Punching Strengthening of Concrete Slab-column Connections Using Near Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) Bars

Abstract

This paper investigates experimentally the effect of near surface mounted (NSM) carbon fiber reinforcement polymer (CFRP) bars as externally strengthening on the punching shear behavior of interior slab-column connections. Many researchers used NSM as a novel strengthening technique in various structural elements. However, the strengthening of slab-column connections using NSN is relatively new. Seven Reinforced concrete (RC) square slabs with a concentric column were tested over simply supported four sides. One control specimen was tested without strengthening, four specimens were strengthened using NSM-CFRP bar installed in pre-cut groove surrounded the column at the tension side of the slab, and two specimens were strengthened using externally bonded (EB) CFRP strips which have the same tensile force of the CFRP bars. The arrangement and the location of the strengthened materials were also test variables. The test results showed that using NSM strengthening technique significantly increased the punching shear capacity and ultimate stiffness compared to using EB strengthening technique. Where the increasing in the punching capacity and ultimate stiffness were 18% and 13-18%, respectively. Moreover, the NSM-CFRP bars greatly reduced the cracks in the punching shear zone around the columns. The measured ultimate punching shear capacity for the tested specimens showed very reasonable agreement with the calculated punching loads based on an analytical model for slab-column connections strengthened using FRP that account for its arrangement and location.

Punching strengthening of reinforced concrete slab-Column connection using different techniques

“…Figures. [5][6][7][8][9][10][11] show the deflection of the column stub, located at the center of the slab, versus the applied load according to the test parameters. The curve of control specimen increased almost linear till reached the peak load, and then the load suddenly dropped due to brittle punching shear failure.…”

“…Finally, the surface of the structure element is leveled. The strengthening of RC beams and slabs in flexure by NSM technique using FRP bars [6] [7] [8].Another research investigated the shear performance of RC beams strengthened by the NSM technique using FRP bars in the form of external stirrups [9] [10] .…”

Strengthening of Flat Slabs Connection With Edge Columns Against Punching Shear Using Near Surface Mounted (Nsm) Carbon Fiber Reinforced Polymer (Cfrp) Bars

“…During the ex-decade, research tackled and accomplished on fiber reinforcement polymers (FRP) and its usage as a strengthening material in order to enhance the act of slab-column connections' existence. FRP could help in two different ways; external support [1][2][3][4][5][6] and internal one [7][8][9][10]. The CFRP external strengthening system consisted of one or more FRP sheet -layers attaching to the strain edge of the slab by epoxy resin glue.…”

Predicting of Punching Shear Capacity of Corroded Reinforced Concrete Slab-column Joints Using Artificial Intelligence Techniques

“…Reinforced concrete (RC) slab-column joint (SCJ) structures consisting of slabs and columns are vulnerable to punching shear (PS) because the beams are not arranged according to structural layout considerations under slabs [1]. Under extreme PS loads, the interior slabcolumn joint (SCJ) typically collapses first, followed by the other joints, and the overall structure gradually collapses [2], [3]. Numerous experimental studies on the punching shear resistance have been carried out in order to evaluate the behavior of slab-column structures, particularly the slab-column joints (SCJs).…”