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2013SprShotcreteEMag

how Carl Akeley Saved Christmas By Cathy Burkert F illuminated to signal the official kick-off of of road salt.”winter cycle of freezing and thawing, as well asadditional damage that could come from the use-or more than 50 years, the trees along Chicago’s North Michigan Avenue have been the holiday season and encourage everyone to join During the 6-week rehabilitation project, the in the spirit and enjoy a host of festive experiences on-ramp will be closed to traffic until mid- along Chicago’s Magnificent Mile. November. Northbound vehicles will be rerouted The centerpiece of the day-long festival is the along Inner Lake Shore Drive for 1 mile (1.6 km) evening parade, and the lights on Michigan to LaSalle Drive, where they can proceed north Avenue are illuminated block-by-block as the on Lake Shore Drive. Adjustments to traffic sig- procession passes. More than one million specta- nals and the deployment of traffic control aides tors line the parade route each year to see the will help move vehicles along the detour route. lighted floats, marching bands, balloons, and The $1.78 million project will include the performing artists. The 1.2 mile (1.9 km) parade repair of the underside and topside of the on-ramp route travels under millions of twinkling lights viaduct, repairing the concrete retaining walls, along Michigan Avenue from Oak Street to and miscellaneous electrical and lighting repairs.”2 Wacker Drive.1 American Concrete Restorations (ACR), a However, on October 1, 2012, just 6 weeks Chicago-based shotcrete contractor, was awarded before the day of the festival and parade, the the project due to its vast knowledge, experience, Chicago Department of Transportation (CDOT) and reputation to perform efficiently. ACR wanted to begin a necessary rehabilitation of the accepted the challenge of a rigorous 4-week deteriorated viaduct and retaining walls along the schedule to complete the overhead repairs. How- northbound entrance ramp to Lake Shore Drive ever, many more challenges were in store. The at Michigan Avenue and Oak Street, exactly where entire bottom of the deck, approximately 4000 ft2 the route of the parade begins. As explained by (372 m2), was to be repaired; but due to the extent the city: of deterioration, CDOT required temporary “This repair project is necessary due to the shoring be installed—spaced every 8.5 ft (3 m)— deteriorated condition of the concrete of the via- to support the loads from the traffic above. This duct deck and retaining walls of the ramp, which restricted mobility for equipment and materials. has not seen any significant rehabilitation since The shotcrete contractor, needing access to the its original construction in 1963,” said CDOT 15 ft (5 m) tall underside, required special Commissioner Gabe Klein. “We want to complete equipment to gain access between the 8.5 ft (3 m) this repair work immediately before another spaced shoring towers. The shoring tower arrangement was so restricting that the turning radius of standard manlifts was too large to maneuver between the towers. ACR called five different equipment rental companies with no luck. Finally, one company was found that rented manlifts that would work, but only had two in inventory. They were deliv- ered to the job site the next day and, with fingers crossed, successfully made the tight-radius turn and fit between the towers (Fig. 1). Additionally, due to the congestion of shoring towers and workers from other trades, all equip- ment needed to be staged outside the viaduct. The shotcrete pump, compressors, and water tanks were stored at each end of the bridge and the hoses were lined along the inside of the wall. The center Fig. 1: Shoring towers at 8.5 ft (3 m) apart made for tight access between of the viaduct was to be left open to construction the exposed deteriorated concrete traffic, as seen in Fig. 2. 10 Shotcrete • Spring 2013


2013SprShotcreteEMag
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