# Presentation: 920766

## Rigid Pavement Design Deficiencies

- Major shortcomings of JPCP designs based on 1972-1986 versions of the AASHTO Guide :
- inadequate joint load transfer,
- long joint spacing,
- erosion of base/subbase,
- poor subdrainage
- etc.
- Deterioration occurs early
- Rehabilitation needed

**Notes:**
These and other weaknesses of the JPCP based on 1972 to 1986 AASHTO rigid pavement design procedures have been known for many years.

A significant number of JPCP (and JRCP) pavements have failed because the design procedure was weak.  In the hands of inexperienced engineers, in particular, it provided poor guidance for good design.

## Development of Supplemental AASHTO Design Procedure for JPCP  

- Serious deficiencies noted in 1986 AASHTO procedure
- Studies showed major flaws in base/subgrade support procedures
- No easy fixes
- Improved structural (3D finite element) model for JPCP was developed to correct deficiencies

**Notes:**
The deficiencies of the 1986 AASHTO procedure were serious.
There were no easy fixes.
Structural factors had to be addressed.  
A reliable design procedure is, after all, based on understanding structural factors and modeling them.
To address these problems, a new  structural 3-D finite element model was developed that better characterized the performance of pavements.  

We had learned from LTPP studies across the country over the years more about the performance of pavements (over time and under specific conditions).  This aided in the calibration of the model.

## Development, Validation, Adoption:  1998 Supplemental Rigid Pavement Design Procedure

- Developed under NCHRP Project 1-30
- 	(University of Illinois at Urbana-Champaign)
- Validated under FHWA/LTPP research study
-    (ERES Consultants/ARA)
- Adopted by AASHTO as Supplementary Rigid Pavement Design Procedure (1998)
- FHWA/LTPP - Supplementary Rigid Pavement Design Spreadsheet (ERES Consultants/ARA)

**Notes:**
The new design procedure that resulted from the structural modeling was validated using LTPP data.
The procedure was adopted by AASHTO.

And tools like the design spreadsheet (that we shall get into shortly) are available to help design better JPCP pavements.

## Only JPCP For Now

**Jointed plain **
**concrete pavement**
**(JPCP)**

-  Most constructed rigid
- pavement
-  Basic design procedure
- developed
-  Procedure field verified

**Jointed reinforced**
**concrete pavement**
**(JRCP)**
**Continuously reinforced**
**concrete pavement**
**(CRCP)**

-  Limited field verification

**Notes:**
The structural model was developed specifically for JPCP.
JPCP is by far the most constructed rigid pavement in the United States.
The design procedure is valid for JPCP and has been field tested.

Only limited verification was performed for JPCP and CRCP, and additional verification is needed.

## 1998 AASHTO JPCP Design Is Better

- Improved structural modeling
- Improved subgrade characterization
- Base course as structural layer
- Transverse joint spacing
- Climate at site is considered directly
- Shoulder type and slab width
- Joint faulting and cracking checks

**Notes:**
The 1998 AASHTO design procedure for JPCP is better than previous versions for several reasons as shown on this slide.

## Use of LTPP Data to Verify1998 AASHTO Design

- Design procedure verified using field data from LTPP
- Inputs to 1998 AASHTO design model obtained
- Actual traffic log ESALs compared to predicted log W (ESALs)
- No significant bias found in predicting serviceability of pavements in four climatic zones

**Notes:**
The use of LTPP data to verify the design procedure further validates the fact that we now have a better model of pavement performance, and a much better, and improved design procedure.

In addition, LTPP has developed the Rigid Pavement Design software to help you use the new design procedures to build better pavements.

## PRESENTATION OBJECTIVES

- What is the Rigid Pavement Design (RPD) Software?
- Development of RPD Software
***RPD Software Features and Capabilities ***
- How To Use The RPD Software
- Who Should Use the RPD Software and Why
- How to Get the RPD Software

**Notes:**
Before we get to how one uses the software, let me show you some of the features and capabilities of the software.

## Rigid Pavement Design Spreadsheet: Features

*Information* sheet containing spreadsheet “User Guide”

**Notes:**
The start up sheet in the rigid pavement design software includes information regarding the use and features of the spreadsheet.  

