A New Panel Element Tester for the Investigation of Reinforced Concrete Behavior under Non-proportional Load Paths

The first Panel Element Tester was conceived by Vecchio and Collins at the University of Toronto in the late 1970s. This apparatus allows for the mechanical testing of concrete elements under combined in-plane normal and shear stresses and provided important experimental insights into the behavior of reinforced concrete leading to the development of the Modified Compression Field Theory (MCFT). A next-generation version of this testing rig has been constructed at EPFL, Switzerland, to study reinforced concrete and other materials subject to general, non-proportional load trajectories. The EPFL Panel Element Tester features increased hydraulic capacity as well as servo-actuator control to allow for real-time, independent command of shear and normal stresses, enabling a more extensive range of testing protocols. This paper presents the design of the EPFL Panel Element Tester, including descriptions of the mechanical, hydraulic and control systems. Alternate potential configurations of the modular, bolted design are also presented. Moreover, it is shown through linear analysis that a redesigned connection point eliminating geometric eccentricity between the actuator links and the reinforced concrete panel improves the uniformity of stresses in the tested panel elements