Page 313 - Bridge and Highway Structure Rehabilitation and Repair

288 SECTION 2 STRENGTHENING AND REPAIR WORK

Table 7.2 Useful service life for superstructure and substructure members.
Rehabilitation/ Useful Service Life*
No. Location of Member Protective Measures (Years) Remarks
1A Terminal decks Minor patching and bituminous 5 Maximum life of bituminous
overlay overlay is eight years

1B Deck to remain in place Membrane waterproofi ng and 20 Replace membrane each
bituminous overlay time overlay is replaced
1C -do- Latex modifi ed concrete 20
overlays, cathodic protection
1D New concrete deck With epoxy-coated rebars 40 Can be extended to
50 years with maintenance
2 Deck joints/expansion Periodic replacement of glands 40 -do-
dams or trough
3 Beams and connections Repairs and/or rehabilitation 40 Painting required
4 Other types of -do- 40 Can be extended to
superstructure and 50 years with maintenance
elements
4A New superstructure Replacement 75 Can be extended to
100 years with maintenance
5 Bearings Replacement 75 Require inspections and maintenance

6 Existing substructure Repairs and/or rehabilitation 75 Can be extended to
100 years with maintenance

6A New substructure Replacement 100 Can be extended to
9 100 years with maintenance
7A Existing R.C. retaining Repairs and/or rehabilitation 50 Can be extended to
walls 9 50 years with maintenance
7B New R.C. retaining walls Replacement 75 Can be extended to
9 75 years with maintenance
7C New PMU/earth Replacement 50 Can be extended
reinforced 9 50 years with maintenance

7.3.6 Compare REP/REH Ratios
The next step is to compare rehabilitation and replacement costs assuming both are viable
possibilities. This relationship can be established in terms of the rehabilitation cost being a
percentage of the replacement cost (REP/REH percentage).
1. REP/REH percentage 9 120 percent.
The preliminary choice in this case is replacement. Other factors given below be examined
for compatibility with replacement.
• Constructing a temporary structure may not be possible from a right-of-way point of
view.
• Construction for replacement on a new alignment may not be possible due to right-of-way
restrictions, even with stage construction.