Failure tests on full-scale models of grout laminated wood decks

Abstract

Grout laminated wood decks (GLWDs), representing the third generation of stressed wood decks, comprise either laminates or logs trimmed to obtain two parallel faces. The logs or laminates, running along the span, are held together by means of transverse internal grout cylinders that may be in either compression or tension. Two full-scale models of GLWD were constructed at Dalhousie University, Halifax, one with grout cylinders in compression and the other with the cylinders in tension. Service load tests conducted in Halifax showed that the former deck had better load distribution characteristics. Two years after the tests in Halifax, the models were shipped to The University of Manitoba in Winnipeg, where they were tested to failure under a central patch load. Because of miscommunication with the supplier, the logs of the GLWD with grout cylinders in compression were also trimmed to the third face that was kept at the bottom of the deck. The failure tests showed that despite its superior load distribution characteristics, the deck with grout cylinders in compression failed at a significantly lower load than the GLWD with cylinders in tension. It is argued that a planar surface in the logs at the flexural tension face not only reduces their flexural stiffness but also brings the defects of wood to the surface with maximum stress. The deck with the flat bottom surface underwent tension failure of the most heavily loaded logs, whereas the deck with the intact round surface of the logs at both top and bottom failed by horizontal splitting of all the logs.Key words: articulated plate, bridge deck, grout laminated deck, orthotropic plate, timber.