International Workshop on Earthquake Engineering on Timber Structures, Held on 9-10 November 2006 in Coimbra (Portugal)
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International Workshop on Earthquake Engineering on Timber Structures November 9 – 10, 2006 University of Coimbra Coimbra, Portugal Dear Reader We, as the Management Committee of COST Action E29, would like to extend our warm welcome to you, the reader of the proceedings of this 3rd International Workshop on Earthquake Engineering on Timber Structures, held on 9-10 November 2006 in Coimbra (Portugal). This event was organised by: ¾ Department of Civil Engineering, Faculty of Sciences and Technology, UNIVERSITY OF COIMBRA ¾ Department of Civil Engineering, School of Technology, POLYTECHNIC INSTITUTE OF CASTELO BRANCO Earthquake Engineering is one of the most important safety subjects in the performance of buildings, elements and components. Earthquake Engineering is a specialised field which plays an important safety role in our everyday lives (in general). Earthquake Engineering in lightweight structures such as timber frame buildings plays an important role in safety of people in and around buildings in the World at large. The proceedings of this conference therefore make an important contribution towards the enhancement of the understanding of earthquake engineering in lightweight timber and timber- composite buildings. It is my pleasure, as the Chairman of this COST Action, to have witnessed a series of excellent papers produced and presented in this Workshop by some world experts in the field of Earthquake Engineering for timber structures. The Management Committee and I would like to extend our thanks to all the delegates of the conference, authors and presenters without whom this conference could not have been such a success. Dr Vahik Enjily (Chairman of COST E29) Organizing Committee COST - European Cooperation in the Field of Scientific and Technical Research Action E29: “Innovative Timber & Composite Elements/Components for Buildings” UNIVERSITY OF COIMBRA Department of Civil Engineering Faculty of Sciences and Technology POLYTECHNIC INSTITUTE OF CASTELO BRANCO Department of Civil Engineering School of Technology Sponsorship Table of Contents 1st session: “Traditional Construction” “Dynamic modelling of timber joints in traditional structures” Jorge Branco, Paulo Cruz, Mauricio Piazza and Humberto Varum ……………. 1 “Selected research and case studies in ancient Portuguese structures” Paulo Lourenço and Ricardo Brites …………………………………………….. 17 “Rehabilitation of Lisbon’s old “seismic resistant” timber framed buildings using innovative techniques” Raquel Paula and Vitor Cóias …………………………………………………... 33 2nd session: “Design of Timber Structures” “Utopia pavillon project” Jean Paul Perrin ………………………………………………………………... 47 “Design guidance on Eurocode 8 for practicing engineers for timber structures” Tomi Toratti …………………………………………………………………… 55 “Design detailing for earthquake engineering - Application for timber structures” Eric Fournely and Thierry Lamadon …………………………………………... 71 3rd session: “XLAM Innovative Wooden Structures” “Seismic Behaviour of Multi-Storey XLAM Buildings” Ario Ceccotti and Maurizio Follesa …………………………………………… 81 “Study of Lateral Resistance of massive X-LAM wooden wall system subjected to horizontal loads” Bruno Dujič and Roko Žarnić ............................................................................. 97 “Influence of openings on shear capacity of massive X-LAM wooden walls” Bruno Dujič, Simona Klobcar and Roko Žarnić ………………………………. 105 4th session: “Shear Walls” “Quasi-Static and Pseudo-Dynamic Tests on XLAM Walls and Buildings” Marco Pio Lauriola and Carmen Sandhaas ……………………………………. 119 “Influence of the loading protocols on the Hysteresis response of sheathing to framing nailed joints in shear walls” Tatjana Kočetov Mišulić, Bruno Dujič, Kiril Gramatikov and Roko Žarnić ….. 135 “Pseudo-dynamic test method, experiments and accuracy” Kjell Malo ……………………………………………………………………… 143 5th session: “Joints” “Seismic Performance of Timber Shear walls sheathed with OSB panels” L.A. Fülöp, Ágnes Ruff, S. Bálint-Major and D. Dubina ……………………... 163 “Dynamic performance of wood based panels in roof and floor construction” Mizi Fan and Vahik Enjily …………………………………………………….. 