Importing a DXF file
The Import DXF command is a powerful modeling feature that allows a CAD DXF file to be read in to create the framing in a floor layout type. Grids, grid labels, beams, joists and columns can be imported from a DXF file. With this capability a file received from an architect or created by the drafting staff can be used to generate the model. It also provides a means, together with the DXF export capability, of partially merging two separate RAM Structural System models. As with the Copy command, the Import DXF command may only be invoked for an "empty" floor type.
To invoke this command, first create a new layout type using the command. Next select . A dialog box appears allowing the specification of a DXF file name, the drive and the directory where it is located. Note that the default drive and directory is the DXF subdirectory. The Import DXF dialog box then appears, with which the user specifies Layer Names, Column Block Descriptions or names, and information describing Grid Label and Cantilever symbols.
All of the Layer names within the selected DXF file are listed in the Layer Names drop down list boxes, allowing the specification of the particular Layers associated with Grids, Grid Labels, Slab Edges, Columns, Frame Columns, Beams, Frame Beams, and Joists. For best results, these should each be on separate layers; Grids and Beams must be on separate layers. If there is a layer name corresponding to the default layer name (specified when the program was installed), it will be initially selected; otherwise, "*None" will be shown. To specify a different Layer name, scroll through the list and select the appropriate name. To suppress the reading in of certain entities or if the DXF file does not contain certain entities (e.g., no beams), select "*None".
In order to read in the columns it is necessary to specify the Block name of the Column block. I-shaped (e.g., Wide Flange) and Rectangular (e.g., HSS, TS) columns must be represented by blocks; round columns can be represented either as a block or as a Circle Entity (specified by "*As Circle Entity"). Note that the Import DXF command does not recognize columns that are represented by polyline's. All of the Block names within the DXF file are listed in the Column Block Descriptions drop down list boxes, allowing the specification of the particular Blocks associated with each of the shapes. If there is a block name corresponding to the default block name (specified when the program was installed), it will be initially selected; otherwise, "*None" will be shown. To specify a different Block name, scroll through the list and select the appropriate name. To suppress the reading in of certain entities or if the DXF file does not contain certain entities (e.g., no Pipe columns), select "*None".
In order to read in the Grid Labels associated with the grids it is necessary to specify the type of symbol, text or block, from which the Label text can be retrieved. There are two options: the Labels may either be simple text entities ("*As Text Entity") or they may be an attribute of a block. All of the Block names within the DXF file are listed in the Grid Label Symbol drop down list box, allowing the user to specify the particular Block associated with Grid Labels. If there is a block name corresponding to the default block name (specified when the program was installed), it will be initially selected; otherwise, "*None" will be shown. To specify a different Block name, scroll through the list and select the appropriate name. To suppress the reading in of grid labels, select "*None".
In order to correctly interpret cantilever conditions it is necessary to specify how cantilevers are indicated in the DXF file. There are three options: the cantilevers may be shown with their moment connection symbols where the connection symbol is indicated by a block (for which the user specifies the block name) or by a solid entity ("*As Solid Entity"), or the cantilever may be drawn merely as a continuous extension of the beam line ("*None"). All of the Block names within the DXF file are listed in the Cantilever Symbol drop down list box, as well as the other two options, allowing the user to specify the cantilever symbol. If there is a selection corresponding to the default selection (specified when the program was installed), it will be initially selected; otherwise, "*None" will be shown. To specify a different selection, scroll through the list and select the appropriate name.
Slab edges and openings are always imported with 0.0 as their overhang.
The current settings can be saved permanently as part of the database by selecting Save Settings On OK. If a subsequent DXF file is read in to this database the saved settings will be used as the default settings.
When the desired settings have been selected, select OK. The information will then be transferred from the DXF file to the layout type. Inspect the resulting model carefully, especially columns and cantilevers. If the model does not import properly, delete the layout type, recreate it, and re-invoke the Import DXF command.
After the layout type has been created, assign story data in the Story command. The DataCheck should then be invoked to determine any problems or irregularities.
There is, by necessity, a certain degree of accuracy expected in the DXF file. The Import DXF command must literally interpret the information in the DXF file. For example, if columns are not precisely (within the program’s stringent tolerance) placed at the grid intersection, a new node will be created at the column’s given coordinates, resulting in columns and beams improperly framed. If the grid labels do not precisely (within the program tolerance) align with the grid lines, the labels will not be read in.
It is impossible to accommodate every possible variation of CAD drafting styles and in-house standards. In some cases it may be necessary to make temporary modifications to the CAD file to facilitate the use of the Import DXF command. This may involve separating the various entities onto different levels, using blocks instead of polyline's, etc.
Orthogonal, skewed and radial grids and their labels will be read into the layout type.
Every line on the Grid layer will be interpreted as a grid, and every line on the Beam and Joist layers will be interpreted as a beam or joist.
When creating columns, the program will attempt to determine the appropriate orientation by examining the information in the specified column block. If the program is unable to determine the orientation from that information it will assign an orientation. This may result in columns rotated 90°. If so, use the command to assign the proper orientation.
When columns on transfer girders are included in the DXF file, they should be on a separate layer and not read into the model. Otherwise such columns will be interpreted as columns below, rather than above, the girder.
Do not try to read in beams without reading in the columns. If for any reason the columns are not created properly, beams probably won't be either, especially beams with cantilevers.
It may be a common practice for some to indicate steel joists by using a pair of broken lines with a dash at the midpoint. This will not be correctly interpreted by the program as a single joist. Beams and joists should be represented by a single continuous line segment.
It is also common practice to shorten the beam lines, leaving a gap between beam ends and the supporting girders, and between beam ends and columns. This is acceptable for use with the program. The program projects the beam lines to determine the supports, and creates the layout accordingly.
When the columns and beams are read in, they are assigned the properties currently assigned as the Modeler defaults.
The DXF file should use coordinates based on an origin (0.0, 0.0) that is in proximity to the framing. The coordinates of the members should not be excessively large, as can occur if the structure is offset, for example, 2,000 ft or so from the origin, If necessary, modify the CAD file so that the structure is in proximity to the origin prior to importing into the RAM Modeler.