External Loads - general

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Topics here are mostly if not entirely concerned with Part 1 Appendix G.


Why does Clause G2 refer to API RP 1102 (1993) which has been superseded by later editions?

This was an error. The use of latest revisions is always preferred and in this case the changes to API RP 1102 have no material impact. (Nick Kastelein)


Clause G4 (i) and (ii) refer to A160 and M1600 loads and the applied surface pressures are calculated based on the AS 5100.2 tyre footprints (Ap = 0.10 m2 and 0.08 m2). However the note in Clause G5 states that per API RP 1102 Ap must remain as 0.093 m2? So, which Ap is meant to be used?

In the API RP 1102 methodology Ap must be taken as constant, not variable. It is hardwired into the calculation. Refer to this detailed article in PipelinesOZ2: https://pipelinesoz2.wordpress.com/2019/02/14/guest-post-surface-vehicle-loading/ (Nick Kastelein)


In Clause G4 (ii) M1600 is based on a number of tri-axle groups each with a 360 kN load plus a 6 kN/m linear load. Here it is recommended to be applied as a 360 kN tandem axle load. However the indicated 750 kPa bearing pressure has been correctly calculated based on a tri-axle configuration. So, should the Standard say 360 kN tri-axle load? However API RP 1102 considers only single and tandem axles so perhaps is should say 240 kN tandem axle load? Or 120 kN single axle load?

The idea is to apply a 360 kN tandem axle because API RP 1102 does not have tri-axle factors. It is a conservative equivalence, and if it passes you have nothing to worry about.

Importantly, it is only very conservative near the surface. The deeper you go the more it is correct.

This too is discussed in detail in PipelinesOZ2: https://pipelinesoz2.wordpress.com/2019/02/14/guest-post-surface-vehicle-loading/

(Nick Kastelein)


Coming soon (we hope): Discussion of API 1102 vs. Spangler methods