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Structural systems – glue-laminated timber

Glue-laminated timber (glulam) is the name given to large solid wood members manufactured by gluing many smaller pieces together.

 

Glulam is an engineered structural material consisting of a number of graded, kiln dried and selected full length laminations – usually 45 mm thick – bonded with proven adhesives, to form a solid member of practically any length, shape or size.

The main reason for laminating is to produce larger size members than possible in solid sawn timber.

There is also an increase in strength. The strength of a single piece of timber is as strong as its weakest point, which is usually the largest knot.

In laminating, the weakest point of one piece of timber is bonded to the higher strength of adjoining pieces, thus forming a homogeneous structural component of great efficiency.

It therefore is possible to manufacture a beam with high strength timber in areas of high stress and utilise more economical lower grades in areas of low stress.

The use of thin laminations also permits better penetration of preservative, enables better and more even drying, eliminating checking, and member size is virtually limitless.

In addition the thin laminates enable the member to be finished with a curve if desired to accomplish striking architectural features.

In many ways glulam is a most versatile construction material. Members can be manufactured in uniform or varying depth to give strength where it is required.

They may be straight or curved to practically any shape, either for aesthetic reasons or to provide more structurally efficient designs than can be achieved with straight members.

Stratalam

Stratalam is the New Zealand engineered wood product that offers a high standard for cutting edge design.

It is an umbrella New Zealand brand, a quality symbol adopted by a committed group of New Zealand’s leading glulam manufacturers.

Stratalam website

Benefits
Glulam is produced from New Zealand’s renewable plantation forests.

Benefits of Glulam include:

Glulam is a very strong structural material in a strength-for-weight comparison

Depending on specific loading conditions a steel beam may be 20% heavier and a reinforced concrete beam 600% heavier than an equivalent glulam beam to carry the same load. The resulting lighter superstructure can lead to significant economy in foundation construction.

Glulam is resistant to chemical attack and is often used in structures involved with corrosive substances such as urea, potash, fertilisers, or in tanning and pulping processes, swimming pool enclosures, and marine environments.

In environmental impact terms, glulam is extremely cost efficient to produce. The energy consumed in producing a glulam beam from the log is only a fraction of the energy required for the production of steel from ore or concrete from limestone.

Glulam’s natural aesthetic qualities allow the designer to express these structural elements within the building without any false facing or camouflage as is often required with other materials. Glulam is quickly and easily handled by carpenters who are familiar and confident in working with timber. As a result erection times are significantly reduced in glulam structures. Sub trades also find glulam structures easier and quicker for making connections and installations.

Applications
Applications of glulam include:

  • Beams and columns
  • Curved beams
  • Portal frames
  • Arches
  • Flooring
  • Bridges
  • Scaffold planks

More information on Applications of Glulam  (.pdf) 

Manufacture
The .pdf below contains information on the following:

  • Species
  • Kiln drying
  • Grading
  • End jointing of laminations
  • Adhesives
  • Curved members
  • Camber
  • Finishes
  • Quality control

Manufacture of Glulam (.pdf) 

Availability
Glulam beams can be custom built to almost any shape and size allowing the designer great freedom in design form.

Straight beams are usually made up from 45 mm thick laminations to the depth required.

Beams almost 2 metres deep have been produced in New Zealand.

Standard finished glulam widths are 42, 65, 90, 115, 135, 180 and 230 mm.

The most common widths for structural beams are 90 and 135 mm. (from 100 and 150 mm original sizes). The length of glulam members is generally limited only by transport restrictions.

While beams of up to 28 m are fairly standard, lengths in excess of 40 m have been manufactured.

hinner laminations (from 10 mm to 40 mm thick) may be used for decorative reasons, greater strength, or for curved members. Generally the tighter the curvature the thinner the lamination needed, resulting in increased costs.

Economy will result if standard curvatures are selected.

Suppliers Database

New Zealand Pine Manufacturer’s Association website

Performance
The .pdf below contains information on the following:

  • Characteristic stresses
  • Design
  • Glulam

Performance (.pdf) 

Durability
The.pdf  below contains information on the following:

Weather protection

Exterior exposure

Wrapping for delivery

Storage on site

Fire resistance

Chemical resistance

Low maintenance

Service classes

Preservative treatment

Durability of Glu-lam – .pdf