The RED Letter
RED Engineering & Design
Structural Engineers
March 2016

Engineering in a Box Video Series

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The answer is: 90 mph
Wind and trees

March: in like a lion; out like a lamb. Many times, that's the case with weather in March. So, speaking of coming-in-like-a-lion, scientists have determined, that regardless of species or size, all trees break when wind blows at the same critical speed. That critical speed is when wind speed exceeds 90 mph.

It was January 24, 2009, when Cyclone Klaus made landfall in Bordeaux, France, and traveled across Western Europe into Germany, Italy, Spain and Switzerland. Leaving thousands without power, the wind damage was significant, especially in forests. Meteorologists reported that sustained winds averaged 110 mph.
In the aftermath, damage assessments indicated more than 60% of trees were knocked down in areas where wind speeds topped 90 mph. For trees that had been broken in half by the storm, it didn't matter the height of the tree, the circumference of the trunk, or the species.
To date, conventional thinking a tall thick tree should be as strong as a short thin one. Even Leonardo da Vinci indicated this when explaining the strength of wooden beams. However, through the ages, scientists have not agreed on the force needed to snap a beam based on the scale of its length and diameter. Same for trees, too.
Seeing that more than 60% of trees had snapped during Cyclone Klaus, Emmanuel Virot of the Ecole Polytechnique, France, decided to perform s few simple experiments. Wooden rods made from beech were horizontally positioned with one end fixed. Researches applied increasing pressure on the other end and recorded the curvature of the rod as it bent and ultimately snapped.
The results of these experiments demonstrated that wood breaks at a critical curvature radius depending on the diameter ( D ) and length ( L ) of the rod. They took this relationship, added a model of wind force and came up with a scaling law for the wind speed at which a tree snaps. It boils down to the physics equation: V ~ D 0.75 /L.  Translated, it's when wind speed exceeds 90 mph that trees snap and type doesn't matter the type or size of wood. 
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Dates & Events
March 20, 2016


























New and cool stuff!
Materials to watch in 2016
Solar panels, spider silk, 3D printing, and shrimp shells. There could not be four more disparate things. But, wait. They all do have something in common: structural engineers may be using them on your project in the near future.
Solar panels
While solar panels may have been around forever, after 15 years on the market in Europe, a unique solar panel system has finally made it to the U.S. Originally designed by architect Giuseppe Fent in Switzerland, his solar panels functions as exterior cladding using an aluminum cladding mounting system. This system is specifically designed as a thermal storage device for use in colder climates.

The system consists of a solid wood absorber with slanted horizontal slits that sits behind a back-vented curtain wall made of glass. This protects the wood from the weather and preserves the thermal buffering effect. Behind the wood absorber is conventional masonry or wooden structural wall. R-values can range from 65 to 150 depending on the type of insulated backing.
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Synthetic spider thread
We're all familiar with the mysterious properties of spider silk, not to mention how Spider Man uses it to vault through the concrete canyons of New York City. After a failed attempt by a Canadian company to produce a high-performance, silk-like fiber called BioSteel, the Japanese company, Spiber, has taken the lead.

Scientists at Spiber have developed a synthetic spider thread they call Qmonos-based on the Japanese word for spider web,  kumonosu . Qmonos is derived from a fibroin protein using a bio-engineered bacteria and recombinant DNA. The result is a synthetic silk-like thread that is 340 times tougher than steel. Spiber has also made the production of Qmonos, scalable. They are currently working with North Face and have developed the Moon Parka for use in Antarctica.
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Build a bridge using a 3D printer
While 3D printing has been making in-roads into everything from making 3D printed acoustic guitar to medical models, the technology that started out in 1984 is slated to revolutionize the way we do things like what the internet did to communication. The MX3D bridge project in Amsterdam is proof.
Begun in October of 2015, this will be the world's first 3D-printed bridge, albeit a pedestrian bridge, that will span one of Amsterdam's oldest man-made canals, the Oudezijds Achterburgwal. When completed, the bridge will be 26.2 feet long and 13.1 feet wide. It is the MXD3 printer that is astonishing.

Dutch designer, Joris Laarman, has been working with Autodesk and Heijmans, a construction company, to bring the project to fruition. The MXD3 is a multi-axis metal printing technology that uses industrial robots equipped with welding machines which literally print lines of various metals in mid-air. In a warehouse near the canal, two printers on the endpoints of the bridge start from an anchored surface.  They "print" lines of metal into the air as though an artist were drawing in thin air and in 3D. The process is incremental where the thin short lines of molten metal are allowed to cool and fuse. The pair of MXD3 printers meets in the middle and bridge is finished.
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And, then there are shrimp
Like the peel-&-eat shrimp, and in this case, it is all about the peel. Shrimp are crustaceans and their outside shell-the stuff that goes "crunch," the "peel"-is called chitin, which is made of a long-chain polysaccharide and gives the shrimp its strong outer coat. Bottom line, chitin is a natural polymer.

Scientists at Harvard's Wyss Institute have developed a bioplastic using shrimp shells that have the same structure and composition as chitin. Essentially, it is poised to be the "new plastic," and its characteristics are incredible when compared to today's plastics that involve the use of petroleum. Wyss Institutes' chitin bioplastic can be used to make 3D shapes, is inexpensive, and most impressively, biodegradable. Scientists are now in the process of developing manufacturing methods so the material can go into commercial production.
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