| Applies To | |||
| Product(s): | RAM Structural System | ||
| Version(s): | 13.00.00.00 or later | ||
| Environment: | All | ||
| Area: | Import/Export, Drawings | ||
Importing DXF Files into RAM SS
General
DXF plans can be imported into RAM Modeler. This process is discussed in Section 3.3 of the RAM Modeler documentation. In order to achieve a successful import, it is imperative that you have a properly formatted DXF file that is precise so that the entities can be mapped properly and subtle framing inaccuracies can be avoided. Here is a link to a sample DXF file that is formatted to match the out-of-the-box RAM Structural System defaults. The only exception is the Grid Label Symbol should be changed to the GRIDLABEL block. It contains the "I" shaped column, rectangular shaped column, and grid label block definitions that are mentioned in this document.
DXF files can only be imported into layout types that contain no information. To import a DXF file, create and select a new layout in RAM Modeler and go to Layout > Type > Import from DXF. Select the DXF file and the following dialog box will appear. The default parameters may be changed in the Defaults Utility in RAM Manager. For simplicity, use the same layers in the DXF as the import defaults so the layer names do not need to be changed in the Import DXF dialog box. When a DXF file is imported, RAM Modeler will only look for information on these layers and other layers will be ignored. In order to prevent inaccuracies, it is recommended that you reduce the drawing to its bare essentials prior to importing. This also speeds up the process of regeneration in very large drawing files. If you intend to import the sample.dxf file, the parameters in the Import DXF dialog box should match those shown below.
Grids
RAM Modeler is capable of creating orthogonal and radial grid systems. For grid lines to be recognized as part of a single grid system, they must be drawn accurately. Orthogonal grid systems must have at least one grid in two orthogonal axes to be recognized. For additional grids to be recognized in the same orthogonal grid system, they must be precisely parallel. If the ‘Split Disconnected Orthogonal Grids' option is selected, any grid lines that do not physically intersect will be treated as separate system. Radial grids must be composed of a circular grid(s) intersected by radial grids lines that pass through the center of the circular grid. Make sure that grid lines are actually lines, not polylines, and not part of a larger block or external reference file. CAD files often have closely spaced grids in which the grid bubbles overlap if they were centered on the grid line. It is common practice to offset the grid bubbles in the drawings using grid extensions. Grid extensions must not exist in the DXF file or they will be erroneously treated as grid lines.
Grid Labels
Grid labels should be drawn on a separate layer than the grid lines. A common problem occurs when users model circles for grid bubbles on the grid lines layer instead of the grid labels layer. The circles will be interpreted as circular grids instead of grid labels. Grid labels should preferably be defined by as a block with a text attribute.
The insertion point should be at the exact center so the grid bubbles are located precisely on the grid lines. Alternatively, draw the grid labels as simple pieces of text that are middle center justified and located at the end of the grid. If desired, grid labels can be added in RAM Modeler so it is not a necessity to have a grid labels in the DXF file.
Columns
Columns should be drawn as blocks. The program will recognize one type of block for "I" sections, Rectangular HS sections, and Round HS sections. You cannot use more than one block type to represent different column sizes within the same drawing and there should not be separate blocks for gravity and lateral columns. When defining the blocks, make sure that the insertion point of the block is in the exact center which is then placed precisely on the grid line. It is required to have all of the gravity columns on a single layer. Likewise, all lateral columns must exist on a single layer.
Beams and Joists
All beams and joists should be lines, not polylines. Use snaps to place lines from column to column as required. The finished beam line should be cut back from the supports just as a beam would typically be drawn on a structural framing plan. The dimension of the offset should be between 6 and 24 inches to maintain accuracy. Joist and infill beams can be drawn in the DXF import file or simply added in the RAM Modeler using the various member generation features available. If they are to be drawn in the DXF import file, remember to use a distinct layer for joists.
Cantilevers
For cantilever beams, draw lines continuous over supports (whether columns or other beams). End the line at the exact endpoint of the cantilever and do not trim it back. Members that frame into the end of the cantilever are then cut back as typical beams. Be sure that the apparent intersection of these beams matches the exact endpoint of the cantilever. Alternatively, cantilevers can be indicated using a block inserted at the end of the beams where the moment connection occurs as shown below. Notice how the cantilever tips extend to the actual location and are not cut back.
Slab Edges and Openings
Slab edges/openings should be lines, not polylines. Slab edges and slab openings are imported as free formed edges/openings with a zero inch offset. Therefore, the slab edges/openings are not tied to the perimeter beams/walls. This is acceptable but can lead to problems building the framing tables when complicated perimeter geometry exists and there are one way slabs. For this reason, it is recommended that slab edges/openings only be imported for two way slabs.
Concrete
The DXF import facility is only for steel members at this time. If you are trying to import concrete columns or beams, first import them as steel members using the procedures above, then use the Modeler Layout - Column (or Beam) - Change Material command to convert the imported members over to Concrete.
Since concrete is not supported, walls are also not imported. It may help to import two columns at the wall CL endpoints so that drawing in walls in Modeler is easier.
Concrete columns, walls and slabs can also be exported from RAM Concept to a new RAM SS layer using RAM Concept - File menu - Sync Ram Structural System - Export Geometry to RAM.
Tips and Tricks
If you are working in English units, verify that the drawing units are architectural. If other units are being used it is necessary for one drawing unit to equal 1 inch. If not, the drawing may need to be scaled. For metric or SI drawings, one unit should equal 1 millimeter.
Establish a logical origin point for the drawing that will assure precise locations for grid intersections, and relocate the drawing if necessary. Large coordinates are known to cause problems in RAM Structural System. These problems can be related to graphical issues such that some view tools in RAM Frame can become corrupt and can prevent the user from rotating the model or zooming in/out when in the module. Typically, the column in the lower left hand corner of the plan should be moved to (0, 0, 0) unless a more logical origin exists. Be sure to reference the World Coordinate system and not a local UCS, since the World coordinates are always referenced in the DXF file.
When saving the drawing as a DXF file in AutoCAD, go to Tools > Options in the Save As dialog box. In the DXF options tab you have the ability to specify the number of decimal places of accuracy. Reducing the decimal places in the DXF file might help eliminate minor framing discrepancies. For example, imagine two grids defined by end points (0, 0, 0) ; (0, 1200, 0) and (240, 0, 0) ; (240.0003, 1200, 0). These two lines are not parallel because of the small inaccuracy in the X coordinates of the second line and would import as separate grid systems. However, if the decimal places where rounded to 3, this inaccuracy would be resolved and the grids would import as a single system as intended. RAM Structural System only displays to three decimal places of an inch but may be stored internally at a higher precision. However, be careful if you have skewed framing or radial grids. Eliminating too many decimal places might cause framing errors in RAM Structural System. In these situations it might be best to save the DXF with 4 decimal places and be certain that the framing is drawn very accurately in CAD. RAM Structural System expects framing locations to be accurate to 3 decimal places of an inch to avoid tolerance related problems.
Once the framing has been imported, try to add a slab edge around the whole perimeter. If there are any other modeling errors they will likely be indicated at this time. If this works fine, then you should add a deck and surface load to the whole floor, assign story data, run the data check, and perform the beam design, all before you make any minor changes to the file.
See Also
RAM SS - Using DXF as a Reference Layout
Integrated Structural Modeling Home
Structural Product TechNotes And FAQs