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3 days ago
Topic:
Deflection at the 200 mm offset: Warning

Arno Hefer
Arno Hefer
Administrator
Posts: 9
The following figure shows a deviation of the measured deflection at the 200 mm offset from the expected deflection bowl (green line). This phenomenon is typically observed in FWD measurements recorded on highly flexible pavements. This error occurs due to the positioning of the sensor at the 200 mm offset close to the edge of the load plate; essentially the result of a stress wave induced by the impact load and non-uniform stress distribution under the relatively rigid load plate, with higher stress intensity towards the plate edge.


Recommendations on deflection analysis where deviation of the deflection at the 200 mm offset is present:
  • Deflection bowl parameters: Deflection based parameters that rely on the deflection at the 200 mm offset, such as the Radius of Curvature, should be interpreted and use with caution where this phenomenon occurs.
  • Backcalculation: When fitting the theoretical deflection bowl, the process should focus on the adjacent sensors while omitting the deflection recorded at the 200 mm offset.

edited by on 1/20/2021
edited by on 1/20/2021
10 days ago
Topic:
How to use the LET Axle Spectrum Analysis Tool

Sonia Stamatelos
Sonia Stamatelos
Administrator
Posts: 10
The LET Axle Spectrum Analysis allows you to evaluate the impact of an axle spectrum on a pavement’s design capacity. An axle spectrum can be built and analysed for a specific design situation. The axle spectrum can consist of any number of axle types, with optional seasonal variation of both the axle spectrum and material properties.


Getting Started

The LET Axle Spectrum Analysis 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.



Once you have created a new project or selected an existing project, click on the “Design Tools” menu and select “LET Axle Spectrum Analysis” from the list. A LET Axle Spectrum Analysis page will open. Proceed with the following steps to complete the analysis, working from left to right.









Note, if loads are not available for selection it means that the default loads have not been setup or selected and you will need to pre-define your loads before you can proceed further. Default loads and materials can be defined by clicking on “Settings” from the left-hand navigation menu.



Defining the Pavement Structure