Title:
Predicting Strength Capacity of Three-Dimensional Concrete Struts in Pile Caps
Author(s):
Ridha Boulifa, Mohamed Laid Samai, Mohamed Tayeb Benhassine, and Abdelhadi Tekkouk
Publication:
Structural Journal
Volume:
118
Issue:
2
Appears on pages(s):
111-126
Keywords:
confinement cylinder; pile caps; specimens; strength capacity; strut-and-tie model
DOI:
10.14359/51729344
Date:
3/1/2021
Abstract:
The strength predictions of reinforced concrete pile caps are mainly influenced by the cross section and the compressed concrete strut’s inclination. However, for the case of four-pile caps with top-inclined slabs (tapered footings), many authors show that the cracking load decreased as the reinforcement ratio increased. In the present paper, a new experimental study is performed using a vertical penetration of a cylindrical plated bar in a cylindrical confined specimen with a crown-shaped base. The specimens are entirely confined using cylindrical steel tubes. The thickness of the crown and the specimen’s height governs the inclination of the punching failure cone. The present study’s objective is to evaluate three-dimensional pile caps’ strength capacity by developing an analytical relationship taking into consideration the main parameter, which is the shear-span depth ratio. This relationship is based on the determination of the resulting shear in the most solicited vertical plane considering the confinement thanks to longitudinal reinforcement during loading. Thus, the proposed relationship is on the safety side following the failure mode imposed, which is the critical one (by punching). The proposed approach provides more accurate predictions of the strength for the tests performed and existing pile cap’s tests with lower scatter compared to design approaches in the literature and ACI 318 Code.
Related References:
1. Muttoni, A., “Punching Shear Strength of Reinforced Concrete Slabs without Transverse Reinforcement,” ACI Structural Journal, V. 105, No. 4, July-Aug. 2008, pp. 440-450.
2. Menétrey, P., “Synthesis of Punching Failure in Reinforced Concrete,” Cement and Concrete Composites, V. 24, No. 6, 2002, pp. 497-507. doi: 10.1016/S0958-9465(01)00066-X
3. Boulifa, R.; Samai, M. L.; and Benhassine, M. T., “A New Technique for Studying the Behaviour of Concrete in Shear,” Journal of King Saud University—Engineering and Science, V. 25, No. 2, 2013, pp. 149-159.
4. Guo, H., “Evaluation of Column Load for Generally Uniform Grid-Reinforced Pile Cap Failing in Punching,” ACI Structural Journal, V. 112, No. 2, Mar.-Apr. 2015, pp. 123-134. doi: 10.14359/51687420
5. Suzuki, K.; Otsuki, K.; and Tsubata, T., “Experimental Study on Four-Pile Caps with Taper,” Transactions of the Japan Concrete Institute, V. 21, 1999, pp. 327-334.
6. Adebar, P., and Zhou, Z., “Bearing Strength of Compressive Struts Confined by Plain Concrete,” ACI Structural Journal, V. 90, No. 5, Sept.-Oct. 1993, pp. 534-541.
7. Schlaich, J.; Schaefer, K.; and Jennewein, M., “Towards a Consistent Design of Structural Concrete,” Journal - Prestressed Concrete Institute, V. 32, No. 3, 1987, pp. 74-150. doi: 10.15554/pcij.05011987.74.150
8. Wight, J., and MacGregor, J., Reinforced Concrete Mechanics and Design, sixth edition, Pearson, Upper Saddle River, NJ, 2012.
9. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2014.
10. Suzuki, K.; Otsuki, K.; and Tsubata, T., “Influence of Bar Arrangement on Ultimate Strength of Four-Pile Caps,” Transactions of the Japan Concrete Institute, V. 20, 1998, pp. 195-202.
11. Suzuki, K., and Otsuki, K., “Experimental Study on Corner Shear Failure of Pile Caps,” Transactions of the Japan Concrete Institute, V. 23, 2002, pp. 303-310.
