What is ISM?
Bentley’s Integrated Structural Modeling (ISM) is a technology for sharing structural engineering project information among structural modeling, analysis, design, drafting, and detailing applications. ISM is similar to Building Information Modeling (BIM), but focuses on the information that is important in the design, construction, and modification of the load bearing components of buildings, bridges, and other structures.
Purpose
There are two related purposes for ISM:
- The transfer of structural information between applications.
- The coordination of structural information between applications.
To provide for the first purpose (transferring information), ISM provides a means of defining, storing, reading, and querying repositories.
To provide for the second purpose (coordination of information), ISM additionally provides capabilities to detect differences between repositories and to selectively (based on user selection) update either an repository or an application’s data to provide a user-controlled level of consistency between the two data sets.
ISM and Application Data
ISM is not intended to store all of the information that all of its client applications contain. Rather, it is intended to store and communicate a consensus view of data that is common to two or more of its client applications, such as ProStructures or Autodesk® Revit® .
The client application continues to hold and maintain its own private copy of project data. Some of the application data will duplicate that of the associated repository. The application data may even conflict with that in the repository. The client application (or you as its user) may decide that a conflict gives the best data for client application’s and ISM’s different uses.
The program provided by ISM for accepting or rejecting model data changes is called Structural Synchronizer. Structural Synchronizer provides you with a powerful set of tools for moving data between the applications used in your workflow. Even relatively small structural models have enormous amounts of data and ISM allows you to re-use this data with ease. Care must be taken that only the data you want transferred between applications is sent, though.
When accepting changes made by client applications to an repository, some attention must be paid to changes are actually being made. A small change in a client application can have unintended repercussions if accepted. A repository is intended to represent the data that is common to the client applications. Some client application models will use only a subset of the repository data but changes made to them can affect the entire repository if these changes are accepted when a repository update action is performed.
Let's take a look at an extended example of a multi-story, concrete building with a post-tensioned slabs:
- The architect on the project sends a Revit model of the building to the structural engineer. From Revit , an repository is created using the ISM Revit Plug-in. The lateral structure will be analyzed and designed using RAM Elements while RAM Concept will be used to design the floor systems.
- The engineer imports the roof slab into a RAM Concept file (each Concept file represents one slab). The 18x24 (450x800) beams are used at all levels, but are found to be inadequate for the roof due to heavy snow loads. The roof beams are changed to be 24x24 (800x800).
- An update to the repository from RAM Concept is performed from the roof-level Concept file. Structural Synchronizer detects the addition of the 24x24 (800x800) rectangular section and the deletion of the 18x24 (450x800) rectangular section. The roof beams have been correctly modified to use the 800x800 section, but the beams on other levels have been changed to have no section specified (since the section they used has been deleted). RAM Concept’s deletion of the 18x24 (450x800) section is correct in the scope of the roof, but this is causing unexpected changes elsewhere.
- The Structural Synchronizer Differencing Window will reveal these changes clearly as all of the modified beams will be shown in blue and listed as modified Since there are blue (modified) beams on levels other than the roof, it is obvious that some undesired changes have occurred.
- To cause the correct changes to be made, the engineer must reject the deletion of the 18x24 (450x800) rectangular section and reject the changes to the beams that are not at the roof level.