In order to obtain an eligible end product, there are several steps that must be followed by the different participants of the entire proceeding: starting with the construction phase and ending with placing the product on the market. In this article we will focus on the responsibilities an engineer is subject to.
The engineer should pursue the BS EN 1090-2 (the Technical Requirements for Steel Structures) requirements and specify the Execution Class for the structure as a whole, the components and the details. It is essential to note that in some cases, the components and details may have distinctive features. Thus, they have to be mentioned accordingly and separately.
In order to determine the Execution Class of the above-mentioned segments, an engineer has to follow a four step process, namely he has to: determine the Consequence Class, define the Service and the Production Categories and, derive the Execution Class.
1. Determine the Consequence ClassThe categorization of a Consequence Class (CC) aims to ensure that buildings and other structures are constructed with the appropriate level of quality control within the fabrication process. Consequence Classes are derived on the basis of building type, building height (number of storeys), floor plan area per storey (for retail) and occupancy. There are three types of CCs which embody different categories of buildings. The CC1 unit is intended for constructions which have a low consequence for the loss of human life and negligible or small economic, social or environmental repercussions. The CC2 is used to mark buildings with a medium consequence for the loss of human life and considerable economic, social or environmental impact, while the CC3 unit is adopted for constructions with a high consequence for the loss of human life or when the economic, social or environmental impacts are very great.
The following table provides the complete and necessary information on the previously mentioned categories essential for a better comprehension of the Consequence Classes:
2. Define Service CategoryThe Service Categories address the actions and risks to which the buildings are exposed during the construction phase and, later on, usage. The factors which may pose threats are fatigue, the likelihood of seismic actions and the stress levels in the components in relation to their resistance. In addition, the Service Category is divided into two categories: the SC1 (for buildings and components designed for quasi static actions; for structures and components with their connections designed for seismic actions in regions with low seismic activity and in DCL: ductility classes according to EN 1998-1; and for constructions and components designed for fatigue actions from cranes) and SC2 (for structures and components designed for fatigue actions such as road and railway bridges, cranes, structures susceptible to vibrations caused by wind, crowd or rotating machinery, etc.; and constructions and components with their connections designed for seismic actions in regions with medium or high seismic activity and in DCM and DCH: ductility classes according to EN 1998-1).
3. Define Production Category (PC)A Production Category serves as a measurement for the risk from the complexity of the fabrication of the structure and its components, e.g. application of particular techniques, procedures or controls. When defining a Production Category, an engineer has to be aware of the fact that a building or part of a building may contain components or structural details that belong to different production categories. Hence, he must include the structure in Production Category 1 (for non welded components manufactures from any steel grade products or those below S355) or in PC2 (for welded components manufactured from steel grade products from S355 and above, for components that are essential for structural integrity assembled by welding on construction sites, for the ones with hot forming manufacturing or receiving thermic treatment during manufacturing and, finally, for the components of CHS lattice girders requiring end profile cuts).
4. Derive Execution ClassAfter having determined the Consequence Class, the Service and Production Categories, deriving the Execution Class is the last final step that an engineer has to undertake in order to deliver a final product that is in line with the CE Marking standards. The derivation of the Execution Class should always be based on the design parameters appropriate to each project. However, in order to avoid the introduction of unnecessary costs, the engineer should be cautious not to over-specify the Execution Class.
For the readers’ general understanding of the Execution Class determination, the following table contains the matrix of all data classification:
Steelwork Contractor Requirements for CE MarkingFor a CE marked product, the steelwork contractor needs to declare the performance to the System 2+ level of assessment. As a consequence, they must undertake an initial type-testing of the product; a Factory Production Control (FPC) which has to include the implementation of FPC system procedures, the appointment of a responsible welding coordinator and the implementation of welding quality management system (WQMS) procedures; and, finally, a further testing of samples taken at the factory in accordance with the prescribed test plan. The contractor will be assessed by a Notified Body that will complete an initial inspection of the manufacturing plant and of the FPC. The body will further undertake continuous surveillance, assessment and approval of the FPC, which will include an annual audit to ensure continued competence to the declared Execution Class. These steps will be concluded with the issuance of a FPC Certificate and a Welding Certificate Identifying the Execution Class that has been achieved by the steelwork contractor.
It’s needless to say that the new requirements are no burden for large companies, but how have the smaller and medium ones adapted to the change? How have they been affected by the new requirements?
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