Work Zone Mobility and Safety Program

CA4PRS Use in Washington State

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CA4PRS Use in Washington State

by
Jeff Uhlmeyer, State Pavement Engineer


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WSDOT Efforts to Mitigate Construction Impacts:

  • Alternative contracting
  • Rapid construction strategies
  • Alternative closure windows
  • Specialized materials
  • Training and education


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CA4PRS: A tool for estimating contractor productivity

  • Estimates contractor productivity given:
    • Traffic closure window
    • Lane availability and use for construction
    • Construction materials
    • Pavement structure
    • Scheduling constraints
    • Resource constraints


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Screen shot of the CA4PRS Construction Analysis for Pavement Rehabilitation Strategies tool's PCCP Probabilistic - I-5 Early Scoping and Design Screen. The resource profile table, shown, requires user inputs for demolition hauling truck, batch plant, concrete delivery truck, base delivery truck, and paver.



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Analysis Options and Results
Construction Window: Weekend Closure (55 hours/weekend)
Working Method: Sequential Single Lane (T2)
Section Profile: PCCP: 13.0 inches, New Base: 0.0 inches
Curing Time: 8 hours
Objective (lane-miles): 2.22
Maximum Possible (lane-miles) 0.57
Maximum Possible (c/l-miles) 0.57
Construction Windows Needed to Meet Objective: 3.90


Resource Utilization
Resource Allocated Utilized
Demolition Hauling Truck (per hour per team) 6.0 6.0
Base Delivery Truck (per hour) 8.0 0.0
Batch Plant (cu-yd/hour) 200.0 77.1
Concrete Delivery Truck (per hour) 12.5 10.3


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CA4PRS productivity estimates can assist:

  1. Evaluating different closure scenarios
  2. Selecting most appropriate closure strategy
  3. Identifying equipment and material requirements
  4. Identifying ranges of potential contractor productivity
  5. Verifying contractor productivity estimates


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CA4PRS and WSDOT

  1. Is CA4PRS appropriate for projects in Washington State?
  2. At what level of project planning is CA4PRS applicable?
  3. How should WSDOT use CA4PRS?


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I-5 Olive to James Rehabilitation

  • Reconstructed outside lanes, drop lanes and ramp segments
  • Removed of 6,500 yd3 of material
  • Placed of 2,500 tons of HMA base and 5,640 yd3 concrete pavement
  • Four 55-hour weekend closures
Three maps of the I-5 rehabilitation project area: macroscopic, mesoscopic, and microscopic (i.e., aerial). The mesoscopic and microscopic maps highlighted the segment of I-5 to be rehabilitated.

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Project Location

Photo of an underpass on I-5.



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Four photos of various construction activities on a section of I-5 that runs under a series of overpasses.

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Paving Quantities and Stage Paving Lengths (lane-miles)

Stage

Fixed Form Paving
(yd3)

 Slipform Paving
(yd3)		 Total Paving Quantity
(yd3)		 Stage Psuedo Length
(lane-miles)
Stage 1 776 1100 1876 0.74
Stage 2 572 995 1567 0.62
Stage 3 488 808 1296 0.51
Stage 4 364 540 904 0.36

Total Paving Quantity: 2.22 (yd3)
Total Stage Psuedo Length: 2.22 lane-miles
Average Paving Length Per Stage: 0.56 lane-miles.


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Construction Sequence

  • Establish traffic control and installation of construction barrier
  • Demolish and remove existing pavement
  • Subgrade repair


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Construction Sequence

  • HMA base paving
  • PCC paving
  • PCC curing, sawcutting and pavement marking
  • Removal of equipment and traffic control


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Job Specific Constraints

  • Narrow work zone
  • Slipform paving machine constraints


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Job Specific Constraints

  • Paving lane access
  • Adjacent commercial development
  • Site access


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Construction Process

Two side-by side photos of the narrow constuction area on I-5 below an overpass, one with traffic congestion and the other with free flowing traffic conditions.



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Job Specific Constraints

Two side-by side photos of the narrow constuction area on I-5 below an overpass.



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1st Analysis: CA4PRS Applicability For Early Scoping and Design Evaluation

  • Sufficient project information available for CA4PRS estimate development
  • Input parameters established from similar and previously completed projects
  • Slipform and fixed form operations combined into a pseudo paving speed of 2.67 ft/min


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1st Analysis: CA4PRS Applicability For Early Scoping and Design Evaluation

Two photos of construction work, one of workers smoothing a cement surface, the other of a concrete paver.

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Combination chart and table show the estimated minimum, mean, and maximum lane-miles paved per weekend closure are 0.54, 0.6, and 0.67, respectively. Number of required weekend closures is 4.11 (minimum), 3.69 (mean), and 3.31 (maximum).



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2nd Analysis: CA4PRS Applicability For Post-Award Pre-Construction Evaluation

  • Contractor schedules used to refine:
    • Construction sequencing
    • Activity lag times
    • Mobilization and demobilization times


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Combination chart and table show the estimated minimum, mean, and maximum lane-miles paved per weekend closure are 0.47, 0.52, and 0.57, respectively. Number of required weekend closures is 4.72 (minimum), 4.28 (mean), and 3.89 (maximum).



