LONG-TERM PERFORMANCE OF POST-INSTALLED CONCRETE SCREWS

Concrete screws are a type of anchor used in structural and non-structural applications in uncracked and cracked concrete. The load transfer is based on mechanical interlock between the threads and concrete. Like all anchor products, they undergo rigorous testing during product assessment which at the moment does not cover the sustained load behavior. This investigation aims at studying the sustained-load behaviour of concrete screws by performing a series of tensile tests. Short-term tests were first performed from which the ultimate load capacity of the screws was determined. Long-term tests were then performed at different load levels, selected as a function of the short-term capacity. The time to failure and displacements were recorded throughout each test. The resulting experimental data was used to generate time-to-failure curves and fit the regression models that are currently used for the long-term assessment of chemically bonded anchors. Finally, the predicted long-term capacity for a 50-year lifetime is presented and compared to adhesive anchors.
EXTENDED ABSTRACT