A hazard map for surface splits in outdoor undercover unfinished glued-laminated timber

Abstract

An Australian hazard map is proposed for surface splits in unfinished horizontally oriented glued laminated timber exposed to outdoor undercover climatic conditions, excluding precipitation. A 69 d field trial of four glued laminated timber surfaces in subtropical Australia determined the daily climatic variables contributing to the occurrence and development of surface splits in both laminates and gluelines. An empirical surface split index (SSI) is proposed using daily 3 pm measurements of both air temperature and relative humidity, as well as solar exposure calculated at 3 pm. Days with a calculated SSI of less than six were associated with the occurrence of new surface splits in glued laminated timber surfaces, whereas days with an SSI greater than six corresponded to the opening or closing of existing surface splits. The proposed SSI algorithm was applied to daily climate data from 2010 to 2021, for 12 Australian weather stations. Distinct SSI differences between stations allowed grouping of weather locations with similar SSI results. This grouping led to the proposal of a five-zone surface split hazard system for Australia, and a surface split hazard map for Australia. The uncertainties associated with the proposed map and its application are discussed.