By: Eric Humphries
The Marquette Interchange, which links nearly one-third of Wisconsin’s freeway traffic to the rest of the country, is undergoing a facelift that will allow the roadway system to accommodate the 300,000 vehicles that travel it each day, as well as make it an important cog in the urban renaissance under way in downtown Milwaukee.
The decision to install transparent noise-barrier sheet manufactured by Evonik CYRO LLC, an Evonik Degussa Corp. group company, is going a long way to accomplishing both those goals.
The core of the project involves rebuilding all but one of the major system ramps connecting I-43, I-94 and I-794. The transparent sheet is being used to improve visibility and reduce noise along the busy exchanges, because the barriers offer a number of design and aesthetic advantages. The latter is a major consideration in the project, as a new approach to transportation project development called community-sensitive design (CSD) is being used. Having a goal of creating highways that are safe, efficient and visually pleasing, CSD was established to raise a community’s quality of life and leave lasting, positive impressions on visitors, tourists, commuters and daily users.
As part of the planning for the Marquette Interchange Project, a Community Sensitive Design Task Force was formed. It consisted of a Central Neighborhood Committee concerned with making areas under I-794 more visually appealing and pedestrian friendly, and an Advisory Committee, whose members focused on the “view from the road,” including the look, feel and overall driving experience motorists will encounter.
Nice views
Having a clear view of the city was of paramount concern for the residents of Milwaukee. From a series of visual preference surveys, Milwaukee residents noted features of the city that they identified with. The most popular feature was the skyline rich with the spires of churches. Regardless of culture or ethnicity, residents felt the skyward-pointing spires defined Milwaukee. Being able to see them from the road and overpasses was of major importance.
Installing a see-through barrier addresses the goals of both committees and residents. Transparent noise barriers are a superior alternative to tall, solid, opaque walls and to concrete walls with little or no aesthetic appeal.
“Transparent walls reduce or eliminate the ‘tunneling’ effect for drivers. Overall, they also improve the overall view and allow clear vistas of the city and its unique skyline,” explained Nicholas Martin, project manager for the Wisconsin Department of Transportation.
CYRO and its noise-barrier sheet distributor, Durisol USA, a division of Armtec Ltd. Partnership, developed several panel configurations to meet project requirements. Among the options developed were four-sided Paraglas Soundstop Ready-Fit Panels that were available with precast concrete, steel or aluminum frames, and traditional “site constructed” wherein the transparent sheet was attached to structural posts with various connection details.
During the first phase of construction, a 2-ft 6-in.-high transparent screen wall was placed on top of a standard 36-in. parapet. At this location, the transparent noise-barrier sheet was physically connected to the structural posts using steel angles and four restraint cables, with no additional framing for the sheet.
The second, much larger phase required a 12-ft 6-in.-high transparent barrier mounted on the bridge parapet. In an effort to reduce field labor and costs, four-sided panels were recommended. It was determined that the horizontal frame on top of the panels was not necessary, so a three-sided version was developed. A temporary steel angle tie, added to the top of the panel for shipping and handling, was removed after the panel was placed into position on the parapet. Four restraint cables were used to securely fasten the sheet and frames to the structural posts in the second phase as well. This design simplified installation, increased productivity and maintained the owner’s requirement for an uninterrupted view through the panel.
Equally important, transparent barrier sheet incorporates polyamide filaments. In the event of impact by a car or truck, the embedded filaments will hold the broken sheet, preventing fragments from falling below and causing injuries.
“Federal regulations require that any barriers constructed must prevent objects and debris from falling off the structure, and these noise barriers perform this function perfectly,” noted Martin. “Because the GS CC grade is ‘self-containing,’ safety netting is not necessary.”
Before the installation of the noise barrier, there was nothing to prevent debris from falling from the old bridge onto the roof of a power plant situated directly underneath. The new system keeps rubble from tumbling over the parapet.
“The walls do what they are meant to do as barriers, but they do not detract aesthetically from the view of the city,” said Martin. “The transparent system has a great look because it feels as though they aren’t there visually. When you see the bridge from afar, they don’t stand out nor take away from the view.”
The lightweight construction of the new barriers also adds to their ease of use. Concrete barriers can be heavy and cumbersome to install. The barriers for the new Marquette Interchange are lightweight, making installation and future repairs simpler by decreasing burdens on lifting and transport.
“Once the design was finished and we were familiar with the transparent barriers, they were rather easy to install,” said Martin. “The lighter panels required less machine and manpower. Overall, the process was much smoother.”
Other benefits include high resistance to weathering from UV exposure, retention of clarity and strength for many years and optional bird-deterrent striping. They are easy to form and fabricate. All in all, the noise barriers have been exactly what everyone associated with the project had hoped.
“They’ve been excellent to date. They were erected easily and will allow motorists to see the beautiful valley and historic sites as they travel. Local officials have seen them and asked why they can’t be used elsewhere,” said Dennis Maney, project manager for Marquette Constructors, the consortium awarded the construction contract.
“Since the completion of construction, the new interchange has already gone through daily traffic and one winter, and it is still looking good,” continued Martin. “And because it’s located on the top of a 150-ft bridge, vandals can’t access it. The surface has maintained its clarity, and as structures the walls are holding up very well.”
Aside from the official response to the new walls, the public reaction has been equally positive. Usually within a few months of final construction when the public has had time for direct interaction, traditional concrete barriers garner at least some unfavorable response from naysayers. However, the transparent sound barriers have not received any negative public reviews to date.
“The public’s quiet acceptance of the new barriers is a sign that they are not displeased,” said Martin. “When it comes to city construction jobs, if the people don’t like what they see, they let you know immediately. We take this silence as a sign of satisfaction from the public.”
About The Author: Humphries is product manager for Paraglas Soundstop at Evonik Cyro LLC, Parsippany, N.J.