12. Suzuki, K.; Otsuki, K.; and Tsuchiya, T., “Influence of Edge Distance on Failure Mechanisms of Pile Caps,” Transactions of the Japan Concrete Institute, V. 22, 2000, pp. 361-368.
13. Adebar, P., and Zhou, Z., “Design of Deep Pile Caps by Strut-and-Tie Models,” ACI Structural Journal, V. 93, No. 4, July-Aug. 1996, pp. 437-448.
14. Park, J.; Kuchma, D. A.; and Souza, R. A., “Strength Predictions of Pile Caps by a Strut-and-Tie Model Approach,” Canadian Journal of Civil Engineering, V. 35, No. 12, 2008, pp. 1399-1413. doi: 10.1139/L08-062
15. Miguel-Tortola, L.; Pallarés, L.; and Miguel, P. F., “Punching Shear Failure in Three-Pile Caps: Influence of the Shear Span-Depth Ratio and Secondary Reinforcement,” Engineering Structures, V. 155, 2018, pp. 127-143. doi: 10.1016/j.engstruct.2017.10.077
16. CEN, “Eurocode 2: Design of Concrete Structures – Part 1–1: General Rules and Rules for Buildings,” Spanish version UNE-EN-1992-1-1:2004; 2013.
17. Otsuki, K., and Suzuki, K., “Experimental Study on Bending Ultimate Strength of Four Pile Caps,” Transactions of the Japan Concrete Institute, V. 61, 1996, pp. 93-102.
18. Clarke, J. L., “Behaviour and Design of Pile Caps with Four Pile Caps,” Cement and Concrete Association, 1973.
19. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2008, 420 pp.
20. Martinez, S.; Nilson, A. H.; and Slate, F. O., “Spirally-Reinforced High-Strength Concrete Columns,” Research Report 1982, No. 82-10, Department of Structural Engineering, Cornell University, Ithaca, NY.
21. Zhang, L. X., and Hsu, T. T. C., “Behavior and Analysis of 100 MPa Concrete Membrane Elements,” Journal of Structural Engineering, ASCE, V. 124, No. 1, 1998, pp. 24-34. doi: 10.1061/(ASCE)0733-9445(1998)124:1(24)
22. Souza, R.; Kuchma, D.; Park, J.; and Bittencourt, T., “Adaptable Strut-and-Tie Model for Design and Verification of Four-Pile Caps,” ACI Structural Journal, V. 106, No. 2, Mar.-Apr. 2009, pp. 142-150.
23. Klein, G. J.; Rezaei, N.; Garber, D.; and Tureyen, A. K., “Shear in Discontinuity Regions: Changes for the ACI 318 Building Code,” Concrete International, V. 41, No. 5, May 2019, pp. 36-41.
24. Guo, H. L.; Ding, D. J.; and Jiang, Y. S., “Study for Load Transfer Mechanism of Space Truss Model Simulating Thick Pile Caps (1),” Industrial Construction, China, V. 27, No. 8, Aug. 1997, pp. 30-35. (in Chinese)
25. Guo, H. L.; Ding, D. J.; and Jiang, Y. S., “Study for Load Transfer Mechanism of Space Truss Model Simulating Thick Pile Caps (2),” Industrial Construction, China, V. 27, No. 9, Sept. 1997, pp. 36-40. (in Chinese)
26. Paulay, T., and Priestley, M. J. N., Seismic Design of Reinforced Concrete and Masonry Buildings, John Wiley and Sons, New York, 1992.
27. AFNOR. DTU P18-702 BAEL 91 (revises 99). Règles techniques de conception et de calcul des ouvrages et constructions en béton armé suivant la méthode des états limites. Fascicule 62, titre 1er du CCTG – Travaux section 1:béton armé; February 2000.
28. Meléndez, C.; Sagaseta, J.; Sosa, P. F. M.; and Rubio, L. P., “Refined Three-Dimensional Strut-and-Tie Model for Analysis and Design of Four-Pile Caps,” ACI Structural Journal, V. 116, No. 4, July 2019, pp. 15-29. doi: 10.14359/51714485