Evaluation of displacements by means of 3D laser scanning in a mechanically loaded replica of a hull section of the Vasa ship

Abstract

For a development of full-scale finite-element models of large objects in cultural heritage, it can be useful to mechanically test replicas of key parts to identify structural properties which would otherwise not be available. This paper presents full scale tests on a replica of a section of the hull of the 17th century warship Vasa in three load configurations. We focus on determining a displacement of the loaded replica from 3D laser measurements. Two measures were found useful: (i) 3D displacements at well-defined intersections of the wooden replica, and (ii) normal displacements of larger surfaces. Wood surfaces were preferred to steel parts of the rig since the latter showed more scatter in displacement values in their point clouds caused by their reflective properties. The measurements were verified with draw-wire sensors. Some of these sensors were attached to the steel rig supporting the replica and, therefore, measured relative displacements. The scanning data was also useful to quantify the absolute movement of the steel rig supporting the replica, which improved the precision of the measurements of replica deformation. Finally, it is discussed how the replica test results can be used in a model of the entire museum ship.