recent posts recent posts - RSS

17 days ago
Topic:
Selection and application of drainage coefficients

Arno Hefer
Arno Hefer
Administrator
Posts: 8
The AASHTO Structural Number (SN) makes provision for the effects of certain levels of drainage on predicted pavement performance. This is achieved using a drainage coefficient (mi) to modify the layer coefficient (ai) integrated into the SN equation along with the layer thickness (Di) input:


SN = a1ˑD1 + a2ˑm2ˑD2 + a3ˑm3ˑD3


The drainage coefficient only applies to the effects of drainage on untreated/natural materials. The designer should assess the level or quality of drainage achieved considering average rainfall and prevailing drainage conditions. The following table contains definitions of drainage levels associated with typical mi ranges as a function of percentage time during a year the pavement structure would approach saturating moisture levels.


For comparison purposes, the conditions at the AASHTO Road Test site are considered “Fair” (free water removed within 1 week) with a drainage coefficient of 1.0.


Recommended drainage coefficient values for modifying the layer structural layer coefficients of untreated layers in flexible pavements (adapted from AASHTO, 1993)



Reference: AASHTO Guide for Design of Pavement Structures (1993). American Association of State Highway and Transportation Officials, Washington, D.C.
edited by on 10/21/2020
10/1/2020
Topic:
Using the Automated Backcalculation Tool

thomas.potgieter@lonrix.com
thomas.potgieter@lonrix.com
Administrator
Posts: 4
The Automated Backcalculation Deflection Tool allows for the automated backcalculation of layer stiffnesses from Falling Weight Deflectometer (FWD) data. This tool also incorporates built-in reporting and statistical analysis features.



Getting Started


The Automated Backcalculation Deflection Tool is accessed through the Deflection Analysis menu on the Rubicon Toolbox Online Tools.
If this is the first time you are using the Online Tools, you will need to set up a project by clicking on the “Manage Projects” link and create a new project. Alternatively, you can use an existing project if one has already been created.



To start, download the example template, enter the relevant data and save the template.




The Excel Template contains sheets for Data, Thickness, Interpretation and Notes. The template needs to be completed exactly as indicated, detailed notes are provided within the template as guidance.


As indicated in the steps to follow, the online module will prompt you to select an appropriate sheet to use. You may therefore create more than one thickness sheet option, e.g. Thickness (2), which may be used for running different layer configuration setups using the same input file. Remember to adjust or create an interpretation sheet with the same number of layers as defined in the new thickness setup if used.


The Thickness Sheet makes provision for 5 layers (including the Upper Subgrade; excluding the semi-infinite Lower Subgrade). Note that the number of layers defined at each Station must be the same throughout.










Running the Analysis


Once you have completed the template, proceed to complete the analysis.
















The default average error per sensor is 10%. A lower value can be selected and will increase the running time.


All deflection points will be analysed if the default station range at the bottom of the window is left unchanged. You can, however, analyse only a section by selecting the begin and end stations under consideration e.g. matching a uniform section, or to speed up running time if the focus is on a shorter section.


Thicknesses are ignored (thickness setting options inactive) if you imported layer thicknesses as part of the data selection process i.e. if you selected the Thicknesses sheet, from the template.


If you selected “Not Applicable” for your Thicknesses, the thickness settings options will become active and you will be able to manually add or delete layers and populate the thickness column.







Once your backcalculation run has completed, the results will display on-screen in a table format.










Note, for a new analysis, the “Save” option is initially inactive. Once an analysis is saved for the first time, the save option becomes active. For overwriting an existing saved analysis, click on “Save”. To save as an alternative analysis, click on “Save As”. Alternatively you can clone your analysis, from the Online Tools page, and rename it as needed.


Reporting









The report can be copied to the clipboard by right clicking on the report and selecting “Copy image” or “Save image as”. The image can then be inserted into a document of your choice (Word, Excel etc.).


Statistical Summary









The statistical summary can be copied to the clipboard by right clicking on the summary and selecting “Copy image” or “Save image as”. The image can then be inserted into a document of your choice (Word, Excel etc.)
edited by on 10/8/2020
9/15/2020
Topic:
Known Issue with Windows 10 and .NET 1.1

Sonia Stamatelos
Sonia Stamatelos
Administrator
Posts: 1
When installing .NET 1.1 on Windows 10 computers, you may encounter an issue whereby .NET 1.1. will not install, as it is not supported by the windows environment. This is a known issue on Windows 10 computers. The latest version of Rubicon Toolbox (version 4.6) resolves this issue and uses .NET 4.5.