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CA4PRS Guidelines

  • Base decisions on probabilistic outputs
  • Maintain a database of construction productivity
  • Assign triangular distributions to probabilistic inputs if distribution data is unavailable
  • Round estimated construction windows up to nearest whole number


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Evaluation Conclusions

  1. CA4PRS can be used during early scoping and design as well as post-award pre-construction verification
  2. Produce estimates from probabilistic analysis
  3. CA4PRS estimates are reasonably accurate with generic input parameters


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Evaluation Conclusions

  1. Input parameter selection determines estimate accuracy
  2. Input parameter variation may not encompass productivity for constrained projects
  3. CA4PRS requires further refinement to make it more generic and flexible


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CA4PRS at UW

  • The University of Washington graduates 120 civil engineers each year to meet regional demand
  • CEE 404 Infrastructure Construction
    • Transportation project development and construction
    • CA4PRS combines real-world information with project planning


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CA4PRS Analysis
I-5 Bow Hill,
Crack and Seat Overlay



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Project Parameters

  • Crack and Seat and Overlay two NB lanes of I-5 between MP 231.8 to MP 243.33 (south of Bellingham, WA)
  • 20 lane-miles
  • Classified as a rural freeway with a 23,000 ADT and 9% trucks
  • Two 12-ft lanes with a 4 feet inside and a 10 feet outside shoulders
  • Constructed in 1966 using 9 inches of JPCP
  • Rehabilitated in 1993 with a 4 inch HMA overlay and sub-sealing due to considerable faulting


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Construction Process

  • Expose PCCP pavement by milling the 4 inch overlay Shoulders remain as is, no milling
  • Divert traffic on SB I-5 lanes using counter-flow traffic operations
  • Overlay the crack and seat slabs with 8 inches of HMA pavement in three lifts: 4 inch initial lift followed by two additional 2 inch lifts


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Construction Scenarios

  • Baseline. All operations (milling, crack and seat and the full 8 inch overlay paving) are accomplished during each closure.
  • Baseline but with 2 Milling teams and 2 paving teams. It is likely that 2 milling and paving teams (e.g., 2 milling machines and 2 paving machines) can operate in the project area.
  • Just milling 4.2 inches of mainline pavement with 2 milling teams. An obvious breakpoint in the work would be after milling off all the HMA in the mainline.
  • Just milling 4.2 inches of mainline pavement with 4 milling teams 50% efficiency. The lower efficiency is an attempt to account for the added complexity of operations with 4 milling teams.
  • Crack and seat plus a 4.2 inch overlay to bring the mainline pavement height up to the existing shoulder height. This operation would follow the "just milling" one.
  • Overlay the final 4.0 inches for the mainline and shoulders. This operation would follow the "crack and seat plus 4.2 inches overlay" one.


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Baseline Inputs: Activity Constraints
Input Value Distribution/Comments
Mobilization 1.0 hour None – Deterministic.
Set traffic control, mobilize equipment.
Demobilization 2.0 hours

None – Deterministic.
Remove traffic control and equipment.
Half Closure Traffic Switch 0.5 hours Triangular (min = 0.25 hrs, max = 0.75 hrs).
Time to switch traffic if only closing 1 lane in NB direction.


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Baseline Inputs: Resource Profile
Input Value Distribution/Comments
Milling and Hauling
Number of Team 1 team None – Deterministic.
Team Efficiency 0.8 Triangular (min = 0.7, max = 0.9)
Milling Machine
Machine Class Large Choices are large, medium, small
Material Type AC – Hard Good choice for hard rock in western WA
Efficiency Factor 0.7 Triangular (min = 0.6, max = 0.8)
Tooth replacement may affect downtime.
Hauling Truck
Rated Capacity 18.0 tons None – Deterministic.
Trucks/hr/team 13/hr Triangular (min = 11/hr, max = 15/hr)
Packing Efficiency 1 None – Deterministic.


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Baseline Inputs: Resource Profile (cont'd)
Input Value Distribution/Comments
Batch Plant
Capacity 350 t/hr Triangular (min = 300 t/hr, max = 400 t/hr)
Number of Plants None – Deterministic.
HMA Delivery Truck
Capacity 16 tons

None – Deterministic.
Anticipate trucks with pups with total capacity of truck and pup at about 32 tons. This means, on average each dump will be filled with 16 tons of mix.

Trucks per Hour Triangular (min = 11/hr, max = 15/hr)
Packing Efficiency None – Deterministic.
Paver None N/A (no base material)
Non-paving speed 15 mph


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Baseline Schedule Analysis
Input Value Distribution/Comments
Construction Window weekend
nighttime
continuous
 55-hour weekend closures
10-hour nighttime closures
168-hour continuous week-long closures
Section Profile 2-2-4

Bottom lift: 4 inches (0.33 mph for paver)
Middle lift: 2 inches (0.66 mph for paver)
Top lift: 2 inches (0.66 mph for paver)
Change in Roadway Elevation +4 inches
 The new roadway will be 4 inches higher than the old after milling and overlaying.


