Analysis Frequently Asked Questions

This is a spurious error/warning message that occurs when support displacements are applied to a support which is fully fixed in some directions and has a spring stiffness in others. The error message is incorrect and prevents the analysis from completing.

The solution is to change all fixed directions to very stiff spring stiffnesses. Once this is done the error message is no longer produced. The analysis is not affected in any way and the results are reliable (assuming that the data is reliable).

This problem occurs when the structure contains a span end line which runs parallel to the carriageway. Each span end line in the structure must cross the carriageway for the load optimisation to work correctly.

If you experience this problem, click on the Abort Load Optimisation button then delete any span end lines which run parallel to the carriageway. Once you have done this, re-run the load optimisation to create your live loads.

The load optimisation includes an option to allow the user to select the KEL direction which is used. By default this is set to "Most Severe" which allows the KEL to be applied in any orientation. This is to the letter of the design code.

Many users prefer to not use this option so you can select an alternative such as "Square to Design Line" or "Parallel to first abutment". The selection box to the right of the KEL Direction field allows you to specify which influence surfaces the option will be applied too. Most users select "All" in most cases.

Sam will orientate sections defined using parametric shapes or from section files such that the horizontal axis is aligned with the local y axis and the vertical with the local z axis of the beam element.

You can check the orientation of the local axes for a beam element by clicking on "Member Details" at the bottom of the Navigation Pane then clicking on the member you are interested in. Sam will show a thumbnail of the beam element with its local axes displayed.

You can show the local axes for the whole structure by going to the "General" tab on the graphics window and ticking the "Local Axes" check box.

Sam uses the direction assigned to the longitudinal and transverse members in a model or the direction assigned to a finite element mesh to orientate a beam file when it assigned to the structure. Sam will always assign the beam so that it runs from left to right in the direction of the arrow.

The direction of the longitudinal and transverse members is indicated by an arrow head at the end of the members. To see it, click on the Longitudinal or Transverse member node on the Structure tree in Sam. You can change the direction of a member by selecting it and clicking on the "Reverse Order" option in the "Beam Tasks" list on the Longitudinal Beams and Trasverse Beams forms.

The direction of a finite element mesh is indicated by an arrow head at the centre of the mesh. To see it, click on the mesh in the relevant sub-model on the Structure tree. You can change the orientation of the mesh by click on the "Rotate Mesh" button on the Define Mesh form.

Once you've assigned a beam file to the structure, you can use the 3D Elements View to confirm that it has been assigned in the correct way.

The minimum spacing between connected joints in Sam is 50mm. The program will ignore any beam element which is shorter than 50mm or any finite element with a side shorter than 50mm.

The BD 21/01 load optimisation form allows you to create loads for accidental wheel loads and HA loads.

If you want to create loads for accidental vehicles, set the Accidental loading field to either "Wheel (cantivelevered member)" or "Vehicle (non-cantilevered member)" depending on your structure and deselect the "HA UDL and KEL", "Single Axle Load" and "Single Wheel Load" tick boxes.

If you want to create loads for accidental vehicles, set the Accidental loading field to either "None (effective barriers)" and select the "HA UDL and KEL", "Single Axle Load" and "Single Wheel Load" tick boxes as required.

Sam is able to import models from DXF and DWG files created in CAD. When you select a file to be imported, Sam will give a list of the layers in the file and allow you to select which ones you want to import. It will then scan the selected layers for LINE entities, which will be read in as beam members, and for 3DFACE and SOLID entities, which it will read as finite elements. All other entities are ignored.

You can import design lines from DXF and DWG files. When you select a file to be imported, Sam will give a list of the layers in the file and allow you to select which one you want to import. Only one layer may be selected for import. Only LINES, POLYLINES and ARCS may be imported as sections of a design line. For entities to be imported as a design line they must satisfy the following criteria.

• Must be a LINE, POLYLINE or ARC.
• Must be on the selected layer.
• Must be connected to the other entities that make the design line. The first entity in the DXF file is imported and all subsequent entities must have a direct or indirect connection to this entity.
• The angles at the connecting endpoints of two entities must match (to a tolerance of 1 degree).
• POLYLINES are imported as transient segments. The points must be arranged to give a non-intersecting, strictly increasing polyline.
• If the imported layer consists entirely of LINES then a transient segment shall be created. The points must be arranged to give a non-intersecting, strictly increasing transient segment otherwise the data will be discarded.

Sam always positions carriageways at Z=0. It uses it to apply loads to the beam elements or finite elements which are defined as deck elements. Sam positions the highest deck element at the Z=0 level.

When you import a 3D model into Sam there are no deck elements defined. You need to tell the program which elements make up the deck so it can apply load from carriageways correctly.

To do this, click on the Member Details node in the Structure tree to open the Member Details form. Click on the Define Deck option in the Member Tasks list to open the Define Deck Members form. This allows you to select members graphically and select members at a specified level to be in the deck. Once you have selected all the members of the deck, click OK. Sam will automatically translate the structure such that the highest member in the deck is at the Z=0 level.

It is important to ensure that the deck forms a single level with no part of the deck lying beneath another part.

Sam offers several methods to split a beam element. First you need to select the beam element or elements you wish to split. To do this, click on the Sub Model Members node in the Structure tree within the Sub Model which contains the members to be split. Next, click on the Split Beam Element option within the Member Tasks list to open the Split Beam Element form. Select the member or members to be split on the graphics window then use the various options on the form to split the member.

Method 2 calculation results are the 'basic' resolved forces and moments in a slice through the elements on each side of a given composite member node. The plane of the slice is perpendicular to each particular segment of the composite axis (except when the composite member is linked to a SAM beam file, in which case the plane is vertical, but perpendicular to the composite axis in the horizontal direction). Directly adjacent segments may have significantly different uniform effects and this is reflected in the saw-tooth appearance of these results when composite member nodes coincide with finite element edges. However, results of method 2 are smooth (and most representative of real effects) when composite member nodes coincide with finite element centroids.

Method 1 is a refinement of the basic results of Method 2 (above). Method 1 takes the average shear over a composite member segment to be uniform (the average of that at each end). Moments at each node are then adjusted according to statics so that the segment is in equilibrium. Shear forces are then smoothed between the mid-points of segments (except that at points of shear reversal (ie support or large loading) they are extrapolated). Method 1 gives a smoother appearance and more accurate loads near supports or under concentrated loading when composite member nodes.

There is a known issue when running Sam in 64-bit Windows 7. When running a structural analysis under 64-bit Windows 7, the analysis sometimes fails immediately with an error message referring to a log file. The log file contains no information. The solution to the problem is to start Sam in Windows Vista compatibility mode. To do this you need to modify your Sam shortcut as follows:

1. Right click on the Sam Version 6.50 shortcut on your desktop and choose Properties
2. Click on the Compatibility tab
3. Tick the "Run this program in compatibility mode for" check box and select "Windows Vista (Service Pack 2)" from the selection box below.
4. Click OK to change the settings

If you are running Sam by double clicking on data files you will need to carry out the same steps on the Sam6.exe program file in the C:\Program Files (x86)\Bestech\Sam6 folder.