THE NEW BRIDGE CODE

This article introduces, in general terms, the new British standard code of practice for steel, concrete and composite bridges (BS 5400) indicating changes from current concrete design practices. The general philosophy of the new code is studied. Safety and serviceability are considered in probabilistic rather than deterministic terms. The current elastic methods of analysis will still be used for the majority of structures. Nominal loads, given in part 2 of the code, include a new single point load of 250 kn acting in any direction parallel to the surface. Other major differences in loading are explained. Design criteria at the serviceability limit state discussed include stresses and crack widths in reinforced concrete and stresses in prestressed concrete. Three calculations under different loadings are now used in the design of reinforced concrete to check stress and strength. Design considerations for prestressed concrete remain the same. The new code will lead to more design effort because of the increased number of local position, combination and limit states. However because the new code has been chosen to give similar designs to those in current use, it is unlikely that significant economies in the use of materials will result in the near future, except for long span bridges. /TRRL/