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Baseline Inputs: Resource Profile (cont'd)
Input Value Distribution/Comments
Shoulder Overlay Simultaneous Shoulders already contain 4.2 inches of HMA. They will be overlayed with an additional 4 inches of HMA.

Working Method
 Full closure Only allowed option in CA4PRS.
Cooling Time Analysis
 User Spec.

Time calculated in MultiCool and manually entered
Lane Widths
No. of Lanes 2
Lane Widths
 12 ft each Travelled lanes only


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MultiCool Input Parameters: Constant Inputs for All Scenarios
Input Value
Start Time 1000, 7/15/2011
Environmental Conditions
Ambient Air Temp. 60°F
Average Wind Speed 5 mph
Sky Conditions Clear&Dry
Latitude 44° North
Existing Surface
Material Type PCC
Moisture Content N/A
State of Moisture N/A
Surface Temp. 55°F


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MultiCool Inputs in All Scenarios (cont'd)
Input Value
Mix Specifications
Mix Type Dense Graded
PG Grade 70-22
Delivery Temp. 300°F
Stop Temp. 130°F
Lift Thicknesses
1st 4 inches of HMA Paved as one 4-inch lift
2nd 4 inches of HMA Paved as two 2-inch lifts


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Baseline Results
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures Not possible N/A N/A
55-hour weekend closures 1.01 lane-miles 19.71 1084.3 hrs
Continuous closure 38 days to pave 20 lane-miles 38 days to pave 20 lane-miles 905.4 hrs
Constraints: Milling Machines, HMA trucks


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Milling Teams and 2 Paving Teams
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures Not possible N/A N/A
55-hour weekend closures 1.92 lane-miles 10.43 573.7 hrs
Continuous closure 21 days to pave 20 lane-miles 21 days to pave 20 lane-miles 498.3 hrs
Constraints: HMA batch plant, Milling machine


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Just Milling with 2 Milling Teams
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures 1.47 lane-miles 13.60 190.4 hrs
55-hour weekend closures 7.01 lane-miles 2.85 156.9 hrs
Continuous closure 7 days to mill 20 lane-miles 7 days to mill 20 lane-miles 498.3 hrs
Constraints: Milling machine


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Just Milling with 4 Milling Teams at 50% efficiency due to congestion
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures 1.84 lane-miles 10.89 52.5 hrs
55-hour weekend closures 8.75 lane-miles 2.29 125.7 hrs
Continuous closure 6 days to mill 20 lane-miles 7 days to mill 20 lane-miles 498.3 hrs
Constraints: Milling machine


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Crack and Seat + Overlay first 4.2 inches (4 inches mainline, no shoulder paving)
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures 0.09 lane-miles 233.34 3266.7 hrs
55-hour weekend closures 11.82 lane-miles 1.69 93.0 hrs
Continuous closure 4 days to pave 20 lane-miles 4 days to pave 20 lane-miles 88.7 hrs
Constraints: Batch plant


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Just Overlay final 4.0 inches (4 inches mainline and shoulder paving)
Scenario Closure Production Construction Windows Total Working Hours
14-hour nighttime closures 0.65 lane-miles 30.99 733.9 hrs
55-hour weekend closures 7.25 lane-miles 2.76 151.7 hrs
Continuous closure 6 days to pave 20 lane-miles 6 days to pave 20 lane-miles 157.2 hrs
Constraints: Batch plant


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Graph shows a comparison of the number of 14-hour night closures reqiuired for each operation. Milling with 2 teams would take 14 closures, milling with 4 teams would take 11 closures, CSOL for the first 4.2 inches would require 234 night closures, and a final 4 inch overlay would require 31 night closures.



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Graph shows a comparison of the number of 55-hour weekend closures required for each operation. The entire operation would taek 10.43 closures, milling with 2 teams would take 2.85 closures, milling with 4 teams would take 2.29 closures, CSOL for the first 4.2 inches would require 1.69 closures, and a final 4 inch overlay would require 2.76 closures.



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Graph shows comparison of the number of continuous 24-hour per day closures required for each operation. The entire operation would take 21 such closures, milling with 2 teams would take 7 closures, milling with 4 teams would take 6 closures, CSOL for the first 4.2 inches would require 4 closures, and a final 4 inch overlay would require 6 closures.



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Observations

  • 10-hour nighttime closures were not considered. They are less productivity than 14-hour closures
  • Milling may be possible during 14-hour nighttime closures. No other modeled operation seems feasible
  • No probabilistic scenarios were run but it is reasonable to add the following uncertainties to the estimates:
    • 14-hour nighttime closures: ±5 days
    • 55-hour weekend closures: ±1 weekend
    • Continuous closures: ±2 days


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Observations

  • The best possible solution is likely a combination of closure scenarios
    • Milling – performed over 14 nighttime (14 hour closures)
    • CSOL and overlays (8 inch total) performed over five 55 hour closures
  • No traffic analysis was done at this point. Results may become clearer with traffic numbers


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Contact Information

Jeff Uhlmeyer, State Pavement Engineer

Washington State Department of Transportation


360-709-5485


uhlmeyj@wsdot.wa.gov

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