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Concrete In Australia : June 2014
36 Concrete in Australia Vol 40 No 2 INVITED PAPER: SHEAR Vu,cal/Vu,test fc [MPa] Figure 11: Ratio between calculated and tested shear capacity vs compressive strength. CONCLUSIONS A plasticity based procedure for shear strength prediction of prestressed hollow core slabs has been described. The capacity is calculated by considering a crack sliding mechanism and a rotational mechanism involving pull out of strands. Both mechanisms are assumed to take place upon the development of a critical diagonal crack. The calculations have been compared with 257 shear test results. The mean value of Vu,cal/Vu,test was found to be 1.05 and the standard deviation amounted to 17%. The obtained result is judged to be satisfactory, especially when considering the simplicity of the outlined method. The calculations show that the rotation failure with pull out of strands (i.e. an anchorage failure) is critical when: 1. The level of prestressing is high 2. The depth h is larger than app. 300 mm 3. The shear span to depth ratio is small. High prestressing level and/or large h is relevant in practice when the span of the hollow core slabs is relatively long. This means that in such cases, the shear capacity of the slabs may be governed by a rotation failure with pull out of strands. This is rather unfortunate as this failure mode is solely dependent on the tensile strength of concrete. In practice, special attention should therefore be paid to the support conditions when dealing with long span elements. ACKNOWLEDGEMENT References 7, 8 and 14 have kindly been provided by Dr. G. Bertagnoli from Politecnico di Torino. REFERENCES 1. Bertagnoli G, Mancini G (2009). Failure analysis of hollow core slabs tested in shear. Structural Concrete, Vol. 10, No. 3, Sept. 2009. 2. Engström B (1999). Beräkning av förspända betongkonstruktioner (Analysis of prestressed concrete structures). Division of Concrete Structures, Chalmers University of Technology, Göteborg. 3. Fellinger JHH, Breunese AJ (2005). Standard shear tests on prestressed hollow core slabs according to EN 1168: 2005. TNO report, TNO Building and construction research, Delft, Netherlands. 4. FIP (1988). Precast prestressed hollow core floors: FIP recommendations. Thomas Telford, London, 1988. 5. Hoang LC (1997). Shear Strength of Non-Shear Reinforced Concrete Elements. Part 3. Prestressed hollow- core slabs. Technical University of Denmark, Department of Structural Engineering and Materials. Series R, No. 30. 1997. 6. International federation for structural concrete (2000). Special design considerations for precast prestressed hollow core floors. Guideline to good practice, fib bulletin 6. Lausanne, Switzerland, 2000. 7. Istituto di Ricerche e Collaudi M. Masini (1995). Rapporto di Prova no. 5386, 12/07/1995. 8. Istituto di Ricerche e Collaudi M. Masini (2005). Manufatto sottoposto a prova di taglio – Prove di carico su lastre RAP20 – Rapporto di Prova No. 1471-2005. 9. Jørgensen HB (2014). Collection of shear tests on hollow-core slabs and comparisons with shear strength calculations based on the crack sliding model. Internal note. Dept. of Technology and Innovation, Faculty of Engineering, University of Southern Denmark. Odense, Denmark, 2014. 10. Muttoni A (1992). Die Anwendbarkeit der Plastizitätstheorie in der Bemessung von Stahlbeton (The Application of the Theory of Plasticity for the Design of Reinforced Concrete). Institut für Baustatik und Konstruktion, ETH Zürich, Bericht Nr. 176, 1990. 11. Nielsen MP, Hoang LC (2011). Limit analysis and concrete plasticity. 3rd edition, CRC Press, Boca Raton, Florida, 2011. 12. Olsen DH, Ganwei C, Nielsen MP (1990). Plastic shear solutions of prestressed hollow-core concrete slabs. Technical University of Denmark, Department of Structural Engineering, Report R No. 257, Lyngby. 13. Pajari M (2005). Resistance of Prestressed hollow-core Slabs against Web Shear Failure. ESPOO, Finland, VTT Research Notes 2292. 14. Università dell’ Aquila (1998 & 2003). Prove di carico statico su solai alveolari Spiroll. Dipartmento di Ingegneria delle Strutture delle Acque e del Terreno, Università Degli Studi di ĺAquila. Report of Generale Prefabbricati, December 1998, June 2003, December 2003. 15. Walraven JC (1982). Design principles for hollow- core-slabs and transverse load bearing capacity, splitting control. FIP Technical Paper, October 1982. 16. Walraven JC, Mercx WPM (1983). The Bearing Capacity of Prestressed Hollow-core Slabs. Heron, Vol. 28, No. 3, Delft University of Technology, 1983. 17. Yang L (1994). Design of prestressed hollow-core slabs with reference to web shear failure. Journal of Structural Engineering. Vol. 120, No. 9, September 1994. 18. Zhang JP (1994). Strength of Cracked Concrete, Part 1 – Shear Strength of Conventional Reinforced Concrete Beams, Deep Beams, Corbels and Prestressed Reinforced Concrete Beams without Shear Reinforcement. PhD thesis, Department of Structural Engineering and Materials, Technical University of Denmark. Series R, No 311. 30-36 - Hoang.indd 36 30-36 - Hoang.indd 36 21/05/14 8:39 AM 21/05/14 8:39 AM