Clarification of Building Structural Steel Design Type
Apr 29, 2021
11
| Statement of Problem: At bid time GM provided LGR structural reference drawings for their press bay addition. These drawings employed a single-column design concept with a cantilevered bracket to support the crane girders. However, nothing in the RFPS stated that Pontiac had to use a single-column design or copy the LGR structural steel design. While the LGR drawings provided an incredibly useful resource for IBI/CCC, the intent of the single-column concept was missed. At bid time IBI provided to CCC structural bridging documents which employed a two column laced system for building and crane girder, to match existing plant condition and also due to AISC recommendation for class D crane. At design kickoff IBI started designing the building structure based on this method. However in early design meetings it was determined between GM Global Facilities and the press group that the structure had to be single-column design to keep as much open space as possible in the press bay and press basement. This lead to numerous meetings to review the design change and cost impacts, which could not be fully realized until the structural steel design was completed. It also delayed project design since IBI had to start over. Course of Action: CCC directed IBI to revise design to the single-column concept and re-engineer structure per GM direction. Numerous meetings had to be held with the steel fabricator subcontractor to reconcile the differences in the weight of steel and the amount of labor, and the change resulted in a very large additional cost. In the end, the large column section size needed for single-column concept did not allow for much space to be saved in the bay at all. Lesson Learned for Future Projects: In this instance a lot of delays and meetings could have been saved had CCC or another contractor asked in the Q&A. However to guarantee that contractors bid with a design that holds no surprises for the GM team, the RFPS must clearly state if a specific structural design concept needs to be employed to fit the needs of the customer. Or, require contractors to submit their bridging drawings at bid time. |
