Structural Engineering and Mechanics

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Minimum thickness of flat plates considering construction load effect

  • Hwang, Hyeon-Jong (College of Civil Engineering and Hunan Provincial Key Lab on Damage Diagnosis for Engineering Structures, Hunan Univ.) ;
  • Ma, Gao (College of Civil Engineering and Hunan Provincial Key Lab on Damage Diagnosis for Engineering Structures, Hunan Univ.) ;
  • Kim, Chang-Soo (School of Architecture, Seoul National University of Science and Technology)
  • Received : 2018.03.22
  • Accepted : 2018.11.29
  • Published : 2019.01.10
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Abstract

In the construction of flat plate slabs, which are widely used for tall buildings but have relatively low flexural stiffness, serviceability problems such as excessive deflections and cracks are of great concern. To prevent excessive deflections at service load levels, current design codes require the minimum slab thickness, but the requirement could be unconservative because it is independent on loading and elastic modulus of concrete, both of which have significant effects on slab deflections. In the present study, to investigate the effects of the construction load of shored slabs, reduced flexural stiffness and moment distribution of early-age slabs, and creep and shrinkage of concrete on immediate and time-dependent deflections, numerical analysis was performed using the previously developed numerical models. A parametric study was performed for various design and construction conditions of practical ranges, and a new minimum permissible thickness of flat plate slabs was proposed satisfying the serviceability requirement for deflection. The proposed minimum slab thickness was compared with current design code provisions and numerical analysis results, and it agreed well with the numerical analysis results.

Keywords

Acknowledgement

Supported by : National Natural Science Foundation of China

References

  1. ACI Committee 209 (1992), Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures (ACI 209R-92), American Concrete Institute, Farmington Hills, Michigan, U.S.A.
  2. ACI Committee 318 (2014), Building Code Requirements for Structural Concrete and Commentary (ACI 318-14), American Concrete Institute, Farmington Hills, Michigan, U.S.A.
  3. ACI Committee 347 (2005), Guide for Shoring/Reshoring of Concrete Multistory Buildings (ACI 347.2R-05), American Concrete Institute, Farmington Hills, Michigan, U.S.A.
  4. AIK (2016), Korean Building Code, Architectural Institute of Korea, Kimundang, Seoul, Republic of Korea.
  5. Bischoff, P.H. and Scanlon, A. (2007), "Effective moment of inertia for calculating deflections of concrete members containing steel reinforcement and fiber-reinforced polymer reinforcement", ACI Struct. J., 104(1), 68-75.
  6. Branson, D.E. (1963), Instantaneous and Time-Dependent Deflections of Simple and Continuous Reinforced Concrete Beams, Alabama Highway Research Department, Bureau of Public Roads, Report No.7, Part I, l-78.
  7. Carino, N.J. and Lew, H.S. (1983), "Temperature effects on strength-maturity relations of mortar", ACI J. Proc., 80(3), 177-182.
  8. CEB-FIP (1993), CEB-FIP Model Code 1990: Design Code, Euro-International Committee for Concrete, Thomas Telford, London, U.K.
  9. CEN (2004), Eurocode 2: Design of Concrete Structures-Part 1-1: General Rules and Rules for Buildings, European Committee for Standardization, Brussels, Belgium.
  10. Corley, W.G. and Jirsa, J.O. (1970), "Equivalent frame analysis for slab design", ACI J., 67(11), 875-884.
  11. El-Shahhat, A.M. and Chen, W.F. (1992), "Improved analysis of shore-slab Iiteraction", ACI Struct. J., 89(5), 528-537.
  12. Firky, A.M. and Thomas, C. (1988), "Development of a model for the effective moment of inertia of one-way reinforcement concrete elements", ACI Struct. J., 95(4), 444-455.
  13. Gardner, N.J. and Fu, H.C. (1987), "Effects of high construction loads on the long-term deflections of flat slabs", ACI Struct. J., 84(3), 349-360.
  14. Gilbert, R.I. (1999), "Deflection calculation for reinforced concrete structures-why we sometimes get it wrong", ACI Struct. J., 96(6), 1027-1033.
  15. Grundy, P. and Kabaila, A. (1963), "Construction loads on slabs with shored formwork in multistory buildings", ACI J. Proc., 60(12), 1729-1738.
  16. Hossain, T.R. and Vollum, R.L. (2002), "Prediction of slab deflections and validation against cardington data", Proceedings of the ICE-Structures and Buildings, 152(3), 235-248. https://doi.org/10.1680/stbu.2002.152.3.235
  17. Hossain, T.R., Vollum, R.L. and Ahmed, S.U. (2011), "Deflection estimation of reinforced concrete flat plates using ACI method", ACI Struct. J., 108(4), 405-413.
  18. Hwang, H.J., Park, H.G., Hong, G.H., Kim, J.Y. and Kim, Y.N. (2016), "Time-dependent deflection of slab affected by construction load", ACI Struct. J., 113(3), 557-566.
  19. Kang, S., Choi, K. and Park, H. (2003), "Minimum thickness requirements of flat plate affected by construction load", J. Kor. Concrete Inst., 15(5), 650-661. https://doi.org/10.4334/JKCI.2003.15.5.650
  20. Kim, J. (2009), "Applications of practical analysis scheme for evaluating effects of over-loads during construction on deflections of flat plate system", J. Comput. Struct. Eng. Inst. Kor., 22(1), 25-34.
  21. Kim, J.Y. and Kang, S.M. (2017), "Simulations of short-and long-term deflections of flat plates considering effects of construction sequences", Struct. Eng. Mech., 62(4), 477-485. https://doi.org/10.12989/sem.2017.62.4.477
  22. Lee, J.I., Scanlon, A. and Scanlon, M.A. (2007), "Effect of early age loading on time-dependent deflection and shrinkage restraint cracking of slabs with low reinforcement ratios", Struct. Implicat. Shrinkag. Creep Concrete, Am. Concrete Inst., SP-246-9, 149-166.
  23. Lee, Y.H. and Scanlon, A. (2010), "Comparison of one- and two-way slab minimum thickness provisions in building codes and standards", ACI Struct. J., 107(2), 157-163.
  24. Liu, X., Chen, W.F. and Bowman, M.D. (1985), "Construction load analysis for concrete structures", J. Struct. Eng., 111(5), 1019-1036. https://doi.org/10.1061/(ASCE)0733-9445(1985)111:5(1019)
  25. Mehta, P.K. and Monteiro, P.J.M. (2006), Concrete Microstructure, Properties, and Materials, 3rd Edition, McGraw-Hill, New York, U.S.A.
  26. Mosallam, K.H. and Chen, W.F. (1991), "Determining shoring loads for reinforced concrete construction", ACI Struct. J., 88(3), 340-350.
  27. Park, H., Hwang, H., Hong, G., Kim, Y. and Kim, J. (2011), "Slab construction load affected by shore stiffness and concrete cracking", ACI Struct. J., 108(6), 679-688.
  28. Park, H., Hwang, H., Hong, G., Kim, Y. and Kim, J. (2012), "Immediate and long-term deflections of reinforced concrete slab affected by early-age loading and low temperature", ACI Struct. J., 109(3), 413-422.
  29. Scanlon, A. and Lee, Y.H. (2006), "Unified span-to-depth ratio equation for non-prestressed concrete beams and slabs", ACI Struct. J., 103(1), 142-148.
  30. Vollum, R.L., Moss, R.M. and Hossain, T.R. (2002), "Slab deflections in the cardington in-situ concrete frame building", Mag. Concrete Res., 54(1), 23-34. https://doi.org/10.1680/macr.2002.54.1.23

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