Bent-Glued Constructions, Bent Beams

The use of bent-laminated wood as wooden panels, slabs, beams, beams is becoming more popular every year and is actually becoming a trend in the construction of the 21st century. What is this concept, what varieties are there, and where are they used, what is the Ukrainian manufacturer ready to offer today? More on this later in the article.

First experience in construction using bent-laminated structures

Construction using bent-laminated wooden structures was used in various fields and crafts several centuries ago and again acquired a wide scope abroad since the late 1980s. One of the officially documented cases of the use of laminated timber frames in 1827 was the construction of a lantern-shaped roof on Old Rusholme Road in Manchester (UK), which served until 1962, when the entire building was demolished.

Although mechanically bonded bent wood laminated construction was already in use in a series of wooden bridges built in Bavaria by Carl von Wiebeking from 1807-1809, these structures were only partially glued in some places.

Further, until the beginning of the 20th century, layer-by-layer glued (laminated), bent wood in the form of beams, beams, trusses, structures was used everywhere in shipbuilding, aircraft construction, as ceilings for vaults and towers of libraries, train stations, municipal and residential buildings.

In the first half of the 20th century, the metallurgical and chemical industries promised to provide most industries with high-quality and technologically advanced raw materials and rolled products. Khimprom offered metal-polymer compositions, and foundries offered high-quality alloyed alloys, and wood as a structural material was gradually forgotten.

However, nowadays, more and more attention is gradually being paid to bent-laminated wooden structures, both load-bearing and decorative, giving preference to this solution. And there are three good reasons for this:

3 good reasons to use bent-laminated timber beams and structures

1. Less specific gravity. With equal length parameters and the same load-bearing load, wooden structures are lighter and cheaper than metal ones.
2. Best appearance. The appearance of wooden structures is superior to metal and serves not only as a support or ceiling, but also as an accent decoration in the form of a visible load-bearing beam.
3. 3. Degree of safety in force majeure conditionsThe fire safety of wooden beams, as paradoxical as it may sound, has a higher degree of safety compared to metal ones. When heated strongly, a metal beam or truss quickly loses its load-bearing capacity and bends and collapses. While the wooden one, although it burns, holds the load much longer. Thus, the time to leave a burning building with wooden floors is sufficient for the safe evacuation of people. On the contrary, the risk of the collapse of hot metal ceilings is very high in the shortest possible time after a fire occurs. The reason for this is the property of metal to instantly transmit high temperature throughout the entire structure.

Metal beams and trusses are expensive and heavy; they require massive foundations and powerful reinforced concrete supports, which takes a toll both in time and money. High-quality metal-plastic prefabricated blocks are light and frost-resistant, with a sufficient heat saving coefficient, and the pleasure is not cheap.

Therefore, the use of bent-laminated beams and frame structures made of laminated veneer lumber and wooden laminated beams is becoming relevant and more in demand, given the development of technological solutions, and consequently the expansion of the scope of their application in design, architecture and construction.

Curved laminated beams are used wherever large spans need to be covered; they simplify the design of large rooms and give individuality to the structure. Lightness, reliability and strength, as well as high load-bearing capacity are the main characteristics of laminated wood structures that are used in modern construction.

Bent-glued structures are resistant to the external environment, not subject to bio-impact, and are easy to process. They can be used to build bridges, arched covers for swimming pools, ice arenas, storage facilities, and much more. etc.

Use of laminated wood abroad

The European market distinguishes three possible categories of consumers for this type of product:

1. Buildings (including multi-storey ones) for permanent residence, as well as public purposes and operation. This also includes shopping, entertainment, business centers, sports facilities and indoor arenas containing laminated veneer lumber and other structural wood. This option provides for a mixed type of construction, where elements of brickwork, reinforced concrete, and metal can be combined. Here they usually use sets of identical parts (serial production of several types of large quantities of parts).
2. Buildings made entirely of woodincluding laminated timber, curved laminated beams, trusses, structures and laminated wood. As a rule, the repetition of identical sets of parts and designs is moderate or high here, with a tendency to increase the types of sets and reduce the number of parts of each type.
3. 3. Individual architectural solutions. Most often, in such projects, only the details within each structure are repeated (for example, beams, roof segments, wall panels), since the project is individual and does not provide for mass production.

