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Wird Holz als nachwachsender Werkstoff das Baumaterial des XXI. Jahrhunderts? In der heutigen Zeit, in der okologische Uberlegungen zunehmend an Bedeutung gewinnen, kann der Werkstoff Holz vor allem unter dem Aspekt der CO2-Emissionen und energetischer Gesichtspunkte gewichtige Trumpfe ausspielen. Zum einen benotigt die Verarbeitung im Vergleich zu anderen Baustoffen nur sehr wenig fossile Energie. Daruber hinaus kann das im Holz abgelagerte CO2 nicht nur sinnvoll “entsorgt” sprich verbaut werden, sondern neues CO2 der Atmosphare durch Wiederaufforstung gebunden werden.

This paper details the implementation of an innovative timber bridge technology developed for secondary road applications. A pilot bridge was constructed and field tested under loads comparable to required design loads. A through-girder primary system with transverse floor beams and longitudinal wood deck secondary system are involved. A unique steel hanger system for suspending the transverse floor beams and providing I-beam action under lateral load was configured. Results of the field load test program and analytical predictions from a computer model are described. The pilot bridge proved to be economically competitive and structurally effective.

Friction welding is a new technology in the course of which wood pieces are subjected to circular or linear movements in a welding machine. The wood in the contact zone is heated and melted. Aiming at a better understanding of the thermal alteration of wood and the formation of a viscous layer acting as adhesive, the thermally changed material was taken to be analysed by chemical and spectroscopic methods. As a manifestation of thermally splitting of wood, the total amount of extractable compounds within the joint material (JM) is higher than that of unaltered spruce. Cellulose was found less altered than the other essential wood components. Polyoses, on the other hand, are less stable under the conditions of friction welding; they are detectable only in small amounts in the altered zone. Lignin also suffers distinct changes as demonstrated by the increase of free phenolic groups and the decrease of the typical bonds between the phenolpropane units. Furan derivatives were detected within the volatiles of the smoke gas, arising mainly from the polyoses. It is obvious that reactions between furfural and other furan derivatives with lignin belong to the main reactions in the friction zone leading to cross-linking of the JM.

A welding technique has been developed to join wooden work pieces by frictional heat without any wood glue. During the welding process 'melting' of the surfaces, resulting from the influence of pressure and frictional heat, was observed. Solidification and bond formation between the welded pieces happened during cool down of the heat-affected zone. The solidification of the heat-affected zone is explained. Tests were carried out to determine the resistance of the joint as a function of the interfacial temperature and the solidification time. The results show that after 20 s of cooling, the shear strength of the welded bonds amounted to 70% of the ultimate shear strength of the connection after 15 min of solidification. This behaviour allows continuous welding of multilayered wood laminates. Due to the use of natural materials only, the welded products are environmentally compatible. In case of disposal, the welded components can be burned in the same way as natural wood without the evolution of toxic comp...

An initial stage of research on the feasibility of a composite concrete–wood commercial floors system is described. The floors are comprised of concrete placed atop a solid layer of dimension lumber. A notched shear key/anchor detail is used for interlayer connection. This connection detail transfers interlayer force by bearing adjacent materials in the notch. The anchor serves to tighten the layers after curing of the concrete. Initial testing included pull-out tests on the anchor and interlayer slip tests to define the geometry of the connection detail. Test results indicated the structural merit of the connection concept compared to the use of ordinary mechanical connectors.

(2004). Timber-Glass-Composite Girders for a Hotel in Switzerland. Structural Engineering International: Vol. 14, No. 2, pp. 149-168.

A methodology for modeling multi-layered structures is presented. The formulation is easily utilized in the framework of existing structural analysis programs to compute internal forces and the global and local deformations of multi-layered structural members and systems. The methodology is fully applied and verified for the case of multi-layered timber beams with semi-rigid connections between the layers. The verifications are performed using both static experimentation and detailed computational modeling with linear and nonlinear finite element analyses. Extension to curved members is also included where emphasis is focused on residual stresses due to construction procedures of layered timber arches. Finally, experimental and computational demonstration of the methodology is given from timber ribbed shells where reasonable agreement between model predictions and experiments is illustrated.