## Rigid Pavement Design Spreadsheet: Features

- Command buttons for easy navigation between sheets

**Notes:**
The spreadsheet has command button macros for easy navigation between sheets.

## Rigid Pavement Design Spreadsheet: Features

- Command button links to reference tables

**Notes:**
The spreadsheet also has links to tables.  For example:  Table 14 button is a link to a table that has values for slab base friction factor that can be used for different base types.

## Rigid Pavement Design Spreadsheet: Features

**Notes:**
Joint spacing and edge support conditions are direct inputs to the supplemental rigid pavement design 

## Rigid Pavement Design Spreadsheet: Features

- True subgrade k-value is used (not adjusted for top-of-base)

**Notes:**
Climatic properties such as mean annual wind speed, mean annual air temperature, and mean annual precipitation are direct inputs to the supplemental rigid pavement design procedure.

The k-value used in the supplemental rigid pavement design procedure is a true subgrade k-value adjusted only for seasonal changes and fill/rigid layer.  No adjustment is made for base layer.  The base layer is treated as a structural layer rather than through an increase in subgrade k-value.

## Rigid Pavement Design Spreadsheet: Features

- Easy links to sensitivity analysis for various design inputs

**Notes:**
Sensitivity analysis can be performed after an initial design.  After entering the slab thickness, an option button such as that for k-value or joint spacing or modulus of rupture etc. can be clicked which is a link to the corresponding sensitivity analysis chart.

## Rigid Pavement Design Spreadsheet: Features

- Project data can be saved in rows and exported to the main sheets

**Notes:**
By using the Save Data feature of the spreadsheet, inputs for one design can be saved and a new design can be started on the same spreadsheet.  This eliminates saving this 1+ MB spreadsheet over and over again for each design.  The saved data can easily be retrieved by selecting a row and clicking on the export button.

## Rigid Pavement Design Spreadsheet: Features

- Sensitivity Analysis plot displays inputs held constant

**Notes:**
The sensitivity analysis is a plot of the design variable (eg. Joint spacing) versus design traffic given all other inputs are constant.  The constant inputs are displayed along side the graph for easy reference. 

## Rigid Pavement Design Spreadsheet: Features

*Results* sheet can be viewed on screen or can be printed

**Notes:**
The rigid pavement design spreadsheet also has a Results sheet that can be view on screen or can be printed.

## Rigid Pavement Design Spreadsheet: Features

*Calculation* sheet shows all calculations and displays design traffic for different slab thicknesses

**Notes:**
The Calculation  sheet of the rigid pavement design software shows all the calculations for different thicknesses and traffic.  As you scroll to the right of this sheet all inputs and calculated values can be seen.

## Rigid Pavement Design Spreadsheet: Features

*Faulting Check* sheet used to estimate faulting over design life for doweled and nondoweled pavements

**Notes:**
A faulting check is performed in the rigid pavement design spreadsheet separately for both doweled and nondoweled pavements.  The average faulting can be estimated over the design life of the pavement.  This can be compared with critical values.  If the faulting at the end of the design life is greater than the critical value, then the design needs to be changed. 

## PRESENTATION OBJECTIVES

- What is the Rigid Pavement Design (RPD) Software?
- Development of the RPD Software
- RPD Software Features and Capabilities
***How To Use The RPD Software***
- Who Should Use the RPD Software and Why
- How to Get the RPD Software

**Notes:**
So how does one use the Rigid Pavement Design software?

## Systems Requirements

- IBM PC running:
- 	Microsoft Office 95 or 97 or
-    Microsoft Excel 7.0

**Notes:**
First, here are the system requirements for using the software.

## Using The RPD Software

- Copy the Rigid Pavement Design (RPD) Software spreadsheet to the hard drive
- The RPD software cannot be run from the floppy drive
- Open the RPD spreadsheet using Microsoft Excel

**Notes:**
Once you’ve identified that you have the appropriate system, then the rigid pavement design spreadsheet needs to be copied to the hard drive before it can be executed.  The RPD spreadsheet can be opened and run in MS Excel versions 95 or higher.

