Step 2: Bridge Concepts
Step 2:
AAT (Area Advisory Team), BSMT (Bi-State Management Team), RAC (Regional Advisory Committee)
Box-Girder
(Roll-over red dots for detail)
A box-girder bridge, one of several different types of girder
bridges, is a member of a family of perhaps the most common
and basic bridge types. Unlike many of the other long-span
bridge types, the support for this bridge is entirely supported
from beneath the deck. In its simplest form, a log across a
creek is an example of a girder bridge. Box-girder bridges
are typically used for spans up to 800 feet.
Cable-Stayed
(Roll-over red dots for detail)
A relatively new type of long-span bridge is the cable-stayed bridge, which has one or more towers with large diagonal steel cables supporting the deck. Cable-stayed bridges are sometimes confused with suspension bridges. A key difference is that the cables on a cable-stayed bridge connect the deck directly with the tower. For suspension bridges, there is a large suspension cable draped over the towers, and the deck is connected to the suspension cable with vertical "suspenders". Cable-stayed bridges are normally used for spans of 360 - 1570 feet.
Arch
(Roll-over red dots for detail)
Arch bridges are comprised of semicircular structures with abutments on each end. These curved structures with high resistance to bending forces are often best used when crossing over a valley or river. Steel cables attaching the arch with the deck are called hangers. Usually made with steel or concrete, this bridge type is used often for spans of 130 - 490 feet.
Truss
(Roll-over red dots for detail)
Truss bridges have a simple skeletal structure, typically with steel structural elements arranged as a series of triangles, a very stable shape. Trusses are lightweight, can span long distances and can support large amounts of weight. For these reasons many long-span railroad bridges are trusses. For highway bridges, trusses are normally used for spans of 130 - 1640 feet.
In Step Two of the Bridge Type Selection Process, the East End Bridge and Downtown
Bridge design teams and the community examined a number of different bridge concepts
for each bridge location. The four long-span bridge types that were feasible in these
locations were truss, cable-stayed, arch and box girder.
There were a number of design parameters required by the Record of Decision and various
local, state and national design codes and standards. These parameters included details
like span length and vertical clearance.
Each bridge has a team of designers who developed general bridge type concepts during
this step, which was used to solicit feedback and preferences on overall aesthetics.
The concepts were presented to the project advisory teams and then to the public
at a series of open houses.
Visualization tools and computer imaging showed each of the various bridge type
concepts in context at each location. Lifelike digital renderings of the downtown
area with existing bridges and parks showed a concept of the new bridge next to
the Kennedy. This allowed people to see what the combination might look like.
The community also saw what a bridge linking Prospect and Utica might look like.
Various perspectives of each bridge showed what a new bridge would look like
from the river, the shoreline and from nearby businesses or houses.
After the information from Step Two was analyzed, Steps Three and Four of the Bridge
Type Selection Process resulted in more detailed bridge type alternatives designed
to meet the project parameters and design guidelines while being consistent with
the general aesthetic preferences that were gathered from the community.
Click here to read about the next step.