Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Review of design approaches and test results on brittle failure modes of connections loaded at an angle to the grain Robert Jockwer a, ⁎ , Philipp Dietsch b a ETH Zurich, Institute of Structural Engineering, Stefano-Franscini-Platz 5, CH-8093 Zürich, Switzerland b Technical University Munich, Chair of Timber Structures and Building Construction, Arcisstraße 21, 80333 München, Germany ARTICLE INFO Keywords: Brittle failure Tension perpendicular to grain Dowel-type fasteners Connections ABSTRACT Connections in timber beams loaded perpendicular to grain are prone to brittle failure due to fracture induced by tension perpendicular to grain stresses in the surrounding timber. Different approaches can be found in literature and design codes to account for the reduction of load-carrying capacity in the design of the structure. In this study selected design approaches are discussed and their behaviour with regard to different geometrical para- meters is analysed. The structural behaviour of connections loaded perpendicular to grain is evaluated on the basis of test results from literature. The impact of different geometrical parameters on the load-carrying capacity is demonstrated and the design approaches are benchmarked against a large number of individual test results. Recommendations for a more reliable design are given. 1. Introduction 1.1. General In connections in timber global failure can occur either due to local failure of the fasteners and the adjacent timber or due to failure in the timber around the connection. Failure of the fasteners can be accounted for by designing them according to appropriate design rules, e.g. the so called European yield model (for dowel type fasteners) [1,2]. Design to prevent this failure mechanism includes prevention of embedment failure in the timber or failure of the metallic fasteners. However, in certain cases such a design of the connection is not sufficient because splitting of the timber next to the connection might occur, hence, design has to account for this failure as well. Timber exhibits good strength and stiffness properties parallel to the grain but only very low strength and stiffness perpendicular to the grain. As a general rule situations where timber is subjected to tension perpendicular to the grain should be avoided. Structural details like connections, where tensile forces perpendicular to the grain are in- troduced in the timber, exhibit a high risk of fracture due to the low strength in combination with brittle failure mechanism of timber in tension perpendicular to grain. Careful design of such connections is required in order to reach the level of reliability required by design codes. Design procedures for such details can be found in literature. These exhibit different degree in complexity. In this paper the failure mechanisms of unreinforced connections loaded perpendicular to the grain will be explained, corresponding design approaches will be evaluated and benchmarked against test re- sults from literature. Following this, recommendations for a more re- liable design of such connections will be given. 1.2. Types of connections loaded perpendicular to the grain Connections loaded perpendicular to the grain are often made by means of nails, dowels, bolts, (self-tapping) screws, glued-in rods or shear connectors. The number of fasteners in a connection depends on the type of fastener used. Small diameter fasteners like nails or rivets are often used in larger quantities within one connection whereas large diameter fasteners like bolts, glued-in rods or shear connectors are also used individually. Connections can either be made as timber/timber connections which is often the case for shear connectors, or can be made in com- bination with steel parts such as (3-dimensional) nailing plates or dowelled slotted-in metal plates. Glued-in rods or self-tapping screws can directly be loaded in tension and do not need additional elements for hanging loads. 1.3. Geometry The geometrical properties and denotations of a connection loaded perpendicular to the grain are illustrated in Fig. 1. The level of tensile stresses perpendicular to the grain depends amongst others on the https://doi.org/10.1016/j.engstruct.2018.05.061 Received 10 December 2017; Received in revised form 30 April 2018; Accepted 16 May 2018 ⁎ Corresponding author. E-mail addresses: jockwer@ibk.baug.ethz.ch (R. Jockwer), dietsch@tum.de (P. Dietsch). Engineering Structures 171 (2018) 362–372 0141-0296/ © 2018 Elsevier Ltd. All rights reserved. T