Title:
Shear Strength of Extruded, Prestressed Steel Fiber- Reinforced Concrete Hollow-Core Slabs
Author(s):
Gustavo Parra-Montesinos, Luis B. Fargier-Gabaldon, and Mohamed Al-Tameemi
Publication:
Structural Journal
Volume:
120
Issue:
4
Appears on pages(s):
127-136
Keywords:
extrusion; hooked fibers; precast; shear failure; web cracking
DOI:
10.14359/51738770
Date:
7/1/2023
Abstract:
ACI 318-19 requires that prestressed concrete hollow-core slabswith depths exceeding 12.5 in. (320 mm) and subjected to a factored shear greater than half the design web-cracking shear strength be provided with at least minimum shear reinforcement. Because the use of bar-type shear reinforcement in hollow-core slabs is generally not possible, this requirement limits the use of these members in shear-critical cases. In this research, the use of hooked steelfibers as a means to increase the shear strength of deep hollowcore slabs was evaluated through 14 tests on extruded hollow-core slabs. Slab thickness was 16 in. (406 mm) and the shear span-effective depth ratio (a/d) was either 3.0 or 3.5. Two types of hooked steel fibers were evaluated at dosages between 40 and 62 lb/yd3 (24 and 37 kg/m3). Type 1 fibers had a single hook at each end and Type 2 fibers had double hooks at each end. The fiber-reinforced concrete slabs exhibited peak shear strengths that ranged between 0.94 and 1.29 times the ACI 318-19 calculated web-cracking shear strength Vcw, while the two slabs without fibers failed at shear forces corresponding to 0.93 and 0.87Vcw. Besides an increase in shear strength, the presence of fibers, particularly Type 2 fibers, led to a more gradual post-peak strength decay. Failure of the hollowcoreslabs without fibers occurred as soon as one web exhibitedweb-shear cracking. In the hollow-core slabs with fibers, on theother hand, fibers bridging the first web-shear crack preventedthis web from experiencing a sudden loss of shear capacity, which allowed the slabs to sustain additional shear until multiple webs had cracked in shear.