Strengthening of Reinforced Concrete Slab-Column Connection Subjected to Punching Shear with FRP Systems

Abstract

Abstract-This study aims to determine the efficiency of using Fiber Reinforced Polymers (FRP) systems to strengthen the slab-column connections subjected to punching shear. The used strengthening systems consisted of external FRP stirrups made from glass and carbon fibers. The stirrups were installed around the column. Also, external steel links were used as a conventional strengthening method for comparison. Over the last few years, the use of FRP for strengthening of concrete structures has been investigated by many researchers, whichconcerning with the strengthening of reinforced concrete slabs, beams and columns. The use of FRP in strengthening concrete slabs in flexure is done by bonding it to the tension face of the slabs. The use of FRP for strengthening the flat slabs against punching shear can be considered as a new application. This research shows the results obtained from an experimental investigation of 4 half-scale two-way slab-column interior connections, which were constructed and tested under punching shear caused by centric vertical load. The research included one unstrengthened specimen, which considered as control specimen, one specimen strengthened with steel links, one specimen strengthened with external stirrups made from Glass Fiber Reinforced Polymer (GFRP), and one specimen strengthened with external stirrups made from Carbon Fiber Reinforced Polymer (CFRP). So, the type of strengthening material is the basic parameter in this study. The experimental results showed a noticeable increase in punching shear resistance and flexural stiffness for the strengthened specimens compared to control specimen. Also, the strengthened tested slabs showed a relative ductility enhancement.Finally, equations for punching shear strength prediction of slab-column connections strengthened using different materials (Steel, GFRP & CFRP) were applied and compared with the experimental results.Index Terms-Fiber reinforced polymer, punching shear, reinforced concrete slab-column connection, Strengthening and repair.

A comparative case study on seismic design of tall RC frame-core-tube structures in China and USA

“…The slab-column connections are prone to brittle punching failure under gravity and/or earthquake loads without enough warning. Prior to punching failure, the lateral drift capacities of the connections are also limited (Chen, 2003;Khaleel et al, 2013;Rha et al, 2014;Ruiz et al, 2013;Yi et al, 2014). Such a failure mode can hardly produce an overall ductile yield mechanism in the structure.…”

Resistance of Punching Shear Strength of RC Flat Slabs According to Laboratory and Finite Element Analysis Study Comparison of International Codes

“…Many researchers have studied the punching shear behavior of reinforced concrete flat slabs [3][4][5][6]. The punching shear strength and deformation capacity are strongly influenced by the type and characteristics of the shear reinforcing system [7][8][9][10][11][12][13]. The slabs punching shear reinforcing system are:…”

“…The finite element (FE) analysis software program (ANSYS V. 19) was used to create the models and investigate the effects of some parameters on punching shear of reinforced concrete flat slabs. Ten variable parameters are taken into consideration during study full scale flat slab models to account the influence of: (1) concrete compressive strength fcu; (2) reinforcing steel yield strength fy; (3) slab thickness (ts); (4) shear studs and stirrups diameter (Db); (5) shear studs (stirrups) spacing /ts ratio (Sb/ts); (6) shear studs stirrups spacing/ts ratio (D/ ts); (7) main steel ratio/ max (  / max); (8) top steel ratio/ max (` / max); (9) drop thickness/ts ratio (td/ ts) and (10) drop diameter/ts ratio (Dd/ ts).The numerical results were compared with the analytical results calculated from ECP 203-2017 [1] and ACI 318-19 [2]. The comparison showed a great match between the numerical results and the results of the two codes, especially ACI 318-19 [2].…”

Punching shear resistance of strengthened reinforced concrete interior slab–column connections using ultra-high-performance strain-hardening cementitious composite material

“…Over years, various enhancement/strengthening techniques have been developed in order to improve the punching shear resistance for RC flat slabs. These techniques include using traditional shear reinforcement in the form of single- and multiple-leg stirrups, swimmer shear bars, bent-up bars, inclined stirrups, inclined shear band reinforcement, post-installed reinforcement, steel links, external steel plates with steel anchor shear studs, steel shear head, shear stud with single or double head, helical reinforcement, external carbon fiber reinforced polymer (CFRP)/glass fiber reinforced polymer (GFRP) stirrups/rods or externally bonded (EB) CFRP/GFRP laminates/strips, and mesh reinforcement (ACI 318-14, 2014; Al-Nasra et al, 2013; Bartolac et al, 2015; Binici and Bayrak, 2003, 2005a, 2005b; Chen and Li, 2005; Corely and Hawkins, 1968; Durucan and Anil, 2015; Elbakry and Allam, 2015; Esfahani et al, 2009; Faria et al, 2014; Ferreira et al, 2014; Harajli and Soudki, 2003; Kang and Wallace, 2005; Khaleel et al, 2013; Meisami et al, 2013; Najmi and Marahlah, 2015; Oliveira et al, 2000; Park et al, 2007, 2012; Pilakoutas and Li, 2003; Ruiz et al, 2010; Sissakis and Sheikh, 2007; Soudki et al, 2012; Tassinari et al, 2011). Providing internal short steel/fabric fibers into the entire slab or a partial area near the slab–column connection is another technique used for enhancing the behavior of the cracked tension region as well as the undamaged concrete in the compression zone (Cheng and Parra-Montesinos, 2010; Choi et al, 2007, 2012; El-Ghandour et al, 2003; Harajli et al, 1995; Hassan et al, 2015; Ju et al, 2015; Mandl, 2008; Tan and Paramasivam, 1994).…”