Civil Engineering Reference
In-Depth Information
Figure 7.21
Areas beneath bending moment diagrams
and to temperature gradients through the deck, both of which are absent in a simply
supported deck. On the other hand, statically determinate beams show some small
savings in concrete and simplifi cations in construction due to the lack of anchorage
blisters within the span and to the use of thinner webs near the supports, as the prestress
may be effectively tuned to counteract shear force.
In practice, for prestressed concrete decks below about 45 m span, continuity saves
about 20 per cent of the prestress. Although this saving is substantial, for these short-
span bridges the most appropriate method of construction will generally dictate the
form of bridge. For longer spans, where self weight predominates, the savings offered
by continuity are greater; it is most unusual to see statically determinate beams with
spans exceeding 45 m.
