Glue Laminated Timber (GLULAM)
Glue laminated timber(Glulam) is a structural material that is made by joining separate pieces of timber with adhesives (typically Melamine or Polyurethane resin adhesives). This type of timber can be produced in large sizes and unique shapes. Layers of dimensional timber are stacked one on top of the other and joined using strong structural adhesives that are moisture-resistant such that all of the grain runs parallel to the longitudinal axis to create the structural engineered wood product known as glulam.
This type of structural wood has many benefits, including the simplicity with which it can be easily shaped into arched shapes or curves in beams or pillars, making it excellent for use on beams, pillars, ceilings, stairs, panels, and cladding. Pine and eucalyptus, which come in beige-pink and brown-pink colors, are the most common timber species used for glulam composites.
Types of Adhesives Used For Glue Laminated Timber (GLULAM)
There are numerous types of adhesives that can be used for laminating structural wooden beams (cross laminated beams and glue laminated beams). Each type offers solid connections and improves the beam's ability to support weight. The type of wood, the needs of the environment, the preferred application technique, and the most practical curing procedure should all be taken into consideration when deciding between the different types of adhesive. The compatibility of the preservative and laminating glue must be confirmed if the timber has been treated with a preservative before laminating.
Three of the most popular adhesive solutions for glulam are described below. The types can be altered to satisfy particular specifications necessary for your application, and they can be differentiated from one another by consistency and curing technique.
Melamine (urea) formaldehyde adhesives
Phenol Resorcinol formaldehyde adhesives
Laminating timber with polyurethane adhesives
Melamine (urea) Formaldehyde Adhesives
Melamine formaldehyde (MF) and melamine urea formaldehyde (MUF) adhesives are polycondensate adhesives, which now dominate the timber adhesives market. A hardener is necessary for multi-component glues like MF and MUF to set and cure. By eliminating the water, these adhesives for laminating wood become hardened. The melamine-based adhesives give timber colored glue lines with better water resistance. Furthermore, MUF adhesives in particular have an inherent fire resistance and can laminate wood beams even in difficult circumstances.
The melamine (urea) formaldehyde adhesives are the most flexible glues for wood. They can be utilized for other smaller constructions even though they were designed for load-bearing structures.
Formaldehyde, which is present in MF and MUF adhesives, is occasionally a chemical that should be avoided due to the emissions it can emit. The good news is that contemporary technology makes very sustainable melamine formaldehyde systems possible, with emission rates that are comparable to those of real wood. These adhesives aren’t readily available at the moment, but demand is growing swiftly.
Phenol Resorcinol Formaldehyde Adhesives
Phenol resorcinol formaldehyde adhesives (PRF) are multi-component systems that cure through polycondensation. The dark colored glue lines that PRF adhesives produce are very strong and resistant to both weather and water.
The most popular glues for laminating wood in load-bearing and non-load-bearing buildings are those containing phenol resorcinol formaldehyde. Many manufacturers of wall beams, straight laminated beams, and curved laminated beams (glulam) rely on it as a traditional system.
Laminating Timber With Polyurethane Adhesives
A more recent substitute for the traditional systems that contain formaldehyde is polyurethane (PUR) adhesive. The PUR adhesives are typically one component, moisture curing (polyaddition) systems that use the water in the wood structure to set and harden. This enables quick curing at room temperature. The technique is also quicker and more effective because the adhesive doesn’t need to be mixed and no hardener is required. The lack of formaldehyde in polyurethane wood laminating adhesives makes them a more environmentally friendly option than the alternatives.
PUR offers a more ductile alternative that is suitable for various timber laminating applications, from classic bearing and non-bearing constructions to contactless finger jointing, where PRF, MUF, and MF adhesives can be brittle and stiff.
Manufacturing Procedure of Glue Laminated Timber ( GLULAM)
The creation of glulam involves the fusion of two really old woodworking techniques:
laminating
gluing
Laminating
To create a strong laminate, stack several dried pieces of wood together with the grain running parallel. (In cross-laminated timber, the wood grain is perpendicular.) Pine, larch, spruce, hemlock, and even fir slats may be utilized, depending on the area.
Gluing
In order to create useful structural parts, the slats must be joined with waterproof adhesives that are powerful enough to replace the traditional steel and screw connectors.
Once glulam reaches the minimum size, it is regarded as “large lumber” in accordance with the CCQ. Therefore, it must be produced in accordance with CSA O122, “Structural Glued-Laminated Timber,” and the producer must meet CSA O177, “Qualification Code for Manufacturers of Structural Glued-Laminated Timber.”
The classification of glulam produced in Canada as “generic” or “proprietary” is determined by evaluation criteria such as the piece’s permissible bending stress (x10² psi) and the homogeneity of the laminations utilized.
In order to reduce shrinkage and expansion and ensure the material’s structural stability, Glued Laminated Wood is produced with the optimum amount of humidity.
