Description: B-3167 - DUPLIN COUNTY LOCATION: SR-1723 over Cabin Creek
ITEM(S) OF INTEREST: Bridge Maintenance Unit Purchase Order Contract (POC) job. Contrast this project with normal TIP jobs, particularly how the Bridge Maintenance Unit handles roadway approach work on bridge replacements.
Observations and Points of Discussion:
2-span (25' - 50') cored slab bridge with precast NJ shape barrier rail with cast in place barrier rail transition, and a 6% superelevation.
The bridge is in a location with a low sag vertical curve with potential for overtopping.
Minimal approach roadway work was appropriate for the scope of the project
Demonstrated a reasonable balance between bridge length and maintaining the grade.
Demonstrated that approaches do not need to be widened for bridge with large shoulders.
Bridge is a good example of a situation where a single span box-beam superstructure would have been appropriate.
The new process document will include details on how the Structure Design Unit will interact with Hydraulics in order to eliminate undesirable span arrangements.
Recommendations:
Develop guidelines to determine situations where widening roadway approaches is appropriate,
Roadway Design and Structure Design Units should not design bridges for more than 2 lanes if the approach roadway is only two lanes,
In some situations allow shorter approach slabs in lieu of the current 25'-0". A suggestion is to base the approach slab length on the design ADT.
NC DOT
NC DOH
NC GOV
