Glulam construction

Glulam has greater strength and stiffness than structural timber of similar dimensions. Glulam also has a better strength to weight ratio than steel. This means that glulam beams can span large distances with a minimal need of intermediate supports. It also means architects and engineers have virtually unlimited possibilities when designing their own constructions in glulam, whether the task is a small house, the roof of a department store or a road bridge.

Modern glulam technology

Wood is one of the oldest construction materials in the world. Buildings, bridges and ships have been built in timber for many centuries. No other material has such a wide range of uses. Glulam – glued laminated timber – opens up still further possibilities for wood building technology.

Glulam technology was developed in Germany at the end of the nineteenth century and the world’s oldest glulam factory, Töreboda in Sweden is still in use today. Glulam has many applications: schools, sports halls, railway stations, industrial, agricultural and commercial buildings, shopping centres, bridges and even homes.

Glulam consists of individual laminates of structural timber, providing a highly effective utilization of the raw material. The laminates are finger-jointed to give greater lengths and then glued together to produce the desired size. Due to the production technology, very large structural components are possible. Little energy is needed for the manufacture of glulam.

Structural design

The glulam technology allows the manufacture of thick, wide and very long components; not just simple straight but curved elements too. Straight beams are manufactured with a constant cross-sectional dimension, mono-pitched or double-pitched. For larger buildings, two or three pin trusses, portal frames or arch frames of glulam components are suitable.

Portal frames can have curved or finger-jointed haunches. Glulam beams can be arranged in the form of a grid. Shell structures provide a wide choice of advanced forms free from columns. There are also many complex structural systems, e.g. arch and beam frame. One advantage is that all glulam components can be made in the factory in suitable sections for transportation, and then assembled on the building site. Glulam is an exciting construction material, partly because it lends itself so well to curved forms, such as arches, frames etc., and partly because its strength is particularly favourable for large spans. Free spans of over 100 m have been built.

Architectural design and construction

No other building material can be compared with glulam for expressing architectural or structural possibilities. Leading architects all over the world have demonstrated their credentials with spectacular glulam constructions. When dealing with wide spans, glulam products are the best choice for framing.

Glulam structures can be erected quickly and simply by using prefabricated units. The parts are assembled by nailing, screwing or bolting, unaffected by the time of the year or the weather, and any adjustments can be made with simple hand tools. A glulam frame can carry its full load immediately after the assembly. It is a well tested building material which, correctly used, has extremely good durability.

Glulam

Glulam is the term used for beams, arches or columns consisting of several laminates of timber arranged parallel to the longitudinal axis of the member; the individual pieces being assembled with their grains approximately parallel and glued together to form a member which functions as a single structural unit.

In elements of this type, any characteristics or features, such as knots, which may exist in the individual laminates, are equally spread, unlike a solid timber element from the same species. Furthermore, when using glulam it is possible to obtain larger cross-sectional dimensions and longer lengths than solid construction timber. Certified glulam is the accepted term for glulam with at least four laminates, that has been manufactured, controlled and marked according to certain rules.

EN 14080 Timber Structures – Glued laminated timber – Requirements is the European standard specifies the requirements for glued laminated timber products used in load-bearing structures, and deviations from target size corresponding to tolerance class requirements. Certified glulam is marked in accordance with the standard.

Glulam that has been manufactured in accordance with the rules given in national or European codes is graded in strength classes. The appropriate class is determined by the strength of the timber used and its position in the cross-section. The strength and stiffness values of the various strength classes are then given in the code. Glulam manufactured in Sweden corresponds to strength classes in accordance with Eurocode 5. Glulam manufactured by other methods than according to the regulations contained in the codes, e.g. with a different layup of the cross-section, can be used structurally if it is an approved product.

The glue used in glulam manufacturing has documented high strength and durability under long-term loading. Only glues of which the industry has long-term practical experience are used. The formal requirements are given in EN 301, which classifies two types of glue: I and II. Glue type I may be used for glulam construction in any climate class, while glue type II is limited to climate classes 1-2. A list of approved glues is kept by the Nordic Glulam Control Board.

Glulam production standards – stock sizes

Straight glulam components of rectangular cross-sectional dimensions are normally made of 45 mm thick laminates in widths corresponding to the sawmills’ standard range. After planing of the sides, the finished width is a few millimetres less than the width of the laminates.

Here is an example of Swedish glulam cross-sectional dimensions below. The following sizes in the table are in stock and should be the first choice, especially if only a few beams are involved. The sizes apply to components with planed surfaces at a moisture content of 12%. Other dimensions are also available depending on the factories' capability.

Thickness x Width (mm)

90 x 90

66 x 315

115 x 360

115 x 115

90 x 180

115 x 405

140 x 135

90 x 225

115 x 450

140 x 140

90 x 270

115 x 495

160 x 160

90 x 315

115 x 630

165 x 165

90 x 360

140 x 225

42 x 180

90 x 405

140 x 270

42 x 225

90 x 450

140 x 315

42 x 270

115 x 180

140 x 360

56 x 225

115 x 225

140 x 405

56 x 270

115 x 270

66 x 270

115 x 315

Advantages of using glulam

An appealing aesthetic appearance which acts as a valuable addition to the interior and exterior environment.

A high strength to weight ratio, enabling wide spans.

Small manufacturing tolerances and good form stability within normal temperature and moisture conditions.

High resistance to fire – often a requirement in public buildings.

Good heat insulating characteristics, reducing the effect of cold bridges and the risk of condensation.

Low weight, resulting in low transport and erection costs and reducing the cost of foundations.

Long life in chemically demanding environments.

Flexible production, enabling curved structural components to be produced at lower costs than other materials.

Glulam construction of Swedish Pavilion at 2010 Shanghai Expo
Glulam construction of Swedish Pavilion at 2010 Shanghai Expo
Glulam of Swedish Pavilion at 2010 Shanghai Expo
Glulam of Swedish Pavilion
at 2010 Shanghai Expo
A stadium with glulam in Aalborg, Denmark
A stadium with glulam
in Aalborg, Denmark
Älvsbackabron Bridge, Sweden
Älvsbackabron Bridge, Sweden
Renovation of Koldinghus with glulam in Kolding, Denmark
Renovation of Koldinghus with glulam in Kolding, Denmark

 
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