8. Basis for Comparison
Basis for Comparison: Life Cycle Costs
Initial cost to construct
Annual work activities, maintenance and inspections
Repair and Preservation Activities (10 years)
Minor rehabilitation projects (20 years)
Major rehabilitation projects (50 years)
Residual Values
Net Present Value (NPV)
10. Life Cycle Costs: Net Present Values
Cost basis = Year of Bid Tabulation Data
Design Life Term = 75 years
Interval timeline = 10 years; 20 years; 50 years
Discount rate = 2.7% per year
n
NPV = Σ RCFt / (1+i)t
t=0
where:
RCFt
i
n
=
=
=
Real Cash Flow
Annual Discount Rate
term
to calculate NPV:
11. Life Cycle Costs: Net Present Values
Calculations
Microsoft Office Excel Function
13. Purpose of the Papers
To give local infrastructure managers a guide and
reference to use when scoping and evaluating a site
for a bridge project.
Ensures all costs and factors are considered,
including life cycle costs.
Real world sites and examples.
14. Case Study – Rail Grade Separation
Structure Type Study
Narrative (19 Pages)
Alternate Descriptions
Life Cycle Cost Analysis
Evaluation Matrix
Evaluation of Alternatives
Evaluation of NPV of
Alternatives
Conclusion & Summary
4 Appendices with drawings,
cost estimates, etc.
15. • Low structural rating
• Single lane
• Blind curves on
approach roadway
Ezell Road (Before)
16. 2009 and 2011 aerials provided by USDA NCRS
Ezell Road Alignment (Before & After)
17. Early Feasibility Decisions
One track & two tracks considered along with One
Span and Three Span bridges.
Crane Location & Lifting Method
19. Span Arrangements – Ezell Road
Number of
Spans
Single or Double
Track
Main Span
over Track
(29˚ Skew)
Total
Bridge
Length
Three Single* 45 feet 113 feet
Three Double 62 feet 154 feet
One Single* 112.5 feet 112.5 feet
One Double* 112.5 feet 112.5 feet
*CSXT requested that the bridge span two tracks in the future, although it
was not planned, in terms of which side the track would be added, or if
the tracks would be realigned, symmetrically along the centerline. It was
therefore permitted to assume that the future project would construct
retaining walls using soil nailing or tie backs to accommodate the
required area.
20. Lifting Method – Ezell Road
Lifting
Method
Temporary
Haul Road &
Staging Area
Crane Size
& Crane Pads
Railroad
Impacts
Track Side
• Haul road
envisioned down
the side slopes
of the railroad
cut
• Limited storage
area at track
level
• Lighter Cranes
• Smaller Pads
• More Force
Account Work
and Flagman
Controls
• Slow Progress
• Diminished
Safety
Approach
Roadway
• No haul road
• Simpler staging
• Heavier Cranes
• Larger Pads
• Less Force
Account Work
• Faster Progress
21. Alternatives – Ezell Road
Final Alternates:
Alt. 1 – Single Span P/S AASHTO Girders
Alt. 2 – Single Span Steel Plate Girders
Alt. 3 – Single Span Steel Pony Truss Girders
23. Compare Depths & Weights
Four - AASHTO IV (54”) Girders
Indiv. Girder Weight = 91,130 lbs.
Superstructure Members: $101,250
Grade Raised by 6.5 ft.
Four - 55 3/16” Plate Girders
Indiv. Girder Weight = 27,705 lbs.
Superstructure Members: $112,720
Grade Raised by 5.0 ft.
W30x108 Floor Beam
Indiv. Truss Girder Weight = 35,060 lbs.
Superstructure Members: $200,000
Grade Raised by 3.6 ft
24. Results - Ezell Road
Comparisons Alternate 1
(Single-Span
P/S Girders)
Alternate 2
(Single-Span
Steel Plate Girders)
Alternate 3
(Single-Span Steel
Truss Girders)
Initial Project
Cost (+/- % Min.)
$1,039,609
(+31.2%)
$1,033,157
(+30.4%)
$792,142
(0.0%)
Life Cycle Cost
(+/- % Min.)
$1,402,9417
(+29.7%)
$1,388,823
(+28.4%)
$1,082,055
(0.0%)
Disturbed Area 1.3 Acres 1.1 Acres 0.9 Acres
Right of Way 0.30 Acres 0.28 Acres 0.2 Acres
Profile Grade/
Structure Depth
Raised by 6.5 ft
Ttotal 5.72 ft
Raised by 5.0 ft
Ttotal 4.60 ft
Raised by 3.6 ft
Ttotal 3.56 ft
Foundation
- Pile caps (43’x3.5’)
- Six HP 14x73 /abut
- Pile Wt. = 42,415
lbs
- Retaining walls
- Pile caps (43’x3.0’)
- Four HP 14x73
/abut
- Pile Wt. = 28,035
lbs
- Pile caps (41’x3.0’)
- Eight HP12x53
/abut
- Pile Wt. = 40,600
lbs
Savings of $241,000
Grade change reduction of 2.90
ft.
25. Results – Ezell Road
Comparisons Alternate 1
(Single-Span
P/S Girders)
Alternate 2
(Single-Span
Steel Plate Girders)
Alternate 3
(Single-Span Steel
Truss Girders)
Environmenta
l
Impact
• SWPPP req’d for
disturbance over 1 acre
• Add’l permitting &
const- ruction
inspections
• SWPPP req’d for
disturbance over 1 acre
• Add’l permitting & const-
ruction inspections
• Land disturbance less
than one acre
Construction
Method
• Long beams are difficult
to transport
• Heavy crane and track-
level staging area
req’d for lifting beams
(91 kips)
• Long beams are difficult
to transport
•Medium crane and track-
level staging are req’d for
lifting beam pairs (28
kips)
• Trusses transported in
sections with
bolted conn.’s
• Medium crane and small
staging area from the
approach roadway (35
kips)
Construction
Schedule
• Estimated 10 weeks in
the railroad red
zone
• Add’l time for grading
activities and construction
of retaining walls
• Estimated between 2 and
10 weeks in the
railroad red zone
• Shop welding is labor QC
intensive
• Estimated 2 weeks in the
railroad red zone
• Trusses are
prefabricated
26. Conclusions – Ezell Road
A single span alternative was selected as a prudent
way to minimize current construction costs while
providing for expansion to two tracks in the future.
Alternate 3 (steel truss) had the least impacts to the
project footprint in terms of raised grade, disturbed
area and right-of-way acquisition.
Alternate 3 (steel truss) was the least cost
alternative of the final superstructure alternates
saving the client $241,000.
Alternate 3 (steel truss) has the 2nd lightest
foundation and 2nd lightest crane lifts among the
alternatives.
27. What Have We Learned
Comprehensive costs are important to evaluate.
In the case of smaller bridge projects, changes in
profile grade have a great affect on the overall
project costs.
Costs embedded in items such as “Mobilization”,
“Cofferdams-/Cribbing/Sheeting”, or permitting can
also affect the overall costs and should be evaluated
appropriately.
For certain span lengths and certain sites, steel truss
bridges provide a way to shorten the length that a
controlling member must span and therefore they
provide a way to reduce the project’s profile impacts.