Version 4.6 is available for download on our website at www.rubicontoolbox.com. This download is only available for users with a current subscription and a download code is required. Please contact support@rubicontoolbox.com for the download code.
8/27/2020
Topic:
DEMAC Materials Classification System (2020)

thomas.potgieter@lonrix.com
thomas.potgieter@lonrix.com
Administrator
Posts: 4
The DEMAC Material Classification System tool determines the certainty that a material can be classified as a particular material class, based on the standard South African material classes.

Getting Started


The DEMAC Material Classification System Tool is accessed through the Design Tools menu on the Rubicon Toolbox Online Tools.


If this is the first time you are using the Online Tools, you will need to set up a project by clicking on the “Manage Projects” link and create a new project. Alternatively, you can use an existing project if one has already been created.



Click on the “Design Tools” menu and select DEMAC Material Classification System from the list of design tools. Note, there are two versions (2009 and 2020) of this tool available for selection. Depending on which version was selected, the corresponding Materials Classification Report page will open.


To start, download the example template, enter the relevant data and save the template.



Follow the instructions provided closely to complete the Excel template. Test or indicator types should be selected from a drop-down list.




Running the Analysis


Once you have completed the template, proceed to complete the analysis.






Reporting


Once the report options have been set, the Materials Classification Report will generate and display on-screen.




The report can be copied to the clipboard by right clicking on the report and selecting “Copy image” or “Save image as”. The image can then be inserted into a document of your choice (Word, Excel etc.).

Since the template is saved on your PC, the analysis is not saved online. The analysis can be repeated, as and when required.
edited by on 8/28/2020
8/24/2020
Topic:
Layered Elastic Theory Algorithm Accuracy

Fritz Jooste
Fritz Jooste
Administrator
Posts: 6
This post gives an example of the accuracy of the Rubicon Online Tools' Layered Elastic Theory (LET) algorithm. This algorithm is coded in the C# language specifically for Rubicon Toolbox online tools and can handle any number of layers, although generally Rubicon Toolbox online tools restrict you to between 6 and 8 layers depending on the tool you are using.

In this post, we show how the Rubicon Toolbox Online Tools LET Algorithm compares with other well-established and proven algorithms. Specifically, we use the example on page 120 to 122 of Huang's book on Pavement Analysis and Design. Please note that the example provided here is from the First Edition of Huang's book.

The pavement structure used in Huang's analysis is given in the figure below. Note that Huang only provides Imperial units and thus there is a degree of rounding error in the conversion of thicknesses and stiffness values and - more importantly - in the conversion of stresses and strains between these two unit systems. Huang's results are reported only in Imperial units with one or two decimal rounding.

In Huang's example, a rather complex load configuration is assumed. The load configuration is given below, with evaluation positions numbered and indicated in red dots. For each of the four evaluation positions, stresses and strains are evaluated at the bottom of the asphalt layer (depth 151.9 mm) and at the top of the subgrade (457.02 mm).



In Huang's book, stresses, strains and deflections are provided at each evaluation position for the Kenlayer and ELSYM5 algorithms. Huang shows that Kenlayer's results are generally within 2% of those of the older, more established ELSYM5 algorithm.

In the table below, we compare the results obtained with Rubicon Toolbox's Stress-Strain calculator with those given by Huang for ELSYM5. Please note that results had to be converted from SI Units (which are used in Rubicon Toolbox), to Imperial Units. Some errors due to rounding can therefore be expected. We present the comparison of results in three tables: (a) Vertical Deflection; (b) Strains; and (c) Principal Stresses:

The "% Difference" column values were calculated using the ELSYM5 results as base value. Positions where the % difference is above 2% are highlighted in red. A discussion of these results follows below the three tables.

Table (a): Vertical Deflection




Table (b): Strains



Table (c): Principal Stresses


Discussion:
The three tables above shows a close agreement between the Rubicon Online Tools LET Algorithm and the results given by the ELSYM5 algorithm. In most cases, the differences are below 2%, similar to the comparison between Kenlayer and ELSYM5 reported by Huang.

