Holdfast Training Services Trial Blog

I am currently designing a turning dolphin for a tideway project in the Boston Barrier area. The dolphin will consist of steel tubular piles driven into the river bed with a 2m deep RC pile cap. The cap will have a bollard fixed for mooring ships. The dolphin will also require fendering.

Fendering forces (for those that don’t know) are calculated from the berthing energy being dissipated over distance and time. This means that you can only calculate a “fendering force” once the fender has been chosen.

The problem has arisen when deciding the forces on the dolphin. It is BAM Nuttall’s opinion that we should be provided with the forces to expect from mooring and fendering and design a structure to resist those forces. The client has paid for a navsim analysis of the shipping externally and they have provided a line force (fendering) and point load (mooring) for the structure with a caveat that these numbers should be used to validate our own and not be used as a design value. These simulations and calculations were executed with assumed fendering choices and are therefore not really worth the paper they’re written on.

The elephant in the room is nobody thinks it’s their responsibility to provide the fendering solution and nobody wants to stick their neck out and offer up a design value. In our eyes this is a dispute between the client and HR Wallingford but we are caught in the middle. If the client isn’t paying Wallingford to provide us with these forces then why are they paying them? When BAM bid for the design, they did not include the cost of calculating these forces into our quote. This means if we are stuck with having to do it we will need to subcontract this out (as we do not hold the specialty within the department) and will not be able to recover the cost.

As I have no view of the contracts between each party I am simply an outside observer speculating on what disputes may arise from this project. I thought it was an interesting question to ask though about where design responsibility for determining forces lies. Of course we would assume responsibility for calculating wind forces on a hoarding so why not fendering on a dolphin?