Applications of Glue Laminated Timber ( GLULAM)
Glue laminated timber is recommended for all kinds of construction, from household renovations to commercial structures. The following structural components of a building can be made with this kind of structural composite lumber:
Lintels
Floor
Joists
Beams
Columns
Pillars
Uprights
Additionally, a wide range of supporting arches and roof truss designs can be constructed using glulam.
Advantages of Glue Laminated Timber (GLULAM)
Contractors are increasingly adopting glulam in their institutional, commercial, and residential construction projects. Some of the benefits of using glue laminated timber include;
Aesthetics
The framework of a building can be constructed using a variety of wood beam types, although few are as aesthetically beautiful as glulam. The diversity of wood slats that make up the piece and their placement, which can produce interesting contrasts, give it a distinctive appearance.
It can be Applied to Construct Open Areas.
Glulam is a lightweight material with a high load-bearing capacity that may be utilized to build huge open spaces without the requirement of support beams. Without additional supports in between, it can stretch up to 100 meters.
Resistance to Humidity and Chemical Attack
The chemical resistance of glulam is very good. Additionally, it is immune to damage brought on by moisture, such as warping.
It can be Used to Build Arches and Curved Beams.
With solid lumber, curved, bowed, and bending shapes are particularly challenging to produce. The pieces of glulam, however, don’t necessarily need to adhere to a tree’s structure because they are constructed of little slats.
It has Outstanding Fire Resistance.
Structures made with glulam are less susceptible to fire damage than steel that is not fire-protected. The charred coating that forms around the glulam’s core during a fire reduces oxygen consumption and delays combustion.
It is More Stable Than Solid Lumber
With a relative humidity of 65% and an equilibrium moisture content of 68 °F, which is roughly comparable to most indoor conditions, about 12% of glulam is moist. As a result, thermal expansion and contraction are lessened.
It Reduces The Need for Fittings and Joints.
Glulam structures and frames often need fewer connections and fittings to span large open spaces without the use of intermediate supports.
It is a Lightweight Material
Due to its light weight, glulam is easy to put together, maintain, and disassemble. Studies show that glulam beams are around five times lighter and equally strong than concrete beams of the same volume.
Higher Strength And Stiffness Than Conventional Construction Materials
In comparison to steel and concrete, glulam offers a superior strength to weight ratio. Additionally, because glulam minimizes the effect that wood flaws have on the strength of the member, it is stronger than sawn timber. In comparison to steel, glulam has been shown to have a better resistance to lateral-torsional buckling.
Environmental Friendliness
Compared to reinforced concrete and steel, glulam has a substantially lower embodied energy because the laminating method enables the use of the timber for much longer spans, greater loads, and more complex geometries. Its production requires a sixth of the energy used during the production of steel of similar strength. Another benefit of glulam is that it naturally sequesters carbon because it is made of wood, preventing its release into the atmosphere. Glulam is a renewable resource, provided that the wood used to create the structural parts originates from sustainably managed forests.
Lower Construction Costs
Not only does glulam have great strength, but it also requires significantly less time to rework and construct on site, which means the project’s budget will be reduced and time will be saved.
Since glulam is an engineered wood product, its technology has made it simpler for installers to cut, nail, drill, and perform other installation tasks than it could be for conventional solid wood materials, which may call for specialized knowledge and equipment. Installation of glulam does not necessitate specialized equipment. Additionally, these unique characteristics speed up the construction process and require less work to complete glulam constructions.
Appearance Classes For Glue Laminated Timber Beams
In APA-EWS Form No. EWS Y110 and ANSI A190.1, four fundamental appearance classes for glulam beams are specified (although in ANSI A190.1 they are referred to as glulam appearance “grades”). These classes include;
Framing Appearance
This classification is offered to correspond to common dimension lumber widths, which are typically 3 ½” and 5 ½” wide. Members of Glulam will be planed in a “Hit & Miss” manner. Low laminations, glueline squeezeout, end joint offsets, and glue smear are all acceptable. Splits, waning, and knot holes are also acceptable and will not be filled.
Industrial Appearance
When appearance is not the main consideration, this classification should be utilized. Putty will be used to fill in loose knots and knot holes that form on the wide face of the laminations (bottom of the beam) that is visible, but not voids that appear on the margins of the laminations. Misses, low laminations, and waning are occasionally acceptable.
Architectural Appearance
This high grade appearance is appropriate for applications where aesthetics are essential but not the primary factor. Using a wood-tone filler, all exposed knot holes and voids larger than ¾” will be sealed. The bottom corners (edges) will be rounded off, and exposed surfaces will be smooth.
Premium Appearance
This rating of glulam appearance is the highest. A wood-tone filler will be used to fill in all visible knot holes and gaps. The bottom corners will be rounded off, and exposed surfaces will be smooth.
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