Title:
Post-Cracking Shear Capacity of Precast Hollow-Core Floor Units
Author(s):
Mohamed Mostafa, Richard S. Henry, and Kenneth J. Elwood
Publication:
Structural Journal
Volume:
123
Issue:
3
Appears on pages(s):
281-294
Keywords:
hollow core; post-cracking behavior; precast concrete; prestressed concrete; residual shear strength; seismic assessment; shear failure; web cracking
DOI:
10.14359/51749308
Date:
5/1/2026
Abstract:
Precast concrete hollow-core floor units have been shown to sustain cracking to their unreinforced webs near the end support during earthquakes. Post-cracking shear strength is essential to maintain gravity loads following earthquakes. This paper presents the results of an experimental program that examined the post-cracking shear capacity of 12 full-scale hollow-core floor units. Variables included different support seating lengths, shear span-depth ratios, and loading protocols. Results showed that cracking in the unreinforced webs of hollow-core floor units can reduce shear capacity by at least 60% relative to uncracked strength. Additionally, reduced support seating length markedly decreased post-cracking shear strength: 30 mm (1.2 in.) seating provided no residual capacity, while 50 and 100 mm (2 and 4 in.) lengths retained approximately 50% and 100% of the calculated uncracked section capacity, respectively. The findings from this study provide a basis to quantify the residual capacity of web-cracked hollow-core floor units, which can be used in post-earthquake structural assessments.
Related References:
1. fib, “Special Design Considerations for Precast Prestressed Hollow Core Floors: Guide to Good Practice,” fib Bulletin No. 6, International Federation for Structural Concrete, Lausanne, Switzerland, 2000, 180 pp.
2. fib, “Seismic Design of Precast Concrete Building Structures: State-of-Art Report,” fib Bulletin No. 27, International Federation for Structural Concrete, Lausanne, Switzerland, 2003, 262 pp.
3. Park, R., “A Perspective on the Seismic Design of Precast Concrete Structures in New Zealand,” PCI Journal, V. 40, No. 3, May-June 1995, pp. 40-60. doi: 10.15554/pcij.05011995.40.60
4. Mostafa, M.; Hogan, L.; and Elwood, K. J., “Seismic Performance of Hollow-Core Floors with Modern Detailing: A Case Study,” Journal of the Structural Engineering Society of New Zealand Inc., V. 35, No. 1, Apr. 2022, pp. 86-100.
5. Büker, F.; Parr, M.; De Francesco, G.; Hogan, L. S.; Bull, D. K.; Elwood, K. J.; Liu, A.; and Sullivan, T. J., “Seismic Damage Observations of Precast Hollow-Core Floors from Two Full-Scale Super-Assembly Tests,” Journal of the Structural Engineering Society of New Zealand Inc., V. 35, No. 1, Apr. 2022, pp. 125-147.
6. Mostafa, M.; Hogan, L.; Stephens, M. T.; Olsen, M. J.; and Elwood, K. J., “A Detailed Damage Investigation of an Instrumented Ductile Reinforced Concrete Building Following the M-7.8 Kaikoura Earthquake,” Earthquake Spectra, V. 40, No. 3, Aug. 2024, pp. 2179-2209. doi: 10.1177/87552930231218750
7. Corney, S. R.; Puranam, A. Y.; Elwood, K. J.; Henry, R. S.; and Bull, D., “Seismic Performance of Precast Hollow-Core Floors: Part 1—Experimental Data,” ACI Structural Journal, V. 118, No. 5, Sept. 2021, pp. 49-63. doi: 10.14359/51732821
8. Puranam, A. Y.; Corney, S. R.; Elwood, K. J.; Henry, R. S.; and Bull, D., “Seismic Performance of Precast Hollow-Core Floors: Part 2—Assessment of Existing Buildings,” ACI Structural Journal, V. 118, No. 5, Sept. 2021, pp. 65-77.
9. Liew, H. Y., “Performance of Hollowcore Floor Seating Connection Details,” master’s thesis, University of Canterbury, Christchurch, New Zealand, 2004, 140 pp.
10. Jensen, J., “The Seismic Behaviour of Existing Hollowcore Seating Connections Pre and Post Retrofit,” master’s thesis, University of Canterbury, Christchurch, New Zealand, 2006, 292 pp.
11. Woods, L. J., “The Significance of Negative Bending Moments in the Seismic Performance of Hollow-Core Flooring,” master’s thesis, University of Canterbury, Christchurch, New Zealand, 2008, 294 pp.
12. Walraven, J. C., and Mercx, W. P. M., “The Bearing Capacity of Prestressed Hollow Core Slabs,” HERON, V. 28, No. 3, 1983, pp. 1-46.
13. Yang, L., “Design of Prestressed Hollow Core Slabs with Reference to Web Shear Failure,” Journal of Structural Engineering, ASCE, V. 120, No. 9, Sept. 1994, pp. 2675-2696. doi: 10.1061/(ASCE)0733-9445(1994)120:9(2675)
14. Pisanty, A., “The Shear Strength of Extruded Hollow-Core Slabs,” Materials and Structures, V. 25, No. 4, May 1992, pp. 224-230. doi: 10.1007/BF02473067
15. Tawadrous, R., and Morcous, G., “Shear Strength of Deep Hollow-Core Slabs,” ACI Structural Journal, V. 115, No. 3, May 2018, pp. 699-709.
