A new eight-storey concrete building has been built without eight columns after they were omitted from the ground and first floor drawings, a structural safety report has found.
The report by safety body Cross said without the columns a 225mm thick reinforced concrete slab was required to span up to 14m.
According to Cross, the omission was picked up by the concrete frame company’s project manager for some of the locations, but others were not immediately obvious due to transfer structures and column plan positions changing up the building.
The unnamed firm behind the design blamed the BIM software modelling tool it was using, but did not state how the error had arisen.
Cross surmised the mistake could have been made when transferring the model between BIM and an analysis programme or a separate discipline may have deleted the columns when clashes occurred.
“It is unusual to lose complete elements but it is possible that the columns were deleted by someone not appreciating their structural role,” stated the report. “The BIM model would likely have been a multidisciplinary model and there is the possibility of another discipline inadvertently deleting the columns due to clashes with their elements.”
However it went on to say that structural engineers needed to appreciate that they were still required to check the final output regardless of whether it appeared to simply be a copy of the analysis model.
“As BIM becomes more common, engineers need to improve their skills and develop tools to check final BIM models against their design intent,” it said. “It is they who are responsible for design, not the software.
“On a wider theme, the history of failures reveals a frequent pattern of gross error; that is an error so bad, you wonder how no one spotted it. This report seems to fall into that category. A lesson is for engineers to always start with looking at the big picture: are the load paths clear, is there a stability system and so on? - all before they get down to detail.”
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