Truck Distribution for Flexible Pavement Design



PAVEMENT DESIGN

FOR

KASOLD DRIVE

CLINTON PARKWAY TO 15TH STREET

LAWRENCE, KANSAS

Project No. 14251.001 BARTLETT & WEST ENGINEERS, INC.

September, 2004 628 Vermont Street

Lawrence, Kansas 66044

INTRODUCTION

In this report, rigid and flexible pavement systems are designed for the proposed Kasold Road project, from Clinton Parkway to 15th Street in Lawrence, Kansas. The arterial will consist of four to five lanes with concrete curb and gutter and necessary storm sewer improvements. The purpose of this report is for the design and comparison of pavement systems for the project. The road design for the project is being done by Bartlett & West Engineers, Inc. and construction is planned to begin in 2005. The pavement systems are designed for the street in accordance with the methods described in the “American Association of State Highway and Transportation Officials Guide for Design of Pavement Structures”, 1993 edition (AASHTO Guide).

DESIGN PARAMETERS

The AASHTO Guide pavement design method requires input parameters relative to the pavement system which describe the traffic loadings that will be imposed on the system, soil conditions, concrete parameters, pavement design reliability, and pavement serviceability. The pavement design criteria will be taken the Kansas Department of Transportation and from AASHTO. The analysis period for the pavement design will be 30 years. Listed below are the values used for these design parameters in this report.

Traffic

Traffic loadings over the design life of the pavement are expressed as equivalent 18-kip single axle loads (ESAL). This expression is used as a common unit of measure which allows summation of different axle loads and configurations from a mixed traffic stream.

2025 future traffic volumes, provided by the City of Lawrence, were used in this analysis. These traffic volumes and distribution are attached at the end of this document. Assuming a linear relationship, the traffic volumes are averaged to calculate the daily two-way traffic volume for the 30 year analysis period. A directional distribution factor of 60% and a lane distribution factor of 100% are applied to the daily traffic volume.

Once the traffic volume is established, the traffic mix must be determined to assess the weights and axle loadings which will be applied to the pavement system over the analysis period. Due to the lack of statistical information in the immediate area of the proposed improvements, average distribution values were used. These values are based upon similar traffic mixes, as stated in the Kansas Department of Transportation (KDOT) study “Kansas Truck Weight Survey 1994 and 1992-1994 Combined”. Refer to Appendix A for a complete listing of the traffic distribution. Average axle load equivalency factors are also taken from the study to convert the loadings into ESALS.

Soil Conditions

Site geotechnical investigations were performed by GeoSystems / Kleinfelder, in June 2004. Soil samples were taken from 14 borings extending 6 to 10 feet below the existing ground surface drilled on the proposed project site.

The borings were monitored while drilling and after completion for the presence and level of groundwater. Groundwater was not observed in the borings. This may have been influenced by the time of year and the low permeability of the cohesive soils encountered in the borings.

Typically, the subgrade material is a fat clay material. Most of the soils encountered in the borings will have a high shrink-swell potential. Based on this typical classification, we estimate the soil design characteristics to be:

Subgrade Modulus, k, = 165 p.c.i.

Modulus of Elasticity = 4000 p.s.i.

The subgrade modulus was adjusted to account for loss of support using AASHTO Guide methods. A loss of support factor of 0.80 was used for a fly-ash treated subgrade. The resulting effective modulus of subgrade reaction is 100 p.c.i.

Fly-ash treatment of the clay subgrade soils will significantly reduce the shrink-swell potential. The City has had success on recent projects using fly-ash treated subgrades. Therefore, only fly-ash treated subgrades were looked at in this report.

Other Design Parameters

The characteristics and joint transfer information pertaining to the rigid pavement system and statistical standard deviation estimates were generally obtained from recommendations listed in the AASHTO Guide. A reliability factor of 90%, design period of 30 years, and serviceability loss of 2.5 also reflect values recommended by AASHTO Guide for urban arterials.

PAVEMENT SYSTEMS

In this pavement design both rigid and flexible pavement systems are analyzed. The flexible system is an asphaltic concrete surface course, asphaltic concrete base course, a bound drainable base course on a fly-ash treated subgrade. The rigid systems analyzed include a full-depth concrete pavement with a fly-ash treated subgrade.

