Distributed strain monitoring of two-way slabs

Abstract

Two-way slab design and assessment is often based on conservative approaches due to a lack of data regarding slab behaviour. Distributed fibre optic strain sensors have the potential to provide extensive data sets for both lab experiments and field assessments. A proof of concept study was undertaken that involved four two-way slabs, with varying reinforcement ratios and levels of axial restraint, that were instrumented with distributed fibre optic strain sensors and tested under a central point load. The slabs with less reinforcement demonstrated a ductile flexural failure while the more heavily reinforced slabs failed due to punching shear. The axial restraint system developed for this research provided partial restraint and enhanced the capacity of both restrained specimens compared to the control specimens. The strain data enabled differences in support conditions (both vertical and axial) to be identified. Additionally, the data enabled the onset of reinforcement yielding to be captured and thus proved it to be a promising approach for measuring the beneficial of effects of membrane action. The results of the experiments were compared to a yield-line analysis and were found to be within 5% for the unrestrained specimens and within 10% for the axially restrained specimens despite the fact that two specimens failed in punching shear.