COST Timber Bridge Conference – CTBC 2014 25–26 September 2014 Bern University of Applied Sciences Biel, Switzerland Edited by Steffen Franke Bettina Franke Robert Widmann ‣ Institute for Timber Construction, Structures and Architecture COST ACTION FP1004 and FP1101 COST TIMBER BRIDGE CONFERENCE CTBC 2014 September 25-26, 2014 Bern University of Applied Sciences, Institute for Timber Construction, Structures and Architecture Biel, Switzerland Edited by Steffen Franke Bettina Franke Robert Widmann ECOST-MEETING-FP1004-240914-048999 ISBN 978-3-9523787-4-8 Published by Bern University of Applied Sciences, Switzerland Institute for Timber Construction, Structures and Architecture All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise without per- mission in writing of the publisher. I PREFACE Bridges are the most demanding of structures. They are often long-span, subject to large and variable dynamic loads, exposed to the weather, require low maintainance and, being seen as “gateway” or “landmark” structures by the public, are subject to close scrutiny. Timber bridges occupy a special place within the timber engineering community. For many professionals in- volved in this field, from the planning engineer, to the timber manufacturer and to the responsible for the opera- tion and maintenance – the owner -, timber bridges represent the highest achievement in the art and science of wooden architecture and construction. Within Europe (and in the rest of the world) there are many different approaches to deal with this topic. The history of the wooden bridges has seen many stories – for example the ones old bridges which have survived for centuries, and of those in need of repair or even demolition after only a decade of being in use. The combination of large spans with heavy loads and major climatic actions on bridges is a big challenge for everybody involved in planning, constructing and maintaining these special timber structures. This requires that all effected parties have, in addition to the possibly large emotional devotion to such an object, above all, an extensive knowledge and experience in the planning, implementation and maintenance of timber bridges. Since timber bridges are not built in a dozen every day, it is important that an active exchange of knowledge between parties takes place. This is what the COST Timber Bridges Conference CTBC2014 in Biel aims to contribute to. At this conference, which is jointly supported by the COST Actions FP1004 and FP1101, young researchers as well as old hands in the field of timber bridges get the opportunity to share their own knowledge while –at the same time- learning from others. The joint participation of the two Cost Actions, FP1004 focusing on Enhamce- ment of mechanical properties of timber products and structures, FP1101 focusing on Assessment, Strengthening and Monitoring of existing timber Structures, ensures that a vast field of knowledge is being covered. This ranges from the enhancement of wooden materials and components for new timber bridges to the assessment, strengthening and monitoring of existing bridges, both modern and historic ones. Following the conference, in which the theoretical foundations are highlighted, a field trip and excursion to existing old and new timber bridges will provide the opportunity to learn from real cases and continue the knowledge exchange on-site. The programme of the conference is designed to stimulate and facilitate discussion from the delegates, and we hope that it will contribute to build bridges between young and old researchers, theorist and practitioners as well as between fellows from regions with high timber bridges "populations" and people coming from regions where even the term "timber bridge" sounds very strange. Besides the genuine interest for the subject, that gave us the impetous to organize this event, building these last mentioned bridges is a main goal of the COST framework. Let's go for it! Representing the organizing committee Robert Widmann - Co Organizer Steffen Franke – Organizer and Host Bettina Franke – Organizer and Host Dina D'Ayala - Chair COST Action FP1101 Richard Harris - Chair COST Action FP1004 September 2014 II About COST Action FP1004 Enhance mechanical properties of timber, engineered wood products and timber structures Timber and wood-based engineered products are becoming very important as structural materials, especially in the drive towards sustainable technologies and construction. For structural wooden products, it is very important to improve their properties to be more competitive and reliable as a sustainable low-carbon material and a major contributor to affordable buildings. This applies particularly to larger, more complicated structures where timber is becoming a realistic alternative. This Action aims to boost the performance of structural timber products and construction, thereby improving use of timber in construction in existing and new applications. This includes the enhanced predictability and reliabil- ity of timber structures. Improving the mechanical performance of connections and reinforcing timber in weak zones are large-scale research domains in Europe, which will require coordination and scientific/engineering approaches. This COST Action will deliver increased knowledge of improving strengthening, stiffening and toughening techniques, modeling enhanced performance and experience in real projects to create new opportuni- ties for timber construction. Exchanging information will highlight gaps in knowledge and inform future work and potential collaboration between research groups, supporting timber construction and its wider uptake in the European construction industry. This Action may also create opportunities for patenting possible new technolo- gies and products for reinforcing timber mechanical properties. The scientific program is divided into three main scientific areas expressed as Work Groups (WG) with the same aims but different perspectives: WG 1: Enhance performance of connections and structural timber in weak zones • Identifying and categorising weak zones (type of failure, relevance) and respective mechanical proper- ties; • Grouping of connections (load level, type of failure, dissipation of energy); • Using glued-in rods or self-tapping screws as reinforcements; • Using densified wood or modified wood; • Using other Engineered Wood Products (EWP) e.g. plywood, LVL or cross-laminated timber (CLT) as reinforcement; • Using fibre reinforced polymers (FRPs) as reinforcement WG 2: Enhance the mechanical properties of heavy timber structures with particular emphasis to timber bridges • Identification of properties to be enhanced; • More effective timber decks as a result of effective pre-stressing; • Increase stiffness and strength by reinforcement; • Energy dissipation capacity of structures. WG 3: Modeling the mechanical performance of enhanced wood-based systems • Identification of properties to be enhanced • Material properties needed in numerical models • Design and performance models of enhanced timber structures • Cracks parallel to the grain related to moisture content variations and different longitudinal shrinkage III About COST Action FP1101 Assessment, Reinforcement and Monitoring of Timber Structures In recent years, the use of timber in structures has become particularly important, considering that it is the only truly renewable building material and carbon storage. Timber has been used as structural material for centuries and numerous examples demonstrate its durability if properly designed and built and when adequate assessment and monitoring has been applied. The objective of the Action is to increase the acceptance of timber in the de- sign of new structures and in the repair of old buildings by developing and disseminating methods to assess, reinforce and monitor them. The need for assessment, reinforcement and monitoring of timber structures can arise from multiple motivations such as the expiration of the planned lifetime, materials aging, exceptional inci- dents, and ever more important, a change of use. The Action will benefit from multidisciplinary views of the problems and followed innovative solutions by the involved stakeholders, enable synergies between them and provide an effective way of discussing and disseminating the results from ongoing projects within this research area to the European industry. The Action will increase the confidence of designers, authorities and end-users in the safe, durable and efficient use of timber and consequently increase its use in construction. The scientific programme is divided into three main scientific areas expressed as Work Groups (WG) with the same aims but different perspectives: WG 1: Assessment of Timber Structures • Increasing knowledge and experience in non- and semi-destructive techniques and combinations thereof to improve applicability of results to asses the remaining structural capacity; • Compiling methods which deliver reliable and robust results that can subsequently be incorporated into analytical and probabilistic structural models; • Promoting the cross-validation of data obtained during inspection using similar methods in different projects; • Combining visual grading, vibrational methods and mechanical tests, for the decay characterisation and the mechanical characterisation of the material; • Developing specific in-situ