Trying to balance the needs of the environment with active pedestrians resulted in the David Kreitzer Lake Hodges Bicycle Pedestrian Bridge.
The stress ribbon bridge provides a link to the north side of Lake Hodges from the south side and serves pedestrians and bicyclists.
One of the keys that shaped the project was the need to limit the bridge’s impact on the lake. The project team used the stress ribbon design method to limit the number of supports in the lake to two. The use of precast panels eliminated the need for falsework within the lake, as well.
The bridge – about 1,000 ft across the lake – used 330-ft spans that helped limit the supports to two.
The bridge may look simple, but the project team used complex analytical methods to capture the non-linear and time-dependent behavior of the bridge. The bridge’s engineers evaluated the time-dependent effects due to concrete creep and shrinkage and performed stage construction analysis to capture the stresses that are locked-in as the bridge was constructed.
Another challenge for the project team was trying to find the time to build the bridge.
Due to the environmentally sensitive area over which the bridge spans, access to the construction site was a significant obstacle throughout the project. Construction on the bridge was limited to the winter months so that construction during the breeding seasons of various sensitive animal species would be avoided. This limitation forced construction to be split into three calendar phases: February 2007 to May 2007, September 2007 to May 2008 and September 2008 to May 2009. The precast deck segments were fabricated during offseason and erected during the final phase of construction.
The project was also limited by funding sources at times.
During construction of the first phase of the project, the owner obtained the additional funding necessary to construct the rest of the bridge, and that portion of the project was bid.
During construction, modifications were made where possible to lower the costs of certain items, and thus the net change orders on the project were a negative dollar value. Costs were reduced by eliminating electrical service, to be replaced by solar power lights, railing paint was eliminated in lieu of galvanizing, and other minor items.
Project TeamOwner: San Dieguito River Park Joint Powers Authority, San Diego
General Contractor: Flatiron, Longmont, Colo.
Design Firm: T.Y. Lin International, San Diego
Architect: Safdie Rabines Architects, San Diego