The following criteria were developed by BCDC and were published, along with Caltrans selection and design criteria, as part of the competition program.
SAN FRANCISCO BAY CONSERVATION AND DEVELOPMENT COMMISSION
Thirty Van Ness Avenue . Suite 2011 . San Francisco, California 94102 . (415) 557-3685 . FAX (415) 557-3767
April 9, 1997
TO: Bay Bridge Design Task Force, Engineering and Design Advisory Panel
FROM: Will Travis, Executive Director
SUBJECT: Draft Bay Bridge-East Span Replacement and West Span Retrofit Design Criteria
San Francisco Oakland Bay Bridge-East Span Replacement and West Span Retrofit
Draft Design Criteria
- Placing the east and westbound roadways on the same level, side by side, will diminish the visual access to the Bay by at least 50 percent, because only two lanes will adjoin the bridge edge, versus the four lanes that adjoin it currently on the east span. This reduction may be further compounded by the addition of shoulders and pedestrian and bicycle access.
- The existing east span will need to be torn down to prevent damage to the new span from an earthquake, to avoid unnecessary maintenance costs, and to reduce navigational hazards.
- The existing east span of the Bridge is eligible for the National Register of Historic Structures and may be protected under State and local historic preservation requirements.
- The new east span will be aligned to avoid sensitive wetland areas in the Emeryville Crescent which provide habitat for endangered species.
- The existing east and west span bridges have several elements which create a design continuity between them including:
- a continuous double level truss extending form San Francisco to Oakland:
- steel cross-bracing used throughout both spans; and
- visual continuity established by the continuous size and shape of the east bound tunnel, the braced frames on the westbound east span and the open deck of the west span.
- The replacement span should be designed to fulfill its purpose in the optimum way. The structure should reveal in itself a pure and clear form by manifesting its structural anatomy, and should impart a feeling of stability, confidence and simplicity.
- The design of the replacement span should adhere to the established principles of design so that the structure's form, alignment, and detailing exhibit continuity and order. The bridge and its members should be scaled in harmonious proportions to one another. Order should be achieved by limiting the direction of lines and edges in space, and by establishing a consistent rhythm of spans, column size, span depth and spacing of elements. The design should be so refined that
Draft Bay Bridge EAst Span Replacement and
West Span Retrofit Design Criteria
April 9, 1997
no element can be added or removed without disturbing the harmony of the whole. The new bridge should achieve a clean and well-defined anatomical construction, devoid of any deception and unnecessary detail, and with directness of line both pleasing to the eye and responsive to the senses.
- The bridge should integrate into the site and surrounding environment by reflecting the grand scale of the San Francisco Bay, by harmonizing with the existing west span of the bridge and landing gracefully on the Oakland and Yerba Buena Island landfalls. The new east span design should reflect design continuity within itself and should relate and integrate with the retrofitted west span structure.
- Where spans or structural systems change within the new east span, structural system integration will be important for visual continuity, using a consistent vocabulary within the different systems for design continuity and integrity.
- The alignment of the roadway into and out of the tunnel on the east side should be improved. The abrupt angle of the existing east span bridge at the tunnel is awkward. The alignment of the new bridge should provide a safe, easily driven alignment that also enhances the motorist's and cyclist's view of the Bay and the surrounding land forms.
- The roadway should provide for safe motoring and contribute to the graceful form of the bridge in the landscape.
- The ascent of the bridge from the Oakland landfall to Yerba Buena Island should be consistent and should flatten out before the tunnel so that the bridge gracefully engages the island and the tunnel as viewed from available vantage points.
- The minimum allowable span width for the channel should be maintained.
- Design continuity is a high priority. If a double level is considered, it will need to be an open truss design for view and light considerations and consistency with the west span.
- The bridge design should not be a fshion statement, but should resolve itself in a timeless manner suitable to its central prominence in the Bay. The structure design should exhibit a natural balance and form in a manner which leads to the least possible disturbance of the Bay and its shoreline.
- The design for the east span should reflect that the existing two-level truss is a very strong unifying element between the east and west spans, both because it projects from San Francisco to Oakland, interrupted only by the Yerba Buena Island tunnel and because it visually establishes a very strong line from one end to the other.
- Material selection should reflect long-term maintenance and construction cost considerations. Maintenance considerations would favor concrete and seismic perfomance considerations may favor steel, which would require higher maintenance.
- Any bicycle and pedestrian way should be integrated into the bridge design so that it contributes to the overall order and continuity of the bridge design. Periodic outlooks should be provided at intervals along the bicycle-pedestrian way.
Draft Bay Bridge East Span Replacement and
West Span Retrofit Design Criteria
April 9, 1997
- The east span replacement bridge should provide a measure of visual continuity for motorists, regardless of what structural system is used, equal to that of the existing westbound portion of the east span bridge, which establishes a visual continuity for motorists because the trusses maintain a consistent rhythm of form, creating a lacy tunnel through which motorists.
- The girders, piers, and rails of the bridge should generally appear slender and should provide for views of the Bay by motorists using the bridge.
- The east span replacement bridge should provide adequate on and off-ramp capacity to and from Treasure and Yerba Buena Island. Capacity projections should be based and current redevelopment plans for Treasure Island.
Detailed Design Criteria
- Guard rails and hand rails should be designed to provide maximum transparency for maintaining views of the Bay and shall meet all appropriate safety criteria.
- The retrofit of the west span should remove non-structural panels which block Bay views and replace them with panels which provide views.
- Details of the bridge should be simple in appearance.
- The bridge should generally not have any intrusive ornamentation.
- Large expanses of concrete surface on the new east span should be textured.
- A concrete bridge should be colored in such hues as off-white, tan, reddish brown, or gray if possible.
- Landscaping around the bridge should replicate the existing natural surrounding of the Bay shoreline.