South Bayfront Pedestrian Bridge & Horton Landing Park

A rail yard essentially sliced Emeryville, Calif., into two pieces for pedestrians and cyclists along Horton Street in the city’s southern half.

The area has bridges over the sprawling Union Pacific Railroad (UPRR) right-of-way at Powell Street and 40th Street. The vehicle bridge at 40th Street has a painted bike lane but doesn’t qualify as usable by people of all ages and abilities. The Powell Street bridge does not allow bikes at all.

It begged for a pedestrian and bike-only bridge somewhere in the middle, especially with the rapidly growing Bay Street Center mixed-used development on the east side of the tracks. The city’s Horton Landing Park project near Bay Street Center and the Emeryville Greenway--completed shortly after the bridge--provided the necessary final push. A transformative project like it couldn’t meet its goals with poor pedestrian access.

Now, a 230-ft single-span bridge across the tracks provides that long-overdue link and boosts Emeryville’s walkability. Its combination of an S-curved deck and asymmetrical single tied-arch creates a striking image while resolving complex site conditions.

The South Bayfront Bridge’s design and construction highlight why steel is a strong choice for single-span structures that exceed 200 ft in length. The single straight bowstring truss/arch that extends diagonally across the deck consists of a pair of steel tubes, from which cables connect to the deck framing and create an aesthetically appealing structure.

The City of Emeryville showed the value of patience, partnership, and persistence during the process. The bridge is the start of crossing brownfield sites to build a more sustainable and united community. It spans a mainline rail corridor and rail yard and links major employment and commercial centers. It’s a crucial connection between the city’s Park Avenue District and the Bay Street retail and residential development. Most importantly, it has prioritized active transportation, providing safe access for multi-modal transportation across the railroad tracks.

Construction of the South Bayfront Bridge included the main bridge structure, access ramps, stairs, landscaping, community outreach, stakeholder coordination, and permitting for all elements of the project. The bridge and ramps accommodate bicycles and pedestrians and are Americans with Disabilities Act compliant. It’s a tied single-arch structure designed for construction over nine UPRR tracks within a rigid and limited track closure window.

The main span consists of the S-curved single span, supported at its ends by concrete bents. It’s supported by a straight bowstring truss/arch extending diagonally across the deck. The top chord/ arch rib is a pair of steel tubes, the bottom chord/tension tie is within the deck framing, and the cable diagonals/suspenders support the deck edges. A concrete slab travel way, with fencing and lighting, is carried by the steel deck framing.

The bridge design was also developed in close coordination with the adjacent property owners and UPRR.

The bridge approaches combine for more than 1,000 ft of ramps. The west ramp is a switch-back ramp that connects to the Bay Street shopping center. The west ramp is adjacent to the mall’s parking structure within a 30-ft setback from the UPRR property line. The east ramp connects to Horton Landing Park. Both ramp structures are cast-in-place concrete structures. The project also included access stair structures on each side of the railroad corridor for pedestrian access to the main bridge.

A detailed construction management plan was necessary to oversee the project’s complex construction on a site near and over an active railway corridor for numerous daily freight, Amtrak, and Capitol Corridor trains, plus the UPRR train yard. Additionally, the project required UPRR-specific agreements, permits, and flagging responsibilities that were tracked and followed carefully.

The design and construction team worked closely with stakeholders to plan and schedule the bridge assembly outside of the UPRR right-of-way in the future Horton Landing Park. Deck and arch components were welded and bolted together, and temporary towers ensured the appropriate geometries conformed to the design. Full assembly took place at the temporary Horton Landing Park staging area, and the completed bridge was lifted into place over the tracks under the tightly restricted timeline.

Months of extensive planning and preparation preceded the bridge lift and placement. The key components were:

• Review and approvals of submittals by UPRR, which took approximately seven months

• Utilities realignment and site preparation

• Excavations adjacent to the UPRR tracks required shoring designs that met UPRR requirements and review and approval by UPRR prior to start of construction

• Bridge abutment construction on the east and west sides, including installation of driven piles to support the structure

• Crane mats and steel plates placement to support the cranes and provide an even traveling surface for the cranes to move the bridge

• Crane erection and bridge load balancing

The bridge lift operation was completed within a three-day continuous effort window, possible only with collaboration and intense planning and preparation. The team worked 24 hours each day to ensure a safe and efficient operation with minimal impact on train operations.

Elsewhere, a variety of water and electrical connections were removed from the project to reduce maintenance costs and prevent vandalism. The construction management team used a cloud-based system to administer the project. Team members could pull up project documents anytime through their computer, tablet, or smartphone.

Extensive surveying was performed during the entire construction process to ensure the main bridge would fit during the final installation, including high-level surveys while installing the tie-down bolts for the bridge on both abutments piers to ensure they were consistent with the designed bridge length. That survey was repeated during the fabrication and installation processes.

Stinger Bridge & Iron performed fabrication at its Arizona facility and completed initial assembly in October 2020. The bridge deck and arch components were shipped by truck to Horton Landing Park in early November 2020.

Stinger fabricated the bridge and provided design assistance to the engineer before fabrication. Design assist measures included 3D scanning of the foundations, 3D modeling of the new structure, engineering analysis of site conditions, re-design to incorporate required changes, engineering design to change field-welded connections to bolted connections to expedite field erection, and full shop preassembly to ensure bridge geometry and expedite field erection.

Stinger’s prefabrication efforts and design assist measures ensured that the fabricated structure fit perfectly on the constructed foundations. Prior planning and field verification of dimensions simplified the erection, making everything fit as designed.

Three special design features provide critical structural functions while giving Emeryville an iconic signature bridge.

The cable layout was developed to enhance the buckling stability of the arch. The Nielsen cable arrangement significantly increased the arch’s buckling strength while minimizing the number of cables required in a network cable arrangement. The cable arrangement satisfied structural efficiency and aesthetic appeal.

The single-arch member design in a high-seismic location like the San Francisco Bay Area was a considerable challenge. The design goal was to avoid inelastic behavior in the arch during the design seismic loading. To maintain elastic behavior, a reduced-beam-section (RBS) comprises the end member at the arch’s base. The RBS is similar to an RBS used in building design. It absorbs the high seismic energy and maintains an elastic response in the single arch.

The deck truss serves two critical structural functions: the tension-tie that resists the thrust and compression delivered by the arch, and the lateral diaphragm that delivers the seismic loading from the deck to the support columns.

Project Team

• Owner: City of Emeryville, Emeryville, Calif.

• General contractor: Ghilotti Construction, Inc., Santa Rosa, Calif.

• Structural engineer: Biggs Cardosa Associates, Inc., San Francisco

• Steel team:

  • Fabricator/detailer: Steel Girder LLC dba Stinger Bridge and Iron, Coolidge, Ariz. *AISC full member; AISC-Certified fabricator and erector*

  • Detailer: SSP Engineering, Queen Creek, Ariz. *AISC associate member* Bender-roller: Albina Co. Inc., Tualatin, Ore. *AISC associate member*

  • Erectors: Stinger Bridge & Iron *AISC full member; AISC-Certified fabricator and erector*; Adams & Smith, Lindon, Utah *AISC associate member; AISC-Certified erector*