Do Sonic Tomography and Static Load Tests Yield Comparable Values of Load-Bearing Capacity?

Abstract

We tested the hypothesis that the loss of load-bearing capacity, as estimated by means of static load tests and from sonic tomography, is comparable. This is of practical importance for arborists when they have to assess results reported by different consultants or when they have to choose between applying one of these two methods in a specific case. A total of 59 trees, primarily Fagus sylvatica and Quercus robur, were subjected to static load tests and sonic tomography. The pulling test method yielded the residual stiffness of the stem at every position tested with a strain sensor as an intermediate quality parameter used to merely validate the actual estimations of safety against fracture. Based on the shape of the parts of the stem cross-section that are considered load bearing, sonic tomograms can be further processed in order to assess the loss of load-bearing capacity from defects like decay. We analyzed the correlation of these biomechanically equivalent parameters. This was only the case to a very limited extent. Sonic tomography and static load tests cannot replace each other, but they can complement each other.