CROSS Safety Report
Lack of experience on steel column erection
This report is over 2 years old
Overview
A reporter highlights how works progressed on site without a detailed method statement being provided by the contractor even though it had been requested.
Key Learning Outcomes
For the construction team:
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Quality control and competent supervision on site can help to ensure that the structure is built in accordance with the design
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Having a competent temporary works designer/adviser in place to supply an engineered solution can ensure all temporary works are carefully considered and planned
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Verification of temporary works erection by a competent person who can oversee and coordinate the whole process can also ensure the works are installed correctly
For civil and structural design engineers:
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This report highlights the potential value of visits by the design team who may (as on this occasion) identify a problem. If you are unable to attend site, ask the contractor for site photos of the installation of critical structural elements such as bracing members.
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Specific to steel framed building, the British Constructional Steelwork Association (BCSA) Guide to the Erection of Multi-Storey Buildings provides advice on maintaining stability during construction
Full Report
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
Geometric constraints, explains a reporter, required that some column baseplates used a 2-bolt solution with the bolts located between the flanges of the UC sections. Notes on the drawings identified a temporary stability issue and said that the columns required propping until fully grouted.
Several requests were made to the contractor to provide a method statement for erection, but this was not provided, and the reporter only noticed via a project webcam that the works had started. The erection was being carried out by a large civil engineering contractor who had chosen to procure from a supplier and erect themselves rather than sub-contract the package to a steelwork specialist.
The site team, says the reporter, did not have much experience in steelwork erection and did not understand the importance of the temporary stability notes. The reporter also believes they were too programme-focused to respond to his requests for a method statement.
While the column posts were only 2m tall, they were 6 storeys up and adjacent to a train line. Had the correspondent not noticed the works on the webcam then progress would have continued un-checked and, had there been windy weather conditions, there could have been a serious accident.
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Feedback
Design responsibility of steel to concrete connections. It is common pratice for main consulting engineers to design steel frames but leave it to the steel fabricator to design the connections. Design engineers working for steel fabricators tend to be very good at designing the steel connections but their knowledge can be very limited when it comes to concrete design. This presents a problem when it comes to designing steel to concrete connections. This may be column to foundation or steel beam to concrete beam. The Steel Industry Guidance Notes has a document SN51 01/2011 that describes how the design responsibility works. Basically the main consultant provides the loads, the steel fabricator proposes a suitable connection detail and then the main consultant should confirm the adequacy of the anchorage. Recent experience has led me to believe that the vast majority of consulting engineers do not believe it is their responsibility to confirm the adequacy of the anchorage. They believe their responsibility ends when they have submitted the loads. In the vast majority of cases this does not represent a problem but where we have braced bay columns with high uplifts and then site constraints mean the concrete edge is close to the bolts then potentially it can be a problem. The solution to the problem is a bigger base or steel reinforcement to the base that will aid the pullout forces. Both of these factors fall outside the control of the steel fabricator. It is my belief that in most projects neither the steel fabricator or the main consulting engineer are checking this potential problem properly. I am an engineer who specialises in working for steel fabricators and I am happy to admit my knowledge of concrete is limited. I have tried raising this issue several times but get chastised for it. Main consulting engineers simply tell me that connection design is not their responsibility and they seem quite happy to walk away from the issue.
Expert Panel Comments
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A proper system of work is a pre-requisite to any safety-critical action on site and should be recognised. In this case it appears that information was given by the designer regarding stability but ignored by the contractor. An unstable column high above a railway line is a safety-critical situation which carries considerable risk and warrants immediate attention.
There have been cases where insufficiently supported or braced steelwork has fallen and resulted in fatalities. It is another case where competency may have been assumed but in the event was not justified. As more and more high rise towers are built in cities it is of utmost importance for industry to address such issues.
There have been cases where insufficiently supported or braced steelwork has fallen and resulted in fatalities.
In 2004 a UK company was fined a total of £100,000 following the death of a 16-year-old ground worker in an incident in which two structural steel columns were blown down by the wind. The need for temporary propping in such situations should be considered the norm. Locating bolts are not the same as holding down bolts and this is another case where temporary works should be designed to avoid such problems.