REDISCOVERING TIMBER

How to build a timber construction on a point-supported flat slab.

Timber, one of the oldest construction materials, in the last two centuries has been surpassed by more technologically advanced materials: it is time for it to restore its former glory.
In recent years a new sensitivity towards environmental issues has led to a rediscovery of timber material, characterized by a very low ecological footprint. In addition, a “technological revolution” of the entire timber supply chain has made it possible to make a quantum leap, with the construction of small 24-storey skyscrapers with height up to 85 m. Today a material that was once reserved to small structures only can aim to replace steel and reinforced concrete, even for buildings of considerable size and complexity.
In particular there is new exciting opportunity risen within this technological revolution: the SPIDER connector, a fixing system developed and certified by Rothoblaas in collaboration with the University of Innsbruck (Austria).
The research project
When the academic world and industry combine their skills to translate a brilliant intuition into a tangible and practical solution, it is often a sure success. This is, indeed, how the SPIDER project has started in 2016. The Arbeitsbereich für Holzbau (Department of Timber Construction) at the University of Innsbruck envisioned its innovative concept and proposed the development primacy to two companies. Rothoblaas saw the potential and therefore accepted the challenge, sharing its technical know-how and collaborating with the University to bring this visionary system to life.

The ambitious research project, co-financed by the Österreichische Forschungsförderungsgesellschaft (Austrian Research Promotion Agency), led to the development of a metal connector for the construction of point supported flat CLT floors, for the first time in the world. After 4 intense years of work and many tests and trials the project was finally marked successful with the marketing of the notable, CE marked SPIDER connector.

The SPIDER connector
The connector consists of several steel components, fixed to the timber elements with fully threaded screws.
The SPIDER connector performs three distinct tasks:
1.   Load transmission from the upper to the lower column, without compressing the CLT floor (green arrows);
2.   Suspension of the floor: the floor is not simply resting on the column, but is “suspended” from the six steel arms of the SPIDER by means of full threaded screws, which work in traction (blue arrows);
3.  Shear reinforcement: all vertical loads applied to the floor are concentrated in a small portion of the panel around the column. This causes high shear forces in the floor, which can result in rolling shear failures. The inclined screws also act as reinforcement, “sewing” the various layers of the panel.

Now, the obvious question is: at what distance can the columns be positioned using the SPIDER connector? In principle, a 7 m x 7 m mesh can be indicated as the maximum limit that a SPIDER connector can support. It is possible to install the floors with two different configurations, to create a real flat slab floor or a cross-panelled floor.
Just to make it clear, it will be possible to construct buildings with the same structural mesh as the U.B.C. Brock Commons in BC, Canada but 50 storeys high!
Spider has been officially launched in Spring 2020 and is featured in the new plates and connectors catalogue by Rothoblaas.

Join the challenge!
Timber construction is still in an initial phase of rediscovery and deserves full attention and consideration. After decades where steel and reinforced concrete have ruled undisturbed, now timber construction is becoming more mature, getting some popularity for its sustainable and biophilic nature. However, to withstand a credible and competitive advantage it needs to borrow some of standard construction’s strengths.
SPIDER is a clear step forward for buildings made of wood and unlocks paths to possibilities that now also timber, over reinforced concrete, can have the luxury to dare to.
The challenge of innovation has just started, now it’s up to both designers and manufacturers to believe in it and seize this new opportunity!

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