A BRIEF OUTLINE OF THE MAJOR TYPES OF TIMBER STRUCTURES
GLUED LAMINATED TIMBER STRUCTURES
Glulam timber structures have been growing in popularity in recent years due to their unique properties, natural look and continuous efforts of the population to use renewable natural resources to which wood indisputably belongs.
These structures are most suitable to be used for the roofs of medium and large-size buildings (large-span buildings, gyms, pool halls, etc.) as well as much larger spaces such as ice rinks, indoor tennis courts or exhibition halls.
Their cost efficiency is increasing proportionately to the growing span and area when compared to the steel and combined structures. Besides their enhanced fire-resistance performance, they generally require less maintenance than the steel structures.
NAILED TRUSS SYSTEMS
Roofs and timber structures using nailed trusses are classified as light-weight structures. Their main advantage lies in a favourable price and perfect suitability for larger roof frame spans and a quick installation.
The most frequently used type is the Gang-Nail truss with connector plates, which is widely used in many applications.
The assembly is less demanding than in case of a conventional roof frame; even if the roof shape is complicated, the installation can be done in only a few days.
The main disadvantage lies in the truss members as they make the use of the space between the trusses for an occupancy loft or similar purposes more difficult. However, suitable solutions can be found and the design of the trusses can be adapted, as far as possible, to meet the demands on the use of those spaces.
TRADITIONALLY FRAMED ROOFS (RAFTER AND TRUSS ROOF SYSTEMS)
Traditional structures using stick-built elements and simple framing, so called rafter and purlin roof, are being and still will be used for the buildings, in particular in the construction of all-masonry private homes and smaller buildings as well as the renovation or repair of older buildings, at which the roof frame shall primarily carry the roof or be used as an element exposed to the interior.
In most cases the individual types of structures are combined with the traditional roof frame, so called truss framing. For example, glulam beams as the main roof frame component are combined with sawn purlins (rafters laid in parallel to the eaves) or a principal central beam made out of a gangnail truss has the rafters laid on. The use of trusses often enables cost savings and is the right solution if a simple construction is in focus.
In most cases, atypical structures are a combination of the above mentioned types. However, much higher standards as regards the overall appearance, the structure itself and the resistance to the ambient effects are expected to be met in order to comply with the requirements of the architects and planners, which often prove to be extremely difficult. The buildings completed so far are the best evidence of our ability to successfully meet such challenges. The architects also use to address the specialized firms and institutions yet before the final decision on the planned project is made, and such an approach is definitely ended up with a successful completion of the whole project and its handover to the satisfied client.
RENOVATION OF TIMBER COMPONENTS
Renovation of the timber components of the buildings is another subset of carpentry that is being often marginalised. Not every firm has enough capabilities to renovate larger buildings. These are definitely labour demanding and time consuming jobs which in many cases also includes necessary survey and expert appraisal of the scope of fungal and insect attack and damage to the timber structures and roof framing.
Unprofessional intervention may result in further damage that may be unintentional, e.g. if the damaged materials are not fully removed and repaired properly or if the structural stability of the roof frame is affected. In many cases, wood can be affected insofar that the renovation of the structure would be more expensive than its full removal and installation of a new structure.
If a more extensive intervention into the existing structure and the building layout is required, new structural analysis must be performed.
WIND BRACING AND STIFFNESS OF TIMBER STRUCTURES
Every timber roof truss and timber building must include both the longitudinal and transverse wind braces. In addition to that, the roof truss must have enough spatial stiffness. When designing the roof framing and timber buildings, loading forces transferred by the timber structure to the substructure and other adjoining structures must be taken into consideration and the structures must be dimensioned in order to sustain such forces.
TIMBER STRUCTURES – basic glossary
25.05.2012 - The assembly of the timber frame at the KI Lecture Hall in Stockholm has been successfully completed. The opening ceremony to launch the new building will be held in May 2013. You can still watch the ongoing work in progress on-line through the webcam http://aula.ahsdrift.se/view/viewer_index.shtml?id=31991