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ESDEP WG 3

FABRICATION AND ERECTION

Lecture 3.2.1: Erection I

OBJECTIVE/SCOPE

To give undergraduates, young engineers and managers an introduction to the trade of steel erection.

PREREQUISITES

None are essential.

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 3.2.2: Erection II

Lecture 3.2.3: Erection III

Lecture 3.5: Fabrication/Erection of Buildings

Lecture 15A.8: Offshore: Fabrication

Lecture 15B.12: Introduction to Bridge Construction

SUMMARY

The lecture emphasizes the importance of considering erection during all phases of the project. It outlines the principal requirements for a technical specification and also deals with the organisational aspects on site.

1. INTRODUCTION

It is important that the erection of the steelwork is considered from the very first stages of a project. Both design engineer and fabricator must consider the following:

The erection team on site must ensure that :

Erection of structural steelwork is, therefore, an activity that requires detailed consideration from both an engineering design and organisational point of view. Sections 2 and 3 of this lecture discuss these matters under the headings of: Technical Specification and Site Organisation.

2. TECHNICAL SPECIFICATION

The Technical Specification for Erection should be developed as early as possible and should outline the conditions required on site and the technical standards in force. The documentation should deal with the following matters:

Specification for Erection

The specification for erection should include, in as much detail as possible, the following information:

  1. Requirements for unloading, storage, and handling.
  2. Details of any preassembly required on site.
  3. Dimensional and levelling tolerances, including those required for foundations and baseplates.
  4. Specification for activities relating to the assembly itself such as bolting, welding and testing.

3. SITE ORGANISATION

3.1 Principal Jobs on Site

The site organisation required depends largely on the size of contract; in the case of a major project it could, for example, be subdivided into the following sections:

3.2 Estimation of needs

Figure 1 gives an example of an Organisation Chart for the extreme case of a project for the erection of a large steel frame. The chart is applicable to a direct assembly workforce of approximately 125 men.

3.3 Basic Installations and Site Conditions

The Erector must have adequate facilities available on site for his personnel, including appropriate office accommodation, sanitary services and storage areas. He must also ensure that the site is properly supplied with mechanical services necessary for erection such as electricity, gas, compressed air, etc. These facilities and installations must comply with the following requirements:

  1. They should be situated, where possible, in close proximity to the work site, giving easy access to the site without interfering in any way with the progress of the work;
  2. They should be adequately constructed to, at least, the minimum legal requirements;
  3. They should have communication facilities;
  4. They must be maintained in satisfactory condition throughout the work and removed on its completion.

3.4 Direct Manpower

It is essential to estimate the direct manpower resources required in order to properly programme the erection process and accurately forecast the time of completion and the costs incurred.

Manpower resources are normally estimated by calculating the number of direct man-hours required in steel frame erection. An adequate estimate can be obtained based on the erection weight broken down item by item (columns, beams, bracings, floors, etc.), and applying various weight rates (in hours) obtained from past experience.

For a more accurate estimate, each activity can be evaluated, not only in terms of its duration, but also in terms of personnel required to complete it. The product of the time (in hours) multiplied by the number of people in the team will give the man hours for each activity which can be totalled to give the direct man-hours required for the whole job.

3.5 Cranes, Tools and other Equipment

Once the activities involved in the erection have been decided, the tools and equipment required to carry out the work can be defined; these may include:

The heaviest or highest element to be erected, or the part which requires the greatest lifting capacity (radius-weight) determines the minimum crane capacity to be used.

Figure 2 shows the various lifting capacities of a tower crane.

4. CONCLUDING SUMMARY

5. ADDITIONAL READING

  1. Arch, H., Erection, Chapters 33 - Steel Designers' Manual, Oxford, Blackwell Scientific Publications, 1992.
  2. Thornton, W. A., "Design for Cost Effective Fabrication and Construction", Chapter 7.1 Constructional Steel Design, London, Elsevier Applied Science, 1992.
  3. Miller, E. W., "Erection of Steel Structures", Chapter 7.2 Construction Steel Design, London, Elsevier Applied Science, 1992.
  4. Potter, P. D., "Fast Steel Erection": Steel Fabrication Journal, No. 46, February 1983, Australian Institute of Steel Construction.
  5. 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.
  6. 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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