6a. Algor Surface


Structural Simulation using Algor

Surface structure Tokyo Cathedral


User Interface

Tree views: The tree view shows the analysis parameters that will be used. Each of the environments (the tabs at the bottom of the tree view) perform a different function, as described below.

FEM Editor: This environment is the primary modeling environment. This environment is used to create meshes, apply loads and constraints, define element, material and analysis parameters and perform the analysis.

Results: This environment is used to view the results of all analyses.

Report: This environment is used to generate an HTML report to present the results of the analysis.  Images and animations created in the Results environment can be inserted in to the report.

1 Importing model

After modeling in Rhino, click ‘Autudesk Aglor’ and ‘Mesh’. The model will be directly imported to Algor. You can also import the model by .step file.

Scene after importing to Algor

Units can be changed by double clicking ‘Models Units’ in the tree views.

2 Contact

By default, different parts of model are bonded together. The other types of contact are welded, free/no contact, surface contact, edge contact. The details of different types of contact will be discussed in the following parts.

Bolded: The two surfaces will be in perfect contact and the loads are transmitted from one part to the adjacent part.

Welded: Only the nodes along the edges of the contact surfaces will be ‘bonded’. The nodes along the interior of these surfaces would be ‘free/no contact’.

A test is shown as below.

A surface fixed on ground is overlapping with a smaller surface. The surfaces are welded. An upward force is applied at the centre of smaller surface. The edge of the smaller surface is remain attached to the larger surface, but the central part is pulled upwards.



Free/No contact: The two surfaces are totally separated

Surface contact: Two surfaces contacted together with friction  

Edge contact: Only the nodes along the edges of the contact surfaces will be ‘surface contact’.

3 Meshing

Click ‘Mesh’ in the menu bar and select ‘Model Mesh Settings’.

Select ‘Plate/Shell’ and preferable mesh size. For further information about Solid, Midplane and Plate/Shell, please refer to Help menu: Model mesh settings.

In the ‘options’, you can further adjust the mesh size. For example, by select ‘Absolute mesh size’ in ‘surface’, you can input the size of the mesh with the absolute size.


Selecting ‘Use automatic geometry-based mesh size function’ in ‘model’, the size of the mesh is different in each part and is based on the size of the part.

4 Element Definition

You can select different object (part, surface, edge, vertices…etc) using different selection tools, like point, rectangle, polygon or circle.

You can directly select the objects in the display area or in the tree views.

In the tree view, you can select the part you want to modify and the part will be highlighted in the display area. The sub-elements will also be shown in the tree view.

Highlighting all the parts in the display area or in tree view using the shift/ ctrl key.

Right click in the display area and select ‘modify’ and ‘element data’

Change the thickness of the material to 150mm and click ‘OK’

5 Material

Highlighting the parts again

Right click in the display area and select ‘modify’ and ‘material’

Select ‘Concrete (High Strength)’ on the left hand column. By selecting ‘Create New Library’, you can also define a new material.

The following are the references of stress and strain curves of two different materials. Please mind that the analysis type in this report is ‘static stress with linear material’, so the material property is following a linear stress and strain relationship (a straight line with slope at the beginning part of the stress and strain curve)


6 Boundary condition

Change the elevation view using the view icons in the toolbar.

Using the rectangle selection tool to select all the edges at the bottom of the model.

Right click in the display area and select ‘Add’ and ‘Edges boundary conditions’

Select ‘Fixed’

You can also define the boundary as ‘Fixed’, ‘Free’, ‘Pinned’ or ‘No rotation’ in other cases.

You can see the nodes on the edges at the bottom of the model are marked with triangle. You can also see the boundary condition in the tree view, under FEA Object Groups.

7 Loading

Using ‘point select’ to select the surfaces which will receive wind load.

Right click in the display area and select ‘Add’ and ‘Surface pressure’. Set the wind direction (x direction -1) and the amount of loading (0.001 N/sq mm, refer to the following part for reference of loading). Rename the active function as shown below. Press ‘OK’. For unit conversion, please visit www.translatorscafe.com

The surface applied loading will be highlighted.

To add the gravity load, double click ‘Analysis Type’ in the tree view. Make sure that ‘Accel/Gravity’ under ‘Multipliers’ is set to ‘1’

Click ‘Gravity/Acceleration’ and ‘Set for standard gravity to set the gravity load. Press ‘OK’

References for other loadings

Unit conversion: 1 psf = 0.00004788N/ sq mm

Wind load:


70mph = 0.000986 N/sq mm

80mph = 0.00129 N/sq mm


32.5 m/s=70mph = ~0.00066 N/sq mm

Dead load:

Please mind that, when we assign the material to the model, the analysis has already calculated the weight of the structural parts. The following information are extracted for the roof finishing. The dead load of other material can be referred to the following link.



Mineral fiber (fiberglass)                0.000000313 N/ cubic mm

Extruded polystyrene                        0.000000283 N/ cubic mm

Expanded polystyrene                       0.000000236 N/ cubic mm


Asphalt Shingles                                0.000000471 N/ cubic mm

¼ in. slate                                            0.00000157 N/ cubic mm

Aluminum (26 gauge)                       0.0000000471 N/ cubic mm

Steel (29 gauge)                                   0.000000126 N/ cubic mm

Built-up 3 ply & gravel                       0.000000864 N/ cubic mm

Sand                                                        0.000408 N/ cubic mm

Water                                                      0.00000980 N/ cubic mm

Please mind that the dead load is listed with density unit, N/ cubic mm. In order to change it to pressure, please use the following equation.

Pressure (N/sq mm) = Density (N/ cubic mm) X Material thickness (mm)

Live load:


Passenger cars   0.00239 N/sq mm

Trucks and Buses   0.00239 N/sq mm


Light   0.00479 N/sq mm

Heavy   0.00718 N/sq mm

Office Buildings

Offices   0.00239 N/sq mm

Lobbies   0.00479 N/sq mm


Attics 0.000958 N/sq mm

Dwelling units   0.00192 N/sq mm

Sleeping rooms   0.00144 N/sq mm

Sidewalks       0.012 N/sq mm

Storage Area

Light      0.006 N/sq mm

Heavy      0.012 N/sq mm

Yards and terraces, pedestrians 0.00479 N/sq mm

8 Result

Click the icon of ‘Perform analysis’ to start analyzing the model

Wait until the analysis is completed

While the analysis is completed, different results can be shown by selecting ‘deformed Shape’, ‘Displacement’, ‘Strain’ or ‘Stress’ on the tree view.

Select ‘Result Options’ in the menu bar and then ‘Displaces Model Options’. The scale of the deformation can be multiplied by the scale factor.

If we select ‘As a Absolute Value’ and enter ‘1’ in the Scale Factor, the model would show with a actual scale of deformation.

By turning on ‘Maximum Result Probe’ and ‘Minimum Result Probe’ in the tool bar, the location with maximum or minimum displacement, stress, strain will be shown in the model.

We can start the animation by selecting ‘Animation’ in Menu bar and click ‘Start Animation’.

You can display a range of value that you want to display. Click ‘Display Options’ and ‘plot setting’. In the page of Range Setting, under ‘Current Range’

Uncheck the bos of ‘Automically calculate value range’ and input the range of value. Press ‘Apply ‘ to preview or ‘OK’ to see the result.

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