Estimation of the maximum end buffer impact force for a given level of reliability

Abstract

The first paper in this set of two, titled The effect of parameters on the end buffer impact force history of the crane (see page 55), examined the effect of a change in the magnitude of the parameter on the end buffer impact force history. This paper investigates to what degree a change in the magnitude of the parameter alters the impact force history. This was accomplished through a sensitivity analysis performed by individually varying the magnitude of the parameter in the FE model. For each case individual maximum impact forces were obtained. The maximum impact force could not simply be selected by choosing the greatest value from the sensitivity study. A constraint optimisation technique for a given level of reliability ((3) using the FE simulation data was used to determine the maximum impact force. A comparison between the constraint optimisation and codified results showed that SABS 0160-1989 underestimates the impact force by 18%, while SANS 10160-2010 substantially overestimates the impact force by 64% for a level of reliability of β = 3. If the relevant clauses of SANS 10160-6 that pertain to end stop design are used in their present form, this will result in a conservative design, whereas SABS 0160 has a probability of 2.3% of being exceeded.

Keywords

• crane
• impact force
• constraint optimisation