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Riveting and bolting are the most commonly adopted procedure used for connecting steel members in a steel structure. The detailed procedures for performing proper riveting and bolting operations are discussed in this article.
A riveted steel connection is made between two plates overlapping at edges, making holes through-thickness of both the members, passing the stem of the rivet through holes, and creating the head at the end of the stem on the other side.
Bolted steel connection is one of the most common elements in steel structure. It consists of a bolt that is secured with the mating of screw threads on the other end. The two main types of bolted joints are tension joints and shear joints.
Preliminaries Before Riveting
The members to be riveted must have all the parts firmly drawn and held together before and during riveting. For multiple riveted connections, a service bolt shall be provided in every third or fourth hole.
Process of Riveting in Steel Structure
- Riveting shall be carried out by using machines of the steady pressure type.
- However, when such facilities are not available, hand riveting may be permitted by the engineer.
- The rivets shall be heated red hot, care being taken to control the temperature of heating so as not to burn the steel.
- The rivets of diameter less than 10 mm may be driven cold. Rivets shall be finished neat, with heads full and of equal size.
- The heads shall be central on shanks and shall grip the assembled members firmly.
- All loose, burnt, or badly formed rivets with eccentric or deficient heads shall be cut out and replaced.
- In cutting out rivets, care shall be taken so as not to injure the assembled members.
- Caulking and re-cupping shall not be permitted.
- For testing rivets, a hammer weighing approx. 0.25 kg shall be used, and both heads of the rivet (especially the machine head) shall be tapped.
- When tested, the rivets shall not give a hollow sound of a jar.
- Where so specified, other tests shall be carried out to ensure the soundness of rivets.
- All rivet heads shall be painted with approved steel primer paint within a week of their fixing.
Process of Bolting in Steel Structure
- The nominal length of the bolt used in the steel structure shall be the distance from the underside of the head to the further end of the shank.
- The nominal diameter of the bolt used in the steel structure shall be the diameter at the shank above the screwed threads, bolts, nuts, and washers shall be thoroughly cleaned and dipped in double-boiled linseed oil, before use.
- All bolt heads and nuts shall be hexagonal unless otherwise specified.
- The bolts length shall be such that it must project at least two clear threads beyond the nuts when fixed in position, and these shall fit in the holes without shaking.
- Wherever necessary, washers shall be tapered to give the heads of nuts and bolts a satisfactory bearing.
- The threaded portion of each bolt must project at least two threads through the nut.
- In all cases where the full bearing of the bolt is to be achieved, the bolt must be provided with a washer of sufficient thickness under the nuts to avoid any threaded portion of the bolt within the thickness of the parts bolted together.
- Where there is a risk of the nuts being removed or becoming loose due to vibrations or reversal of stresses, these shall be secured from slackening by the use of lock nuts, spring washers, as directed by the engineer.
Erection of Bolted and Riveted Member
- The steelwork shall be hoisted and erected carefully in position, without any damage to itself, other structures and equipment, and injury to workmen.
- The method of hoisting and erection proposed to be adopted by the contractor shall be approved by the engineer in advance.
- The contractor, however, shall be fully responsible for the work being carried out in a safe and proper environment without unduly stressing the various members.
- The use of proper equipment such as derricks, lifting tackles, winches, ropes, etc. should be ensured.
- The work may be erected in suitable units as directed by the engineer.
- Fabricated members shall be lifted at such points to avoid deformation or excessive stress in members.
- The structure or part of it placed in position shall be secured against overturning or collapse by suitable means.
- During execution, the steelwork shall be securely bolted or otherwise fastened and when necessary temporarily braced to provide for all loads to be carried safely by the structure during erection including those due to erection equipment and its operations.
- The steelwork shall be placed in the proper position as per the approved drawing, final riveting or permanent bolting shall be done after proper alignment has been checked and confirmed.
- Trusses shall be lifted only at nodes.
- The trusses above 10 mm in a spans should not be lifted by slinging at two midpoints of rafters, which shall be temporarily braced by a wooden member of a suitable section.
- After the trusses are placed in position, purlins and wind bracings shall be fixed as soon as possible.
- The end of the truss which faces the prevailing winds shall be fixed with holding down bolts, and the other end kept free to move.
- In case of trusses of spans up to 10 m, the free end of the truss shall be laid on a lead sheet or steel plate as per design, and the holes for holding down bolts shall be made in the form of oblong slots so as to permit free movement of the truss end.
- For large spans, the truss shall be provided with proper bearing as per the design.
- The columns and stanchions shall be erected truly vertical with the necessary cross bracing etc. and the base shall be properly fixed with the foundation concrete by means of anchor bolts, etc. as per drawing.
- The anchor bolts to be placed in the concrete foundation should be held in a position with a wooden template.
- At the time of concreting, the anchor bolt locations shall be provided with suitable timber mold or pipe sleeve to allow for adjustment which shall be removed after the initial setting of concrete.
- The spaces left around anchor bolts shall be linked to a shopping channel in the concrete leading to the side of the pedestal and on the underside of the base plate to allow the spaces to be grouted up after the base plate is fixed in the position along with the column footing.
- The grouting shall be of cement mortar 1:3 (1 cement 3 coarse sand) or as specified.