Strengthening the Self Compacting Reinforced Concrete Dapped Ends with Near Surface Mounted (NSM) Steel Bar Technique

Qasim M. Shakir, Ruqyia Alliwe

Abstract


An experimental study has been conducted to explore the response of reinforced self-compacting concrete dapped ends retrofitted with NSM steel bars. Eleven specimens are tested with two shear slenderness ratio values (a/d), namely (1.0 and 1.5). Deficiencies in reinforcement in the nib and hanger zone are considered. The response is studied in terms of loading history, cracking and failure load, failure mode, cracking pattern, toughness, stiffness, and ductility. It is observed that retrofitting the nib region with horizontal bars improved the capacity by 29% and 20% for the two shears span/depth (a/d) values, respectively. The maximum enhancement in the capacity for upgraded hanger regions with a/d= 1 is about 21%. Regarding toughness, this research indicated that for reduced nib steel specimens with a/d=1.0 and 1.5, a reduction by 17% and 27%, respectively, were obtained. Whereas reducing the hanger steel by 30% led to a drop by 29%. Strengthening of deficient nib reinforced specimens with a/d =1.0 and 1.5 led to an improvement in toughness by 43% and 62%, respectively. For specimens with deficient hanger steel (a/d=1.0), the strengthening led to toughness enhancement by 87%. Strengthening of deficiently reinforced nib end with the two a/d values resulted in improving stiffness by 18% and 24%, whereas when strengthening the hanger zone, an enhancement of 9% is obtained. For ductility, it is concluded that the prediction of ductility ratio using the displacement ratio method is more efficient than the toughness ratio method because it is considered the premature failure cases. Also, it is obtained that increasing the a/d value resulted in reducing the ductility ratio.

Keywords


High strength; self-compacting; NSM steel bar; strengthening; dapped end beam; fictitious hinge.

Full Text:

PDF

References


Precast Prestressed Concrete Institute. (2010). PCI Design Handbook: Precast and Prestressed Concrete 7th Ed.,2010. Chicago, IL.

Atta A. and Taman M., Innovative method for strengthening dapped-end beams using an external prestressing technique. Materials and Structures, 2016 49:3005–3019. DOI 10.1617/s11527-015-0701-8.

Mattock, A. H., and Chan, T. C., "Design and Behavior of dapped End Beams", PCI Journal, November-December, V.24, No. 6, pp. 28-45, 1979.

S. K. Liem, Maximum Shear Strength of Dapped-end or Corbel. MSc Thesis, College of Engineering, University Concordia, Montreal, Quebec, Canada, August 1983.

Lu W., Lin I., Hwang S. and Lin Y., ''Shear strength of high strength concrete dappedâ€end Beams'', Journal of the Chinese Institute of Engineers, Vol. 26, No. 5, pp. 671-680, 2003,

Ahmad S., Elahi A., Hafeez J., Fawad M. and Ahsan Z., "Evaluation of the Shear Strength of Dapped Ended Beam", Life Science Journal, V. 10, No. 3, pp. 1038-1044, 2013.

Aswin M., Mohammed B. S., Liew M. S., and Syed Z. I., "Shear Failure of RC Dapped-End Beams", Hindawi Publishing Corporation Advances in Materials Science and Engineering, 2015.

Tan K. H..," Shear Strengthening of Dapped Beams Using FRP Systems". FRPRCS-5: Vol. 1: Proceedings of the fifth international conference on Fibre-reinforced plastics for reinforced concrete structures, Cambridge, UK, 16–18 July 2001.

Nanni A. and Huang P. C., ''Validation of an Alternative Reinforcing Detail for the Dapped Ends of Pestressed Double Tees'' University of Missouri-Rolla 224 Engineering Research Laboratory, PCI journal, 2002.

Afefy, H. M. E., Mahmoud, M. H., Fawzy T. M., "Rehabilitation of defected RC stepped beams using CFRP"; Engineering Structures, Vol. 49, pp. 295–305, 2013.