## Using The RPD Software

- Click on *Enable Macros* to allow execution of spreadsheet macros

**Notes:**
When the RPD spreadsheet is opened, Microsoft Excel detects the macros in the spreadsheet and asks whether they should be enabled or disabled.  Macros are visual basic programs written in the spreadsheet to execute certain tasks.

The RPD software can only be used if the Enable Macros button is selected.

## Using The RPD Software

- Click on *Input Form* to access the main sheet

**Notes:**
The RPD spreadsheet software opens on the Information sheet.  This sheet contains general information and guidance for using the program.  This sheet also contains reference tables for guidance regarding input values.

Click on Input Form to open the main sheet.

## Using The RPD Software

- Enter General Information for the project as shown below:

**Notes:**
General information for the project is for reference only and is not used in the analysis.

## Using The RPD Software

- Scroll down to enter Serviceability and PCC Properties

**Notes:**
The inputs for this design problem include:

Initial Serviceability: 4.5
Terminal Serviceability: 2.7
PCC Modulus of Rupture: 700 psi
PCC Elastic Modulus: 4,200,000 psi
PCC Poisson’s Ratio: 0.15

## Using The RPD Software

- Enter Base Properties, Reliability, and Standard Deviation

- Click on *Table 14* for friction factors for different base types

**Notes:**
This design example is for a PCC pavement with a 6-in bituminous-treated base.  Click on Table 14 button for a table that displays elastic moduli and friction factors for various base types.  For this design example:

Elastic modulus of base: 350,000 psi
Base thickness: 6 in
Slab-base friction factor: 5.8

Reliability: 90%
Standard Deviation: 0.34

Note that for the supplemental rigid pavement design procedure a lower standard deviation of 0.34 (compared to 0.39) can be used.  

## Using The RPD Software

- Click on *Input Form* to navigate back to the main screen

**Notes:**
The Table 14 button on the previous slides is a link to the table shown above.  Click on the Input Form button to return to the main screen.

## Using The RPD Software

- Select Pavement Type and Edge Support Condition

- Enter Joint Spacing

**Notes:**
Enter the joint spacing and select pavement type and edge support conditions.  For this design example:

Joint spacing: 15 ft
Jointed plain concrete pavement with tied concrete shoulders. 

## Using The RPD Software

- Enter Climatic Properties for the design region.  Click on *Table 15* for climatic properties for major metropolitan areas in each State.

- For the _first run_ enter the approximate subgrade k-value

**Notes:**
Enter Climatic Properties for the design region.  The Table 15 button is a link to a table containing climatic properties for major metropolitan areas.  For this design example:

Mean annual wind speed: 8 mph
Mean annual air temperature: 52.5 0F
Mean annual precipitation: 45.5 in

For the first run, enter the approximate subgrade k-value (without seasonal adjustment).  This is required to calculate an approximate thickness.  The seasonal adjustment is based on this approximate thickness.  If a seasonal adjustment is not performed then an iteration is not required and the value entered should be the design subgrade k-value.

It is important to note that the value entered here is the true subgrade k-value and not and effective or “bumped-up” k-value.

## Using The RPD Software

- Click on *Calculate Traffic* for traffic calculation worksheet

**Notes:**
The traffic value can either be entered directly on the main sheet or can be calculated in the traffic calculation worksheet and exported to the main sheet.

## Using The RPD Software

- After entering traffic design inputs click *Calculate*

- Click *Export to Input Form*

**Notes:**
The traffic calculation worksheet has 13 rows to enter percent of ADT, growth rate, truck factor, and truck factor growth rate for each FHWA vehicle class.  After entering the other inputs including performance period, two-way ADT, number of lanes in each direction, and lane and directional distribution factors click on Calculate button.  Note that the total percent of the 13 FHWA vehicle classes should equal 100.

The design traffic for this example is 21.3 million ESALs.  Click on Export to Input Form to export this value to the main form. 

## Using The RPD Software

- Click on *Calculate* on the main sheet to calculate thickness for design inputs

- Click on *Calculate Seasonal k-Value* for calculating seasonally adjusted k-value

**Notes:**
Click on the Calculate button to calculate the thickness for the design inputs.  The calculated thickness for the design inputs is 10.04 in.

