GM Pontiac Substation W Equipment Floor Loading Issue
May 07, 2021
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| STATEMENT OF PROBLEM CCC received the substation equipment shop drawings from GM late in the project, at end of July. In August CCC worked with GM on the rigging plan for hoisting the new substation equipment into the penthouse. IBI performed a structural analysis of the penthouse framing steel and the hoist beam to ensure the capacity was sufficient for the lift. However, a structural analysis was not performed for the penthouse floor slab to ensure that the floor could take the load of the new, much heavier (19,000 lbs) transformer. Once IBI performed the analysis, it was found that the floor slab would require steel reinforcement to prevent slab failure. Upon learning that the floor slab would require reinforcing, a strategy was discussed by CCC to spread the load of the new transformer out over a greater surface area in order to slide over plates to the final resting spot. This could not be accomplished since the transformer had to move through a very tight space between existing transformers and switches. The only solution was to provide permanent steel reinforcing below the penthouse floor to support the slab for the path of travel of the new transformer, as well as its final resting spot. CCC felt that this solution was also more beneficial to GM for any future rework to the substation equipment. The downside is that to do this work, several weeks of lead paint abatement and steel installation had to take place in an area very near to AA0 press where other work was ongoing. Additionally, to perform the abatement, tight areas had to be reached where a lift would not work and temporary scaffolding had to be erected. COURSE OF ACTION IBI quickly and efficiently performed an analysis and provided a framing plan with the necessary steel to support the floor slab. CCC produced shop drawings quickly in order to get the materials ordered. GM issued a field order for the work, which took place on second shift. LESSON LEARNED 1) CCC/IBI should have immediately evaluated the floor capacity once the substation equipment drawings were received. This could have saved a couple weeks'''' time in performing the work. 2) GM needs to order equipment earlier in the project and provide shop equipment drawings of this nature much sooner. Originally the equipment work was to be done in february. This could have prevented such a lengthy delay in completing the work. |
