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Why wood is an excellent material to build bridges with.

The borrowed text below was written by Michael A. Ritter, Structural Engineer, United States Department of Agriculture Forest Service. It is from a document/book that he wrote titled "Timber Bridges Design, Construction, Inspection, and Maintenance." The source of this text is hosted on the United States Department of Agriculture Forest Service website at URL www.fpl.fs.fed.us/.../em7700_8--entire-publication.pdf . Note that this document is 17 Megs. You can select smaller sized individual chapters of this publication by visiting URL: www.fpl.fs.fed.us/.../em7700_8/

Borrowed text follows:

The age of wood spans human history. The stone, iron, and bronze ages were dramatic interims in human progress, but wood-a renewable resource- has always been at hand. As a building material, wood is abundant, versatile, and easily obtainable. Without it, civilization as we know it would have been impossible. One-third of the area of the United States is forest land. If scientifically managed and protected from natural disasters caused by fire, insects, and disease, forests will last forever. As older trees are harvested, they are replaced by young trees to replenish the wood supply for future generations. The cycle of regeneration, or sustained yield, can equal or surpass the volume being harvested.

Wood was probably the first material used by humans to construct a bridge. Although in the 20th century concrete and steel replaced wood as the major materials for bridge construction, wood is still widely used for short- and medium-span bridges. Of the bridges in the United States with spans longer than 20 feet, approximately 12 percent of them, or 71,200 bridges, are made of timber. In the USDA Forest Service alone, approximately 7,500 timber bridges are in use, and more are built each year. The railroads have more than 1,500 miles of timber bridges and trestles in service. In addition, timber bridges recently have attracted the attention of international organizations and foreign countries, including the United Nations, Canada , England , Japan , and Australia.

Timber's strength, light weight, and energy-absorbing properties furnish features desirable for bridge construction. Timber is capable of supporting short-term overloads without adverse effects. Contrary to popular belief, large wood members provide good fire resistance qualities that meet or exceed those of other materials in severe fire exposures. From an economic standpoint, wood is competitive with other materials on a first-cost basis and shows advantages when life cycle costs are compared. Timber bridges can be constructed in virtually any weather conditions, without detriment to the material. Wood is not damaged by continuous freezing and thawing and resists harmful effects of de-icing agents, which cause deterioration in other bridge materials. Timber bridges do not require special equipment for installation and can normally be constructed without highly skilled labor. They also present a natural and aesthetically pleasing appearance, particularly in natural surroundings.

The misconception that wood provides a short service life has plagued timber as a construction material. Although wood is susceptible to decay or insect attack under specific conditions, it is inherently a very durable material when protected from moisture. Many covered bridges built during the 19th century have lasted over 100 years because they were protected from direct exposure to the elements. In modern applications, it is seldom practical or economical to cover bridges; however, the use of wood preservatives has extended the life of wood used in exposed bridge applications.

Using modern application techniques and preservative chemicals, wood can now be effectively protected from deterioration for periods of 50 years or longer. In addition, wood treated with preservatives requires little maintenance and no painting.

Another misconception about wood as a bridge material is that its use is limited to minor structures of no appreciable size. This belief is probably based on the fact that trees for commercial timber are limited in size and are normally harvested before they reach maximum size. Although tree diameter limits the size of sawn lumber, the advent of glued-laminated timber (Glulam) some 40 years ago provided designers with several compensating alternatives. Glulam, which is the most widely used modern timber bridge material, is manufactured by bonding sawn lumber laminations together with waterproof structural adhesives. Thus, Glulam members are virtually unlimited in depth, width, and length and can be manufactured in a wide range of shapes. Glulam provides higher design strengths than sawn lumber and provides better utilization of the available timber resource by permitting the manufacture of large wood structural elements from smaller lumber sizes. Technological advances in laminating over the past four decades have further increased the suitability and performance of wood for modern highway bridge applications.

Promising green transportation technology.

It is an undeniable truth that efficient, effective, and expedient transportation systems play key roles in developing, maintaining, and supporting the infrastructure upon which societies are built. Just as the internet allows for the instantaneous free flow of data and ideas, healthy transportation systems nourish the backbone that supports societies.