Sas G., Dăescu C., Popescu C., Nagy-György T., "Numerical optimization of strengthening disturbed regions of dapped-end beams using NSM and EBR CFRP",. Composites: Part B., 2014.

Taher S. F., "External Strengthening of Critically Designed RC Girders with Highly Stressed Dapped-Ends" Structural Engineering Department, Faculty of Engineering, Tanta University. Structures & Buildings, 24 March, 2015.

Qasim M. Shakir, Baneen B. Abd "Strengthening of Self Compacting Reinforced Concrete Dapped End Beams with CFRP Sheets", Journal of materials and Engineering Structures,Vol. 6, 359–374, 2019.

Al-Mahmoud F., Castel A., François R., Tourneur C., "RC beams strengthened with NSM CFRP rods and modeling of peeling-off failure",Composite Structures, Vol. 92, pp 1920–1930, 2010.

Sabau C., Popescu C., Sas G., Schmidt J. W., Blanksvärd T., Täljsten B., "Strengthening of RC beams using bottom and side NSM reinforcement",Composites Part B, Vol. 149, pp 82–91, 2018.

Carrillo de Albornoz V.A., García del Toro E. M., Más-López M. I. and Patiño A. L.," Experimental Study of a New Strengthening Technique of RC Beams Using Prestressed NSM CFRP Bars", Sustainability, Vol.11, No. 1374; doi:10.3390/su11051374, 2019.

Yang Y., Fahmy M. F.M., Cui J., Pan Z., Shi J., "Nonlinear behavior analysis of flexural strengthening of RC beams with NSM FRP laminates", Structures,Vol. 20, 374–384, 2019.

Al Rjoub Y. S., Ashteyat A.M., Obaidat Y. T. & Bani-Youniss S., "Shear strengthening of RC beams using near-surface mounted carbon fibre-reinforced polymers", Australian Journal of Structural Engineering, Vol. 20, issue 1, 2019.

Yu X., Xing G., Chang Z., "Flexural behavior of reinforced concrete beams strengthened with near - surface mounted 7075 aluminum alloy bars", Journal of Building Engineering, Vol. 31 101393, 2020.

Askandar N.and Mahmood A., "Comparative Investigation on Torsional Behaviour of RC Beam Strengthened with CFRP Fabric Wrapping and Near-Surface Mounted (NSM) Steel Bar", Advances in Civil Engineering, Vol. 2019, https://doi.org/10.1155/2019/9061703.

Qasim M. Shakir, Hayder H. H. Kamonna., "The Behavior of High Strength Self-Compacting Reinforced Concrete Corbels Strengthened with NSM Steel Bars". International journal on Advanced Science Engineering Information Technology Vol. 8, No. 4, 2018.

Wang Q., Guo Z., Hoogenboom, P. CJ, "Experimental investigation on the shear capacity of RC dapped end beams and design recommendations", Structural Engineering and Mechanics, Vol. 21,No. 2, pp 221-235, 2005.

Vu N. S.,.Bing L,. Beyer K," Effective stiffness of reinforced concrete coupling beams", Engineering Structures, Vol. 76, pp 371–382, 2014.

Rakhshanimehr M., Esfahani M. R., Kianoush M. R., Mohammadzadeh B. A, and Mousavi S. R, "Flexural ductility of reinforced concrete beams with lap-spliced bars", Can. J. Civ. Eng., Vol. 41, No. 7, pp 594–604, 2014.

Naaman A.and Jeong S.," Structural ductility of concrete beams prestressed with FRP tendons", In: Proc. Second Int. RILEM Symp. (FRPRCS- 2) Non-Metallic Concr. Struct., Ghent, Belgium, pp 379–86, 1995.




DOI: http://dx.doi.org/10.18517/ijaseit.11.2.8059

Refbacks

  • There are currently no refbacks.


Published by INSIGHT - Indonesian Society for Knowledge and Human Development