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CROSS Safety Report

Columns missing due to 3D modelling

Report ID: 614 Published: 1 January 2017 Region: CROSS-UK

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Overview

A new eight storey residential concrete frame building was being constructed and several columns were omitted from the ground and first floor level drawings, says a reporter.

Key Learning Outcomes

For civil and structural design engineers:

  • A strict quality control system that includes the checking of drawings can avoid errors and near misses like this from occurring

  • Consider introducing a quality control system that ensures the checking of drawings has been conducted in 3D as well as 2D.

Full Report

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A new eight storey residential concrete frame building was being constructed and several columns were omitted from the ground and first floor level drawings, says a reporter.

Without the columns, a 225mm thick reinforced concrete slab was being asked to span up to 14m. Some of the missing columns were spotted by the concrete frame company's project manager. Others were not immediately obvious due to transfer structures and column plan positions changing up the building.

Consequently, these columns were not built by the contractor, who continued to prop off the slab in the usual way during construction of the upper floors.

Consequently, these columns were not built by the contractor, who continued to prop off the slab in the usual way during construction of the upper floors

The consulting engineers cited the use of Building Information Modelling (BIM) modelling software as the reason for these serious omissions. Is the use of 3D modelling a distraction to producing clear, accurate and well thought out construction drawings?

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

This report has generated a lot of comment from our Expert Panel. Is this a case of the following:

  • User incompetence

  • Lack of experienced engineering supervision

  • Lack of checking

  • Lack of ability to understand conceptual design, or all of the above?

It would be hoped that any engineer would spot such gross errors in his/her checks, yet in this case it was missed. BIM is a great tool to assist with sequencing and fit, but it must be operated or overseen by experienced engineers who have a full grasp of conceptual design and can recognise fundamentals such as columns being missed. Whatever the system, clear, accurate and well thought out construction drawings are an absolute necessity.

Are different models leading to confusion during the review process?

It is not stated how the issue arose with the 3D BIM model. However, it is possible that the BIM model used different software to the analysis model. It is becoming more common to import the analysis model into the BIM model and when this works the advantages are clear but, in many cases, the imported model needs tidying up.

It is unusual to lose complete elements, but it is possible that the columns were deleted by someone not appreciating their structural role. 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.

Who is responsible for checking BIM models?

Structural engineers need to appreciate that they are still required to check the final output regardless if this appears to simply be a copy of their analysis. As BIM becomes more common, engineers need to improve their skills and develop tools to check final BIM models against their design intent. It is they who are responsible for design, not the software. 

Structural engineers need to appreciate that they are still required to check the final output regardless if this appears to simply be a copy of their analysis

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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