Section 4 Design criteria

4.1.1 The allowable stress criteria to be used for walkways are as defined in Pt 3, Ch 5, 4.1 Allowable stress - Elastic failure, Pt 3, Ch 6, 4.2 Deflection criteria, Pt 3, Ch 6, 4.3 Hoisting and slewing arrangements, Pt 3, Ch 6, 4.4 Safety restraints inclusive.

4.2.1 The allowable deflection criteria for walkways is as defined in Pt 3, Ch 5, 4.6 Deflection criteria.

4.3.1 The safety factors for chains and steel wire ropes used for hoisting or slewing operations is as defined in Pt 3, Ch 5, 4.7 Hoisting and slewing arrangements.

4.4.1 Where a bridge or ramp is retained in position by a single articulated mechanical connection, a suitable means is to be provided to prevent the complete detachment of the bridge or ramp from the support in the event of failure of the joint.

4.4.2 Chains or wire ropes used for this purpose are to take due account of the kinetic energy developed by the falling structure and are to have a safety factor of at least 2,0.

4.4.3 To prevent movement and consequent failure, pins for all primary hinges and articulations are to be locked in position by adequate keep plates, castellated and wired nuts, and cover plates or other suitable means.