Consider the beginning of where many errors are generated: in the dimensions on the structural framing plans. If inconsistencies in dimension and placement are built into the contract drawings, the fabrication detailer's mission to accurately depict all the members gets bogged down in a plethora of requests for information (RFIs).
Most architectural, engineering, and design firms produce drawings (with or without CAD software) in which every line is drawn as a single graphic entity. This is time consuming and especially cumbersome when design changes dictate adjustments to column grids, requiring that coordination with equipment clearances be rechecked.
Parametric models, or 3D digital constructions, are proving to be more efficient at rendering and discovering conflicts, but they still pose a problem: When changes are made to the model, how does the fabricator know what has changed? Now, software technologies are emerging to solve this dilemma.
We are testing structural applications that recognize when dimensions are adjusted, trim the details of overlapping assemblies, and point out dimensional conflicts as changes are made.
These changes can be exported to the fabricator to highlight the adjustments that are needed to the listing schedules. The software will not allow designers to ignore a dimension that will not work; it enforces the resolution of conflicts as you design.
Overview of the Process
Based on the architect's design, engineers perform structural analysis and design with a system like STAAD. They set performance criteria, develop a framing model, and use tables to determine the shapes that are currently available from the mill.
The architect and engineer produce documents that are developed enough to delineate project scope and obtain the building permit. However, many connection details, such as whether to use bolts or welds, are left up to the detailer.
After the architect has created the parametric model and the engineer has specified structural shapes and sizes, the fabricators download the model and periodic changes that highlight what was changed.
To be qualified to bid on a digital-model-based project, fabricators must be trained on and have been using the system for at least 24 months. Bids are reviewed and selected based on performance criteria, price, and ability to accommodate the schedule.
They then develop the detailing in solid model format, which verifies and further details all connections. They also double check all dimensions — the check-and-balance process is not eliminated just because a digital model is used.
Beams that are incorrectly designed, such as a beam that is undersized, will be kicked out of the system during this process. All geometry and work points are checked. This is where most of the little corrections are required; this careful process is invaluable in preventing future problems in the field or shop.
The largest amount of detailing time is needed for the many minor assemblies — hangars, brackets, stairs, miscellaneous supports, details. Modelers can improve their efficiency by adding these repetitive items through 3D object libraries.
It is extremely important that the construction manager list all the assemblies the detailer is responsible for. Easily overlooked Items such as pour stops or reinforcements for penetrations for equipment piping and roof drains can add to further delays and headaches in construction.
Preferred Software for Architects
Our research indicates the "best of breed" parametric modeling programs for the various trades. They are: for architects, Revit and Bricsnet Architecturals; for structural engineers, RAM Steel and Structural Desktop; for fabricators, SDS/2 and Xsteel. Key to the use of all these systems is user training.
Revit models "intelligent" building components, views, and annotations. All are associated bidirectionally through a high-performance change propagation engine. Revit supports design changes anywhere, anytime by instantly updating the entire document set whenever a design modification is made.
Bricsnet Architecturals operates with AutoCAD and IntelliCAD, allowing you to take advantage of 3D object modeling in your familiar 2D environment without additional applets or enablers.
Additional advantages include extraordinary intelligence and programmability; an aggressive price for the functionality; and a forward-looking emphasis on the underlying data acquisition, integration, and transmission throughout the building life cycle.
A disadvantage of Bricnet's approach is that users must buy, learn, and integrate two tools from two different vendors. This could create incompatibilities if future upgrades from Autodesk and Bricsnet are not in sync.
Software for Structural Engineers
RAM Steel, a module of the RAM Structural System, is the predominant steel design package for engineers in North America. It performs most of the tedious structural analysis work, allowing the engineer to concentrate on a more economical design.
RAM Steel is unique in that it allows the engineer to lay out the framing systems in three dimensions; then the software applies floor loads and wind or earthquake loads, automatically distributes those loads to the appropriate members, and performs analysis, member optimization, and design, and produces 2D working drawings.
Recently, RAM Steel was enhanced to export its designs in a CIMsteel Integration Standards (CIS/2) format, allowing engineers to transfer data electronically directly to the software used by detailers and fabricators.
We believe this technology will become more commonplace over the next several years, leading to a more turnkey design and construction process.
Also useful is Structural Desktop for converting the results of analysis to 2D drawing files.
Software for Fabricators
SDS/2 from Design Data automates details, computer numerically controlled (CNC) data, inventory control, shipping tickets, and cutting lists.
Design Data's products reduce the time spent to produce drawings, order material, and fabricate steel. At the same time, SDS/2 automatically designs connections, automatically adjusting opposing connections and member end preparations.
Xsteel provides an integration of the model, producing reports, detail drawings, material lists, and CNC files. The software can accommodate an unlimited number of joints and members for large structures.
These new techniques allow the fabricator to get into the detail very quickly, but clear performance criteria set by the engineer of record is critical. The time typically required for this procurement process can often be reduced from 20 weeks to less than four.
John Jurewicz is an architect with McClier in Chicago.