Hybrid steel tubular column/flat slab construction — Development of a shearhead system to improve punching shear resistance

• New shearhead system to enable hybrid steel tube/concrete flat slab construction
• Detailed study of effects of different design parameters on punching shear resistance
• Simplified design method for punching shear resistance calculation

This paper presents the results of an extensive numerical parametric study to investigate the effects of different design parameters on the punching shear resistance of a hybrid steel tubular column/reinforced concrete flat slab system using shearhead arms. The parameters investigated include those related to the steel tubular column (diameter, shape), the shearhead arms (cross-section dimensions, length, end angle and position in the slab) and the slab (thickness and amount of reinforcement). The results of the parametric study indicate that for calculating the slab punching shear resistance, the shearhead system can be considered to be an enlarged column. The size of the enlarged column is equal to the original column dimensions plus the effective lengths of the shearhead arms. To calculate the effective length of the shearhead arm, it is assumed that the applied load is distributed underneath the inclined surfaces of the shearhead arm. Provided the shearhead arm has sufficient bending moment and shear resistances under the assumed load distribution, the entire shearhead arm is effective. The enlarged column size can be used to calculate the punching shear resistance as for reinforced concrete flat slab using either Eurocode EN 1992-1-1 or British Standard BS 8110. A comparison between the calculation results and the numerical simulation results suggests that the design calculation results are conservative and the BS 8110 calculations give slightly more accurate results.