Title: Influence of Unbalanced Moment on Punching Shear Behavior of Footings

Author(s): Jan Ungermann, Matthias Kalus, and Josef Hegger

Publication: Symposium Paper

Volume: 357

Issue:

Appears on pages(s): 240-255

Keywords: punching shear; spread footings; unbalanced moments; load eccentricities; design provisions; ACI 318-19; Eurocode 2; stable version of new Eurocode 2; innovative strain measurements

DOI: 10.14359/51738768

Date: 4/1/2023

Abstract:
While the punching shear behavior of centrically loaded footings has been investigated in the past, the influence of unbalanced moments has remained almost uninvestigated for footings. Nevertheless, unbalanced moments are also transferred into the column by shear stresses requiring consideration in punching shear design. Here, design approaches often use coefficients to increase the load on action side or to decrease the resistance. To fill the gap in test data necessary for validation of design approaches, tests of four centrically and fourteen eccentrically loaded footings without shear reinforcement were conducted. Here, innovative measurement techniques were used to determine the development of the compression ring at the column-footing connection. While the constriction of the concrete compression zone due to the multiaxial load transfer leads to the formation of a circumferential compression ring with multiaxial concrete strains for centrally loaded slabs, which enhances the punching shear resistance compared to one-way shear, this compression ring only develops to a reduced extent with increasing load eccentricity. Based on the test results, a new proposal for consideration of unbalanced moments is proposed and compared to existing design approaches according to ACI 318-19, Eurocode 2 and the stable version of new Eurocode 2.