Comparison of single-leg shear bars and double-headed shear studs in seismic strengthening of RC slabs: An experimental study

Reinforced concrete (RC) flat slabs are widely used in modern construction due to their structural efficiency and architectural simplicity. However, their susceptibility to punching shear failure remains a critical issue, particularly under seismic loading. Although researchers have investigated various strengthening techniques, the influence of anchorage configuration on the comparative cyclic response of externally strengthened slab-column connections remains insufficiently understood. This study presents an exploratory experimental comparison of two post-installed shear-strengthening systems, namely single-leg shear bars with 90° hooks at both ends and pretensioned double-headed shear studs. Three interior slab-column connections were constructed, including one control specimen and two externally strengthened specimens, which were tested under combined gravity and reversed cyclic loading. All specimens had identical geometry and flexural reinforcement, comprising a 1900-mm-square, 150-mm-thick slab with a longitudinal reinforcement ratio of 0.8%. The post-installed shear elements were arranged in a combined orthogonal–radial configuration at a row spacing of 60 mm, with the first row located 30 mm from the column face. Experimental results showed that double-headed shear studs produced about a 10.4% increase in peak lateral load, but a remarkable 54.6% increase in ductility compared with the specimen reinforced with single-leg shear bars. The specimen strengthened with double-headed shear studs also exhibited a higher pinching width ratio than the specimen strengthened with single-leg shear bars, indicating reduced pinching and a more stable cyclic response under the investigated test conditions.