This thickness is required to calculate seasonal adjustment for k-value.  If the k-value entered needs to be adjusted for seasonal variations click on the Calculate Seasonal k-Value button to navigate to the seasonal k-value worksheet. 

## Using The RPD Software

- Enter number of months and subgrade k-value for each season.  Click *Calculate.*

**Notes:**
The k-Value information button can be used to access information regarding procedures for calculating subgrade k-values.

Enter the number of months in each season and the corresponding subgrade k-value.  Click on the Calculate button for the seasonally adjusted subgrade k-value.  If no adjustment for fill or rigid layer is required click on Export to Input Form to export the calculated k-value to the input form.

If an adjustment to the subgrade k-value is to be made for the effect of fill or rigid layer click on Export to Fill/Rigid Adjustment Sheet.  

## Using The RPD Software

- Use the chart to estimate adjusted k-value for fill layer above the subgrade and/or rigid layer beneath the subgrade

**Notes:**
Use the chart on Fill/Rigid Layer Adjustment Worksheet to adjust subgrade k-value for fill layers above the subgrade or rigid layers in the subgrade.

Enter this value in the space provided and click on the Export to Input Form button to export this adjusted value to the main sheet.

## Using The RPD Software

- Click on *Calculate* on the main sheet to recalculate thickness for design inputs with the adjusted k-value

**Notes:**
The design thickness needs to be recalculated for the adjusted k-value by clicking on the Calculate button.

The new design thickness is 10.03 in.

## Using The RPD Software

- Enter thickness for sensitivity analysis

- Click *Slab Thickness Sensitivity* for sensitivity analysis of design traffic to slab thickness

- Click on radial buttons for sensitivity analysis of design traffic to different design inputs

**Notes:**
Sensitivity analysis of design traffic to slab thickness can be performed by clicking on Slab Thickness Sensitivity.

Sensitivity analysis of design traffic to other design variables can be performed by clicking on the appropriate radial button. 

## Using The RPD Software

**Notes:**
Clicking on the Slab Thickness Sensitivity  on the previous screen performs the sensitivity analysis and opens the worksheet displaying the sensitivity analysis chart.

## Using The RPD Software

**Notes:**
Clicking on the radial button for k-value sensitivity performs the corresponding sensitivity analysis and displays the corresponding chart.  Note that the other design inputs that are held constant are displayed along side the graph.

## Using The RPD Software

- Click on *Faulting Check* to perform checks for doweled and nondoweled faulting

**Notes:**
The next step after designing the slab thickness (which is a function of other design features such as base type and thickness, joint spacing, and shoulder type) is to perform the faulting checks.

## Using The RPD Software

- Enter dowel diameter and other design inputs for doweled pavements

**Notes:**
Many of the values for doweled faulting such as elastic modulus of dowel bar, modulus of dowel support etc. have default values that have already been entered.  These can be changed if needed.  Enter the dowel diameter and the slab thickness.

Dowel diameter: 1.5 in
Slab thickness: 10.00 in

(Assume that the slab thickness calculated in the design sheet is rounded to 10 in).

## Using The RPD Software

- Click on *FI Table* or *Drainage Coeff. Table* for tables containing information regarding these inputs

- Click *Calculate* to obtain estimated faulting at end of design life

- Click *Results* to view and print results

**Notes:**
For the design input entered, the calculated faulting using 1.5 in dowels is 0.06 in.  Because this faulting is less than the critical value provided, the faulting check indicates “PASS.”

Design inputs:

Freezing index: 250 0F-days
Annual temperature range: 65 0F
Drainage coefficient: 1.00
Age: 30 years
Traffic: 21.3 million ESALs.

## Using The RPD Software

- Enter design inputs for nondoweled faulting check and click *Calculate*

- Click *Corner Break Check* to perform top-down cracking analysis

**Notes:**
For the design input entered, the calculated faulting for nondoweled pavement is 0.10 in.  Because this faulting is more than the critical value provided, the faulting check indicates “FAIL.”

Design inputs:

Freezing index: 250 0F-days
Number of days above 900 F:  20
Drainage coefficient: 1.00
Age: 30 years
Traffic: 21.3 million ESALs.

