Tillämpning av nya beräkningsmetoder för branddimensionering av  träkonstruktioner - analyser och jämförelser

Sammanfattning: To build high-rise buildings made of timber has for long been limited by national laws, due to the lack of knowledge in engineering solutions. Frame structures made of wood has for a long time been associated with major fire hazards and consequently lower safety and this connection is still being made today. The increased environmental awareness in recent years has contributed to the exploitation of indigenous building materials, including wood from our own Swedish forests and has become increasingly common. Increased knowledge about how structures behave in fire and how they can be protected in order to achieve safe timber structures has resulted in a growing interest in these structures in the construction industry. Research in the area is constantly updated and new laws allow any number of storeys in wooden buildings in Sweden as long as the performance requirements are fulfilled. The main part of this work has involved calculations of the fire resistance and load bearing capacity of floor and wall constructions. The calculations are based on different models, both old and new. There are many alternative ways to handle the problems. The report presents three different approaches that have been generalized into three calculation methods. The names used here for the methods are the same as the two manuals: Brandsäkra trähus version 2 and Fire Safety In Timber Buildings, as well as the standard Eurocode 5, where a detailed description of the methods of calculation are introduced. This work has resulted in a number of updated tables in order to exemplify the fire resistance and load bearing capacity during fire for selected timber structures according to the latest calculation methods. In addition, values of bearing capacity for cross-laminated structures are included. The tables are grouped according to type of construction, namely, walls and floors.  A selection of relevant structures of varying claddings can be found in the tables, including single gypsum plasterboard, double plasterboard and gypsum plasterboard with plywood behind that protect underlying wood studs. Tables of cross-laminated elements are presented separately. Cross laminated structures are composed of 3, 5 or 7 layers of timber and can be either unprotected or protected with a single gypsum board. The thickness of the load bearing and non-bearing layers has also been varied in different ways in order to investigate how the bearing capacity is affected. Finally obtained values are discussed and compared.