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Rational use of HPFRC in slab – column connections under reversed horizontal cyclic loading

Ramos, António / Isufi, Brisid / Marreiros, Rui / Bolešová, Mária / Gajdošová, Katarina

Highlights • Excellent behaviour of slab – column connections under lateral loading achieved by applying HPFRC near the column. • Economic use of HPFRC in slab – column connections is possible. • HPFRC has potential to be used as a substitute for punching shear reinforcement under seismic loading conditions. • HPFRC shown to be better than that High Strength Concrete in improving the seismic performance of slab – column connections.

Abstract Slab – column connections that are subjected to combined gravity and horizontal loading during an earthquake are prone to premature failure due to punching shear. Traditional solutions to avoid punching failure and to increase the displacement capacity of this type of connection include using stirrups and double-headed studs as shear reinforcement. The use of High-Performance Fiber Reinforced Concrete (HPFRC) in a small region of the slab around the column as a substitute for traditional solutions is investigated in this paper, because this material has the potential to reduce labor and material costs. To fulfill this objective, four slab specimens with a thickness of 150 mm were tested under combined gravity and reversed horizontal drifts. The results are discussed in detail. The experimental variables considered were the top flexural reinforcement ratio, the size of the HPFRC zone and the intensity of the gravity load. Previously published tests that serve as reference specimens are used to compare the results. The behavior of the specimens with HPFRC was substantially improved compared to the reference specimens in terms of drift capacity: from only 1.0% drift to above 5.5%, even though a very small quantity of HPFRC was used, extended up to only 1.5 times the effective depth of the slab from the face of the column. Specimens with HPFRC also behaved better when compared to specimens with High-Strength Concrete (HSC). Side effects of using HPFRC in the slab in the vicinity of the column include an increase of the unbalanced moment transfer capacity and lateral stiffness, as well as a reduction of the deflections of the slab.