In the case of strain comparisons, two locations (positions 1 and 3, top of the subgrade) have horizontal tensile strains that differ by 7.4% and 8.6% respectively. The reason for this deviation is not known, but comparisons between the (also well established) WESLEA algorithm suggested less than 1% difference between the Rubicon Online Tools algorithm and the WESLEA algorithm.

It is suspected that these differences represent edge cases where small differences between the inputs used by Huang for ELSYM5, and here with the Online Tools, have a significant impact on the results. We believe the weaker correspondence is due to these differences in setup/input assumptions, combined with conversion of printed values, rather than an algorithmic error. It should also be noted that tensile strains at the top of the subgrade are not commonly used in mechanistic analyses.

In the case of Principal Stresses, most results are close to or below 2%. One value, at the top of the subgrade, position 2, has a difference of 5.7%. This higher difference is believed to be a result of the rounding issues related to conversion of results between unit systems. Again, when comparing the results of the Rubicon Online tools with WESLEA, differences are below 1%.
edited by Fritz Jooste on 8/24/2020
8/24/2020
Topic:
DEMAC Material Classification System (2009)

thomas.potgieter@lonrix.com
thomas.potgieter@lonrix.com
Administrator
Posts: 4
The DEMAC Material Classification System tool determines the certainty that a material can be classified as a particular material class, based on the standard South African material classes.


Getting Started


The DEMAC Material Classification System Tool is accessed through the Design Tools menu on the Rubicon Toolbox Online Tools.


If this is the first time you are using the Online Tools, you will need to set up a project by clicking on the “Manage Projects” link and create a new project. Alternatively, you can use an existing project if one has already been created.




Click on the “Design Tools” menu and select DEMAC Material Classification System from the list of design tools. Note, there are two versions (2009 and 2020) of this tool available for selection. Depending on which version was selected, the corresponding Materials Classification Report page will open.


To start, download the example template, enter the relevant data and save the template.




Follow the instructions provided closely to complete the Excel template. Test or indicator types should be selected from a drop-down list.




Running the Analysis


Once you have completed the template, proceed to complete the analysis.








Reporting


Once the report options have been set, the Materials Classification Report will generate and display on-screen.



The report can be copied to the clipboard by right clicking on the report and selecting “Copy image” or “Save image as”. The image can then be inserted into a document of your choice (Word, Excel etc.).


Since the template is saved on your PC, the analysis is not saved online. The analysis can be repeated, as and when required.
edited by on 8/25/2020
edited by on 8/27/2020
7/29/2020
Topic:
How to use the LET Stress-Strain Calculator

thomas.potgieter@lonrix.com
thomas.potgieter@lonrix.com
Administrator
Posts: 4
The LET Stress-Strain Calculator allows you to perform assessments of the stress and strain in one or more pavements. The results of these analyses are exported to a spreadsheet.

The LET Stress-Strain calculator is accessed through the Design Tools menu on the Rubicon Toolbox Online Tools. To start, download the example template and enter the relevant data (load information, contact pressure, and positions of the load).



All inputs are entered through the template for this tool.


Ensure all inputs are correct and save the template on your computer.



Once you have clicked on “OK”, the outputs will automatically download to an Excel file confirming the calculation has run successfully.


Open the sheet to view the results:

edited by on 8/3/2020
edited by on 8/3/2020
edited by on 8/3/2020
5/1/2020
Topic:
Number of layers for analysis

Arno Hefer
Arno Hefer
Administrator
Posts: 8
Arno Hefer
Arno Hefer
Administrator
Posts: 8
Topic: Number of layers for analysis
Since May 2020 the Online Automated Backcalculation Tool can accommodate a minimum of 3 layers and a maximum of 5 layers - including the upper subgrade but excluding the semi-infinite lower subgrade layer.
5/1/2020
Topic:
Temperature Correction of Backcalculated Moduli

Arno Hefer
Arno Hefer
Administrator
Posts: 8
Daily temperature variations occur during deflection surveys, and modulus values determined from backcalculation may therefore exhibit similar trends.
While temperature can affect the modulus values of all pavement layers (including unbound layers) stiffness moduli of thick asphalt layers are normally considered for adjustment during routine analysis and design. The adjustment essentially represents normalization of moduli from varying field temperatures to a reference temperature (20 to 25 degrees Celsius)

The Rubicon Toolbox backcalculation templates make provision for surface and air temperature data measured at each test location. These temperatures are, however, not used in any calculations but only stored in the template and output files for future reference.

