Effect of Adding High Strength Concrete Topping on Flexural and Shear Behavior of Hollow Core Pre-stressed Slabs
Enhancing shear and flexural strength of hollow-core slabs
Keywords:
Hollow core pre-stressed slab, Topping, Cracking, Deflection, Shear strength, Flexural strengthAbstract
This paper presents an experimental study regarding the effect of adding extra topping on flexural& shear capacity of hollow core pre-stressed concrete slabsand mainly focuses on how to increase shear and flexural capacity of slabs on site with the help of in-situ concrete topping. There may arise a situation where a depth greater than 200 mm and less than 265 mm may be required due to particular applied loading. Such extra depths can only be produced by applying in-situ concrete topping layer. High strength concrete toppings of 32 mm and 65 mm thicknesses were used on slabs of 200 mm original depth and were also compared with slab of 265mm depth. Out of four topped slabs tested in the program, two were tested under flexure and the other two under shear loading. Two control slabs of 200 and 265 mm but without extra topping were also tested in the same way. The ultimate load capacity, shear capacity, deflection, crack pattern, crack width and modes of failure were investigated for each slab. From the findings, it was concluded that the addition of concrete topping could enhance the flexural and shear capacity of hollow core units. For flexural loads, the increase was up to sixty percent for 65 mm topping and twenty-three percent for 32 mm topping. For shear testing, the increase was almost hundred percent for 65 mm topping and fifty-six percent for 32 mm topping. It was also observed that both flexural and shear strength of topped slabs was almost equal to the strength of un-topped slabs of same original depth. In cost comparison, the topped up slab came out to be 8.45% expensive as compared to hollow-core slab of similar depth.
References
Wolanski, A. Flexural behaviour of reinforced and prestressed concrete beams using Finite Element Analysis. MSc thesis, Faculty of Graduate School, Marquette University, Milwaukee, Wisconsin, USA (2009).
Elliott, J. &D. Nethercot, Non-composite Flexural and Shear Tests on CF70 Decking.Report SR-91033. Department of Civil Engineering, University of Nottingham, Nottingham (1991).
Scott, N. Performance of precast prestressed hollow core slab with composite concrete topping. PCI Journal 18: 64–77 (1973).
Bayasi, Z. & H. Kaiser. Flexural behaviour of composite concrete slabs using carbon fibre laminate decks. ACI Material Journal 100:274–279 (2003).
Dowell, R.& J. Smith. Structural tests of precast, prestressed concrete deck panels for California freeway bridges. PCI Journal 51:76–87 (2006).
Rahman, M., Baluch, M., Said, M. & M. Shazali. Flexural and Shear Strength of Prestressed Precast Hollow-Core Slabs. Arabian Journal for Science and Engineering 37: 443-455 (2012).
Silfwerbrand, J. Shear bond strength in repaired concrete structures. Materials and Structures36:419–424 (2003).
Micallef, P.Assessment of Shear Capacity of Pre-stressed Hollow Core Floor Units in the Local Construction Industry. Department of Architecture and Civil Engineering, University of Malta(2005).
Broo, H. & K. Lundgren. Finite Element Analyses of Hollow Core Units Subjected to Shear and Torsion. Technical Report 1. Shear and torsion interaction of hollow core slabs. Chalmers University of Technology, Goteborg, Sweden (2002).
Hawkins, N. & S. Ghosh. Shear strength of Hollow-core slabs. PCI journal51:110-114 (2006).
Girhammar, U. &M. Pajari.Tests and analysis on shear strength of composite slabs of hollow core units and concrete topping.Construction and Building Materials 22: 1708–1722 (2008).
Ibrahim, I.S., Elliott, K.S., Abdullah, R., Kueh, A.B.H. & N.N. Sarbini. Experimental study on the shear behaviour of precast concrete hollow core slabs with concrete topping. Engineering Structures 125: 80-90 (2016).
Eom, T.S., Hwang, I.H. & T.W. Park.Evaluation of Shear Strength of Non-prestressed Reinforced Concrete Hollow-Core Slabs. Journal of Korean Society of Hazard Mitigation 15: 43-54 (2015).
Pachalla, S.K.S. & S.S. Prakash. Load resistance and failure modes of GFRP composite strengthened hollow core slabs with openings. Materials and Structures 50: 1-14 (2017).
Hwang, S., Seo, S., Lee, K. & S. Lee. Flexural Capacity of Precast Concrete Triple Ribs Slab. Journal of the Korea Concrete Institute 28: 3-11 (2016).
Elliott, K. Precast Concrete Structures, 1st edition, Antony Rowe Ltd. 98. Oxford (2002).
Foubert, S. Flexural strengthening of prestressed hollowcore slabs using near-surface mounted (nsm) cfrp reinforcement, MSc Thesis, Submitted to University of Manitoba, Canada (2014). 267p
Bhatt, P. Reinforced concrete: design theory and examples. 3rd ed. Taylor & Francis, London (2006).
