RMCalc is a Windows-based software program to compute restraint moments in precast prestressed concrete girder bridges constructed with continuous spans. It uses the same algorithms as BRIDGERM, an older FORTRAN based program written as part of the Transportation Research Board''s NCHRP Report 322.
What are restraint moments?
Precast prestressed concrete girders have a tendency to creep upwards over time due to the prestressing force and other effects. If a girder''s ends are restrained by a pier or diaphragm, forces will build up in the girder due to the creep. Typically, the ultimate restraint moment in a girder is a positive moment. This moment combines with other moments in the girder, creating an increase in the mid-span positive moment and a decrease in the negative moment over the piers. In essence, the continuity of the girder is reduced, and the continuous forces move towards simple-span values.
Why would I want to calculate restraint moments?
Without calculating restraint moments, you don''t know how much of your continuity will be lost during the life of the bridge. Therefore, many designers in the past have designed entirely for simple-span forces, even on bridges that are constructed with continuous spans. By knowing the value of restraint moments in the bridge, a designer can design for continuity, and account for restraint moment effects. Depending on the level of continuity, bridges designed for continuous-span forces can have a more cost-effective design than those designed for simple-span forces
This software was generously contributed to the Alternate Route Project by Mike McDonagh of ABAM Engineering in Federal Way, Washington