Structural performance of finger-jointed black spruce lumber with different joint configurations (original) (raw)
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Annals of Warsaw University of Life Sciences. Forestry and Wood Technology No 73
2011
This study was carried out to evaluate the strength of the three most frequent joints in the upholstered furniture frames, made of beech and poplar solid wood. The research included the following joints: Mortise and Tenon, double Dowel and double Gusset Plates, which were constructed and tested both in corner and middle joints. In the corner joints we examined the compression strength of the joints and in the middle joints the tension strength was thoroughly investigated. The results of the bending (compression) test indicated that bending strength values of the four different joints were strongly correlated to tension strength values of the corresponding joints, whether they were constructed with beech or poplar wood. Also, a correlation was noticed between the bending strength values of the joints constructed with beech and the bending strength values of the respective joints made of poplar wood. Relative to tension strength values, a strong relationship was also recorded between ...
Timber as a Structural Material 1.1 INTRODUCTION
Timber from well-managed forests is one of the most sustainable resources available and it is one of the oldest known materials used in construction. It has a very high strength to weight ratio, is capable of transferring both tension and compression forces, and is naturally suitable as a flexural member. Timber is a material that is used for a variety of structural forms such as beams, columns, trusses, girders, and is also used in building systems such as piles, deck members, railway sleepers and in formwork for concrete. There are a number of inherent characteristics that make timber an ideal construction material. These include its high strength to weight ratio, its impressive record for durability and performance and good insulating properties against heat and sound. Timber also benefits from its natural growth characteristics such as grain patterns, colours and its availability in many species, sizes and shapes that make it a remarkably versatile and an aesthetically pleasing material. Timber can easily be shaped and connected using nails, screws, bolts and dowels or adhesively bonded together. The limitations in maximum cross-sectional dimensions and lengths of solid sawn timbers, due to available log sizes and natural defects, are overcome by the recent developments in composite and engineered wood products. Finger jointing and various lamination techniques have enabled timbers (elements and systems) of uniform and high quality in any shape, form and size to be constructed; being only limited by the manufacturing and/or transportation boundaries. Timber structures can be highly durable when properly treated, detailed and built. Examples of this are seen in many historic buildings all around the world. Timber structures can easily be reshaped or altered, and if damaged they can be repaired. Extensive research over the past few decades has resulted in comprehensive information on material properties of timber and its reconstituted and engineered products and their effects on structural design and service performance. Centuries of experience of use of timber in buildings has shown us the safe methods of construction, connection details and design limitations. This chapter provides a brief description of the engineering properties of timber that are of interest to design engineers and architects, and it highlights that, unlike some structural materials such as steel or concrete, the properties of timber are very sensitive to environmental conditions; for example moisture content, which has a direct effect on the strength and stiffness, swelling or shrinkage of timber. A proper understanding of the physical characteristics of timber enables the building of safe and durable timber structures.
European Journal of Wood and Wood Products, 2019
Finger joints in structural timber and glulam lamellae are often used to enable production of long members or to allow for re-connection of parts of a member after removal of weak sections. According to the European Standard EN 15497, certain margins are required between knots and a finger joint in structural timber, which means that a considerable amount of clear wood becomes waste when finger joints are applied. The purpose of this paper was to investigate the possibility of reducing the quantity of waste using different criteria for placement of finger joints. The investigation was based on (1) application of methods of colour scanning and tracheid effect scanning to detect knots and grain disturbance on board surfaces, and (2) interpretation of the requirements of EN 15497 regarding where finger joints may be placed. The standard’s requirement when producing finger joints is that the minimum distance between a knot and a finger joint is three times the knot diameter. The standar...
Župčić , Vlaović , Domljan , Grbac : Infl uence of Various Wood Species and Cross-Sections
2014
Rotation welding is a new method used in wood welding. Heat that develops due to the friction on contact surfaces softens and melts the wood structure (melt is produced). When the friction stops, the melt cools down and solidifi es forming a fi rm joint. This research is based on the examination of the infl uence of various wood species and cross-sections on the strength of joints produced by rotational welding. Using rotation frequency and shifts in the orientation of the horizontal axis, a beech dowel is welded to a base made of common beach (Fagus sylvatica L.), pedunculate oak (Quercus robur L.) and Norway spruce (Picea abies L.) (hereinafter only beech, oak and spruce). Welding direction is both parallel to the orientation of the base fi bres (PP) and perpendicular to the orientation of the base fi bres (R, RT, T). Research results indicate that the dowel welded to the beech base retains the largest strength, whereas the dowel welded to the spruce base reveals the weakest resul...