An Iconic Wisconsin Landmark Rises Again and Takes Flight: The Eagle Tower Project

The original Eagle Tower, erected in 1932 in Peninsula State Park – Photo Credit: Yinan Chen – Friends of the Peninsula State Park

If you live in Wisconsin, chances are that you at least know of Eagle Tower. More likely, you—along with thousands of visitors from around the world—have had indelible experiences of taking in spectacular views of Lake Michigan, the surrounding islands, and Michigan’s Upper Peninsula. Eagle tower offered a captivating and much beloved panorama of Peninsula State Park.

Built in 1932, the observation tower was a 76-foot timber structure. But in 2015 the tower’s deteriorating state caused the Wisconsin Department of Natural Resources (DNR) to have serious concerns about its structural integrity and safety. The Wisconsin DNR asked Forest Products Laboratory (FPL) to assess the structure. “Nondestructive Assessment of Wood Members from a Historic Viewing Tower” is a detailed publication of their findings on Eagle Tower’s condition.

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110 Years of FPL: Laminated Wood Products

In celebration of 110 years of research at the Forest Products Laboratory (FPL), we are revisiting blog posts that detail some of our most interesting historic people, places, and projects. Enjoy!

FPL’s pioneering work on the engineering design of glued-laminated construction helped launch the laminating industry in the United States. Much of the research on laminated wood originated at the time of the first World War when the Bureau of Aircraft Production approached FPL with a need for lightweight airplane wings.

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Tales from the Test Floor: Glulam Arches

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Researchers here at the Forest Products Laboratory (FPL) wrapped up testing a set of glued laminated (glulam) arches with a bang by breaking the last arch in a series of three. The arches measure 30-feet tall by 30-feet wide. Only ten arches have been tested worldwide.

This experimental work is evaluating the seismic design parameters of glulam arches by simulating the forces of an earthquake and measuring how the arches perform under such stress. The collected data will be analyzed and results published in the near future to serve as a reference for architects and engineers looking to design buildings using glulam arches.

The test took place on the strong floor in FPL’s Engineering Mechanics and Remote Sensing Laboratory (EMRSL). Here, researchers conduct physical and mechanical tests on a wide range of materials, building systems, and structures – from houses to bridges. Results inform the development of building codes and structural design standards.

 

Back to Basics Training on Engineered Wood Products: Free Webinars Begin in April

APA – The Engineered Wood Association is hosting a series of free webinars in April and May 2016 focusing on engineered wood products.

Composit-framingAccording to APA’s website, “Manufacturers, distributors, and builders are all reporting a critical need for training as they rebuild from the recession and hire new employees. New hires often lack knowledge and understanding of engineered wood products, design considerations, and installation recommendations. Even experienced sales personnel can benefit from a refresher. APA’s new, comprehensive training series includes six “back to basics” modules that cover key topics related to I-joists, Rim Board®, laminated veneer lumber, and glulam. This training targets distribution sales staffs who can, in turn, share the knowledge and training with their retail and builder customers.”

Six training modules will be offered as a weekly series beginning Friday, April 8. Modules run between 30-90 minutes. The first four are designed to be completed in sequence with progressively complex content, while the last two can be taken as stand-alone presentations.

For detailed information on the webinars and to register as a participant, visit www.apawood.org/back-to-basics

Better Bridges: Considering Wood-Concrete Construction

The United States is facing an infrastructure crisis. According to the American Road & Transportation Builders Association, over 61,000 bridges in America are structurally deficient. Although expensive to maintain, particularly in these tough economic times, when these vital pieces of our transportation system fail, the human toll is incalculable.

One needs to look no further for a reminder than the 2007 collapse of the Interstate 35 bridge near Minneapolis, Minnesota. The steel truss arch bridge suddenly failed under the load of rush hour traffic, plunging into the Mississippi river below. The bridge had consistently ranked near the bottom of nationwide federal inspection ratings, and its collapse claimed 13 lives. In the disaster’s wake, fearing similar incidents, federal and state governments mobilized to assess the condition of their own bridges.

As states continue to evaluate and improve their transportation infrastructure, researchers at the Forest Products Laboratory (FPL) are working hard envisioning the future of durable and cost-effective bridges. They believe that the answer may lie in wood, one of mankind’s oldest construction materials, used in conjunction with another time-tested material, concrete.

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An example of a composite timber girder–concrete deck bridge

In cooperation with Iowa State University, Research General Engineer Jim Wacker from the Engineering Properties of Wood, Wood Based Materials, and Structures unit at FPL, has set out to investigate the state-of-the-practice related to the use of concrete decks supported by glued-laminated (glulam) timber girders for highway bridge applications. Glulam timber bridges have already proven themselves in our nation’s National Forests, but the practice of using them in conjunction with concrete decks is relatively scarce across the highways of America. The project, which commenced earlier this year, is expected to be finished June 2017.

A composite timber-concrete bridge consists of a concrete slab rigidly connected to supporting timber sections so that the combination functions as a unit. There are two types of composite timber-concrete bridges: T-beam decks and slab decks.

T-beam decks are constructed by casting a concrete deck, which forms the flange of the T, on a glulam beam, which forms the web of the T. Composite slab decks on the other hand are constructed by casting a concrete layer on a continuous base of longitudinal nail-laminated sawn lumber.

Recent research has found that performance of timber bridges constructed 50 to 70 years ago is above average, but despite this, only a small percentage of new bridges built every year are built with graded and engineered lumber. This project hopes to change that.

Composite slab decks have been used as far back as the 1930s, and Wacker’s reassessment of concrete-timber bridge construction will arm bridge engineers with a wealth of knowledge on the best practices of the past — so that bridges of the future can be as cost-effective, durable, and safe as possible.

For more information, please see the FPL Research in Progress publication Investigation of Glulam Girder Bridges with Composite Concrete Decks.