Focusing on these three market segments, the industry is developing 3 main and 2 modified or variable types of products, united by one term “glulam”:

Main branches of development of glulam products
	GST (Glued Solid Timber), or sometimes Glued Laminated Beams, wood, or timber made from glued lamellas
	LVL (Laminated Veneer Lumber), or Solid Veneer Lumber, is often confused with SVL - laminated wood (veneer) panels, reminiscent of plywood, only much thicker. In the same way, timber or beams of wooden structures are made.
	CLT (Cross Laminated Timber) - panels, beams, beams of almost any thickness or shape (depending on the equipment), obtained by gluing layers of wooden lamellas crosswise, where each layer is glued to the previous one perpendicularly.
Modifications
	SVL (Structural Veneer Lumber) – A type of LVL produced to create spatial 3D structures and installations, usually curved in different planes or spherically
	SCL (Structural Composite Lumber) - essentially composite wood from which panels and beams are made. For example, the OSB boards we know are one of the SCL options, although technologies are developing, and new solutions and modifications appear every year (PSL, LSL, OSL).

LVL and SCL methods contain a higher percentage of glue, composite wood and polymers; wood contains recycled materials, shavings, and waste more often than high-quality veneer. Therefore, some types of these products have a low cost and are offered for mass sale.

At the same time, the European market is more focused on the mass production of bent-laminated wood products. Modern architecture, including individual and even unique projects (eg SVL-3D installations), tends to contain a large number of identical parts, manufactured in advance. Then, more complex structures are formed from a certain type of simple parts (primitives).

On the American continent, bent-laminated structures are called “engineered wood”, but demand is biased towards individual architectural solutions, where a small number of uniquely shaped beams are used.

Parameters for the production of bent-glued structures

For the manufacture of bent-laminated beams and glued laminated structures, softwood is used as standard. Most often spruce, pine, larch. The humidity of the lamellas should not exceed 12% with an acceptable error of 2%.

The company "Modern Wooden Houses" offers the production of bent-laminated wooden beams, as well as products up to 24 meters long with a maximum section of 220 mm x 2500 mm. In this case, the section width varies from 60 to 220 mm, and the height from 100 to 2500 mm. The minimum arch radius starts from 2500 mm or more. The thickness of solid wood lamellas in structures also depends on the purpose, type and position of the building elements in the overall design of the project and is determined by the design engineer.

The safety and durability of the entire structure depends on the quality of assembly of the lamellas and their gluing into wooden structures, especially for load-bearing elements. The Modern Wooden Houses company produces them from solid wood and controls quality at all stages of production: sorting of raw materials, accuracy of parameters, splicing, gluing, appearance. By following woodworking technology, having technological equipment, wood and special types of glue, we achieve high quality of our products.

Not all types of glue for laminated wood can provide strength to load-bearing structures. We use special compounds for loaded and load-bearing wooden structures with strength classes - GL24, GL28, GL32c - in accordance with current European standards.

Our experience in construction using curved-laminated structures

The calling card of the Modern Wooden Houses company is our office, built using curved-laminated arched structures according to an individual architectural solution. The construction uses bent-laminated beams with a cross-section of 150x600 mm. This is a frame-timbered building with wooden cladding and mineral insulation. The content and layering of external walls, ceilings and internal partitions is the company’s own development of engineers. It can be safely called an “eco-house”, since construction was carried out only from environmentally friendly materials.

Dome houses are another opportunity to get an organically distributed space under a domed vault. Bent-laminated beams are assembled into a single structure, into a hemisphere of the correct shape. Internal partitions are not load-bearing and can be located in any convenient way at the request of the owner. The ergonomic shape allows you to reduce energy consumption, and the frame sandwich effectively retains heat indoors for as long as possible. The domed house from the SDD company is assembled only from environmentally friendly building materials and complies with all current building codes and regulations.

Curved laminated beams have proven themselves well not only as elements of an arched roof or floor trusses of large spans. Very successfully, they became the basis for the structure of the dome of a wooden church; a beautiful and reliable bridge was built from them, as well as a large number of long-span wooden beams and timber used in floors, frame walls and structures produced by our company.

Photos of bent-glued structures, bent-glued products