北美土木工程代写 | Life Cycle Cost Analysis

Homework 1:  Life Cycle Cost Analysis

On the basis of present value analysis select one of the three alternative designs for the reconstruction or rehabilitation of 30 lane-km (5 km section, three lanes in one direction and three lanes in the other direction in the project) of an existing rural asphalt concrete pavement that has asphalt concrete shoulders.  Also calculate the Equivalent Uniform Annual Cost for each strategy.

Use a 40 year comparison period and an interest rate of 4 percent.  Comment on whether this is an appropriate analysis period.  Include the salvage value of the pavement layers and traffic delay in your analysis, using a straight line life depreciation curve (assume that the value depreciates linearly over the service life). Note that this is a deterministic analysis.

Show your time and cost graphically for each option.

Assume a 3.7 m lane width, and that the densities of asphalt concrete and portland cement concrete are 2,400 kg/m3 (2.4 tonnes/m3 or 150 pcf), and of open graded asphalt concrete is 1,400 kg/m3. Be careful of units (design is old and metric, costs will be new and English; “tonne” is a metric system unit of mass equal to 1,000 kg [2,204.6 lbs]. “ton” is US short ton that equals to 907.2 kg [2000 lbs])

Use data from across the state.  Prepare plots using data from all districts with data, of unit cost (y-axis) versus average units per project (total amount/number of projects) to pick an appropriate unit cost for each material.

Traffic delay cost is \$10,000 per day for the entire project.  This is referred to as the “lane rental” cost.  It is estimated here.  Contractors will bid how many days they will close, and will pay this rental fee.

Note that these service lives are made up, and may not actually reflect actual performance.

Strategy A.  Concrete whitetopping, JPC with doweled joints

 Activity (Item Code) Service Life (years) Year work done Traffic Delay lane rental (days) Concrete 145 mm overlay (401050) 20 0 15 Remove 145 mm concrete pavement (item says remove asphalt, assume the same, 398000) Concrete 145 mm overlay (401050) 20 20 17 Annual routine maintenance cost Annual cost per lane-mile = \$800 Every year 0

Strategy B.  Repeated rubberized asphalt concrete overlays, mill and fill.

 Activity (Item Code) Service Life (years) Year work done Traffic Delay lane rental (days) Asphalt Concrete 100 mm (390132), 60 mm Rubberized Asphalt Concrete overlay (390137) 17 0 8 Cold plane asphalt pavement (153103), Asphalt Concrete 100 mm (390132), 60 mm Rubberized Asphalt Concrete overlay (390137) 17 17 10 Cold plane asphalt pavement (153103), Asphalt Concrete 100 mm (390132), 60 mm Rubberized Asphalt Concrete overlay (390137) 17 34 10 Annual routine maintenance cost Annual cost per lane-mile = \$2500 Every Year 0

Strategy C. Grind existing AC into aggregate base and compact, place thin overlays, high maintainenance.

 Activity (Item Code) Service Life (years) Year work done Traffic Delay lane rental (days) Full-depth reclamation of 200 mm of asphalt with 4% cement by mass (304000, 304100, 304400) 45 0 18 Asphalt Concrete 60 mm overlay,  (390132), 60 mm Rubberized Asphalt Concrete overlay (390137) 20 0 6 Seal random cracks (374207) 3 17 2 Rubberized open-graded Asphalt Concrete 60 mm overlay (390137) 15 20 6 Cold plane asphalt pavement (153103), Rubberized open-graded Asphalt Concrete 60 mm overlay (390137) 15 35 10 Annual routine maintenance cost Annual cost per lane-mile = \$3000 Every year 0

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