16. Truderung, K. A.; El-Ragaby, A.; Mady, M.; and El-Salakawy, E., “Shear Capacity of Dry-Cast Extruded Precast, Prestressed Concrete Hollow-Core Slabs,” PCI Journal, V. 64, No. 4, July-Aug. 2019, pp. 71-83. doi: 10.15554/pcij64.4-01
17. de Lima Araújo, D.; Sales, M. W. R.; Silva, R. P. M.; Antunes, C. F. M.; and Ferreira, M. A., “Shear Strength of Prestressed 160 mm Deep Hollow Core Slabs,” Engineering Structures, V. 218, Sept. 2020, Article No. 110723. doi: 10.1016/j.engstruct.2020.110723
18. Jonsson, E., “Shear Capacity of Prestressed Extruded Hollow-Core Slabs,” Nordic Concrete Research, V. 7, 1988, pp. 167-187.
19. Hernández, E.; Matthews, B.; Granello, G.; and Palermo, A., “Post-Cracking Web-Shear Response of Hollow Core Slabs with Low Steel Fiber-Volume Fractions,” ACI Structural Journal, V. 119, No. 6, Nov. 2022, pp. 53-66.
20. NZSEE, SESOC, and Concrete NZ Learned Society, “Technical Proposal to Revise the Engineering Assessment Guidelines: Part C—Section C5: Concrete Buildings,” New Zealand Society for Earthquake Engineering, Wellington, New Zealand, 2018, 252 pp.
21. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) (Reapproved 2022),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.
22. BS EN 1168:2005+A3:2011, “Precast Concrete Products — Hollow Core Slabs,” British Standards Institution, London, UK, 2005, 84 pp.
23. NZS 3101.1&2:2006, “Concrete Structures Standard,” Standards New Zealand, Wellington, New Zealand, 2017, 754 pp.
24. Fenwick, R. C., and Megget, L. M., “Elongation and Load Deflection Characteristics of Reinforced Concrete Members Containing Plastic Hinges,” Bulletin of the New Zealand Society for Earthquake Engineering, V. 26, No. 1, 1993, pp. 28-41. doi: 10.5459/bnzsee.26.1.28-41
25. Fenwick, R.; Bull, D.; and Gardiner, D., “Assessment of Hollow-Core Floors for Seismic Performance,” Research Report 2010-02, University of Canterbury, Christchurch, New Zealand, 2010, 164 pp.
26. Matthews, J., “Hollow-Core Floor Slab Performance Following a Severe Earthquake,” PhD thesis, University of Canterbury, Christchurch, New Zealand, 2004, 523 pp.
27. Lindsay, R., “Experiments on the Seismic Performance of Hollow-Core Floor Systems in Precast Concrete Buildings,” master’s thesis, University of Canterbury, Christchurch, New Zealand, 2004, 340 pp.
28. MacPherson, C., “Seismic Performance and Forensic Analysis of a Precast Concrete Hollow-Core Floor Super-Assemblage,” master’s thesis, University of Canterbury, Christchurch, New Zealand, 2005, 342 pp.
29. Puranam, A.; Filippova, O.; Pastor-Paz, J.; Stephens, M.; Elwood, K. J.; Ismail, N.; Noy, I.; and Opabola, E., “A Detailed Inventory of Medium to High-Rise Buildings in Wellington’s Central Business District,” Bulletin of the New Zealand Society for Earthquake Engineering, V. 52, No. 4, 2019, pp. 172-192. doi: 10.5459/bnzsee.52.4.172-192
30. fib, “Quality Assurance of Hollow Core Slab Floors,” International Federation for Structural Concrete, Lausanne, Switzerland, 1992, 30 pp.
31. NZS 3112.2:1986, “Methods of Test for Concrete: Part 2: Tests Relating to the Determination of Strength of Concrete,” Standards New Zealand, Wellington, New Zealand, 1986, 22 pp.
32. ASTM C496/C496M-17, “Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, 2017, 5 pp.
33. ASTM C78-09, “Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading),” ASTM International, West Conshohocken, PA, 2009, 4 pp.
34. Büker, F., “Experimental Evaluation of the Seismic Performance of Hollow-Core Floors and Retrofits,” PhD thesis, University of Auckland, Auckland, New Zealand, 2023, 491 pp.
35. Hawkins, N. M.; Kuchma, D. A.; Mast, R. F.; Marsh, M. L.; and Reineck, K.-H., “Simplified Shear Design of Structural Concrete Members,” NCHRP Report 549, Transportation Research Board, Washington, DC, 2005, 64 pp.
36. Henry, R. S.; Dizhur, D.; Elwood, K. J.; Hare, J.; and Brunsdon, D., “Damage to Concrete Buildings With Precast Floors During The 2016 Kaikoura Earthquake,” Bulletin of the New Zealand Society for Earthquake Engineering, V. 50, No. 2, 2017, pp. 174-186