Marcus Ricker

Punching Strength of Reinforced Concrete Footings

This study investigates the punching shear behavior of reinforced concrete footings. Punching tests were conducted on 17 reinforced concrete footings were tested to study the parameters assumed to affect the punching shear strength of footings. These parameters included shear span-depth ratio (a/d), concrete strength, and punching shear reinforcement. The (a/d) ranged between 1.25 and 2.0, while the concrete strength ranged between 20 and 40 MPa (2.9 and 5.8 ksi). To study the effect of soil-structure interaction, five footings were realistically supported on sand. The remaining specimens were supported on a column stub and a uniform surface load was applied. The present experimental investigations indicated that the angle of the failure shear crack is steeper in punching tests on compact footings than observed in tests on more slender slabs. Furthermore, the (a/d) significantly affects the punching shear capacity. The provisions of ACI and Eurocode 2 are evaluated by comparing them with experimental results. Modifications are proposed to overcome the deficiencies of these codes.

Experimental Investigations on Punching Behavior of Reinforced Concrete Footings

This article reports on a study of 5 reinforced concrete footings that were tested to investigate the punching shear failure of footings. Contrary to most of the research in this area, in which footings are supported on springs or on a column slab, this study used concrete column footings realistically supported on sand. The tested specimens had different slab thicknesses and reinforcement ratios. The consistency of the sand was also varied as a test parameter (dense and loose). Four footings had no shear reinforcement, whereas the fifth one included shear reinforcement (vertical bars mechanically anchored at top and bottom by welded anchor plates). Results showed that the angle of the failure shear crack is steeper than that observed by punching tests of flat slabs. In addition, the shear slenderness seems to significantly affect the punching shear capacity. The consistency of the sand has no other influence on the soil pressure distribution underneath the footing. The authors report on their study and review other tests from the literature, developing a test data bank. They also compare ACI and Eurocode 2 provisions and rules for the design of footings with their present test results as well as the information from the test data bank.