Behavior of Steel Fiber Concrete Beams with Different Reinforcement Method Around Opening

Abstract

Openings in concrete beams is preferred than using extended dropped ceilings to accommodate utility ducts and pipes. This leads to significant cost saving but unfortunately, beam strength and serviceability are affected. Experimental study of behavior of steel fiber concrete beams with different reinforcement methods around opening by using external glass fiber reinforced polymer (GFRP) or internal additional steel bars in addition to opening size is conducted. Load deflection curves and load strain curves are discussed. Beam dimensions studied are scaled to half their actual dimensions where the studied dimensions are common in beams. The authors only choose one size for all models to make it easy to compare the results. Other dimensions should be studied in the future. The only two specimens with openings that maintain ductile behavior are when adding steel fibers to concrete not containing GFRP and adding GFRP around the opening in concrete without steel fibers. When comparing a specimen with same opening dimension to another containing steel fibers without GFRP, the usage of steel fibers increases ultimate load (P u ) by 24% and deflection (∆ u ) by 69% with elastic plastic behavior and initial stiffness (I.S) increases by 17%, post cracking stiffness (P.I) decrease by 24% and energy absorption (E.A) increase by two times. On the other hand, GFRP is used in beam specimen that doesn’t contain steel fibers in the concrete mixture, P u increases by 42% and ∆u increases by 88%.