This paper presents the results of a research work aimed to determine the efficiency
of using different materials to increase the punching shear strength of slab–column
connections. These materials are near-surface mounted steel bars, and glass or carbon
fiber reinforced polymers as shear reinforcement stirrups.
Over the last few years, the use of Fiber Reinforced Polymer (FRP) for
strengthening of concrete structures has been investigated by many researchers. Most of
these researchers studied the repair and strengthening of reinforced concrete beams and
columns. The use of FRP in strengthening concrete slabs in flexure is done by bonding it
to the tension face of these slabs. The use of FRP in repair and strengthening punching
shear in flat plates is a new application.
This research shows the results obtained from an experimental investigation on
atotal of 26 half -scale two-way slab-column interior connections were constrcted and
tested under punching shear, the research included two specimens without shear
reinforcement as control, three specimens reinforced with inner steel stirrups for
comparison, and eighteen specimens strengthened with Glass Fiber Reinforced Polymer
(GFRP), Carbon Fiber Reinforced Polymer (CFRP), and steel reinforcement as external
stirrups. The remaining three specimens repaired with the same materials.
Test parameters investigated were the shape of FRP and steel stirrups, the number
of stirrups rows and the spacing between these rows for the different material types.
The test results showed a noticeable increase in punching shear resistance, and ultimate
flexure stiffness for specimens repaired or strengthened compared to control specimens.
The tested slabs also showed a ductility enhancement. Finally, equations for prediction
the punching shear strength for slab-column connections strengthened or repaired using
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different materials (Steel bars-GFRP-CFRP) were predicted and examined aginst test
results and design equations for punching shear in the common codes. |
