PIANC WG211 was tasked with updating the design approach of marine fender systems. While the load-andresistance- factor design approach is widely adopted in the design of marine structures, the PIANC WG33 design guideline utilizes a global safety factor, referred to as the factor for ‘abnormal’ impact. However, it is unclear whether this global safety factor results in an appropriate reliability level. Several aspects of fender system design that significantly influence the fender reliability level do not appear to have been considered by PIANC WG33, such as, reliability targets, the effect of vessel berthing frequency and multiple fender contact. This paper explores the use of statistical data from recorded berthing velocities, fender manufacturer’s data, and other adjustment factors, to establish suggested partial factors of safety for the selection of fenders. The proposed partial energy factors are intended to provide the industry with greater uniformity in the assessment of the reliability level of fender systems and clearer guidance on the recommended design approach than is presently provided. Furthermore, this method can also be used in conjunction with national codes and standards. It is hoped that port authorities and terminal operators may also be able to use the findings of this study to derive greater insight into the reliability of their own fender systems and to optimize service
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Design of fender systems consists of two distinct steps: selection of an appropriate fender based on berthing energy demands from the berthing vessel and design of the supporting structure based on the reaction force imposed by the fender on the structure. Both steps include load or safety factors to increase the level of safety. The factor applied to the selection of fenders has up until now been referred to as an "abnormal berthing factor," with relatively vague recommendations for suggested values for use, usually between 1.25 and 2.0. British Standards (BS 6349-4:2014) has recently chosen to refer to this value as an "energy factor" instead of the previously used abnormal berthing factor. Codes and standards for design of most structures are often based on methods involving what is often referred to as load factors, partial load factors, or resistance factors. As an example, Load and Resistance Factor Design (LRFD) in the US applies load factors to the different loads acting on a structure, and resistance factors to the capacities provided by the structural elements. Similarly, the Eurocode, OCDI, and British Standards use the partial factor method where the effect of the characteristic action, which can be a specified load or imposed deflection, multiplied by the load factor must not exceed the design resistance, i.e., characteristic resistance divided by the partial factors for materials. Although their applications are seemingly simple, these methodologies are based on substantial statistical work, including extensive collection of statistical data, a careful analysis of the data, and appropriate selections of safety levels and acceptable probabilities of failure. This paper explores how utilizing statistical data from berthing velocities, fender manufacturer data, and other adjustment factors were used to establish suggested partial energy factors for selection of fenders. This is what previously has been described as the abnormal berthing factor. By utilizing this method, energy factors can be recommended based on several factors, such as anticipated vessel traffic, type of terminal, type of fender system, or whether the analysis is done for new or existing structures. The suggested factors will provide much clearer guidance than what is currently given in the current fender design guidelines from PIANC WG33 and will be the basis for recommendations on energy factors in the upcoming document from WG211.

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With the preparation and development of PIANC WG 211, it is evident that clear design recommendations for vessel berthing velocities need to be derived, since this is one of the most critical parameters in fender-system design. This paper discusses recommendations on how to determine the characteristic berthing velocities for the design of fenders systems, with and without the use of field observations. Furthermore, the proposed characteristic berthing velocities have been compared with the guidelines of PIANC WG 33, PIANC WG 145, the German EAU 2012, and the Spanish ROM. Based on the findings of these investigations, some historically embedded hypotheses will need to be reconsidered. The key findings of this study are considered useful for the design of fender systems for new berthing facilities and for the assessment of existing marine structures.

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