Because the nondoweled faulting check has failed either dowels must be used or the design must be changed.  (Example better drainage can be provided to increase the drainage coefficient from 1.0 to 1.1 or 1.2.  This reduces nondoweled faulting to below the critical level.  

## Using The RPD Software

- The critical values for joint faulting can be changed by entering the appropriate values below

**Notes:**
The default critical values for joints spaced less than 25 ft is 0.06 in and for joints spaced more than 25 ft is 0.13 in.  These critical values can be changed by entering the appropriate values.

## Using The RPD Software

- On the *Corner Break Check *worksheet enter the built-in temperature gradient related to construction curling and moisture gradient

**Notes:**
The first step is to enter built-in temperature gradient related to construction curling and moisture gradient.  This is entered in units of 0F/in.  For this design example the value is: 1.5 0F/in

## Using The RPD Software

- Use one of six charts provided to estimate tensile stress at top of slab from total effective negative temperature differential

**Notes:**
Six charts are provided on this sheet for estimation of tensile stress at top of the slab as a function of total effective negative temperature differentail.  Use one or more of these charts to estimate the tensile stress at the top of the slab and enter the value in the space provided.

## Using The RPD Software

- The tensile stress at the top of the slab is less than the bottom up tensile stress for which the pavement is designed

**Notes:**
If the estimated tensile stress at the top of the slab is less than the tensile stress at the bottom of the slab (for which the pavement is designed) then the design is acceptable.

If the estimated tensile stress at the top of the slab is greater than the tensile stress at the bottom of the slab then the design needs to be changed.  One way of doing this is increasing the slab thickness.

The Corner Break Check Worksheet indicates a “PASS” as shown.  Click on Results at the top of this worksheet to navigate to the results sheet.

## Using The RPD Software

*Results* sheet can be viewed on screen or can be printed

- Click *Save Data* to save the design information entered

**Notes:**
The rigid pavement design spreadsheet also has a Results sheet that can be view on screen or can be printed.

## Using The RPD Software

- Enter ID for saving data and click *OK*

**Notes:**
Clicking on Save Data prompts the user to enter the ID for a particular data set.

## Using The RPD Software

- All design information is saved in rows with the first column corresponding to the data set ID

- Select appropriate row and click *Export* to export design information from this sheet to main sheet.  This sheet can be accessed by clicking on *Retrieve Data* on the main sheet.

**Notes:**
Design information is stored in rows on a worksheet named Saved Data.  The first column is the ID for the corresponding row of data.  Select a row and click on Export to export data from this sheet to other sheets in the spreadsheet.

This sheet can be accesssed from the main sheet by clicking on Retrieve Data.  

## PRESENTATION OBJECTIVES

- What is the Rigid Pavement Design (RPD) Software?
- Development of the RPD Software
- RPD Software Features and Capabilities
- How To Use The RPD Software
***Who Should Use the RPD Software & Why***
- How to Get the RPD Software

**Notes:**
Should you use this tool?

## Users of the RPD Software

- State and Provincial Highway Engineers
- Consulting Engineers

**Notes:**
If you are a state of provincial highway engineer or a consulting engineer who provides pavement designs for state/provincial highway agencies, this is a tool for you.

## Benefits of Rigid Pavement Design Software

- Provides key answers not previously addressed:
- How do I adequately characterize the subgrade support?
- What is the best base type for the conditions?
- What is the optimum joint spacing?
- Will this pavement fault or have corner breaks?

**Notes:**
You should use it because it provides answers you were unable to address before.  For example, it will help you:
--  characterize subgrade support,
--  determine the best base type for the conditions,
--  determine optimum joint spacing, 
--  determine if the pavement will fault or have corner breaks.

## PRESENTATION OBJECTIVES

- What is the Rigid Pavement Design (RPD) Software?
- Development of the RPD Software
- RPD Software Features and Capabilities
- How To Use The RPD Software
- Who Should Use the RPD Software & Why
***How to Get the RPD Software***

## Get & Use The Software

** ****Order software:**
**   ****--  Through LTPP homepage**
**	****www.tfhrc.gov**
**   ****--  Through LTPP customer service**
**	****Call 865-481-2967**