From Design to Fabrication: How 3D Steel Detailing Reduces Clashes and Rework

Design Drawings Are Not Fabrication Instructions

Structural design drawings establish the engineering intent and technical requirements of a project. They typically define structural arrangements, member sections, grid lines, levels, design loads, connection criteria, general notes, and applicable material specifications.

For the detailing team, the starting point is generally the Issued for Construction (IFC) drawing package, together with the project specifications, general notes, relevant architectural information, and approved technical requirements.

Shop drawings serve a different purpose: translating the approved design into precise instructions for manufacturing, assembly, and installation.

Design Documentation	Detailing & Fabrication Documentation
Structural arrangements and member sections	Individual part and assembly geometry
Design loads and connection criteria	Detailed connections, bolts, welds, and plates
Grid lines, elevations, and interfaces	Fabrication dimensions and piece marks
General notes and material specifications	Shop drawings, material lists, and CNC data

Before detailed production work begins, the team must identify missing dimensions, conflicting information, unclear connection responsibilities, and discrepancies between disciplines. These issues should be resolved through the project’s formal Request for Information (RFI) and approval procedures.

Modeling and Checking Before Connection Detailing

One of the most important quality-control steps in steel detailing takes place before the connection detailing phase.

After receiving the IFC drawings and specifications, the detailing team develops the initial 3D structural model. At this stage, the primary focus is accurately representing the approved structural arrangement. The model includes the principal members, section sizes, grid positions, elevations, orientations, and other relevant geometric information.

From this model, the team can generate preliminary erection or general arrangement drawings for checking purposes. These drawings are reviewed against the IFC documentation to verify:

• Correct member section sizes and profiles.
• Grid locations, levels, and structural geometry.
• Member orientation and framing arrangements.
• Completeness of the modeled structural members.
• Consistency with approved drawings and specifications.

This preliminary check is essential because an incorrect section size, misplaced member, or misunderstood framing arrangement can affect numerous connections and fabrication drawings.

Connection detailing should proceed only after the initial model has passed the required geometry and design-conformity checks.

The process does not eliminate subsequent checking. Connection detailing, fabrication drawings, and final deliverables require their own verification before release.

Resolving Clashes and Constructability Issues

A coordinated 3D model allows detailers and engineers to examine complex structural interfaces that may be difficult to interpret from separate 2D plans and sections. Typical issues include:

• Gusset plate interferenceConnection plates conflicting with adjacent beam flanges, stiffeners, or secondary framing.
• Bracing conflictsMultiple braces intersecting or competing for space at shared structural work points.
• Bolt and tool accessibilityInsufficient clearance for bolt insertion, wrench access, or tightening equipment.
• MEP and façade interfacesStructural elements conflicting with mechanical services, architectural components, or façade support systems.
• Site interfacesBase plates and connection geometry that do not align with verified field conditions.

Software such as Tekla Structures supports geometric clash checking between modeled steel components and reference models. However, automated clash detection is only part of a complete constructability review. A connection may have no detected geometric intersection and still be difficult to assemble, weld, inspect, or install.

A clash-free model is not necessarily a fabrication-ready or erection-ready model.

Practical experience remains essential when evaluating connection access, installation sequences, field tolerances, and workshop capabilities.

Connection Detailing and Constructability

Once the initial structural model has been checked, the detailing team can proceed with connection detailing using the approved design requirements and applicable connection engineering information.

Connection detailing is particularly sensitive because a connection may satisfy structural design requirements while creating unnecessary difficulties during fabrication or erection. The following considerations are essential.

• Engineering responsibilityConfirm whether connection design is provided by the Engineer of Record (EOR) or delegated to a qualified specialty connection design engineer.
• Design informationEnsure that design reactions, moments, connection schedules, and other required engineering parameters are available.
• Bolt accessibilityVerify adequate space for bolt insertion, tightening, and inspection.
• Welding accessConsider welding positions, torch access, weld sequencing, and potential fabrication distortion.
• Fit-up and erection clearancesProvide practical clearances consistent with the approved connection details and applicable standards.
• Coatings and finishesAccount for relevant effects of galvanizing, protective coatings, and fireproofing on connection assembly and accessibility.

From 3D Models to Shop Drawings and CNC Fabrication

Following connection detailing and the necessary checks, the coordinated model becomes the basis for generating detailed fabrication deliverables. These commonly include:

• Assembly drawingsInstructions showing how individual components are assembled into fabricated steel members.
• Single-part drawingsDimensions, hole patterns, cuts, and other processing details for individual components.
• Final erection drawingsMember locations, piece marks, orientations, and relevant erection information.
• Material take-offs (MTOs)Material quantities, sections, grades, lengths, and other information used for procurement and production planning.
• Machine data filesNC/DSTV, DXF, or other compatible CNC/CAM outputs required by the fabrication facility’s equipment.
• Piece marksIdentifiers connecting individual components and assemblies to drawings, material records, production activities, and erection documentation.

Digital integration between structural models and CNC equipment can substantially reduce manual data-entry errors and improve fabrication efficiency. Nevertheless, model-generated files must still be checked.

The detailing and fabrication teams should verify part orientation, dimensions, hole locations, machine compatibility, piece marks, and applicable revision information before production.

Digital automation improves consistency, but it does not replace technical verification.

Revision Control and Formal Fabrication Release

One of the most damaging coordination failures occurs when different project teams work from inconsistent document revisions.

In practice

Consider a connection that has been modified after the material lists were generated while the fabrication workshop continues using an earlier NC file. Even when the revised design is correct, outdated production information can result in scrap, rework, and delivery delays.

A revision number alone does not authorize fabrication.

For example, Rev 0 does not automatically mean a drawing is approved for manufacturing. The actual approval and release status must be confirmed through the project’s document-control procedure. This distinction is essential when coordinating between detailing offices, engineering teams, fabrication workshops, and project management.

Detailing for Safe and Efficient Erection

Structural steel detailing should consider the requirements of transportation and site installation, not just workshop production. Important coordination areas include:

• Transport constraintsMember lengths, assembly dimensions, vehicle limitations, and delivery arrangements.
• Lifting requirementsAssembly weights, available crane capacities, lifting points, and site access.
• Splice locationsPractical positioning of column, beam, and truss splices to support the planned erection methodology.
• Erection clearancesSuitable fit-up allowances and installation access.
• Field verificationCoordination with site surveys, concrete levels, and anchor rod as-built information.
• Temporary worksCoordination of lifting attachments, temporary stability provisions, and erection-related safety requirements with the responsible specialists.

The erection sequence can also influence how steel members are marked, grouped, transported, and delivered.

Early communication among the detailer, fabricator, and erection contractor helps prevent technically correct fabrication details from becoming difficult or expensive to install.