- This event has passed.
Final Colloquium – Lars Croes
May 17 @ 15:30 - 17:00
Behavior of unreinforced concrete-to-concrete interfaces under shear loading
The aim of this research is to re-evaluate which material parameters influence the adhesion shear transfer in an unreinforced concrete-to-concrete interface. The cause of this research is the partial collapse of the parking garage at Eindhoven Airport on the 27th of May 2017. This partial collapse was caused by the use of a two way spanning composite concrete floor, consisting of precast floor plates and a cast-in-situ compression layer, resulting in a positive moment near the precast floor plate edges. Shear stress capacity of the concrete-to-concrete interface was found to be too low.
At the same time as the four point flexural tests of precast plank floor systems , direct shear tests under compression perpendicular to the interface were performed. Eight test series, consisting of a total of 48 specimens were loaded in compression perpendicular to the interface, then loaded in shear until failure.
Specimens were tested at varying levels of compression perpendicular to the interface, to be able to construct the linear part in the Mohr-Coulomb failure envelope for these interfaces. The found averaged shear strength at , , ranged from to , the found slope coefficient ranged from to .
The test series were fabricated using different concrete types and precast plank surface treatments. Concrete strength was measured by means of cube compressive testing, and interface roughness quantification was performed to document interface roughness parameters.
A correlation analysis was performed on the test results and the obtained material parameters, the relationships described by codes and previous research were investigated.
Test results show a small correlation with both the fib Model Code 2010 and the Eurocode 2 interface shear resistance expressions. The fib Model Code 2010 expression showed a slightly larger correlation with the test results. However, this does not mean the code expressions are suitable to describe the test specimen behavior.
The individual components of these expressions do not show correlation with the found Mohr-Coulomb failure envelope components. The coefficients of cohesion proposed in de codes do not show correlation with the test results, whilst the coefficients of friction proposed in codes show a large negative correlation with the test results. This suggests the proposed coefficients of friction are not suitable to describe the slope of the Mohr-Coulomb failure envelope of the tested unreinforced concrete-to-concrete interfaces.
The influence of differential elasticity moduli between the two concretes was found to have a large negative correlation with the interface shear resistance, suggesting that a large difference in modulus of elasticity between the two concretes may lower interface shear resistance.
No correlation between precast plank surface roughness and interface shear resistance, up until adhesive failure, was found.vVERE