175 International Workshop on "Earthquake Engineering on Timber Structures" Coimbra, Portugal November, 2006 Modelling of timber joints in traditional structures Jorge BRANCO Paulo CRUZ PhD student Associate Professor University of Minho University of Minho [email protected] [email protected] Maurizio PIAZZA Humberto VARUM Professor Assistant Professor University of Trento University of Aveiro [email protected] [email protected] Summary Original unstrengthened timber connections and the effects of different strengthening techniques have been evaluated experimentally with tests on full-scale birdsmouth joints. Experimental results show that structural response of traditional timber connections under cyclic loading cannot be represented by common constraint models, like perfect hinges or rigid joints, but should be using semi-rigid and friction based models. A research program has investigated the behaviour of old timber joints and examined strengthening criteria. The main parameters affecting the mechanical behaviour of the connection have been singled out. A synthetic model of cyclic behaviour has been adapted on the basis of experimental results. Keywords: Cyclic behaviour, traditional timber joints, strengthening, experimental testing 1. Introduction In the field of timber structures, several studies have covered the problem of modelling the behaviour of new engineered connections. Little attention has been devoted to the joints in old, traditional structures that are very frequent in Europe. In Portugal and Italy, for example, timber roof structures, in particular, are part of the constructional tradition, also in earthquake prone areas. From this consideration, the need arises for developing behavioural models of these joints, to be used for the investigation of structural dynamic response [1]. When structural analyses have to be carried out for evaluating the possible need and effect of strengthening, timber are generally impaired by the inadequacy of commercial finite element software in modelling the partial restraint to rotation and the limited moment transmitting capabilities of their connections. The lack of practical, but realistic, models for the joints in old traditional timber structures generally leads to very conservative retrofits and upgrades to satisfy new safety and serviceability requirements. Traditional timber joints, even without any strengthening device, usually have a significant moment capacity. Common constraint models, like hinges or full restraint connections, indeed, cannot satisfactorily describe the real behaviour of these joints. The joint behaviour may be classified as semi-rigid and, being based on friction, is influenced by the time-varying level of compression between the joined members. Joints strengthening can be done in a number of possible ways: from simple replacement or addition of fasteners, to the use of metal plates, glued composites or even full injection with fluid adhesives. Each solution has unique consequences in terms of the joint final strength, stiffness and ductility. The work presented here has been developed within a general research program devoted to the definition of synthetic models for the static and dynamic behaviour description for common timber connections in traditional, old and non-engineered constructions. The study addresses plain timber connections, as well as, connections that are strengthened by steel elements. These devices are extensively used in structural upgrading operations, in order to develop a reliable response in the case of cyclic loading. 2. Model behaviour of semi-rigid timber connections In recent years, considerable research efforts have been devoted to characterise the semi-rigid connections behaviour, particularly for steel and composite structures. For the case of steel 1 International Workshop on "Earthquake Engineering on Timber Structures" Coimbra, Portugal November, 2006 structures, the case of partial flexibility has been early recognized in design codes, with appropriate values to be obtained either by predictive models or from direct experimentation. Semi-rigid modelling of steel connections in seismic design acknowledges and exploits the dissipation capabilities of their hysteretic behaviour. As recognised by Eurocode 8 [2], a similar approach is appropriate also for traditional timber elements and structures. In the case of existing structures to be rehabilitated or eventually upgraded, according to new requirements, a realistic interpretation of the global structural behaviour is a primary need. In some typical structural configurations of timber constructions, the commonly used hinge models are inadequate; because in real structures, where joints have moment resisting capability, the equilibrium conditions may not be reached analytically. The semi-rigid modelling of timber connections, using nonlinear moment-rotation laws and hysteretic rules, intends to represent the seismic behaviour of timber structures with a comparable level of detail for all the structural components. With these models, the seismic design acknowledges and exploits the dissipation capabilities of their hysteretic behaviour. A numerical model for these connections must, then, be sufficiently accurate to describe properly the semi-rigid behaviour, and sufficiently simple, both conceptually and computationally, to allow use in common practice. Different hysteretic