Development and Implementation of a Performance-Related Specification for I-65 Tennessee: Final Report

Chapter 4. Implementation of the Performance-Related Specification

The evaluated I-65 construction work was completed between May and October 2004. It included two outside lanes in both the northbound and southbound directions. Fourteen lots (24 ft [7.3 m] wide) were placed, ranging in length from 1,180 to 2,380 ft (359.7 to 725.4 m). Photos of the PCC pavement placement are shown in figures 5 and 6.

Figure 5. General view of concrete pavement construction on northbound I-65.

Figure 5. Photograph. General view of concrete pavement construction on northbound I-65. View from hillside of paving machine and dump truck operating in northbound lanes with traffic moving in southbound lanes.

Figure 6. General view of concrete pavement construction on northbound I-65.

Figure 6. Photograph. General view of concrete pavement construction on northbound I-65. General view of concrete pavement construction on northbound I-65. View from hillside of paving machine and dump truck operating in northbound lanes with traffic moving in southbound lanes.

Layout of Lots and Sublots

The layout and sampling of typical sublots within a lot are shown in figure 7. The width of the lot is the width of paving: one, two, or more traffic lanes, typically. Sampling is random within each sublot.

Figure 7. Layout and sampling of typical sublots.

Pay Adjustment Computation Equations

The lot composite (overall) pay factor is computed as follows.

PF_composite = (PF_PI*PF_strength*PF_thickness)/10000 (5)

Where:

PF_composite = Composite (overall) pay factor, %
PF_strength = Compressive strength pay factor (obtain from table 9), %
PF_thickness = Slab thickness pay factor (obtain from table 10), %
PF_PI = Initial PI pay factor (obtain from table 11), %

Averaging of pay factors from each AQC could have also been used; however, the multiplicative model is believed to more closely approximate actual performance and LCC analysis.

The actual pay adjustment for an as-constructed lot is computed using the lot composite pay factor as follows. Pay adjustments will be made only on the individual lots.

PAYADJ_Lot = BID * AREA_Lot * (PF_composite – 100)/100 (6)

Where:

PAYADJ_Lot = Pay increase (+) or decrease (-), $
BID = Contractor bid price for pay item (31.95, $/yd²)
AREA_Lot = Measured actual area of the as-constructed lot, yd²
PF_composite = Composite pay factor (from equation 5), percent (e.g., 101 percent is expressed as 101.0)

PAY_Lot = BID * AREA_Lot + PAYADJ_Lot(7)

Where:

PAY_Lot = Adjusted payment for the as-constructed lot, $

The absolute minimum value of the Composite Pay Adjustment Factor for a given lot was limited to 80 percent, and the absolute maximum value was limited to 110 percent.

Testing and Calculations of Pay Factors

Samples were collected and tests were run, as required, for each sublot and lot. The results were recorded in a spreadsheet. The example shown in figure 8 contains results for a typical lot with four sublots. The pay factors were calculated for thickness, strength, and smoothness separately. The overall lot pay factor was then determined, and the contractor pay for the lot was calculated as shown. Results from all 14 lots are provided in appendix B.

A set of expected pay charts are provided in appendix C.

Figure 8. Spreadsheet used for calculating pay factors for thickness, strength, and smoothness for each sublot; overall lot pay factor; and contractor pay.

Click on the image link for a description of the image.

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Updated: 04/07/2011