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ESDEP WG 3
FABRICATION AND ERECTION
Lecture 3.2.3: Erection III
OBJECTIVE/SCOPE
To give guidance on site welding and to discuss the operation of Quality Control and Safety Procedures on site.
PREREQUISITES
Lecture 3.2.1: Erection I
Lecture 3.2.2: Erection II
The following lectures might be helpful:
Lectures 3.1: General Fabrication of Steel Structures
Lecture 3.3: Principles of Welding
Lecture 3.4: Welding Processes
RELATED LECTURES
Lecture 3.5: Fabrication/Erection of Buildings
Lecture 15A.8: Offshore: Fabrication
Lecture 15B.12: Introduction to Bridge Construction
SUMMARY
The lecture deals with the planning and careful preparation required for site welding; it also discusses the requirements of a Quality Control Programme and gives guidelines for improving site safety.
Lecture 3.2.2 discusses, in detail, the technical aspects of steelwork erection including the requirements for bolted connections. In some cases it may not be possible to use bolts and site welding may then be necessary. Where welding is used careful pre-planning is required, as outlined in Section 2 below.
It is always necessary to have quality control and safety procedures in force on site to ensure the successful completion of the project with minimum risk to the workforce. This lecture discusses these matters in detail, outlining the basis for a Quality Control Programme and giving guidelines on how risk to the workforce may be minimised.
It should be the aim of the designer to ensure that site connections are bolted wherever possible. There will be occasions, however, when site welding is necessary. In such cases, careful pre-planning will be required as follows:
- it will be necessary to provide for temporary alignment of the adjacent components which are to be welded together, and to hold them in position until they are welded. The methods adopted for alignment may have to be able to carry the weight of the components and in some cases a substantial load from the structure.
- safe means of access and a secure working platform must be provided for the welder and his equipment. The working platform may also have to incorporate weather protection, since wind, rain and cold can all adversely effect the quality of the weld.
- the design of the weld and the preparation of the components to be joined must take into account the position of those components in the structure; the method statement for the erection and the welding procedure for each joint must take all these factors into account.
- all the welding must be carried out by qualified welders in accordance with approved procedures.
- a detailed welding plan must be made for the more important structural joints as well as for structures to which special specifications apply.
- the earth return of the electric current must never be made through the steel frame of buildings, cranes, or through metallic parts of installations but must be directly connected to the construction part being welded.
- the surface of the zone to be welded must be clean and dry.
The Quality Assurance Manual defines the appropriate procedures required to ensure that the finished product is up to specification. The staff responsible for the erection must be informed of all the variables affecting the quality of the assembly, so that they can be monitored.
The Quality Control Programme is the particular programme, that has been specifically written for the job in hand.
It is based on the following:
- the Quality Assurance Manual.
- the General Contract for the Project.
- the general standards, applicable to the Project.
- the manufacturer's standards, procedures and specification.
The Quality Control Programme will consist of:
- the site-organisation (in relation to Quality Control).
- the (written) procedures.
- the inspection programme.
The Inspection Programme is based on the erection plan and is complemented by written procedures and points of inspection. Its aim is to ensure good standards of workmanship.
It may incorporate the following:
- Reference numbers for the work procedures.
- Revision numbers.
- Written procedures for:
welding
heat-treatment
non-destructive testing
alignment and plumbing
tolerances
HSFG bolting.
By its very nature, erection of a structural frame is a process involving a certain amount of risk. The work is carried out at height and, until it has progressed to a certain point, there is nothing to which a safe working platform can be attached. In fact, it is true to say that the process of establishing a safe working platform can be as hazardous as the erection process itself; a possible solution may be to provide mobile access platforms if ground conditions permit.
The object of a Safety Procedure is to ensure that everything possible is done to eliminate the risk of an accident. In order to achieve this objective the following procedures should be adopted:
- The safety procedure should be communicated to all concerned with its implementation by, for example, issuing abstracts or running courses. In practice, awareness of safety aspects can best be maintained by continually monitoring hazardous areas of the site (restricted areas, scaffolding, plant, etc.) to check that the appropriate restrictions are in force, and by informing the person in authority if potential hazards exist.
- The necessary equipment should be made available on the site and maintained in good condition. This equipment ranges from safety helmets and belts, to ladders, working platforms and properly selected tools.
-
The work should be organised so that as little as possible is done at height. The danger can be minimised as follows:
× by the use of sub-assembly techniques.
× by fixing ladders and working platforms onto the steelwork before it is lifted into place.
× by the early provision of horizontal access walkways.
× by the provision of temporary staircases or hoists, where appropriate.
- It should be ensured that all portable equipment such as gas bottles and welding plant, is firmly anchored while it is being used. Care should be taken to ensure that there are no flammable materials below on which sparks could fall.
- Finally, and fundamentally, the design should be done with safety in mind as follows:
× Splices should be positioned to give simple site connections, bearing in mind that these may have to be connected at height.
× Lifting cleats and connections for heavy and complex components should be incorporated, as far as possible, in the fabricated elements to be connected.
× Consideration should be given, at design stage, to incorporating cleats, brackets or holes in the fabrication to facilitate fixing of safety belts, safety nets and working platforms.
- Careful pre-planning is required if site welding is necessary.
- A Quality Control Programme, involving inspections, should always be implemented.
- All site personnel should be made aware of the safety procedures.
- Safety procedures should be strictly enforced.
- Arch, H., Erection, Chapters 33 - Steel Designers' Manual, Oxford, Blackwell Scientific Publications, 1992.
- Thornton, W. A., "Design for Cost Effective Fabrication and Construction", Chapter 7.1 Constructional Steel Design, London, Elsevier Applied Science, 1992.
- Miller, E. W., "Erection of Steel Structures", Chapter 7.2 Construction Steel Design, London, Elsevier Applied Science, 1992.
- Potter, P. D., "Fast Steel Erection": Steel Fabrication Journal, No. 46, February 1983, Australian Institute of Steel Construction.
- The Steel Construction Industry Code of Practice for Sage Erection of Building Steelwork: Part 2 - Multi-storey Buildings and Structures, Australia, Australian Institute of Steel Construction, 1989.
- Eurocode 3: "Design of Steel Structures": ENV 1993-1-1: Part 1.1: General Rules and Rules for Buildings, CEN, 1992.
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