Abstract
This study investigates the effectiveness of hybrid fibers (steel and macro-synthetic) on the shear behavior of prestressed concrete beams. The hybrid fiber combination was selected to avoid workability issues at high volume dosages and ensure effective crack arresting over the crack opening range. Fracture studies included testing notched concrete prisms to identify the role of hybrid fibers in the crack bridging mechanism. Seven hybrid fiber reinforced prestressed concrete (HFRPC) beams were tested at a low shear span (a) to depth (d) ratio of 2.4. The effects of hybrid fibers on load–deflection behavior and strain in the strand are reported. Similarly, the crack opening, crack slip and crack angle variation regarding applied shear were investigated using the digital image correlation (DIC) technique. Test results of HFRPC beams showed considerable improvements in peak load and the post-peak response with a higher hybrid fiber dosage. The crack opening and crack slip measurement across the major shear crack revealed continuous dilatant behavior. The kinematic response of critical shear crack reflects the sustained dilation response up to the ultimate load, which depends on the critical shear crack angle of the tested beams. As the fiber dosage increases, the shear crack slip and width are reduced, indicating the roles of hybrid fibers in improving ductility and the change in failure mode from brittle shear tension to relatively ductile shear tension.
Highlights
Concrete beams can be very brittle if not adequately reinforced
Not many studies have focused on the shear behavior of hybrid fiber reinforced prestressed concrete (PSC) beams under shear stress
This study aimed to understand the role of hybrid fibers in fracture and shear behavior through digital image correlation (DIC) analysis
Summary
Concrete beams can be very brittle if not adequately reinforced. The addition of discrete and randomly oriented fiber reinforcements in concrete helps to improve its ductility under shear loads. This study focuses on the effects of hybrid combinations of steel fibers (SF) and polyolefin (PO)-based macro-synthetic fibers (MSF), on the shear behavior of prestressed concrete beams. Ensuring adequate ductility is an essential design aspect of reinforced concrete (RC) and prestressed concrete (PSC) beams. Based on previous studies, such as Kani’s classical theory [1], the shear span to depth ratio (a/d) of 2.5 is considered a pivot point, below which the reinforced concrete (RC) beams fail in a shear critical mode. For a/d ratios between 2.5 and 6, possible failures occur via flexure shear mode due to diagonal shear tension after flexure cracking. In this study, a shear span to depth ratio (a/d) of 2.4 was considered to avoid arch action and ensure the diagonal shear tension (DST) mode in prestressed concrete beams [3–6]
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