Automatically Optimize Noise Barriers
CadnaA is able to determine automatically the required height of a noise protection wall/barrier which is needed to obey given maximum levels by means of iterative calculation. The optimization occurs for up to four evaluation parameters.
Note
The wall optimization is limited to a maximum of 100 receivers. In addition, due to the algorithm applied, no multi-threading is used in the calculation, thus requiring more computation time - especially with many active receivers - than a normal calculation at receivers.
Example
Path: Examples\Obstacles\OptimizeBarriers\ OptimizeBarriers_1.cna
Due to the object’s data structure, for such an optimization the object „Embankment“ is used a nd not the object „Barrier“.
The following example shows the sequence of actions.
Road with a Noise Barrier and a Receiver Point
The represented road exceeds the permitted value at the receiver point. Therefore a noise barrier shall be constructed in the given position in such a way that the permitted value is not exceeded.
To perform an optimizing calculation it is necessary to assign the relevant maximum value as a standard Level (in dBA) to the receiver points. It is not relevant whether the maximum value has been entered directly or whether it is determined from the type of land use. In the latter case, it might need to define suitable types of land use first (see Type of Land Use).
The optimization occurs for up to four evaluation parameters simultaneously.
Receiver: standard level assigned
The object „Embankment“ must be given
- a slope of 1:0 and
- a top width of 0
Do not enter a value for height - this is what CadnaA is supposed to determine.
dialog Embankment: all values zero
In the next step we subdivide the noise barrier with the „Break into Pieces“ command from the context menu of the Embankment. In the example 10 sections of identical size have been formed. Now select an appropriate view in the menu Options|3D-View, e.g. isometric.
Options|3-D-View „Isometric“
Start to optimize
In the toolbar of this dialog you can find the symbol „Optimize Barrier“. After clicking, the parameter dialog will open and we can define our strategy of optimization. The table below shows two possible settings:
 |
 |
|---|---|
| Settings A | Settings B |
In the upper text box a pattern similar to the group definition can be entered by which only the walls with identical IDs will be integrated into the optimizing calculation. With settings A all activate embankments are considered within the optimization, while with settings B only the embankments with the string Barrier plus two additional characters.
With every step of the calculation a barrier section is raised by the value given in „element height“. The shorter the sub-elements are and the smaller the element height is, the longer the calculation takes. The result of multiplying „Element Height“ by „Maximum Number of Elements“ is the upper limit for the height of the barrier.
In the following combo box you can select the name „area“ or enter any other name, e.g., the product name of a noise barrier. In the first case, the value 1, in the four subsequent boxes, will remain unchanged and optimization is executed in a way that the entire surface of the noise protection wall is minimized. With the setting A the further sample calculation is executed.
With settings B in the right figure takes into consideration the fact that the costs per square-meter can depend on the height of the noise barrier because costs for a foundation have to be apportioned and because, with the increasing height of the wall, greater wind pressures will have to be withstood. Optimizing is then executed in a way that will minimize the total cost. Please note that the combo box „Cost/m²“ must not be left without an entry. The cost schedule of a noise barrier can be saved/deleted with the corresponding buttons. A saved cost schedule, valid for all projects, will be at your disposal in the combo box.
After the setting A has been confirmed, the optimizing calculation starts.
Subdivision of the noise barrier into sections of 10m each - Calculation with the settings A
An element width of 3 m leads to the following representation.
Subdivision of the noise barrier into sections of 3m each - Calculation with setting B
CadnaA first checks if the maximum value („Standard Level (dBA)“) has been exceeded at the maximum height of all wall elements - in this case a message box will pop up. After the corresponding modification of the configuration the calculation will be restarted.
Please note that with optimizing barriers all settings of the program will be considered. This is valid for projection, reflection and consideration of all activated elements. Owing to the large number of steps of calculation it is always advisable to deactivate all objects that have no effect on the result. Another alternative is to cut the relevant part out of the entire project - the optimized wall will then be imported into the project.
Example
Path: Examples\Obstacles\OptimizeBarrierGap.cna
In the following example a noise barrier will be positioned in the given location in front of a gap in a way that a maximum value, given for the receiver point behind the gap, can be maintained.
Initial Situation
In this case the wall is subdivided into 42 elements with a width of 1 m. This leads to a contour of the upper edge of the wall as shown in the illustration below. Calculation was executed „strictly according to RLS90“ with buildings considered as non-reflecting.
Optimizing a barrier with calculation „strictly according to RLS-90“
Now, the calculation is repeated with buildings considered as reflecting, considering reflections up to the 5th order. Lateral diffraction will also be included, in opposite to the standard procedure of RLS-90. This is appropriate in this case as this situation cannot be evaluated correctly ignoring lateral diffraction. As the result shows, a much higher wall would be necessary to meet this non-trivial situation.
Optimizing a barrier with a 5th order reflection
With the optimization of barriers CadnaA is able to perform an efficient positioning of noise reducing constructions.