The following publications can be used as guidance on temperature corrections of backcalculated pavement layer moduli:
- Publication FHWA-RD-98-012. Mechanistic evaluation of test data from LTPP flexible pavement test sections, Vol.1: Final Report. US Department of Transport, Federal Highway Administration. April 1998.
- Publication FHWA-RD-98-085. Temperature predictions and adjustment factors for asphalt pavements. US Department of Transportation, Federal Highway Administration. June 2000.
edited by Arno Hefer on 5/1/2020
3/31/2020
Topic:
Rubicon Strip Map: Degree-Extent Strip for Visuals

Fritz Jooste
Fritz Jooste
Administrator
Posts: 6
The Degree-Extent strip is designed to plot visual data collected in a Degree and Extent format. Degree and Extent Data can also be plotted in a bar chart format. See this post for details

The Degree-Extent will represent your data by colouring a representative length of each assessment area with the appropriate colour. In the example below, we show Degree = 1 (colour blue) and Extent = 1, mapped to 5% length for the area from 1000 m to 1100 m. Similarly, in the area from 1200 m to 1300 m, we used a Degree = 3 (colour yellow), and Extent 3 (mapped to 30% area). So the idea is that the colours plotted in an area give you a visual idea of the extent of the distress.




Below is an example of how you need to define a Degree-Extent strip in your Stripmap Setup file. The figure below highlights the most important properties that need to be defined for a Degree-Extent strip. For all the other properties, please use the values shown in this example, even though these properties are not explicitly used by the Degree-Extent strip.


Note that the value you supply for the "Decimals" property is used as the Random seed value to randomly position bars over the specified extent. If you do not like the random way the bars are placed, you can try using another value in the Decimals property field. Keeping this value fixed will ensure your plot looks the same every time, unless you change the value in the Decimals field.

You will also note that for the example above, we are retrieving our data from the "Visuals" sheet (you can use any name you want). Also, we are retrieving our Degree ratings from the column "Croc_D" and we get the Extent (%) rating from the "Croc_Perc" column. The figure below shows how your data will typically be defined for this strip type. Note that we are using Excel's VLOOKUP function to convert Extent RATINGS (values typically 1 to 5) to Extent Percentages. For your strip, you need to point to the column that holds the Extent Percentage, and not to the Extent Rating.




To specify the colour ratings for various Degree ratings, you can define and then use an Interpretation Range such as shown below:



Finally, below is an example of a finalized stripmap that includes a Degree-Extent strip at the bottom. You can download the template that was used to create this strip by clicking on the attachments link at the bottom of this post.


edited by Fritz Jooste on 3/31/2020
edited by Fritz Jooste on 3/31/2020
edited by on 9/15/2020
1/30/2020
Topic:
Test Topic Created by Lonrix Team

Karthik Kota
Karthik Kota
Administrator
Posts: 1
Karthik Kota
Karthik Kota
Administrator
Posts: 1
Topic: Test Topic Created by Lonrix Team
This is a test post created by Lonrix Support Team for testing
edited by Karthik Kota on 1/30/2020
edited by on 9/14/2020
1/21/2020
Topic:
Backcalculation Algorithm and Seed Values

Fritz Jooste
Fritz Jooste
Administrator
Posts: 6
The Rubicon Toolbox backcalculation algorithm uses a search methodology which employs heuristics and elements of the Secant-numerical search method. The heuristics component ensures that the search progresses from the lower layers towards to top using a search strategy that approximates the approach an experienced user would adopt when doing manual backcalculation. The Secant-search method ensures a near-optimal convergence rate.

Seed values are simply the mid-points of the search ranges for each layer. This means the search could be made more intelligent and faster when a user selects an appropriate and relatively narrow search range. It is always recommended that a manual backcalculation be performed on a few typical bowls in the set so that the analyst can determine the behaviour patterns and likely deterioration mechanism in the pavement. This will help the analyst pick appropriate search ranges which in turn will ensure the backcalculation results are realistic.

