EXPERIMENTAL STUDY ON MAXIMUM SPACING OF SHEAR REINFORCEMENT FOR WIDE BEAMS

Abstract

abstract The main objective of this study is to investigate the behavior of reinforced concrete wide beams when increasing the maximum shear reinforcement spacing (Smax) from d/2 (limitation of ACI 318M-14). to (0.75d, S, d), Twelve specimens of reinforced concrete beams were experimentally carried out, all beams were tested as simply supported beams under two-point loads with normal concrete strength (30MPa). The experimental program consisted of casting and testing three groups of wide beams specimens with constant dimensions of 1600mm length, 200 mm height with different width. The group one consisted of four wide RC beams by width of 400mm: one of these beams was designed according to ACI-Code (Smax) d/2 (control beam) and the other three beams were designed by increasing shear reinforcement spacing to (0.75d), (0.81d) and (d), the group two consists of four wide RC beams by a width of 500mm:one of these beams was designed according to ACI-Code (Smax) d/2 (control beam) and the other three beams designed by the increasing spacing to (0.65d),(0.75d) and (d),the group three consists of four wide RC beams by width 600mm:one of these beams was designed according to ACI-Code (Smax) d/2 (control beam) and the other three beams designed by increasing spacing to (0.55d),(0.75d) and A(d). v No significant effect in ultimate load for the experimental program by increasing shear spacing to (0.75d ,0.81d and d), where the different was decreased around 5% in group one (width 400mm), where decreased by (2%,4.9%,8.8%) for spacing (0.75d,0.81d, d) but decreased around 6.5% in group two (width 500mm), where decreased by (4.25%,6%,9.5%) for spacing (0.65d,0.81d, d) and decreased around 14.5% in group three (width 600mm), where decreased by (0.5%,13.5%,15.6%) for spacing (0.55d,0.81d, d). No large difference in first flexural crack loud and first diagonal crack loud where the different around (5% and 7.5%) in group one, (10% and 10.5%) in group two and (10.5% and 15.5%) for group three. The test results also indicated that when (Smax) increased from (0.5d to 1.0d), the deflection decreased by about 0.7% to 14%, 6.9% to 22% and 10.8% to 13.25% for group one, two and three. When increasing width of wide beams from 400mm to 500mm in group two and to 600mm in group three, the ultimate load increasing by 2.8% in group two and17.25% in group three, the first flexural crack load increasing by 27.75 in group two and 20% in group three, the first diagonal crack load decreasing in all beams by average 10.6% in group two, and decreased by average 35.75 in group three, the ultimate deflection decreased in all beams of group two by average 15.75%, in group three the ultimate deflection increased in all beams by 16.7 except the beam with spacing (Smax=d) decreased by 1.3%.