Title: Influence of Surface Reinforcement, Member Thickness, and Cracked Concrete on Tensile Capacity of Anchor Bolts

Author(s): R. Nilforoush, M. Nilsson, L. Elfgren, J. Ožbolt, J. Hofmann, and R. Eligehausen

Publication: Structural Journal

Volume: 114

Issue: 6

Appears on pages(s): 1543-1556

Keywords: cone breakout failure; cracked concrete; headed anchor; member thickness; splitting failure; surface reinforcement; tension loading

DOI: 10.14359/51689505

Date: 11/1/2017

Abstract:
An extensive numerical study was carried out to evaluate the influence of concrete member thickness and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts in uncracked concrete members. Anchor bolts at various embedment depths (hef = 50 to 300 mm [1.97 to 11.81 in.]) in unreinforced and reinforced concrete members of various thicknesses (H = 1.5 to 5.0hef) were simulated. The reinforced concrete slabs were considered to be lightly reinforced and over-reinforced to also evaluate the influence of amount of reinforcement. Furthermore, the behavior of anchor bolts at various embedment depths in precracked reinforced concrete members was numerically investigated. The numerical results were compared with predictions from current design models, including the Concrete Capacity (CC) Method. The numerical results show that in uncracked concrete, the tensile capacity of anchor bolts increases up to 20% and the anchorage behavior becomes more ductile with increasing member thickness or by having surface reinforcement. The numerical results also show that the CC Method underestimates the tensile capacity of deep anchors (hef ≥ 200 mm [7.87 in.]), while it slightly overestimates the capacity of short anchors (hef ≤ 100 mm [3.94 in.]) in thin unreinforced members. It was also found that the over-reinforced concrete does not improve the anchorage capacity and performance any further than the lightly reinforced concrete. Based on the numerical results, several recommendations are proposed to account for the influence of member thickness, surface reinforcement, and cracked concrete. Further experimental studies are ongoing to verify and generalize the recommendations of this study.