The process of making connections in steel structure is carried out using one of these three methods: welding, riveting, and bolting. The preliminary works such as laying out, fabrication, making holes, and assembling of steel members before executing the actual connection process are explained in this article.
1. Laying Out of Steel Members
- A drawing of the steel structure to be fabricated shall be drawn on a level platform to full scale.
- This may be done in full or in parts, as shown in the drawings or as directed by the engineer.
- Steel tape shall be used for measurements.
2. Fabrication of Steel Members
- Shop drawings giving detailed information for the fabrication of the component parts of the structure, including the type, location, size, length, and details or rivets, bolts, or welds, shall be prepared in advance, before the actual fabrication.
- The drawings shall indicate the bolts, welds, shop, and field rivets.
- The steel members shall be stenciled or marked with paint for easy identification, as shown in the shop drawing.
- Great accuracy must be observed in the fabrication of various members so that these can be assembled without being unduly packed, strained, or forced into position, and when built up, shall be true and free from twist, kinks, buckles, or open joints.
- Wooden or metal sheet templates shall be made to correspond to each member, and the position of rivet holes shall be marked accurately on them and the holes should be drilled.
- The templates shall then be laid on the steel members, and holes for riveting and bolting shall be marked on them.
- The ends of the steel members shall also be marked for cutting as per the required dimensions.
- The base of the steel columns and the positions of anchor bolts shall be carefully set out at the required location.
- The steel section shall be straight or be straightened or flattened by pressure unless required to be of curvilinear form and shall be free from twists.
- These shall be cut in square either by shearing or sawing to the correct length and measured by steel tape.
- No two pieces shall be welded or joined to make up for the required length of the member.
3. Making Holes for Riveting or Bolting
- The diameter of holes for bolting or riveting which are more than the thickness of the member shall only be drilled after the members are assembled and tightly clamped or bolted together.
- The punching may be permitted before assembly if the holes are punched 3mm lesser than the required size and reamed after assembly to the full diameter.
- The thickness of the steel section punched shall not be greater than 16 mm.
4. Rivet Holes in Steel Members
- The diameter for rivets and black holes shall be taken as the nominal diameter of a rivet plus 1.5 mm for rivets of nominal diameter less than or equal to 25 mm and 2.0 mm for rivets of nominal diameter exceeding 25 mm unless specified otherwise.
- The holes for fitted and turned bolts shall be reamed or drilled large by a range of 0.2 to 8 mm depending upon the diameter of bolts.
- The holes must have their axis perpendicular to the surface of the member.
- The reaming or drilling shall be free from burrs, and the holes shall be clean and accurate.
- The holes for rivets and bolts shall not be formed by the gas cutting process.
- The holes for countersunk bolts must have their bolt or rivet head flush with the surface after fixing.
5. Assembling of Riveted or Bolted Steel Member
- Before making holes in individual members, riveted or bolted steel members shall be assembled and clamped properly and tightly to ensure close abutting or lapping of the different members’ surfaces.
- All stiffeners shall be tightened both at top and bottom without being drawn or caulked.
- The abutting joints shall be cut or dressed, true, and straight and fitted close together.
- Web plates of girders, which have no cover plates, shall have their ends flush with the tops and angles, unless otherwise required.
- The web plates, when spliced, shall have a clearance of not more than 5 mm.
- The erection clearance for cleated ends connecting two steel members shall preferably be not greater than 1.5 mm.
- The column splices and butt joints of struts and compression members depending on contact for stress transmission shall be accurately, machined, and close butted over the whole section.
- In column caps and bases, the ends of shafts together with the attached gussets, angles, channels, etc., after riveting together shall be accurately machined so that the parts connected, butt against each other over the entire surfaces of contact.
- The connecting angles or channels shall be fabricated and placed in position with great accuracy so that they are not unduly reduced in thickness by machining.
- The ends of all bearing stiffeners shall be machined or grounded to fit tightly both at the top and bottom.
The shop drawings give detailed information for the fabrication of the components of the structure, including the type, location, size, length, and details of rivets, bolts, or welds.
The thickness of the steel section punched shall be not greater than 16 mm.
The diameter for rivets and black holes shall be taken as the nominal diameter of a rivet plus 1.5 mm for rivets of nominal diameter less than or equal to 25 mm and 2.0 mm for rivets of nominal diameter exceeding 25 mm unless specified otherwise.
The holes for fitted and turned bolts shall be reamed or drilled large by a range of 0.2 to 8 mm depending upon the diameter of bolts.