X. Shop Assembly¶
1. Purpose¶
To ensure that shop-fabricated components meet the geometric requirements for final erection, strict controls are applied during the assembly process. These components, when assembled, may serve as standalone erected units, such as bridges, or be integrated into existing structures. The shop assembly process is meticulously performed to guarantee that the geometry of the assembled components adheres to the necessary specifications, ensuring structural integrity and proper fit during final erection.
2. Definitions¶
For readability, this section uses the following abbreviations and terms.
- 2.1 Assembly: When two or more components are joined together. Joining methods include welding, bolting, pressure fit, molding, and adhesion.
3. References¶
The following references directly support Seacoast's Welding Process Section:
- 3.1 ANSI/AISC Code of Standard Practice for Steel Buildings and Bridges
- 3.2 G4.1 Steel Bridge Fabrication QC/QA Guidelines
4. Responsibilities¶
- 4.1 Owner of Process: The Engineering Manager is responsible for reviewing and approving changes to this procedure. The procedure will be reviewed periodically, at a minimum, annually.
- 4.2 Shop Engineer: The Shop Engineer collaborates with the Engineering Manager to develop a fabrication plan. Review and understand the assembly procedure, ensuring compliance with contract requirements and quality standards. Monitor quality control processes to ensure all requirements are met throughout the project.
- 4.3 Shop Foreman: Oversees the assembly process to ensure it aligns with the fabrication plan. Manages day-to-day operations in the fabrication area to maintain efficiency and quality.
5. Quality Records¶
Unless otherwise noted, all Quality Records follow the Seacoast "Policy for Maintenance of Quality Records" documented in the QCM Quality Control Plan Article 9. Control of Quality Records.
- 5.1 Released for Construction Drawings: Customer-approved drawings are stamped and released for construction. Document the fabrication requirements. Quality control performs final QC according to these drawings.
- 5.2 Job-Specific Assembly Procedure (if required): Job-specific assembly procedures (if required) will include a table to record vertical and horizontal measurements. This table will also include applicable tolerances for each measurement and the accuracy of the measurement to be taken.
6. Documentation¶
6.1 Overview¶
Welding processes and the associated heating and cooling of the material naturally distort the materials.
6.2 Geometry Overview¶
Delivered products are classified by the complexity of their geometry and the type of field connections required. Both individual components and assemblies are subject to the dimensional control processes outlined in the overall Quality Plan.
Geometry Classification and Description:
| Geometry | Description |
|---|---|
| Single components or minor assemblies that will be connected to existing structures in new holes or by weld | Will be measured to meet the dimensional requirements of the individual components. The fabricated components will be used as templates to drill the new holes in the existing structure in the field. Templates, match-drilled with the bolt patterns of the new fabrications, will be made where they facilitate transferring the pattern to the existing structure. |
| Single components or minor assemblies that will be connected to existing structures in existing holes | Will be fabricated (by order of preference): With blank connection surfaces that will be punch-marked and drilled in the field. By making a template in the field of the connection locations and matching the connection holes with the template in the shop. Dimensioning bolt hole locations in the detail drawings using reference edges or corners that can be matched most closely with the existing structure. Use oversize bolt holes where allowed. Produce members with numerically controlled equipment where allowed. |
| Assemblies that frame in a single plane | Will be assembled on a shop table or the shop floor. After assembly, all connection points for field connection to an existing structure or anchoring will be measured and checked, noting tolerances given on the erection drawing. Shop assemblies will be adjusted, if required, to ensure that the connection points meet the tolerances of the erection drawing or shop assembly procedure as applicable. Reaming of holes for adjustment of geometry may not be performed unless allowed in the procedure, on the shop drawing or by the engineer. |
| Assemblies that frame in multiple planes | Will be shop assembled to ensure proper control of the three-dimensional geometry. Such assemblies will require a job-specific shop assembly procedure on a case-by-case basis, see section "Job Specific Shop Assembly Procedures." |
6.3 Job Specific Shop Assembly Procedures¶
Shop assembly procedures are developed on a job-specific basis when necessary to ensure the control of both horizontal and vertical geometry in the complete assembly. These procedures are tailored to the specific requirements of the project and are critical for maintaining the structural integrity and alignment during assembly.
| Item | Description |
|---|---|
| Horizontal geometry | The shop assembly procedure will have procedures for painting or nailing control points onto the shop floor. Control points will be selected based on the structural member that controls the primary geometry of the overall structure and alignment with the substructure or mating structures. Examples of these primary members are the trunnion centerline of a bascule leaf and the bearing pads of a fixed bridge span. Multiple control points will be surveyed from the main control point and control line and established on the floor by paint or fixed marker. Variation of the assembled structure points to the control points marked on the floor, transferred by plumb bob or other means, must be within the overall shop assembly tolerances, which may be tighter than the field erection tolerances. |
| Vertical geometry | A vertical reference will be established on a plate or post anchored to the floor. This reference will be used as a benchmark for measuring elevation of the various control points of the assembly by survey or total station. Where elevation differences are critical, an engineer's scale will be used in lieu of a standard surveyor's rod. Variation of the assembled structure points to the control elevations must be within the overall shop assembly tolerances, which may be tighter than the field erection tolerances. Cambered members will be shop assembled and supported in the fully cambered shapes. Measured control elevations will consider the cambered shape of the member or assembly. |
| Drilling and reaming of field connections | Bolt holes in assemblies that will mate with field connections, whether substructure or existing structural steel, will be treated similarly to individual components as described previously in this section. Control points marked and measured at shop assembly will include those necessary to ensure field connections are accurately located. Tolerances allowed on these dimensions will consider the possible variations that may exist at the connection to the existing component and will typically be reduced from typical tolerancing. Where necessary, sub-drilled holes will be drilled in the shop to allow shop assembly but leave adjustment room prior to the field drilling of the final connection hole. The sub-drilled hole size and location will be detailed in the shop drawings. |
| Field Connection Repeatability | Preferably, for multi-dimensional assemblies, minimal bolt holes will be drilled until shop assembly is completed and mating components can be match drilled in their assembled, aligned state while being held together by clamps or undersized bolts. Fabrication of members using numerically controlled equipment will be performed when it facilitates quality or production and when allowed by contract. The equipment shall be calibrated on a routine basis, as required of this Quality Plan. Components fabricated using numerically controlled equipment will be fabricated in minimal quantities and test fitted to the greatest extent possible prior to completing the fabrication of the remaining like components to ensure proper fit-up prior to performing multiple production. |
| Match Marking | If the label and location of the match marking are not covered in the erection drawings, they will be included in the shop assembly procedure; otherwise, see the section "Match Marking." |
7. Revision History¶
| Revision Date | Approved By |
|---|---|
| 2026-05-12 | Engineering Manager |
Summary of Change: Reformatted to standard procedure template.