Input parameters and the resulting required pavement depths for the 30-year analysis period are given on the following pages.

FLEXIBLE PAVEMENT SYSTEMS

Kasold Rd. (30-YEAR)

Design ESALs 6,980,000

Reliability (%) 90

Overall Deviation 0.45

Modulus of Elasticity (psi) 4000

Drainage Coefficient 1.20

PSI Loss Due to Traffic 2.14

AASHTO Guide Required Pavement Structural Number (SN) 5.5

The Structural Number relates to the pavement thickness as follows:

SN = a1 D1 + a2 D2 M2 + a3 D3 M3

Where: D1, D2, D3 are layer depths

a1, a2, a3 are layer coefficients

M2, M3 are drainage coefficients

When full depth asphaltic pavements are used, the drainage coefficients are not used. Typically, the following layer coefficient values are used:

asphaltic concrete surface course - 0.42

asphaltic concrete base course - 0.34

bound drainable base - 0.14

fly-ash treated subgrade - 0.11

Actual AASHTO pavement design algorithms and pavement design calculations are available upon request.

Alternate 1 2” asphaltic concrete surface course

10” asphaltic concrete base course

4” bound drainable base

9” fly-ash treated subgrade

RIGID PAVEMENT SYSTEMS

Kasold Rd. (30-YEAR)

Design ESALs 8,520,000

Reliability (%) 90

Overall Deviation 0.35

Concrete Modulus of Rupture (psi) 650

Concrete Modulus of Elasticity (psi) 3,600,000

Pavement Type (Load Transfer) 2.80

Modulus of Subgrade Reaction (pci) (9” lime treated subgrade) 100

Drainage Coefficient 1.15

PSI Loss due to Traffic 2.0

AASHTO Guide Required Pavement Depth

10” Concrete pavement on 9” fly-ash treated subgrade

Actual AASHTO pavement design algorithms and pavement design analysis available upon request.

ECONOMIC ANALYSIS

The KDOT’s Life Cycle Cost Analysis Procedure is chosen to make the economic comparison of the two alternatives. Typical maintenance activities for both flexible and rigid systems were used to determine future maintenance costs. These future maintenance activities for flexible systems include a two inch mill and overlay every 10 years after construction. Crack filling will occur throughout the life of the pavement. Rigid systems do not have a future maintenance planned, they are assumed to last for the entire 30 year design life. Crack and joint sealing will occur as necessary. This analysis procedure assumes that for major rehabilitation projects, the salvage value at the end of the analysis period will be equivalent. Thus this value does not enter into the present worth analysis.

Quantities are calculated for the two pavement systems and future overlays using guidelines from KDOT’s “Design Manual Volume II. Using these quantities and recent bid tab information from KDOT, initial construction costs were determined for each of the pavement systems. The initial construction cost estimate is shown in Table 1.

In the life cycle cost analysis, the present cost of future actions are inflated by 5%. All future costs and salvage values are then discounted at a rate of 7% to attain a present worth to be used for comparison. The present worth calculations for each pavement system are shown below. The following is a summary of the present worth costs of the both pavement system alternatives:

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TABLE 1

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Flexible Alternate $1,574,248.58

Rigid Alternate $1,815,405.74

Flexible Alternate which is a 2” surface course, a 10” base course, a 4” bound drainable base on 9” of fly ash subgrade proved to be the most economical section.

Flexible 30 Year Traffic Volumes & Distribution

|Truck Vehicle Types Based Upon |

|Kansas Truck Weight Survey 1994 and 1992-1994 Combined |

| | | | | | |

|  |  |  |  |PERCENT OF |

|VEHICLE TYPE |TOTAL VOLUME |

|SINGLE |TWO AXLE FOUR TIRE | |14.40 |  |

|UNIT |TWO AXLE SIX TIRE | |1.30 |  |

|TRUCKS |THREE AXLE OR MORE |  |0.80 |  |

|SINGLE |  | | |  |  |

|TRAILER |FOUR AXLE OR LESS | |0.40 |  |

|TRUCKS |FIVE AXLE OR MORE | |1.40 |  |

|  |  |  |  |  |  |

|MULTI-TRAILER |FIVE AXLE OR LESS | |0.08 |  |

|TRUCKS |SIX AXLE OR MORE |  |0.04 |  |

|  |PERCENT HEAVY TRUCKS* |  |4.0 |  |

|*LESS TWO AXLE FOUR TIRE SINGLE UNIT TRUCKS | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

