Punching shear behavior of flat slabs supported by elongated columns with openings

The present paper deals with the punching shear behavior of flat slabs with openings adjacent to the elongated column. The results of an experimental program that included testing six full-scale slabs with a thickness of 200 mm, without transverse reinforcement tested under axis-symmetric conditions, are discussed. One reference slab specimen without openings and five slabs with various arrangements of two openings with the same dimensions were tested until their failure. The results obtained were compared to punching resistances assessed using design equations introduced in current Eurocode 2, ACI 318-19 and in the second generation of Eurocode 2, and to the original CSCT model developed by Muttoni. The tests confirmed the concentration of shear stresses at column edges and premature punching failure. Significant differences on the model's safety level were observed in different positions of the openings and in each design model. Best results were achieved with models in which the reduction of control perimeter length was based on the parallel projection of the openings.