Flexural behavior of PVC stay-in-place formed RC walls

The study experimentally investigates the flexural behavior of concrete wall strips encased with PVC stay-in-place (SIP) concrete forming system. The system consists of interconnected Polyvinyl chloride (PVC) elements; panels, connectors and bracings. Thirty PVC encased wall specimens were cast with dimensions: 457 mm wide by 200 mm or 250 mm deep by 3050 mm long. The variables studied were: the concrete core thickness (200 mm or 250 mm), the reinforcement ratio, and the connector type (middle and braced connector). The connectors used were middle connectors with flat panels or connectors with inclined bracing on the compression side and insulation (foam) on the tension side. All the specimens were tested under four point bending with a shear span of 1150 mm. The test results showed that the PVC stay-in-place formwork system was effective in enhancing the flexural behavior of the encased walls. For a given reinforcement, the PVC encased specimens cracked and failed in the same mode, regardless of the connector type or the concrete core's thickness. The PVC encased walls exhibited higher yield and ultimate loads in comparison to control walls. The increase in load for the PVC encased walls decreased with higher reinforcement ratios. The contribution of the PVC stay-in-place system to the ultimate load increased as the concrete core thickness decreased and/or as the reinforcement ratio decreased. A model based on strain compatibility was developed to predict the flexural capacity of PVC stay-in-place encased walls. Predictions were in close agreement with measured results.