If you flipped thru a history book and looked at how goods were transported over the ages you would quickly find that sooner or later people always migrate to newer technologies that lower costs, increase efficiency, and deliver goods at higher speeds. It wasn't so very long ago that railroads were the great engines that helped to power the development of the US and other countries. Further down the road the internal combustion engine and magnificent highway systems took leading roles. There have indeed been many changes over time, with the invention of the wheel being undoubtedly the single most important.

The issues and technologies that have driven the transportation engines to where they are to date have come to yet another bend in the road. Our world is changing. Populations are growing. Fossil fuel prices are going up. Air pollution is a problem. Traffic on highways is forever increasing. Economic powers are shaken when oil supplies are interrupted. We could go on and on about some of the issues that impact us, our environment, and our transportation systems. Most reasonable people would find it hard not to agree that changes need to be made to elements of our transportation system such that they become cleaner, cheaper, faster, more efficient, and sustainable.

The Freight Shuttle System marks the beginning of another significant turning point in transportation technologies. The Freight Shuttle System is an innovative freight rail system developed by the Texas Transportation Institute (TTI) for container movement to and from ports. It understands the past and present, capitalizes on all current technologies, and charts a well thought out path towards the future.

It is well worth your time to watch the above movie about the Freight Shuttle System. It quickly illustrates how you and I will at some point in the future benefit from the great work that the folks at the Texas Transportation Institute are doing.

At Zipblocks, we share the vision of improving transportation systems.

Here is a glimpse of our vision.

Glued laminated timber (Glulam) is a proven technology. It has been used for over 100 years by the construction industry to build everything from bridges to homes. Wooden Zipblocks take this concept/technology to the "next level." They allow for the instant construction of "Glulam-like" structures of virtually any size or shape. Wooden Zipblocks that have been glued together are ideal for building infrastructure like bridges, columns, and roads. Simply weave structures together with Zipblocks and glue and your structures inherit all the wonderful qualities that wood has to offer.

Here is an idea as to how we want to build rail. Imagine four rail cars on a track. One rail car is the supply car. It is loaded with timbers and other supplies that will be used to construct/lay Zipblocks. The next car is the machining car. This car houses machinery that allows the workers on it to instantly construct Zipblocks that can be virtually any length or radius via the use of some basic robotic machinery. The car up front is the fabrication car. This is where a team of workers simply glue/weave/lay Zipblocks that are fed "real time" off of the machining car. After the track is laid and has dried a planer car is run over it. The planer car planes the surface making it perfectly smooth. All that is left is to place a bit of steel rail on a surface that is amazingly smooth and that gracefully flows over and around obstacles and contours.

Wow what a vision! You don't lay track, you rapidly, yet gracefully manufacture it with sustainable materials like wood!

Our company is still very small. As time and resources allow for it, we will post more information on our site regarding exciting topics like this. Here's an example as to how columns for bridges and/or overpasses could be built.

How to build your invention.

This site ran by Edgar Castelo. Edgar is an extremely creative inventor that will stop at nothing to build his inventions. Edgar shares some very unique tools, ideas, and concepts on his site that can save you a ton of time and money. If you are an inventor you should definitely take a minute or two out of your day and visit his site.

InventorSpot

Most of the people that visit our website are into are interested in science and technology, inventions, robotics, and other similar things. If these are some your interests as well, you might want to take a quick visit to InventorSpot.

We like this site because they allow inventors to post their inventions on their site and they only ask that you put a link to their site on yours. Most sites like to charge several hundred dollars for this type of service. What's nice about this is that this provides a good incentive for inventors to post their inventions to this site. It's kind of like visiting YouTube but instead of seeing a bunch of movies you see and learn about a bunch of inventions. Their site is appealing because the people that visit it contribute to it and make it that way.

What's more is that they really have a lot of cool stuff posted on their site like:

• Plenty of inventions to browse with links back to the inventor or companies sites.
• Lots of interesting articles on promoting inventions.
• Blogs & Forums

In a nutshell they provide some nice and much needed services for inventors.