Dimensional Model Sharing Eliminates Risk,Duplication

June 15, 2004 · by Patrick Mays

By sharing digital models with consultants and subcontractors, the profession can go far beyond improving the way drawings are produced to change the very way buildings are built.

NBBJ has used object based design within the past four years to extract 2D plans, sections, and elevations from a 3D model and coordinate construction drawing sets. The same model is used for visualization and construction documents, and to reduce redundant efforts in computer drawing. However, this has only minimal impact on project profitability, and no major marketing advantage. By sharing digital models with consultants and subcontractors, the profession can go far beyond improving the way drawings are produced to change the very way buildings are built.

Integrating architectural models with structural and mechanical models for coordination and optimization of building systems can yield a significant reduction in conflicts in construction and increase usable floor to ceiling space. There is also a tremendous inefficiency between construction documents and shop drawings, not to mention between shop drawings and fabrication. By better using the model information it is possible to increase profit and improve the quality of the building.

There are clear legal challenges for architects when model data is provided to subcontractors who have traditionally been required to develop their own documents independently. But most subcontractors are willing to sign disclaimers if they can access models, and the improved coordination will most likely reduce risk, not increase it.

Most contractors have become labor brokers, and they are feeling increasing pressure from owners to find better ways to manage their schedules, and provide options for phasing completion. Several contractors are using “4D models,” where the fourth dimension is time, to visualize options in erection sequences. These tools are valuable in managing unexpected material delays or slow downs in parts of a project.

Today, many contractors are creating their own models of the building for this purpose rather than using the models developed by the design team. With a little advanced planning the design and engineering models can be used to update 4D scheduling models.

The Washington State Veteran’s Home is an example of a project which integrates structural and architectural models. KPFF Consulting Engineers built a model of the steel using Structural TriForma from Bentley. Certain parts of the roof were so complicated that they would have been extremely difficult to resolve without a 3D model. Likewise, NBBJ developed all the architectural elements with Architectural TriForma and coordinated them with the structural model. In key areas architects modeled the duct work in TriForma, but on future projects that data will be managed by the MEP design-build consultant. NBBJ has successfully tested the ability to coordinate mechanical, electrical, plumbing, and sprinkler systems. From the single building model NBBJ produced rendered images for client visualization, blocking and stacking diagrams, program area reports, construction documents, and structural drawings. The next logical step is to generate shop drawings, or controlled numeric cutting files for fabrication from this model. NBBJ is working with the contractor, Mortenson, and mechanical sub-contractor, McKinstry, on this project so that the group can enable the next steps on future projects.

The architectural-structural integration on the Washington State Veteran’s Home is now in the construction phase, and the steel was installed exactly as planned. More importantly the potential system conflicts have been resolved in advance, and tight tolerance between the structure and ducts have been worked out successfully.

—Patrick Mays

Mays has more than 20 years experience in architecture and construction. Currently he is a principal and chief information officer at NBBJ; previously he developed innovative systems to manage construction projects while at 3Com Corporation. His work includes: Construction Administration, An Architect's Guide to Surviving Information Overload and The Architect's Handbook of Professional Practice: Information Management and Contract Administration.

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