Reconstruction of the 90’ TPG Swing Span over Bayou Des Allemands
(Room Sagamore 2)
19 Sep 17
11:00 AM
-
11:30 AM
Tracks:
AREMA Full Schedule, AREMA Technical Sessions- Structures
BNSF Bridge 32.06 is located near Des Allemands, Louisiana. The existing swing span was a 90ft TPG. The main span piers were concrete filled cofferdams on timber piles. The project involved replacing the 90ft TPG swing span, two jump spans, underpinning the existing substructure and installation of new machinery and new electrical control system. Accelerated construction techniques were utilized and construction was performed under traffic. Short windows for replacement of the pier caps and replacement of the swing span were permitted. New pivot pier constructed under traffic. The demolition elevation was under the normal water elevation requiring underwater techniques. Micropiles were installed to strengthen the existing foundations. Project utilized wire sawing techniques for concrete demolition to decrease span outage windows. To increase the span ratings, the new swing span dead load was entirely supported on the new micropiles. Challenging conditions were encountered and overcome during design and construction, including but not limited to: 1. New micropiles placed to miss original and retro fitted timber placement. 2. Drilling through the existing concrete pier and tremie concrete which was in fair to poor condition. 3. Underwater concrete demolition. 4. Underwater grouting. 5. Span change out with low head height to water. 6. Large crane radius due to narrow spans and existing fender location. The focus of this presentation will be to present the unique aspects of bridge construction, including the following: • Project planning including innovative gantry utilization for span change out • Discussion of project construction challenges and methods utilized to overcome them.