Punching strengthening of two-way slabs using external steel plates

An experimental and analytical study on the punching strengthening of reinforced concrete two-way slabs using external steel plates is presented. Five reinforced concrete square slabs of 100 mm thickness were tested over simply supported four sides of 1000 mm span under central square patch load of 100 mm size up to failure. One control slab was tested without strengthening; however, four tested slabs were strengthened using four configurations of square steel plates provided with steel anchor shear studs. Such configurations considered two different plate thickness, two plate side dimensions and different arrangement and diameter of shear studs. The strengthened four slabs showed improved stiffness and punching shear capacity. The magnitude of improvement depended on the plate dimensions and the studs diameter and arrangement. An analytical approach was proposed for predicting the punching shear strength increase due to using the strengthening steel plate. The proposed approach was applied to the tested specimens with the use of the punching shear strength equations adopted by several codes of practice and proved to be in good agreement with the test results. Generally, this research presented a practical strengthening concept that can be used to increase the punching shear capacity of two-way slabs.