Ultrasonic Pulse Velocity Technique for Inspection and Evaluation of Timber

The ultrasonic pulse velocity technique was used to assess the structural integrity of timber elements in monumental buildings. Six species of timber of different strength values were selected to establish the pulse velocity ranges. The effect of moisture content, specific gravity, internal voids, and external voids on the pulse velocity was measured from tests on different samples. The pulse velocity perpendicular to the grain was found to increase with increase in specific gravity or compressive strength parallel to the grain. A correlation between compressive strength parallel to the grain and ultrasonic pulse velocity perpendicular to the grain was established from test results on six species of timber. A condition-rating system was developed to estimate the strength and to assess the extent of deterioration or the reduction in strength in timber beams. Tests on laboratory samples and extensive field studies on large timber joists and beams of a nearly 140-year-old church building suggest that the recommended procedure can be used effectively for in-service assessment (nondestructively) of wood.