Comparison of fender dimensions, PIANC WG211 and PIANC WG33

PIANC WG211 was tasked with updating the guidelines for design of marine fender systems. One of the changes to the new guideline is the change in approach to the design. Whilst the load and resistance factor design approach is widely adopted in the design of marine structures, the PIANC WG33 (2002) design guideline utilises a global safety factor, referred to as the factor for ‘abnormal’ impact. Based on statistical data from recorded berthing velocities, fender manufacturers’ data, and adjustment factors for uncertainties in berthing energy calculation, PIANC WG211 has established partial factors of safety for fender selection. To gain clarity on what the effects the updated design approach is, this paper compares the outcomes of the old PIANC WG33 and the new PIANC WG211 guideline. Data from actual project fender design specifications have been considered. Given similar input variables the new design method generally results in marginally smaller fender dimensions. WG211, however, recommends, on the basis of PIANC WG145 (2019), higher berthing velocities for large seagoing vessels compared to Brolsma’s berthing velocity curves in PIANC WG33, which can result in quite large fenders in the absence of site-specific information. During this study, however, the higher berthing velocities recommended by PIANC WG211 were confirmed based on new berthing records collected in a port in the northeast part of Europe. In general, when site-specific information is used to evaluate the navigation conditions and the associated berthing velocity, the design method of PIANC WG211 will result in reasonable fender dimensions. In addition, it was found that the fender dimensions can, in some cases, largely be optimised based on a parametric analysis of the fender pitch. Consequently, the conclusion is that the new design approach results in reasonable fender dimensions for majority of the ports and terminals around the world. Nevertheless, it is crucial to examine the influence of the local navigation conditions, such as wind, wave, currents and berthing manoeuvres, on the berthing velocity and that the asset owner, e.g. port or terminal authority, specifies the required safety level of the fender system specific to the berth.