CROSS Safety Report
Inadequate design and procurement of large steel roof structure
This report demonstrates the importance of following the correct process for project procurement, including preparing a detailed design and project specification, and certificating compliance with the relevant building codes. It also covers the potential consequences when shortcuts are taken.
In the example raised by the reporter, a contractor procured the steelwork for a large span roof from overseas, based on a concept design supplied for pricing, without seeking construction documentation from the original design engineer. Construction proceeded without correctly specified design and construction drawings. As a result of concerns raised by the steelwork erector, an independent review found many deficiencies in the steelwork design and detailing which, combined with a steel grade lower than that indicated in the initial design, resulted in significant delays to the project and increased costs to the contractor.
Key Learning Outcomes
For civil and structural design engineers:
- Carefully consider your involvement with contractors who do not follow the correct procedure for design and construction
- Ensure all important design parameters (such as steel grade) are noted on the shop drawings prior to checking
- Either certify, or require competent third party certification, for connection details designed by the shop detailer
- Ensure that all quality control (including third party certification of steel and steelwork fabrication as required) has been satisfactorily carried out prior to issuing final certification, paying particular regard to overseas fabrication and supply
- Do not commence fabrication without recourse to certified and approved construction drawings
- Carry out the requisite quality control at all stages of construction to ensure compliance of materials and fabrication with Australian Standards (including third party certification as required), particularly when these are procured abroad
- Withhold the issue of Building Approval until satisfactory receipt of adequate design documentation and a Declaration of Design Compliance with the National Construction Code (NCC)
For asset owners and managers:
- Review the risk profile associated with the delivery method, and consider adopting the traditional method of engaging a project engineer for the full design documentation prior to any contractor involvement
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The reporter describes what happened when shortcuts were taken in the procurement process and construction proceeds without detailed design, project specification and certification. In their example, an engineer (Engineer 1) provided a concept design, for pricing purposes, for structural steelwork to be procured from overseas for a large single storey steel-framed building. The importer (contractor) won the project tender and ordered the steelwork to be detailed and fabricated overseas without seeking construction documentation from Engineer 1.
During the erection of the steelwork, concerns were initially raised by the installer over some member deflections and poor details, as well as poor fabrication and welding. As a result, a peer review was undertaken by another engineer (Engineer 2) appointed by the contractor. During the peer review by Engineer 2, several structural issues were noted and Engineer 2 consulted a specialist steel design engineer (Engineer 3) for advice. Engineer 3 found the structural design to be inadequate and undersized. This design was the preliminary design that had been prepared for pricing by Engineer 1, and had been used for fabrication and construction without further input from Engineer 1. Most steel connections were designed by the overseas steel detailer. The steel grade was also questioned and tested. The design was based on grade Q345 steel, but it was found that grade Q235 steel had been supplied.
The design required significant modifications to strengthen the RHS/SHS open web trusses in order to suit the supplied steel grade, as well as additional end wall bracing and modified roof and side wall bracing. Further concerns regarding the welding quality and paint system were reviewed separately. This resulted in delays to the project and increased costs that had to be borne by the contractor.
delays to the project and increased costs ... had to be borne by the contractor
The reporter notes that this exemplifies the importance of following the correct design, project specification and certification procedure- three processes that are generally the responsibility of engineers to complete successfully. If the design is not correct, problems may arise during the construction phase of the project or potentially lead to failures. The supply and performance of materials, fabrication and corrosion protection rely upon the adequacy of the design and construction drawings.
Importance of checking processes
The reporter recommends checking processes at all stages of project delivery, and that any connection details designed by steel detailers should be checked and approved by the responsible design engineer.
The reporter draws attention to the following initiatives of the Australian Steel Institute (ASI) which provide independent third party auditing and certification for structural steelwork projects:
- Steelwork Compliance Australia provides independent third party auditing and certification of fabricators who have the capability to fabricate structures to the specified standards
- ShedSafe is an independent third party shed design certification scheme that can further enhance confidence in the engineering, steel products and specification for steel sheds and other large buildings
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Expert Panel Comments
An Expert Panel 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-US Expert Panel page.
This report highlights a failure to follow due process, which always involves increased risk for the parties concerned - in this case the risks related to safety, as well as delays and costs to the contractor. It also suggests a lack of appropriate contractual arrangements between parties.
Seeking an alternative design and utilising overseas fabrication is now commonplace in the industry and is not, in itself, the issue. However, in the case highlighted in this report the fabrication proceeded without any approved design, on the basis of a preliminary unproven design submitted for costing only. This raises the question of why construction was permitted to proceed without the certifier having possession of the engineer’s approved and certified steel designs.
The adequacy of documentation was one of the issues raised in the Shergold Weir Building Confidence Report (BCR). Under recommendations 13 to 17 the BCR states: 'We recommend that there be a statutory duty on design practitioners to prepare documentation that demonstrates that proposed buildings will comply with the NCC. We recommend a more robust approach to third party review of designs and to the documentation and approval of performance solutions and variations.'
In response to the BCR, the Australian Building Codes Board Implementation Team has produced a series of guidance documents for consideration by State and Territory Governments, including Design acceptance: Model guidance on BCR recommendations 13-16. This is a comprehensive document and includes eight Principles for Design Acceptance.
Principle 2 - Declarations of Design Compliance states: 'That each design practitioner, as listed in the National Registration Framework for building practitioners (the NRF), declare in writing that, to the best of their knowledge, their design complies with the NCC and other prescribed requirements. The declaration will be known as a Declaration of Design Compliance.'
Overseas manufacture causing risks?
Another issue raised by the report is the increased risk of non-compliance with Australian Standards introduced by overseas design and fabrication. This issue has garnered much attention in recent years following a significant increase in non-conformance problems within the construction industry, as reported over the years by the ASI. These issues have come at great cost to the industry.
Where structural steel and components (e.g. bolts) are imported from overseas it is essential to ensure that they comply with Australian Standards in terms of their mechanical and chemical properties. Non-conforming steel may be non-ductile, fail in a brittle manner in an overload situation, and may not be weldable. As a result, overseas design and fabrication deserves close scrutiny by all parties to ensure compliance.
The ASI has committed significant resources to developing a body of documentation to address the problem. These include guidelines for testing in Australia to verify material composition and performance as specified. The Australian and New Zealand Standard AS/NZS 5131: Structural Steelwork – Fabrication and Erection is a case in point. Additional guidance on Steelwork Quality and Compliance can be found on the ASI website.
The situation is no different in New Zealand, where the sourcing and procurement of large quantities of steelwork can be even more difficult to find locally. Importantly, the Australasian Certification Authority for Reinforcing and Structural Steels' (ACRS) Product Certification Scheme certifies steel construction products are manufactured to Australian and New Zealand Standards. It provides users with certainty that steel manufacturers and producers of fabricated materials adhere to the relevant Standards. The requirement for ACRS certification should be written into the relevant specifications.
A further issue raised in the report relates to the development of structural connection details. The report example indicates such details were provided by the shop detailer. This is considered a non-standard situation. If it were to be adopted, the certifying design engineer would have to be prepared to verify the design during a review stage of shop drawings, prior to fabrication.