TIMBER
What is cross-laminated
Gareth Griffiths
Gareth Griffiths
Cross-laminated timber( CLT) is gaining traction as a structural form of timber, in some cases taking on the role of structural steel in large buildings.
Humankind has co-existed with the natural environment and trees for over two hundred millennia. A natural connection with nature is ingrained in humans, but artificial materials and methods have disrupted this bond. Office workers have become increasingly detached from the outdoors. Can this be fixed? The answer is at hand and already in practice.
The construction and operations of buildings has placed a significant burden on the environment, contributing to at least 36 % of global greenhouse gas emissions( GHG emissions), compared with all other sources of GHG emissions.( source: Green Building Council of South Africa) thereby promoting climate change, which endangers the lives and livelihoods of billions of people worldwide.
Originally developed and used in Germany, CLT is regarded as a key element of sustainable construction, including building occupant wellness. Although its application in South Africa remains limited, it is increasing. CLT is an engineered timber manufactured into panels for building houses and commercial structures. It is produced according to specifications issued by relevant authorities.
The use of CLT in Europe increased from the early 1990s, with the first national standards introduced by Austrian authorities in 2002. Uses included housing and multi-storey buildings.
What is inside CLT?
It takes the form of a wood panel product made by glueing together layers of solid-sawn timber, i. e., timber cut from a single log. Each layer of boards is usually oriented perpendicular to the adjacent layers and glued to the wide faces of each board, typically in a symmetrical manner, so that the outer layers share the same orientation.
CLT at the heliport development at the V & A Waterfront. Note the long spans indicating engineered strength.
An odd number of layers is most common, but there are configurations with even numbers as well, which are arranged to form a symmetric pattern. Regular timber is an anisotropic material, meaning that its physical properties vary depending on the direction of the applied force. By glueing layers of wood at right angles, the panel can attain enhanced structural rigidity in both directions. It is similar to plywood but with noticeably thicker laminations.
This design provides structural strength in both linear directions, unlike glue-laminated timber( glulam), which has strength only along the grain.
Known as mass timber construction, many buildings around the world have been built using this type of timber. In South Africa, its use has been increasing, with major developers specifying its application across various building types.
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