Title:
Comparative Study of Punching Shear and Concrete Breakout
Author(s):
Daniel Gaspar Rodriguez and Jack P. Moehle
Publication:
Structural Journal
Volume:
118
Issue:
2
Appears on pages(s):
183-192
Keywords:
anchor group; concrete breakout; footings; headed anchor; punching shear
DOI:
10.14359/51729345
Date:
3/1/2021
Abstract:
A laboratory research program was undertaken to compare the failure mechanisms and strengths of concrete foundation slabs subjected to punching shear and concrete breakout loadings. Four nominally identical reinforced concrete slabs were constructed and tested in a laboratory. One of the slabs was loaded in compression through a bearing surface to produce punching shear failure. The other three slabs were loaded in tension through eight anchor bolts arranged around a square perimeter to produce a similarly sized breakout failure. Variations in bearing area and local reinforcement detailing were introduced in the breakout tests to explore their effect on strength. One additional specimen was cast with a single anchor bolt to gather data on basic breakout strength. The test results indicate that punching shear and anchor breakout developed similar failure modes. Punching shear resulted in the largest strength with the largest failure surface. Ultimate load capacities normalized by the square root of the concrete compressive strength and by an effective failure area showed that the nominal failure stresses were nearly equal for the different test cases. The addition of slab deformed reinforcement in the vicinity of the anchor bearing head and oriented perpendicular to the direction of the anchor bolts resulted in a modest increase of the breakout ultimate capacity and of the residual strength.
Related References:
ACI Committee 318, 2019, “Building Code Requirements for Structural Concrete and Commentary (ACI 318-19),” American Concrete Institute, Farmington Hills, MI, 624 pp.
ASCE 426, 1974, “The Shear Strength of Reinforced Concrete Members – Slabs,” Joint ASCE-ACI Task Committee 426 on Shear and Diagonal Tension of the Committee on Masonry and Reinforced Concrete of the Structural Division, Journal of the Structural Division, V. 100, No. ST8, pp. 1543-1591.
Eligehausen, R.; Mallée, R.; and Silva, J. F., 2006, Anchorage in Concrete Construction, Ernst & Sohn, Berlin, Germany, 2006.
Fuchs, W.; Eligehausen, R.; and Breen, J., 1995, “Concrete Capacity Design (CCD) Approach for Fastening to Concrete,” ACI Structural Journal, V. 92, No. 1, Jan.-Feb., pp. 73-94.
Gaspar Rodriguez, D., 2018, “Comparative Study of Punching Shear and Concrete Breakout Behavior in Reinforced Concrete Foundation Elements,” MS thesis, Civil and Environmental Engineering, University of California, Berkeley, Berkeley, CA, 127 pp.
Hahn, G., and Meeker, W., 1991, Statistical Intervals: A Guide for Practitioners, John Wiley & Sons, New York, 397 pp.
Ospina, C. E., and Hawkins, N. M., 2017, “Effect of Slab Flexural Reinforcement and Depth on Punching Strength,” Punching Shear of Structural Concrete Slabs: Honoring Neil M. Hawkins ACI-fib International Symposium, SP-315, American Concrete Institute, Farmington Hills, MI, pp. 117-140.
RILEM TC, 1994, “FMC 2 Size-Effect Method for Determining Fracture Energy and Process Zone Size of Concrete, 1990,” RILEM Recommendations for the Testing and Use of Construction Materials, RILEM, Paris, France, pp. 102-106.