“Even greater opportunities exist for increases in productivity as more designers allow fabricators greater access to models, models start being reviewed as opposed to detailed drawings, and fabricators open their dimensionally accurate models to other trades and specialties,” said Moor.

To facilitate engineer-fabricator model interchange, engineers should model members to the top of steel on center lines, said Rob Schoen, founder of Axis Steel Detailing Inc., Orem, Utah. Columns should be continuous or break at correct splice elevations. Beams should be continuous or go to the correct work points.

Engineers responded that requests might take some extra effort but could be accommodated without any problems.

Technology is one reason 3D model approval is slow to launch. To facilitate the process, one steel fabricator, the Herrick Corp., has invested in a proprietary application-user interface that sits on top of Tekla Structures 3D modeling and detailing software.

Typically, a detailer extracts 2D drawings from the 3D model and sends the 2D drawings for approval. If the detailer must change the model, the 2D drawing must be either re-created or adjusted.

A rule of thumb is that the fabricator spends 60% of the time modeling and connecting the structure and 40% on extracting the drawings. Changing the model before the 2D drawings are extracted means extracting the drawings only once, says Wayne Morrison, preconstruction manager in Herrick's Stockton, Calif., office.

Herrick has approved models on three projects to date. To use its system, an engineer must have a Tekla engineering license. The engineer exports a file from its model to Herrick.

“We can see all the changes, make corrections and produce the 2D drawings once,” says Morrison. The system cuts approval turnaround time by at least 25%, he adds.