Design Oriented Model for the Assessment of T-Shaped Beam-Column Joints in Reinforced Concrete Frames

Abstract

Abstract:Beam-column joints represent very important elements of reinforced concrete (RC) structures. In fact, beams and columns, at the boundary, generate internal forces acting on concrete core and on reinforcement bars with a very high gradient. To fully understand the seismic performances and the failure modes of T-shaped beam-column joints (external corner-positioned) in RC structures, a simplified analytical model of joint behaviour is proposed and theoretical simulations have been performed. The model is based on the solution of a system of equilibrium equations of cracked joint portions designed to evaluate internal stresses at different values of column shear forces. The main aim of the proposed model is to identify the strength hierarchy. Limit values of different internal stresses allow us to detect the occurrence of different failure modes (namely the failure of the cracked joint, the bond failure of passing through bars, and the flexural/shear failures of columns or beams) associated with column shear forces; the smaller one represents the capacity of the joint. The present work, focusing on T-shaped joints, could represent a useful tool for designers to quantify the performance of new structures or of existing ones. In fact, such a tool allows us to push an initial undesired failure mode to a more appropriate one to be evaluated. Finally, some experimental results of tests available in literature are reported, analysed, and compared to the predictions of the proposed model (by means of a worked example) and of some international codes. The outcomes confirm that failure modes and corresponding joint capacities require an analytical model, like the proposed one, to be accurately predicted.

Structural Behavior of Steel Reinforced Concrete Joint Under Flexural Loads

“…Numerous scientific studies on the behavior of joints in steel-reinforced concrete have been conducted recently. Bossio et al (2017) [13] presented a theoretically simplified formulation regarding the failure behavior of beamcolumn joints, which concluded that it is possible to predict the failure behavior of the joints. Shoukry et al (2022) [14] investigated the behavior of strengthened joints under seismic loads.…”

Effectiveness and Efficiency of Externally Bonded CFRP Sheets for Shear Strengthening of RC Beam-Column Joints

“…For almost two decades since the late 1990s, extensive research has been conducted on FRP-strengthened joints. Investigations were performed on the roles of various parameters on the effectiveness of externally bonded FRPs [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], analytical models were built to predict the shear capacity of FRP-strengthened joints [ 9 , 20 , 24 , 25 , 26 , 27 , 28 , 29 ], and nonlinear finite element (FE) modeling approaches were developed for FRP-strengthened joints [ 30 , 31 , 32 , 33 ]. Nevertheless, most of the studies concentrated on two-dimensional (2D) joints, i.e., no transverse beams [ 34 ].…”

Experimental Study of Steel Reinforced Concrete (SRC) Joints

“…In [15] the authors investigate the corner-positioned reinforced concrete beam-column joints in order to study their seismic behavior and to establish the strength in the case of failure of beam-column joints. Santarsiero [16] proposes simple strengthening solutions created by Fibre Reinforced Polymers (FRP) systems that are able to effectively improve seismic resistance.…”