Controversy Over Cracks in Glued Laminated Timber Beams Anna Al Sabouni-Zawadzka , Wojciech Gilewski (B ) , Pawel A. Król , and Jan Pelczy ´ nski Faculty of Civil Engineering, Warsaw University of Technology, Al. Armii Ludowej 16, 00-637 Warsaw, Poland w.gilewski@il.pw.edu.pl Abstract. The analysis and evaluation of cracks in three different case studies of glued laminated timber structures is presented in the paper. The analysis is performed from the point of view of possible failure due to crack defects. Keywords: Glued laminated timber · Moisture · Cracks 1 Introduction Cracks in wood are one of the well-known defects of this building material [1]. Cracks may be caused by the drying out of the wood, but also by exceeding the relatively small allowable stresses in the direction transverse to the wood grain due to mechanical effects [2, 3]. The latter may be the result of a design error. In any case, the appearance of cracks raises the doubts of users as to the failure-free use of the facility, as it may have a significant impact on the stiffness of structural elements [4, 5]. In addition, cracked wood partially loses its unique aesthetic qualities. There are even supporters of covering wooden elements so that no cracks are visible. However, we will not avoid answering the question whether the presence of cracks is acceptable from the point of view of building safety. The drying process of wood is difficult to be precisely described mathematically [6]. In the literature, attempts are made to numerically model the impact of moisture changes on the wood cracking process (e.g. [7]), along with experimental validation (e.g. [8]), also in the field of glued laminated timber [1, 9]. However, it seems that such modeling is subject to a high level of uncertainty due to the heterogeneity of the wood, twist of the fibers, knots and other material defects. The main objective of the paper is to analyze and evaluate cracks in three case studies for beams made of glued laminated timber. The examples differ significantly from each other and concern girders with relatively large spans and big transverse dimensions. Computational modeling is only mentioned in the paper, although it was done by the authors. Humidity measurements of glued laminated timber elements were performed with a professional HIT-3 hygrometer. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 P. Akimov and N. Vatin (Eds.): RSP 2021, LNCE 189, pp. 81–90, 2022. https://doi.org/10.1007/978-3-030-86001-1_10