|Traffic Volumes |

| | | | | | |

| | | | | | |

| | | | | | |

|2004 Base - 19,800 vehicles per day | | | | |

| | | | | | |

|2025 Future - 31,000 vehicles per day | | | | |

| | | | | | |

|2034 Future - 38,100 vehicles per day | | | | |

| | | | | | |

| | | | | | |

|Worksheet for Calculating 18-kip Equivalent Single Axle Load (ESAL) Applications |

| | | | | | |

|Location: Kasold Road | |Analysis Period = | |30 |Years |

|Lawrence, Kansas | |Assumed SN or D = | |5.5 |= SN |

| | | | | | |

| | | |2004 ADT | |19800 |

| | | |2034 ADT | |38100 |

| | | |%TRUCKS | |4 |

| | | |%Directional Distribution | |60 |

| | | |Number of Lanes | |5 |

| | | |Lane Distribution Factor | |1 |

| | | |Terminal Servicability | |2.5 |

| | | | | | |

|  |  |  |Design |E.S.A.L. |  |

|  |Current |Design |Lane |Factor |Design |

|  |Traffic |Traffic |Traffic |(D) |E.S.A.L. |

|Vehicle Types |(A) |(B) |(C) |per 1000 |(E) |

|  |Daily |Daily |Total |Vehicles |  |

|  |  |  |  |  |  |

|Passenger Cars and Pickup Trucks |19008 |27792 |  |  |  |

|Total Heavy Trucks |792 |1158 |  |  |  |

|Other 2-Axle/4-Tire Trucks |2737 |4169 |27389016 |1 |27389 |

|2 - Axle/6-Tire Trucks |257 |376 |2472620 |250 |618155 |

|3 or More Axle Trucks |158 |232 |1521612 |429 |652772 |

|  |  | |  |  |  |

|4 Axle or less |79 |116 |760806 |610 |464092 |

|5 Axle or more |277 |405 |2662821 |1267 |3373794 |

|  |  | |  |  |  |

|5 Axle or less |16 |23 |152161 |3160 |480829 |

|6 Axle or more |8 |12 |76081 |3006 |228698 |

|  |  |  |  |  |  |

|All Vehicles |19804 |28956 |35035116.3 |  |5845729 |

| | | | | | |

| | | |USE |6,980,000 ESALS |

| | | | | | |

|Sample Calculations: | | | | | |

| | | | | | |

|(C) 30 years x 365 days/yr x (.60) x (1.0) x (Design Traffic Daily (B)) | | |

| | | | | | |

|(D) ESAL Factor for Rural Highway from "Kansas Truck Weight & Volume Study" | |

| | | | | | |

|(E) Design ESAL = (Design Lane Traffic) x (ESAL Factor)/1000 | | |

| | | | | | |

| | | | | | |

| | | | | | |

|The Structural Number relates to the pavement thickness as follows: | | |

| | | | |

| |SN = |a1 D1 + a2 D2 M2 + a3 D3 M3 | |

| |Where: |D1, D2, D3 are layer depths | | |

| | |a1, a2, a3 are layer coefficients | |

| | |M2, M3 are drainage coefficients | |

| | | | | | |

|When full depth asphaltic pavements are used, the drainage coefficients are not used. | |

|Typically, the following layer coefficient values are used: | | | |

| | | | | | |

|asphaltic concrete surface course |0.42 | | | |

|asphaltic concrete base course |0.34 | | | |

|bound drainable base | |0.14 | | | |

|fly-ash treated subgrade | |0.11 | | | |

| | | | | | |

|Based upon the above information, two possible flexible pavement systems are as follows: | |

