Eccentric punching tests on column bases – New insights into the inner concrete strain development

Eccentric punching tests on column bases ‐ Influence of column geometry

“…This results from a larger proportion of deflection caused by rotation due to the linear soil stress distribution. The general effect of load eccentricities on the deflection behavior is similar compared with the results of EF1 and EF2 19–21 …”

“…To evaluate the influence of load eccentricities on the punching shear strength depending on all investigated geometric parameters, Figure 12 compares the experimentally defined β test ‐factors for all four uniaxially loaded test series of the research project 19–21 . In Figure 12a, coefficients β test are related to the ratio of e x / b x , where b x is the width of the footing in direction of load eccentricity.…”

“…In order to analyze the multi‐axial stress state inside the concrete compression zone close to the column, two different measurement techniques were employed to investigate the strain distribution along the assumed compression ring 19 . On the one hand, specially manufactured strain gauge measuring devices (Figure 5d, using steel strain gauges, more detailed description in Reference 19 inspired by Hallgren 35 ) enabled a punctual measurement of inner concrete strains in tangential (DT1–DT8, Figure 5a–c) and radial direction (DR1–DR3, Figure 5a–c).…”

“…After reaching a service load level, 10 load cycles between full and half service load were performed to stabilize the state of cracking. This service load was estimated by dividing the expected failure load by the product of the partial safety factors of γ c = 1.5 for concrete and the factor γ F = 1.4 for external loading (mean safety factor of permanent [ γ F = 1.35] and variable loads [ γ F = 1.5]) 19,21,32,33 . The actual service load level was finally determined during the test by observing the measured changes in thickness of the slab.…”

“…The stable version of prEC2 is analyzed applying the new systematic experimental results presented in this article and is compared with the design results of EC2 and MC10. A detailed explanation of the factors for considering load eccentricities can be found in Reference 19, while Siburg et al 25 gave an illustrative explanation of the different design procedures of EC2 and MC10. A brief overview of the design approaches used to determine the coefficient β (EC2 & prEC2) and control perimeter length reduction coefficient k e (MC10) is given in Table 1.…”