LATERAL RESISTANCE OF LOG TIMBER WALLS SUBJECTED TO HORIZONTAL LOADS Jorge Branco 1 , João Paulo Araújo 2 ABSTRACT: The present works intends to represent a further step in the knowledge of timber log-houses through an experimental approach, from which only few information is available. The main part of the experimental work is based on in-plane static tests conducted on timber log walls with distinct transversal stiffness, two vertical compression levels and two values of slenderness. Monotonic and cyclic tests were performed according to EN 12512:2001. The formers were performed to define the elastic slip values and assessment of the failure mechanisms while the lasts allowed evaluating impairment of strength, to measure the ductility and to quantify the energy dissipation. In a first step research, an extensive characterization of the timber logs was made. The connection between the first timber log and the basement was also evaluated. KEYWORDS: Log-house, characterization, logs, walls, cyclic tests. 1 INTRODUCTION 12 i Timber log constructions are popular in many forest regions of the world, especially in North America and Scandinavia. Their use in earthquake zones is also common, despite design criteria for lateral resistance of log shear walls, have not been given reasonably yet [1]. Timber log constructions are formed by stacking horizontal layers of logs, where log cross-section, grade, and construction details vary among manufacturers. Under vertical loads walls are mainly subjected to low compression perpendicular to the grain. However, wall height changes dimensions as logs lose and absorb moisture while settlements due to logs creep deformation are expected. Lateral loads in log shear walls are generally transferred through: (1) interlocks between logs, (2) wood or steel dowels, (3) vertical through bolts and anchor-bolts, (4) frictions between logs due to vertical loads. As mentioned, some variations to the system and resisting elements can be found. For example, Figure 1 represents the lateral resisting elements of log shear walls produced by Rusticasa, a Portuguese manufacturer that marks since 1978. Existing design standards for log constructions only count wood or steel dowels and vertical through bolts [2]. This is mainly because the interlocks are too variable to be given definite allowable resistance and it is indefinite how to evaluate the frictional resistance due to vertical loads whose effective values may be periodically 1 Jorge Branco, Civil Engineering Department, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal. Email: jbranco@civil.uminho.pt 2 João Paulo Araújo, MSc Student dropped by the vertical components of earthquake forces. Actual contributions of counted or uncounted resisting elements above, however, are mostly unclear [1]. The University of Minho was contacted to perform a series of experimental and numerical studies to support the European Technical Approval of the timber log constructions produced by Rusticasa. This paper presents some of the most important studies carried out according to ETAG-012 [3]. friction between logs dovetail joint connection between the first log and foundation by angle connector halved joint Figure 1: Lateral resisting elements of log shear walls 2 TIMBER LOGS The basic component of this system produced by Rusticasa, are logs obtained from lamellas (40 mm) glued face to face, representing an example of vertical glulam, as defined in EN 386:2001 [4]. Three