these zones. This is why in many cases, headed bars are used. A headed bar is a longitudinal steel reinforcement whose end has a special button added to reduce the bonding length of the steel rebar. This paper establishes a formula predicting the shear strength of exterior RC beam-column connections where the beam longitudinal reinforcements use headed bars. A database was collected, which contained 30 experimental data about the exterior beam-column joints using headed bars and subjected to quasi-static cyclic loading. First, from the collected database, a statistical study was carried out to identify the most influencing parameters on the shear strength of the beam-column joints tested. The three most important parameters were identified and an empirical modified formula was developed based on the formula existing in the standards. The study showed that the results obtained from the modified formula proposed in the present study were closer to the experimental results than that obtained from the formula existing in the standards. Finally, a numerical study was performed on two T-form RC structures and the numerical results were compared with the prediction calculated from the modified formula proposed. For two investigated cases, the proposed formula provided the results in the safety side and the differences with the numerical results were less than 20%. Thus, the proposed formula can be used for a rapid assessment of the shear strength of RC joints using headed bars.

The influence of reverse loading sequence on the behaviour of beam-column joints

“…Tang et al [8] discussed modification of beam-column joint types namely square concrete-filled steel tubular (CFST) to overcome the decrease in beam-column joint capacity due to earthquake load. [9] discussed the prediction of shear strength in beam-column joints, especially in areas experiencing plastic joints.…”

“…Studies were held by [6], [7], [8], and [9] in observing the behaviour of beam-column joints will be used as the guidelines of the earthquake regulations to design a building structure. Certain elements of the building structure are allowed to undergo plastification as a means for dissipation of earthquake energy received by the structure, however, the structure must not collapse [10].…”

Effectiveness of the Novel Rehabilitation Method of Seismically Damaged RC Joints Using C-FRP Ropes and Comparison with Widely Applied Method Using C-FRP Sheets—Experimental Investigation

“…Studies on structural damages caused by earthquakes worldwide have shown that the joint areas of RC frame-system structures are the most vulnerable [9]. A large number of the existing RC buildings have been constructed according to older regulations without particular planning for the reinforcement of the joints [10][11][12].…”

Experimental Study of Steel Reinforced Concrete (SRC) Joints

“…Regarding the role of steel fibers, the effects of the addition of fibers with different geometries and aspect ratios on the mechanical properties of SFRC might significantly vary [19]. Recently, other studies, including [20] have analyzed the shear strength.…”