HDG Case Studies
Zinc has been used in construction for more than 150 years to protect steel from corrosion. Zinc is most commonly used in construction as the protective coating of hot-dip galvanizing or other forms of zinc coatings. However, in Europe, and more recently, in the United States, pure zinc metal sheets have been used in roofing and paneling systems. The following are a few real-world examples of hot-dip galvanized steel projects with sustainable development synergy.
Sustainability in Construction Case Studies
Morris Arboretum - 2009, Philadelphia, PA
Weaving like a spider web throughout the verdant canopy of the Morris Arboretum, the hot-dip galvanized steel walkways of the Out on a Limb Tree Adventure provide a pathway to the treetops for nature enthusiasts. Located just outside of Philadelphia, the exhibit was developed to give visitors a birds eye view of the forest. Consisting of a 450-foot long canopy walk constructed around a 250-year-old chestnut oak tree, the hot-dip galvanized steel structure overlooks the steeply sloped woods of the Wissahickon Valley.
In keeping with the birds eye theme, visitors can walk into a human-sized birds nest constructed of galvanized steel and interwoven with branches hovering at a daring 80 feet above the forest floor. The specifiers originally considered painting the project for corrosion protection, but after considering the life cycle cost savings of a maintenance-free hot-dip galvanized steel corrosion protection system, the choice was obvious. In the forest environment, galvanized steel has a life expectancy of 75+ years before requiring any type of maintenance, making it ideal for this complicated structure. The architect, in consideration of the natural environment of the arboretum, wanted to specify a sustainable structure that would add to the greenness of the trees, rather than detract from it.
The structure is comprised of lightweight, recyclable galvanized steel, and wood, which required less space than concrete foundations, decreasing the risk of damaging the trees and their roots. Utilizing a galvanized steel frame design also allows the owners to easily modify the structure should something happen to one of the surrounding trees. With an aggressive schedule for completion, time was of the essence. The quick turnaround of the pieces some taking less than a day and cooperation of the designers, fabricators, and galvanizer, helped keep the project on schedule. A total of 155 tons of steel was galvanized, including walkways, framing, handrails, canopy, tube steel supports, tower structures, and even the life-size nest structure.
Upon completion, the specifiers had no doubt the contrast of the glinting galvanized steel amidst the lush, green forest would attract many visitors curious to see the 92-acre view from the expansive canopy platform. Thanks to the durable, sustainable protection of hot-dip galvanized steel, the Tree Adventure will remain attractive, structurally safe and environmentally friendly web through the canopy.
7th Avenue LRT Refurbishment- Calgary, Alberta, 2005
The City of Calgary, Alberta is a leader in the use of hot-dip galvanizing and duplex systems for infrastructure. Over the past decade, duplex systems have been used extensively on major overpass guardrails and pedestrian rails. Recently, the city has specified galvanizing for all reinforced steel in bridges. So when the city was ready to refurbish the 7th Avenue Light Rail Transit (LRT) System, hot-dip galvanizing was the logical choice.
Because many commuters rely on the rail system, turnaround time was of the essence. The system had to be de-energized, erected, and re-energized in a 72-hour timeframe to minimize the impact on commuters. To create a uniform appearance, all hardware, hollow structural steel chords, tension members, columns, upper and lower arms, ornamental light posts, handrails, benches, and trash bins were hot-dip galvanized. The durable coating will be able to withstand the extreme winter climate and constant foot and rail traffic, while remaining aesthetically appealing, ensuring more commuters elect to use the environmentally-friendly mass transit system, rather than driving to work individually.
Michigan M-102 (8 Mile Rd) Bridge Rail - 2008
With the original steel guardrail panels galvanized back in 1955, the rails on the M-102 Bridge and Rail Project were due for a safety update. Fortunately, because of the protection provided by the galvanized coating on the railing panels, only 15-20 percent of the more than 300 tons of steel would require replacement due to highway traffic damage. After attending an educational Galvanize It! seminar, Sue Datta of the Michigan Department of Transportation (MDOT) learned many states have been reusing existing guardrail by stripping, regalvanizing, and returning it to service so MDOT decided to regalvanize the existing steel guardrail panels.
MDOT felt recycling the existing steel was an excellent opportunity to contribute to the Keep It Green initiative being supported by the department. The state saved more than half of the budget earmarked for this project because they only had to use 20 percent new material (for damaged panels and to add a new safety rail across the panels). The money saved on this project allowed MDOT to start the next project one originally slated to begin in 2009. The cost savings merely added to the original benefits of galvanizing this project after 50 years of Michigan weather, traffic mishaps, road grime, and salts, the galvanized steel remained corrosion free. In addition to contributing to the Keep It Green effort, the new railings for this project will provide maintenance-free corrosion protection well into the future.