8 STEEL STRUCTURES

8.1 STRUCTURAL STEEL

8.1.1 General

1. This Section includes the production and erection of structural steelwork, as shown on the Contractor’s drawings.

2. All project related steelworks shall be according to QCS - Section 16. Workmanship and materials shall be in accordance with EN 1993 (which shall have priority), EN 10025 and relevant standards.

3. Shop drawings shall include connection designs, complete details and schedules for fabrication and assembly of structural steel members, procedures, diagrams, and erection plans.

8.1.2 Products

1. Materials

(a) All structural steelwork, including structural fasteners and welding consumables etc. shall comply with the EN 1993 and EN 10025.

2. Fabrication

(a) All structural steel, before and after fabrication, shall be straight unless otherwise specified, and shall be free from twists. The fabrication tolerances shall comply with EN 1993.

(b) Appropriate measures shall be taken to prevent internal corrosion of hollow structural steel members.

3. Testing

(a) The tests shall be in accordance with EN 1993. Test certificates for the materials and welding shall be maintained.

4. Tolerances

(a) The tolerances for erected steelwork shall comply with EN 1993.

5. Galvanizing

(a) Galvanising shall be in accordance with EN ISO 1461.

(b) Cold formed or cold worked steel sections shall not be hot dip galvanised.

8.1.3 Execution

1. Erection

(a) Structural steelwork shall be distinctly marked before delivery.

(b) Permanent bolts shall not be used as service bolts during erection, where such use is liable to cause damage to the protective treatment provided to the bolt.

(c) Welds shall be kept free from slag or other inclusions. All adhering slag shall be removed immediately after the completion of each run. Slag and weld spatter shall be removed from surrounding surfaces after welds have been completed.

2. Surface preparation

(a) All surfaces shall be clean before protective treatment is commenced and shall comply with EN 1993.

(b) Blast-cleaned steelwork shall be free from dust.

8.1.4 Protection and repairs

1. General

(a) Protective work shall be carried out in accordance with EN ISO 12944, and all damage shall be repaired.

(b) Protective treatment shall be carried out in the steelwork fabricator's works after fabrication. Shop treatment shall be carried out in a weather-proof structure under clean, dry conditions.

(c) All protective paint systems to structural steel shall have full compatibility between coats and with the metal substrate. There should be adequate adhesion to substrate and between coats over the operating temperature range and there should be no under-softening to cause lifting, wrinkling or bleeding through of stains. All components of a specific paint system shall be from the same manufacturer.

(d) All paints and coatings shall be non-toxic and shall not produce toxic fumes or other toxic substances during application and/or when exposed to fire.

(e) Structural steel shall be degreased prior to painting. Where steelwork is partially embedded in concrete, the steelwork shall be coated over an area extending to at least 100 mm beyond the exposed area.

2. Paints

(a) All paints shall comply with EN ISO 12944.

8.1.5 Bolted connections

1. Bolts shall be threaded only over the length of shank which is outside the parts bolted together. The bolt shall protrude by at least two complete threads and not more than four complete threads beyond the outer face of the tightened nut.

2. Holes shall not be distorted or enlarged by the use of drifts.

3. High strength friction grip bolts shall be fitted in accordance with BS 4604, Part 2.

8.1.6 Welding

1. Welding of structural steelwork shall comply with EN 1011-1.

2. All welders shall possess valid test certificates in accordance with EN 287-1. These test certificates shall be appropriate to the type of work being carried out and shall be always available for inspection.

3. Testing of Welds

(a) Facilities, equipment and qualified personnel shall be provided to carry out any testing and visual inspection of welds. The type of testing shall include but not be limited to the following:

(i) Magnetic particle flaw detection test (to EN 1290);

(ii) Penetrant flaw detection test (to EN 571-1);

(iii) Ultrasonic examination (to EN 1714); and

(iv) Radiographic examination (to EN 1435).

(b) The quality of welds shall be assessed in accordance with the acceptance levels given in EN 15614-1. The visual inspection of fusion welds shall be carried out in accordance with EN 970. All inspection records and test results shall be available on Site for inspection.

(c) Where failures are identified in the weld tests, the Engineer may require any additional testing.

4. Welding procedure

(a) Details of the proposed welding procedures together with diagrams showing the build up of all main welds shall be included in the Contractor’s method statement.

(b) No distortion shall be allowed.

8.2 REINFORCEMENT

8.2.1 General

1. This specification sets out the minimum standards, including but not limited to materials and workmanship as follows:

(a) the steel shall be produced and classified in accordance with EN 10080;

(b) spacers shall be in accordance with BS 7973-1, Product performance requirements and BS 7973-2;

(c) binding wire shall not stain the concrete surface;

(d) wire mesh shall be constructed of transversal and longitudinal wires using B500A quality steel according to EN 1421-2;

(e) mechanical couplers may be used;

(f) galvanised reinforcement shall be hot dip galvanised, after cutting to length and bending;

(g) galvanising shall satisfy the requirements according to standards EN ISO 1460 and EN ISO 1461;

(h) stainless steel reinforcement shall comply according to EN 10088.

8.2.2 Execution – Wire Mesh

1. Wire mesh shall be installed in Sprayed Concrete Lining (SCL) tunnels embedded in shotcrete.

2. In cases where, during the installation of the wire mesh its extension is required, the overlapping of the mesh shall, at a minimum be as follows:

(a) At least equal to 300 mm, concerning extension of the main reinforcement (strength) of the mesh; and

(b) At least equal to 150 mm, concerning extension of the secondary reinforcement (distribution) of the wire mesh.

3 The overlapping edges shall be tightly fixed together through wires, or held by means of standard couplers.

8.2.3 Execution – Bar Bending Schedules

1. The minimum lap lengths and effective anchorage lengths for bars under stress shall be full tension lap lengths in accordance with EN 1992-1-1.

8.2.4 Execution – Bending

1. Bars shall be bent in accordance with the provisions of standard EN 1992-1-1.

2. Any reinforcement showing signs of damage shall be rejected and removed from the Site.

3. The reinforcement shall be accurately cut and bent to the form shown on the bending schedules in accordance with standard EN ISO 3766.

8.2.5 Execution – Fixing

1. The steel for stainless steel tying wire shall be grade 1.4404 in accordance with standard EN 10088-1.

8.2.6 Execution – Reinforcing Steel Testing

1. The methods of testing and the methods of attestation of conformity shall be as defined in standard EN 10080.

8.2.7 Steel Fibres

1. The steel fibres shall comply with standard EN 14889-1.

2. The minimum properties of the steel fibres shall be:

(a) the steel fibres shall be made of low carbon, cold drawn wire (EN 14889: Group 1), have a circular cross section with hooked ends.

(b) Tensile strength of the wire shall be minimum 1100 N/mm².

(c) Nominal length of the steel fibres shall be between 40 and 60 mm.

(d) Aspect ratio (L/D) shall be between 50 and 70.

(e) The steel fibres shall be distributed evenly within the concrete mix.

8.2.8 Glass Fibre Reinforced Plastics (GRP)

1. The design of GRP soft eye structures shall be produced and classified in accordance with standard QCS – Section 8, Part 7.

2. The design of GRP soft eye structures shall be in accordance with standard EN 1992-1-1.

END OF PART