For the sub-stratum layer, the search is automatically limited between a lower stiffness value of 20 MPa (deep/weak/wet substratum) and 1500 MPa (strong sandy or shallow substratum). The initial seed value for the sub-stratum layer is again the midpoint of these two limits, thus 760 MPa.

Note that a distinction is made between the sub-stratum and the upper subgrade. The sub-stratum is assumed to be semi-infinite whereas the upper subgrade is typically assigned a thickness of around 500 mm to 1500 mm depending on the type of subgrade. The user should decide on the most appropriate upper subgrade thickness to use, and experience and site information should be used to guide this decision. If, for example, the subgrade is known to consist of deep clay then the thickness of the upper subgrade should be set to 1500 mm or deeper. If, however, there are signs of a shallow subgrade such as rock outcrops, or if the subgrade consists of coarse-grained, stress-stiffening materials, then a shallower depth should be assumed.

Note that the sub-stratum layer does not have to be included in design forward calculations. This is because the stresses-and-strains in the pavement structure are not influenced by the deeper subgrade. The deflections, however, are influenced by deeper subgrade conditions and therefore in backcalculation the sub-stratum needs to be included to mimic deeper subgrade conditions.

edited by Fritz Jooste on 1/30/2020
9/6/2019
Topic:
The LET Standard Axle Design Tool

Arno Hefer
Arno Hefer
Administrator
Posts: 8
Arno Hefer
Arno Hefer
Administrator
Posts: 8
Topic: The LET Standard Axle Design Tool
Yes, an overloading analysis can be done as suggested. Also see the LET Load Spectrum Analysis Tool which can be setup using real axle load data from weigh-in-motion measurements.
6/11/2019
Topic:
Drawing Visual Assessment Data in a Stripmap

Brenda Umutoni
Brenda Umutoni
Posts: 1
I have used the previous version of the strip map, and now need help using the online version.
1/27/2019
Topic:
Number of layers for analysis

Arno Hefer
Arno Hefer
Administrator
Posts: 8
Arno Hefer
Arno Hefer
Administrator
Posts: 8
Topic: Number of layers for analysis
Hi Donna.
The number of layers for analysis using the online tools is fixed.
The deflection offset at each sensor is read from the excel template column header. The format Dxxx is used, where xxx represents the sensor offset in mm. You can therefore adjust the geophone number and locations as needed.
edited by arnoh@icon.co.za on 1/27/2019
1/9/2019
Topic:
Number of layers for analysis

Donna James
Donna James
Posts: 1
Hi - is there a way to reduce the number of layers for analysis and the location of the geophones?
12/8/2018
Topic:
The LET Standard Axle Design Tool

Hophine Mollel
Hophine Mollel
Posts: 1
Can I do analysis my incrementing the standard axle by lets say 10% overloading 0r 20% 0verloading so that I can see the effect on pavement from the same designed pavement using standard axle.
3/29/2018
Topic:
Problems with installing .NET 1.1

Alan Thomson
Alan Thomson
Posts: 1
Hi
Out IT team are trying to install Rubicon desktop onto some new 64 bit, Windows 10 computers and report that they cannot install .NET 1.1 because it is not supported in this environment. Can you advise if this is a recognised issue, and if so, what is the workaround?
3/25/2018
Topic:
How the Backcalculation Error is Calculated

pieter van niekerk
pieter van niekerk
Posts: 1
Would it not be better to use the Root mean square error rather than pure arithmetic mean.
6/30/2017
Topic:
Backcalculation using Benkelman beam data

Arno Hefer
Arno Hefer
Administrator
Posts: 8
Similar to the desktop Deflection Bowl Analysis module, the Manual Backcalc online tool makes provision for a Benkelman Beam load setup. This process works as follows:
  • Go to Online Tools/ Deflection Analysis/ Manual Backcalc;
  • Download the Template to your computer and populate with the data;
  • In the online tool click on Select Data. Browse and select the data file. You will be prompted to select the data sheet and layer thickness sheet to use;
  • You will be automatically be guided to the Backcalculation Settings window where the appropriate load can be defined.
  • These settings can alternatively be accessed by clicking on the Options button.