Nearly every shape of construction can be built in an economical way from timber if the development of the structure is studied carefully. All new construction is a challenge, and the engineer, in collaboration with the architect, must abandon routine to explore the range of techniques for timber construction. Supported by the latest research, the engineer can find the optimal solution, and adapt to the requirements of modern architecture.

For the central meeting area of the EXPO 2000 in Hanover, Germany, a wide-space roof construction of ten square umbrellas was constructed. Each umbrella covers an area of 40 m x 40 m and is about 26 m high.

The chances of timber engineering and of the use of timber as a load-bearing material depend on the quality criteria. The most important factor is the economical use of timber to increase its utilization in construction and make it competitive in comparison to other construction materials. Timber as a material for load-bearing constructions is an indicative orientation for the use of wood in further constructions. Therefore, all kinds of wood and timber, from round-wood to squared timber through composite sections made of boards and squared timber, as well as glue-laminated timber, plywood, etc, especially when combined with other materials, must be developed and employed.

The “Polydome” is a 25 m-span timber shell exhibition built to commemorate the seven hundredth anniversary of the Swiss Confederation. The project was an opportunity to present concrete evidence or...

This study deals with construction in wood: its historical evolution, technology, execution, demand, future, the choice between artisan-made or series-made, etc. Likewise, several practical examples of buildings constructed of this traditional material are described. The conclusion reached Is that in this type of construction one must necessarily take into account not only the aesthetic aspect but also the economic result., El presente trabajo trata sobre la construcción en madera: su evolución histórica; tecnología; ejecución; demanda; futuro, entre artesanal o en serle; etcétera. Asimismo se describen varios ejemplos prácticos de edificios construidos a base de este tradicional material, llegando a la conclusión de que en este tipo de construcción es imprescindible tomar en consideración no sólo la estética, sino su resultado económico.

At the Chair of Timber Constructions of the Swiss Federal Institute of Technology in Lausanne (EPFL) tests were carried out to join wooden work pieces by friction welding without any additional welding deposit. It could be determined that this kind of technology, which is mainly used for thermoplastics and metal, can also be applied to wood. Tests were carried out to determine the influence of the processing parameters like welding pressure, frequency and amplitude of the circular movement on the welding process and the input of energy at the interface. In addition, the resistance of the joint was examined. The development of the shear strength during solidification of the interface as well as the shear strength achievable after a complete solidification of the interface was the objective of the examinations. Furthermore, the microstructure of the welded joint was studied to reveal the manner in which the thermally decomposed wood forms the connection between the welded pieces.

Research and development was conducted on a prototype timber bridge technology developed for rural bridge sites. The work included conception, computer modeling, laboratory load tests of a reduced size specimen, field construction of a pilot bridge and field load testing. This paper describes the laboratory load test phase. Three loadings comprised of four concentrated loads simulating a truck wheel pattern were conducted. Results of preliminary analytical simulation work is also described. The laboratory specimen demonstrated the structural effectiveness of the concept and led to the final design and implementation of the pilot field bridge. (c) 2005 Elsevier Ltd. All rights reserved.

Diese Veroffentlichung entstand wahrend der laufenden Forschungsarbeit am Lehrstuhl fur Holzkonstruktionen an der Eidgenossischen Technischen Hochschule Lausanne und am Fachgebiet Holzbau der Technischen Universitat Munchen. Sie reprasentiert den Stand der Forschung und soll anhand einer zu Versuchszwecken errichteten Holztonne in Kreuzrippenbauweise das Konstruktionsprinzip, die mathematische Formbeschreibung der Konstruktionsbauteile von Tonnen in dieser Bauweise und die Moglichkeit der Berechnung gemas E DIN 1052, Anhang F aufzeigen. Voranzustellen ist, das der Anhang F eine leicht zu handhabende Berechnungsmethode mit guter Naherung an die mathematisch exakte Differentiallosung reprasentiert. Dieser Aufsatz versteht sich als die Fortsetzung der Veroffentlichungen, welche das Berechnungsverfahren nach der E DIN 1052, Anhang F vorstellen. In dieser Bauweise wurden bereits einige Schalen ausgefuhrt. Ein herausragendes Beispiel sind die Schalen des EXPO-Dachs in Hannover.