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.
Related References:
1. Eligehausen, R.; Mallée, R.; and Silva, J. F., Anchorage in Concrete Construction, Ernst & Sohn, Berlin, Germany, 2006, 378 pp.
2. Fuchs, W.; Eligehausen, R.; and Breen, J. E., “Concrete Capacity Design (CCD) Approach for Fastening to Concrete,” ACI Structural Journal, V. 92, No. 1, Jan.-Feb. 1995, pp. 73-94.
3. ACI Committee 349, “Code Requirements for Nuclear Safety Related Structures (ACI 349-01),” American Concrete Institute, Farmington Hills, MI, 2001, 134 pp.
4. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American Concrete Institute, Farmington Hills, MI, 2014, 520 pp.
5. Comité Euro-International du Béton (CEB), Design of Fastenings in Concrete, Thomas Telford, Lausanne, Switzerland, 1997, 92 pp.
6. CEN/TS 1992-4, “CEN Technical Specification (TS): Design of Fastenings for Use in Concrete,” Final Draft, European Organization for Standardization (CEN), Brussels, Belgium, 2009, 166 pp.
7. fib Bulletin 58, “Design of Anchorages in Concrete: Guide to Good Practice,” International Federation for Concrete (Fédération Internationale du Béton), V. 58, Lausanne, Switzerland, 2011, 280 pp.
8. Nilsson, M.; Ohlsson, U.; and Elfgren, L., “Effects of Surface Reinforcement on Bearing Capacity of Concrete with Anchor Bolts,” Nordic Concrete Research, V. 2011, No. 44, pp. 161-174.
9. Bažant, Z. P., and Prat, P. C., “Microplane Model for Brittle-Plastic Material—Part I: Theory & Part II: Verification,” Journal of Engineering Mechanics, 1988, V. 114, No. 10, pp. 1672-1702.
10. Ožbolt, J.; Li, Y.; and Kožar, I., “Microplane Model for Concrete with Relaxed Kinematic Constraint,” International Journal of Solids and Structures, V. 38, No. 16, 2001, pp. 2683-2711. doi: 10.1016/S0020-7683(00)00177-3
11. Ožbolt, J., “Smeared Fracture Finite Element Analysis—Theory and Examples,” International Symposium on Connections between Steel and Concrete, R. Eligehausen, ed., RILEM Publication, Paris, France, 2001, pp. 609-624.
12. Bažant, Z. P., and Oh, B. H., “Crack Band Theory for Fracture of Concrete,” Materials and Structures, V. 16, No. 3, May-June 1983, pp. 155-177.
13. Ožbolt, J., and Sharma, A., “Numerical Simulation of Reinforced Concrete Beams with Different Shear Reinforcements under Dynamic Impact Loads,” International Journal of Impact Engineering, V. 38, No. 12, 2011, pp. 940-950. doi: 10.1016/j.ijimpeng.2011.08.003
14. Comité Euro-International du Béton and Fédération Internationale de la Précontrainte, “CEB-FIP Model Code 1990,” Thomas Telford, London, UK, 1993, 437 pp.
15. Eligehausen, R.; Bouška, P.; Červenka, V.; and Pukl, R., “Size Effect of the Concrete Cone Failure Load of Anchor Bolts,” 1st International Conference of Fracture Mechanics of Concrete Structures (FRAMCOS 1), Z. P. Bažant, ed., 1992, pp. 517-525
16. Ožbolt, J.; Eligehausen, R.; Periškić, G.; and Mayer, U., “3D FE Analysis of Anchor Bolts with Large Embedment Depths,” Engineering Fracture Mechanics, V. 74, No. 1-2, 2007, pp. 168-178. doi: 10.1016/j.engfracmech.2006.01.019
17. Nilforoush, R.; Nilsson, M.; Elfgren, L.; Ožbolt, J.; Hofmann, J.; and Eligehausen, R., “Tensile Capacity of Anchor Bolts in Concrete: Influence of Member Thickness and Anchor’s Head Size,” ACI Structural Journal, V. 114, No. 6, Nov.-Dec. 2017.
18. Nilforoush, R.; Nilsson, M.; and Elfgren, L., “Experimental Evaluations of Influence of Member Thickness, Anchor-Head Size, and Reinforcement on the Tensile Capacity of Headed Anchors in Uncracked Concrete,” Journal of Structural Engineering, ASCE, 2017 (in press)