Frames for Finnish wide-span buildings
Buildings with separate frames
Columns and beams
The most common frame type for wide-span buildings consists of a series of columns carrying a system of beams, trusses or ties. The columns are normally stiffened along their length in at least one direction. The support type is chosen to suit the desired span, which may be as much as 50 metres. If the use of the space permits a row of columns in the middle, the building can be made into a multi-bay building.
As its name implies, an arched frame is a curved frame resting on foundations which are supported horizontally. An arched frame may have a span of over 100 metres. The foundations are supported either by tying them together, or by tying them into the bedrock, or by tying them to angled piles.
The arch can be built of solid laminated timber, or trusses, and is normally designed to have 2 or 3 pin joints. The arch is supported directly by foundation columns. Because of the huge size of the foundation columns, they often extend from the inside of the building to a point externally beyond the plinth and therefore have to be insulated on the outside. The supporting joint for the arch should be located inside the building.
In ring-beam construction, the construction of roof and walls is joined together with stiff corners so that the foundations can take not only horizontal loads, but also vertical ones. The horizontal loads are supported by tying opposite foundation pads together with ties, or by supporting the foundations directly on the bedrock, or by tying them to angled piles.
Ring-beam types are:
– curved corner, 3 pin-joint
– sharp corner, 3 pin-joint
– trussed corner, 3 pin-joint
The curved corner ring-beam is made of bent laminated timber so that the corner can be made separately of laminated timber or sawn goods. The sharp cornered ring-beam is made of LVL joined to the columns with dowelled joints. The trussed-corner ring-beam is made of wooden beams, wooden braces and ties which may be of timber or steel. Ring beams are generally assembled in situ.
Other frame types
Various envelope and net structures can also be built in timber. Manufacturing on the basis of modelling building components allows the building of structures with complex algorithms.
The most common dome type has a load-bearing structure joined together with steel components to form a network of compression rods made of LVL or laminated timber. This type of structure has been used to build spans as great as 160 metres.
Wide-span buildings with load-bearing walls
In this type of building, the long walls are made load-bearing in order to support the roof. The single-bay building is stiffened with wooden boards. The width of such a building may be about 20 metres and the height about 6 metres. If a greater width is required, the building can be divided into two bays with a line of columns supporting a beam. For such buildings, stiffening of the columns is recommended.