THE CONCRETE BRIDGE MAGAZINE

WINTER 2018

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/922349

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patterns to allow multiple girders to be cast in one bed. Prestressing strands were extended and bent up at the ends of the boxes to provide connections to the cast-in-place diaphragms. The boxes were cast with square ends, and the cast- in-place diaphragms were meticulously detailed to avoid conflicts at the ends of the box girders. The box girders were shipped only 10 miles from the fabrication plant to the Union Station project site where they were erected on the bents. The girders were seated on plain neoprene bearing pads. The biggest lift was about 31 tons, which was easily handled by the equipment on the small site. Precast concrete deck form panels were selected to be used in the s u p e r s t r u c t u r e s y s t e m t o s p e e d construction. Again, close coordination with the precast concrete producer ensured that the panels fit perfectly with the flared and skewed box girder framing near the Carriage Pavilion. Panels slightly wider than standard panel widths were allowed because of the reduced vehicular wheel loading. Deck panels are typically designed for HL-93 wheel loads. However, the design loading for the Union Station bridge was a 100-lb/ft 2 pedestrian loading, a 64-lb/ft 2 vehicular loading, or an H-5 maintenance vehicle which has an 8-kip axle loading, and tended to control the design of the slab, precast concrete p a n e l s , a n d s h o r t e r b o x g i rd e r s . This design loading also allowed for snowplow equipment or other light maintenance vehicles to access the bridge and for pedestrians to occupy the full bridge width, as for a mass exit from a large event at Union Station. The framing and overall geometric c o n t r o l f o r t h e b r i d g e w e r e complicated. Unlike a typical highway or railroad bridge, there was no established stationing or obvious tie to set the horizontal control. The bridge was detailed, fabricated, and constructed using spatial coordinates to locate the nine drilled shafts. This approach was unique but manageable. A construction baseline was established from these coordinates, using a line parallel to the northernmost drilled shafts and the north fascia of the bridge. This baseline was used to set the geometry for the box girders and precast concrete deck form panels. The precaster produced shop drawings and fabricated the girders and deck panels using this baseline, ensuring a perfect fit into the framing system. A precast concrete pedestrian railing was desired for its smoother and more consistent finish. The rail panels were fabricated in lengths up to 15 ft and were installed at the north slab fascia between cast-in-place concrete pilasters. A precaster fabricated the rail for the panels and, as with the box girders, close coordination of the geometrics was critical. The metal forms for the panels were custom crafted in the precast producer's plant, and the spaces between the balusters were formed with expanded polystyrene. The rail panels were reinforced with epoxy-coated steel and designed for pedestrian loading. Summary The bridge structure brings a "heavy" but clean and low-profile aesthetic to the surrounding area, complementing both the majestic historic building and the new north festival plaza and outdoor exhibit space. As endorsed by Union Station's management, "the new Union Station Carriage Pavilion Bridge…is both an engineering marvel and aesthetic masterpiece. A mix of high-function, historic reference, and physical beauty, the bridge immediately solved a long-standing and significant customer experience challenge for the station…moving volumes of pedestrian and vehicular traffic intuitively in and out of our massive historic campus with ease. This cornerstone component of our Western Expansion Project was validated by our guests within the first fifteen minutes of opening, and every day since. In a most literal sense, it's as if the new bridge were always meant to be," said George Guastello II, president and CEO of Union Station Kansas City Inc. ____________ Julie Sarson is the section manager for bridge design at Burns & McDonnell in Kansas City, Mo. Complex geometry at the Carriage Pavilion end of the bridge required a high level of detail for fabricating box girders and deck form panels. Placement of deck concrete. 32 | ASPIRE Winter 2018

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