NDT Investigation of Timber Structural Elements at Campbell’s Stores

Campbell’s Stores was established in 1839 and remains one of the most important heritage-listed building in Sydney. Included in its remediation, GBG Australia (GBG) was commissioned by Taylor Thompson and Whitting to conduct Non-Destructive Testing (NDT) of the timber structural elements. Ground Penetrating Radar (GPR) and Ultrasonic Pulse Velocity (UPV) testing were utilised as the technique to provide information on the building.

The purpose of the investigation was to provide a structural assessment of the current condition of the support and bearers of the heritage-listed building. The results provided were to allow the client to assess any repair and maintenance costs as well as the structural integrity of the building. Visual and tap testing were already completed and provided target areas for NDT testing.

GPR data was collected with a 1.5 Hz surface-couple antenna connected to a GSSI SIR3000. The technique was able to locate evidence of internal rot, soft timber, termite damage, pipes and large splits or shakes. Bearers were images from south to north along the beam where profiles were scanned on either side of the beam as well as the underside. Columns were then scanned from their highest point to the ground on all accessible sides to ensure detection of anomalies in the corners of the beams.

The UPV measurements were recorded to find the material strength of the timber, that any timber loss, moisture content and defects (such as air-filled cracks and voids) will be detected. However, as the natural growth of the timber changes the density of the material and its directional elements, a fixed elastic modulus could not be calculated accurately.

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