Numerical evaluation (FEA) of end stop impact forces for a crane fitted with hydraulic buffers

[摘要] ENGLISH ABSTRACT: End stop impact forces are horizontal longitudinal forces imposed by the crane on the end stops.Both the previous South African loading code SABS 0160:1989 and the current South Africanloading code SANS 10160 , classify end stop impact force as an accidental load case , hence theyare not expected to occur within the expected lifetime when the guide lines for crane operation arestrictly adhered to.In the estimation of end stop impact force, the previous South African loading code SABS0160:1989 gives two guidelines for estimating the end stop impact force. The first guideline issimplistic in its approach and it's based on the assumption that the crane and its supportingstructure act as rigid bodies; hence calculation is based on rigid body mechanics. Literaturereviewed reveals that this is not correct. The second guideline is more explicit in its approach as ittakes into account the crane speed, resilience of the buffers and resilience of the end stops.The current South African loading code, SANS 10160 gives a better representation of thedynamics of the crane movement. However, the dynamic factor recommended for the estimation ofend stop impact force is empirical in nature and thus lacks adequate scientific backing.One of the purposes of this research was to investigate the influence of the stiffness of the cranebridge on the end stop impact force. This was achieved by conducting a series of FEA simulationson the double bridge EOHTC fitted with elastomeric buffers. For this set of simulations, the effect ofeach influencing parameter on the end stop impact force was investigated, and the maximum endstop impact force was obtained using a constraint optimization technique. From the resultsobtained, comparison was then made with the existing maximum end stop impact force for a singlebridge EOHTC fitted with elastomeric buffers.Another purpose of this research was to investigate the end stop impact force for an electricoverhead travelling cranes (EOHTC) fitted with hydraulic buffers taking into account the dynamicsinvolved in the movement of the EOHTC. This was achieved by a series of experimental andnumerical investigation. The numerical investigation was conducted using an existing numericalmodel of an EOHTC which captures the crane and its supporting structure as a coupled system.Finite element analysis (FEA) impact force histories obtained were calibrated to the baseexperimental impact force histories. Thereafter, a series of FEA simulations were conducted by changing the parameters which have a substantial effect on the end stop impact forces. Thisyielded various maximum impact peaks for various parameters. The maximum impact force wasthen mathematical obtained from the FEA impact force histories for a given level of reliability usinga constraint optimization technique. Also, codified end stop impact forces were calculated for theSABS 0160:1989 and SANS 10160-6:2010. From the results obtained, comparison was madebetween the codified end stop impact force and the maximum impact force obtained from theconstraint optimization technique.

[发布机构] Stellenbosch University