Overview:

Structural Modeler and RAM Structural Systems

Structural Modeler (SM) is the Bentley BIM application for 3D modeling, discipline coordination and construction drawing generation of structural systems. RAM Structural Systems (RSS) is a Bentley structural analysis application geared toward building design. Each of these applications can be worked in independently, but Structural Modeler provides analytical importing and exporting capabilities allowing the engineering and modeling departments to work closely on a project. Information need not be duplicated and the data can be shared in a designated workflow in order to coordinate design and consolidate a project schedule.

Users can start a project in SM and export the model to RSS. Structural analysis can be run in RSS and imported back into SM, updating the model to reflect the analytical changes. Or the project can be started in RSS and then imported into SM for coordination and drawing generation. A model can be exported and imported as needed through the project life-cycle.

Due to the nature of each application there are some considerations that should be looked at to facilitate a good export and\or import process. Having a road map on how this process will be integrated into a project can facilitate the sharing of data between the analytical process and the modeling process.

The versions in use at the time of this document creation are:

Structural Modeler V8i (Select series 1) 08.11.07.50
RAM Structural Systems V8i (Select series 1) 14.00.02.00

Structural Modeler Consideration Topics:

Primary and Secondary Structural Files
Model Coordinate Location
Floor Manager
Columns and the Floor Manager
Required Member Data
Cantilevers
Walls
Braces
Bar Joists
Slopes
Automated Structural Drawings on RSS Import
Importing and the Floor Manager file
More Information

Topics:

Primary and Secondary Structural Files

To export to RSS the elements need to exist in one SM model. It could be considered the 'primary' structural file; with other files containing other structural elements that are not included in the analytical process, e.g., bar joists, girts and decking. These models could be considered 'secondary' structural models.

Structural drawings can be created during the RSS import process (see Automated Structural Drawings section below). So, to take advantage of this feature, the 'secondary' files can be referenced into the 'primary' file. The 'primary' file will contain main structural elements themselves and the drawing extraction manager (DEM) definitions, including DEM templates, used to create construction documents utilizing any secondary reference files as needed per extraction.

This arrangement of model files is a little different from a model file organization using 'floor-to-floor' models and an extraction 'master' model. The primary structural file takes the role of modeling and extractions. The secondary structural files can facilitate a workflow that includes multiple users on one project.

The project could start with multiple files arranged however needed (floor-to-floor framing, framing and foundation, etc.) and then merged to create the main structural file before the export to RSS is performed. The primary structural file can then be maintained for additional round tripping between SM and RSS.

Model Coordinate Location

When starting a project in SM and planning on exporting to RSS the physical location of the model in the design cube must be considered.

Model coordinates should be in the positive X,Y,Z coordinate quadrant of the design cube and the bottom of the lowest column should reside at the "0" Z elevation. RSS considers this to be the bottom of the ground floor.

Other disciplines may locate the Z datum elevation at something other than "0", "100" for example. In order to match up the structural models for the other disciplines to reference a 'presentation' model can be created, possibly as a totally separate file, and the primary and secondary structural models can be referenced in and the reference file attachments moved to the Z elevation other disciplines may be using. The other disciplines reference this presentation model for coordination utilizing reference file live nesting. Any structural elements that are needed by other disciplines are 'presented' in this file.

Likewise the other disciplines' models referenced to the structural models will need to be moved to align with the structural Z "0" elevation. Placing and active point or non-plot cell at a monument point in each discipline's master or presentation model could help facilitate and insure that the reference files are in the correct position. The structural user can reference the other disciplines master models utilizing reference file live nesting and make one reference file move operation, snapping to the monument points to align the reference files.

In this respect structural may have a slightly different file organization. The primary file is used to export and import to RSS as well as modify the model and create drawing extractions. The presentation model is used as reference by other disciplines.

Floor Manager

RSS defines elevations of floors as 'Story Data', in SM floor elevations are defined using the Bentley BIM Floor Manager. Floor Manager floors must be set up in order to export to RSS. The Bentley BIM Floor Manager contains properties for adding splices to columns (see the next section). Note that the RSS story data heights are entered as floor-to-floor whereas SM auxiliary coordinates heights are entered from the origin or bottom floor elevation. Also note in the Automated Structural Drawings section below about how the import process affects the Bentley BIM Floor Manager, creating floor manager definitions from the RSS story data. This can affect other disciplines use of the floor manager.

Columns and the Floor Manager

RSS handles columns on a story-by-story basis. In other words a column that spans several floors will be modeled in RSS as separate elements, one for each floor, whereas SM columns are usually modeled as one element. The Bentley BIM Floor Manager has properties that can allow for splicing columns at each floor during the RSS export operation. Each floor in the Floor Manager contains informational properties including Discipline and Column Splice. Setting the Discipline value to 'structural' and the Column Splice Floor to 'true' will facilitate splicing the columns at the floor heights.

Required Member Data

Structural Modeler stores data and member classifications with each member. This data is stored as 'structural data' on the structural elements and is accessed by RSS in the importing and exporting function. Note that is this respect analytical elements need not be present in a SM model to allow exporting to RSS. SM analytical elements have use, specifically in regard to the STADD structural analytical application but are not used in this workflow.

Three properties of the structural data must be present for the structural elements to be read by the export process. These are: Type, Material and Class.

