Mary Avenue Bicycle Footbridge
The Mary Avenue Bicycle Footbridge project included the construction of a 325-ft main span pedestrian and bicycle bridge over 10 lanes of Interstate 280. Including the two 89-ft back spans, the entire bridge length is 503 ft long. The project provides a bicycle and pedestrian connection between Cupertino and Sunnyvale, two cities that were previously divided by the highway, and includes the bridge, gateway paths, extensive landscaping, and public art.
Teamwork and group perseverance in solving technical problems was significant when the project hit a financial, architectural, and schedule snag that almost caused the entire project to not go forward. Originally slated to be a concrete structure with an estimated cost of $6.3 million, the city was shocked when construction bids came in at $12.4 million. Rather than give up, city officials and project architect, Terry Greene, sought alternatives from HNTB, a transportation infrastructure engineering and architectural firm. For six weeks the city worked with numerous consultants and HNTB to redesign the bridge and send it out for bids, all the while making sure the project conformed to Caltrans specifications. It was agreed that a steel design offered several cost-cutting and time-saving advantages.
The project gained second life when five second-round bids came in under the engineer’s estimate with a low bid of $7.3 million – awarded to Golden State Bridge Inc.
The substructure of the bridge consists of numerous cast-in-drilled-hole pilings, each 3 ft in diameter and 90 ft deep. The cable-stayed structure includes two structural steel support towers and 44 locked coil rope cables. Each of the towers is 90 ft tall and weighs 114,000 lbs. The decking consists of 40 pre-cast concrete panels, each one measuring 13-ft by 18-ft and weighing 18,000 lbs. The approach ramps are cast-in-place concrete.
The Mary Avenue Bicycle Footbridge is the first cablestayed crossing over a freeway in California. The bridge positively impacts the surrounding areas, such as De Anza College, Oaks Shopping Center, Homestead High School, Cupertino Middle School and major employment centers in Sunnyvale.
The Footbridge is the final connector of two sections of the Stevens Creek Trail, which promotes exercise and improves the health of users through increased physical activity and reduced dependence on fossil fuel burning automobiles. It is anticipated that 126,000 bicyclists and 65,000 pedestrians will use this bridge every year.
Project TeamDeveloper/Owner: City of Cupertino
General Contractor: Golden State Bridge Inc., Martinez
Architect, Structural and Civil Engineer: HNTB Corp., New York and San Jose
Construction Management: Swinerton Management & Consulting, Concord