Cushing Street / Luis Gutierrez Bridge over Santa Cruz River
This project was named one of the top 10 bridges in the US for 2012 by Roads & Bridges Magazine.
The Cushing Street / Luis G. Gutierrez Bridge designed by Structural Grace Inc., is the first multi-modal (Modern Streetcar, Vehicular, Bicycle and Pedestrian) bridge in the State of Arizona. The 310 foot-long structure links the Santa Cruz River with Tucson’s downtown district and its historic Westside. This area has been continuously inhabited for over 5,000 years making the connection an important amenity for the residents and visitors of Tucson, Arizona.
This was a very challenging project to design and build from its heaviest construction to its delicate steel and cable erection to its extensive fine detail work. The design team was challenged with providing a unique signature bridge while maintaining costs and constructibility. Structural Grace, Inc. achieved this through the use of standard bridge components augmented by unique architectural and artist elements. The bridge addressed hydraulic challenges by crossing the Santa Cruz River with only two spans – it utilizes the longest precast AASHTO girders ever cast in Arizona and the longest drilled shafts ever used for an AASHTO girder bridge in Arizona. Complex architectural and artistic features were incorporated including steps from the deck sidewalks to the multi-use path below at all four corners of the bridge; bridge, step and wall railings made of pre-cast concrete and designed to replicate historic balusters; design, fabrication and erection of structural shade canopies over the promenades; and the incorporation of 12 local historically-significant events in the shade structures and sidewalk deck creating an interactive experience for the visitor.
Engineering efforts began in March 2007 after initial meetings with the City of Tucson, Pima County, Rio Nuevo Development Staff, numerous neighborhood associations and the general public. Per the direction of Rio Nuevo Leadership and the City of Tucson, five bridge design alternatives were developed and presented in a Structure Selection Memo. Rio Nuevo Leadership and the City approved a 3-span bridge with an overall length of 315 feet. 30% design documents, a preliminary estimate and reports were then completed and submitted to the City in early April 2008.
Upon approval, Structural Grace, Inc. began the 60% design for the selected bridge type and incorporated a design process change from a conventional design-bid-build delivery method to a construction manager at risk (CMAR) delivery method. In August 2008, 60% design documents with all ancillary elements, including developed art elements, were submitted to the City of Tucson.
In October 2008, with a goal of reducing the impact of the structure on the high-water elevation, the City requested the design team revisit the bridge type selection. Ultimately the City approved a new bridge type consisting of a 2-span bridge with an overall length of 315 feet. The client also desired the appearance of the new bridge type to remain fundamentally consistent with the designs of the previous bridge alternatives. Additionally, the City returned to a design-bid-build delivery approach.
The final design of the structure evolved to a fairly typical structural system of Super VI Modified AASHTO girders, two spans with a center pier consisting of a two column bent with cantilevered sidewalks, retaining historical detailing, a complex form, architectural quality and proportion which makes for a very unique structure. Integrated public art that grew from an involved public participation process also graces the bridge with meaningful and locally historic motifs.
A successful collaboration between many design, fabrication, construction, public and private entities brought to fruition a bridge that incorporated the goals of the stakeholder group and brought their vision to reality. The consultant team consisted of AMEC, prime consultant; Structural Grace, Inc., bridge design; Sage Landscape Architecture, Inc., landscape architecture and environmental reporting; R.A. Alcala & Associates, Inc., electrical engineering; and Terracon Consultants, Inc., geotechnical analysis.