There are specific values for each of these properties that RSS will use. Following is a table of the various types if elements created in SM and how they should be classified. Note that there are only three acceptable Class values: Gravity, Lateral and Cantilever.

Element Information			Structural Data Values
Structural Modeler Member Type	Internal Type	Placement Point/Baseline	Type	Material	Class	Notes
Beam	STFLinearMember (Structural Element)	Top Center (8)	Beam	Steel, Concrete, Steel Joist or Smart Beam	Gravity or Lateral	Cantilevered members must be divided into spanning and cantilever components. The cantilever portion must then have the type data set to "cantilever", and the segments graphic grouped together.
Column	STFLinearMember (Structural Element)	Center Center (5)	Column	Steel or Concrete	Gravity or Lateral	Columns must be divided among floors. Column located at the extremes of a structure may extend above or below adjacent floors.
Wall (with or without openings)	STFWall (Linear Form)	Center	Wall	Concrete	Gravity or Lateral	Wall exported as a single member. Walls with openings must have Class set to "Lateral" to export the opening. Wall openings must be rectangular with edges parallel to edges of the wall. Wall openings must fully penetrate the wall depth.
Vertical Brace	STFLinearMember (Structural Element)	Center Center (5)	Vertical Brace	Steel or Concrete	Lateral	Each brace member must be a continuous member.
Horizontal Brace	STFLinearMember (Structural Element)	Center Center (5)	Horizontal Brace	Steel or Concrete	Lateral	Each brace member must be a continuous member.
Continuous Foundation	STFSolid (Free Form)	Extrude Direction - Down	Continuous Foundation	Concrete	Not applicable	None
Spread Foundation	STFSolid (Free Form)		Spread Foundation	Concrete	Not applicable	None
Pile Cap	STFSolid (Free Form)		Pile Cap	Concrete	Not applicable	None
Bar Joist	STFLinearMember (Structural Element)	Top Center (8)	Beam	Steel Joist	Gravity or Lateral	Must be Structural forms and not Compound Cells.

Default values for the type, material and class properties can be set in the DataSet Explorer. One workflow is to set all the beam and column types to gravity as a default allowing the structural engineer to make the choice of changing particular members to lateral in the RSS side. Braces can be set to lateral.

The next sections will take a look at the notes included in the table.

Cantilevers

RSS handles cantilevers as two components, a beam and a cantilever with a node in between. To export a cantilever beam from SM we need to draw the cantilever section as a separate structural element from the beam itself and change the structural data class value of the separate cantilever section to 'cantilever'. The beam and cantilever section need to be a graphic group. This can be achieved by using MicroStation's graphic group tools. Each beam\cantilever combination should be a distinct graphic group.

Walls

Walls modeled in SM are generic linear building forms and as such do not have structural data associated with them. SM contains a tool for adding structural data to elements, Apply Structural Attributes to Slab/Free/Linear Form. The tool is located in the Walls and Slabs and Foundations task interfaces groups. As noted in the table above, wall openings require some attention for exporting to RSS; the structural data class must be set to lateral, wall openings must be rectangular with edges parallel to edges of the wall and wall openings must fully penetrate the wall depth.

Braces

As noted in the table, each brace member must be a continuous member.

Bar Joists

If bar joist are going to be exported, bar joists must be Structural forms and not Compound Cells. The structural data properties must be set to Material: Steel Joist, Type: Beam, Class: Gravity. Bar joists do not necessarily need to be exported to RSS and can be modeled in a 'secondary' model in the SM model organization.

Slopes

RSS and SM both have the capabilities to model sloped flooring systems. However exporting sloped framing is limited to a few scenarios. RSS allows for sloping framing by lengthening or shortening columns and walls relative to their story height. RSS does not support beams sloping between Stories. Members are drawn their actual lengths in SM regardless of floor planes. During exporting members are assigned to an ACS plane based on their proximity to each plane starting from the top.

Curved Members

Curved members are not supported in the export to RSS. One possible scenario is to model the curved members on a separate level and model linear members for use in RSS. Any changes to the curved members would have to be manually updated.

Automated Structural Drawings on RSS Import

Automated Structural Drawings functionality encompasses several related technologies used in automatically generating and updating all of the active project model's Structural Plans, Elevations and Steel Column Schedules. Processing involves using the Import from Analysis Program tool, Structural Resymbolization Rules, Drawing Manager, and Families and Parts together with several new Structural Modeler native Automated Structural Drawings tools and settings dialog boxes.

In order to take advantage of automated drawings the 'primary' file (as noted above) used to model in, export to RSS and import from RSS will also contain the drawing extraction definitions. The 'secondary' structural files can be referenced to the 'primary' model for use in extractions as needed.

Extraction models and grid system models that are generated in the import process are named using the RSS story name. To insure file and model naming standards Floor Manager floors should be named accordingly as these become RSS story data names on an export operation and then the story data defines extractions on the import process.

The Structural Drawing Center is a centralized utility that manages automated Structural drawings generated from the active project model. The Drawing Center is typically used after the import process. It can be accessed from the Drawing Manager task.

Importing and the Floor Manager File

The import process will overwrite the Bentley BIM floor manager file. The structural discipline can be set up to use its own floor manager file through configuration variables. An example of configuration settings to allow that follows:

%if defined (STF_DATASETNAME)

#====================

# Structural Specific Floor Manager file: