REINFORCEMENT OF TIMBER STRUCTURES – A NEW SECTION FOR EUROCODE 5 Philipp Dietsch ABSTRACT: The reinforcement of timber structures has seen considerable research and development in recent years. New materials and methods for reinforcement have been developed and are now used in practice. Eurocode 5 in its current edition, however, lacks approaches to design reinforcement for timber members. To close this gap, CEN/TC 250/SC 5, the standardization committee responsible for drafting Eurocode 5, has decided to establish a Working Group (WG) on this item. This Working Group is supported by a Project Team, mandated to draft the associated sections for Eurocode 5. This paper reports on the approach to this task, the work items of WG 7 “Reinforcement”, the current status and the work scheduled for the coming years. The proposed structure of the new section as well as examples of design approaches and the related background information are presented. KEYWORDS: Timber structures, stresses perpendicular to the grain, reinforcement, self-tapping screws, rods, wood- based panels, standard, Eurocode 5 1 INTRODUCTION 123 The reinforcement of timber structures has seen considerable research and development in recent years, see e.g. [1]. New materials like self-tapping screws or wood-based panels offer potential also in view of their use as reinforcement. The European timber design standard, Eurocode 5, in its current edition [2] lacks approaches to design reinforcement for timber members. The standardized use of reinforcement is enabled only in a few European countries by means of non-contradictory information (NCI), given in the National Annexes to Eurocode 5 [3], [4]. Closing the obvious gap between recent developments and practical needs on the one side and missing standardization on the other, reinforcement for stresses perpendicular to the grain was classified high priority when defining the list of work items to be dealt with during the upcoming revision of Eurocode 5 [5]. In 2011, the European standardization committee responsible for Eurocode 5, CEN/TC 250/SC 5, decided to form a Working Group 7 “Reinforcement”. In addition, reinforcement of timber members was prioritized for Phase 1 (of 4 phases) of the standardization work to be mandated by the European Commission. The contracts for this mandated work were signed in 2014, enabling the formation of Project Teams that are mandated to draft specific sections for the Eurocodes. Philipp Dietsch, Dr.-Ing., Technische Universität München, Chair of Timber Structures and Building Construction, Arcisstraße 21, D-80333 München. Email: dietsch@tum.de Within Phase 1, two Project Teams to draft new sections for Eurocode 5 were established and equipped with experts, namely PT SC5.T1 - to draft the sections on cross-laminated timber and reinforcement - and SC5.T2 - to draft a new part on timber-concrete composites. 2 APPROACH Standardization is the culmination of successful research and development that has seen positive application and acceptance in practice, see Figure 1. According to the European position on future standardization [6], harmonized technical rules shall be prepared for “common design cases” and shall contain “only commonly accepted results of research and validated through sufficient practical experience”. The target audience for such rules is “competent civil, structural and geotechnical engineers, typically qualified professionals able to work independently in relevant fields”. Figure 1: Development of products or methods and their legalization Fundamental Research Application- oriented Research Product Development Research & Development Technical Approval, e.g. ETA Verification of Applicability Product Standard & Design Standard