| | | | | | |

|Alternate 1 |2" |asphaltic concrete surface course | |

| |9.5" |asphaltic concrete base course | |

| |4" |bound drainable base | | |

| |9.0" |fly-ash treated subgrade | | |

Rigid 30 Year Traffic Volumes & Distribution

|Truck Vehicle Types Based Upon |

|Kansas Truck Weight Survey 1994 and 1992-1994 Combined |

| | | | | | |

|  |  |  |  |PERCENT OF |

|VEHICLE TYPE |TOTAL VOLUME |

|SINGLE |TWO AXLE FOUR TIRE | |14.40 |  |

|UNIT |TWO AXLE SIX TIRE | |1.30 |  |

|TRUCKS |THREE AXLE OR MORE |  |0.80 |  |

|SINGLE |  | | |  |  |

|TRAILER |FOUR AXLE OR LESS | |0.40 |  |

|TRUCKS |FIVE AXLE OR MORE | |1.40 |  |

|  |  |  |  |  |  |

|MULTI-TRAILER |FIVE AXLE OR LESS | |0.08 |  |

|TRUCKS |SIX AXLE OR MORE |  |0.04 |  |

|  |PERCENT HEAVY TRUCKS* |  |4.0 |  |

| | | | |

|*LESS TWO AXLE FOUR TIRE SINGLE UNIT TRUCKS | | | |

| | | | | | |

| | | | | | |

| | | | | | |

| | | | | | |

|Traffic Volumes |

| | | | | | |

| | | | | | |

| | | | | | |

|2004 Base - 19,800 vehicles per day | | | | |

| | | | | | |

|2025 Future - 31,000 vehicles per day | | | | |

| | | | | | |

|2034 Future - 38,100 vehicles per day | | | | |

| | | | | | |

|Worksheet for Calculating 18-kip Equivalent Single Axle Load (ESAL) Applications |

| | | | | | |

|Location: Kasold Road | |Analysis Period = | |30 |Years |

|Lawrence, Kansas | |Assumed SN or D = | |5.5 |= SN |

| | | | | | |

| | | |2004 ADT | |19800 |

| | | |2034 ADT | |38100 |

| | | |%TRUCKS | |4 |

| | | |%Directional Distribution | |60 |

| | | |Number of Lanes | |5 |

| | | |Lane Distribution Factor | |1 |

| | | |Terminal Servicability | |2.5 |

| | | | | | |

|  |  |  |Design |E.S.A.L. |  |

|  |Current |Design |Lane |Factor |Design |

|  |Traffic |Traffic |Traffic |(D) |E.S.A.L. |

|Vehicle Types |(A) |(B) |(C) |per 1000 |(E) |

|  |Daily |Daily |Total |Vehicles |  |

|  |  |  |  |  |  |

|Passenger Cars and Pickup Trucks |19008 |27792 |  |  |  |

|Total Heavy Trucks |792 |1158 |  |  |  |

|Other 2-Axle/4-Tire Trucks |2737 |4169 |27389016 |1 |27389 |

|2 - Axle/6-Tire Trucks |257 |376 |2472620 |256 |632991 |

|3 or More Axle Trucks |158 |232 |1521612 |646 |982961 |

|  |  | |  |  |  |

|4 Axle or less |79 |116 |760806 |651 |495285 |

|5 Axle or more |277 |405 |2662821 |2119 |5642518 |

|  |  | |  |  |  |

|5 Axle or less |16 |23 |152161 |3225 |490720 |

|6 Axle or more |8 |12 |76081 |3263 |248251 |

|  |  |  |  |  |  |

|All Vehicles |19804 |28956 |35035116.3 |  |8520114 |

| | | | | | |

| | | |USE |8,520,000 esals |

| | | | | | |

| | | | | | |

|Sample Calculations: | | | | | |

| | | | | | |

|(C) 30 years x 365 days/yr x (.60) x (1.0) x (Design Traffic Daily (B)) | | |

| | | | | | |

|(D) ESAL Factor for Rural Highway from "Kansas Truck Weight & Volume Study" | |

| | | | | | |

|(E) Design ESAL = (Design Lane Traffic) x (ESAL Factor)/1000 | | |

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