Connections in Large Timber Beams Free-Form Structures

Abstract

Wood has long been used as a construction material, but the properties of solid wood in relation to strength, maximum length, and natural defects have always been a limiting factor in the construction of more ambitious projects. The development of knowledge in the field of concrete and steel has enabled the construction industry to shape modern society, but it has also brought with it an eminent and gradually increasing abuse of the environment. The rescue of construction using wood represents a conscious step towards sustainable development. Progress in the manufacture of wooden laminated panels and the production of synthetic glues has given greater scope for advances in the fields of engineered wood products. More and more research has focused on improving manufacturing techniques, making glued laminated wood a standardized product available in various shapes and sizes. This product has made possible the execution of works that previously only concrete or steel was capable of, such as bridges, high buildings, and large roof structures. The computer revolution that took place in the 1990s had an immense influence on the construction industry, constructions that were previously mostly constituted by planar elements began to have freely curved building shapes. From this moment on, structural designers and architects have been able to explore fascinating architectural shapes, including the free-form structures. In timber free-form structures, connections are necessary to join single timber elements, which are necessary due to limitations in transportation and production. When using large beams these connections may need to transfer considerable high forces and moments to ensure an efficient structure. Besides the resistance also the stiffness is of high importance for a satisfactory structural behavior and to correspond to the assumptions made in the global model. The aim of this master’s thesis is to gain a deeper understanding of timber connections in large timber beams and point out the connection’s influence on the global behavior of the structure. The study has been applied to a free-form timber roof structure in development at the Danish consultant company COWI. The work presents different design concepts of connections and how these concepts could be optimized.