Civil Engineering Reference
In-Depth Information
Figure 7.12
Flared pier details
used on the Stansted Abbotts Bypass, shown in Figure 10.4) and Figure 7.10 (e). It
is also possible to share the bending moment between a deck diaphragm and a pier
crosshead, Figure 7.10 (f). Crossheads, whether they form part of the deck or the pier
are costly, and should only be used when strictly necessary.
When different types of bridge deck are compared, it is often forgotten that the deck
type may require expensive crossheads, and that this may have a very considerable
infl uence on the cost of the bridge as a whole.
If a box section deck carried by a fl ared column has a trapezoidal cross section, such
as in the STAR project, the bearings will be closer together, reducing the necessary
fl are. This fl are may be further reduced by placing the bearings in-board of the webs,
beneath a deck diaphragm, Figure 7.11, when a price will be paid in reinforcement in
the diaphragm.
Truss analogy may be used to determine the tension force that must be resisted across
the top of a fl ared pier, Figure 7.12 (a). This tensile force may be resisted by passive
