Flexible Dolphins

Crow

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000390995
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Millions of breasting and mooring dolphins have been installed in inland waterways adjacent to jetties and waiting facilities for ship-to-ship transhipment or as crash barriers in commercial port areas throughout the world. A dolphin is a marine structure that is frequently installed in ports, waterways and other places related to marine traffic. Dolphins are typically located adjacent to waterfront structures such as quay walls, jetties, locks and bridge piers. The purpose of a dolphin is threefold:

• Allow ships to berth and moor safely and efficiently
• Protect waterfront structures by acting as a crash barrier and sacrificial structure
• Direct and guide marine traffic by acting as a lead-in dolphin and navigation aid

The main objective of this handbook is to provide engineers, asset managers, suppliers, tender teams, contractors and principals with such guidance on the design and construction of flexible dolphins by collecting and describing knowledge of and experience with these flexible marine structures.This handbook is intended to prevent extensive discussions during the design and construction stages of projects involving flexible dolphins. It is part of a series of Dutch port infrastructure design recommendations that include the Quay Walls handbook and Jetties and Wharfs handbook.

1 Introduction

1.1 History of flexible dolphins

When Arion of Lesbos, the world's most famous lyre player, was doomed by the sailors and forced to cast himself into the sea, a dolphin, charmed by the music of his funeral dirge, carried him on its back and bore him to safety. It was this act of philanthropy and friendliness to man that earned the dolphin, Delphinus, a place among the stars [1.1].

The word dolphin is related to the Greek word Delphina, which means ‘woman from Delphi’. The city of Delphi is connected with Delph, which means hollow and is cognate with the word delve, from Old English delfan, meaning ‘to search deeply or to dig the ground, as with a spade’, and comes from the Indo-European root dhelbh, which means ‘to dig or excavate’ [1.2]. The city of Delft in Holland is related to this root, from where we get Delft glazed earthenware.

Embedded breasting and mooring piles are also installed deeply into the soil. But this does not explain why mooring and berthing structures were called dolphins – but there are a couple of plausible explanations. It should be noted that the old English word for dolphin was delfin and refers in Latin to the shape of a womb, which shows similarities with the shape of a dolphin. From a distance, the shape of a piled offshore structure combined with movements of the water around it typically looks like a diving dolphin. It is most likely that in Germany, the Latin word delfin evolved into the word dalben. Another less plausible explanation is that piled mooring structures were equipped with artillery (e.g. canons) and the shadow of these canons on the water looked like dolphins. In French and Dutch, piled berthing structures are often called duc-d'albe and dukdalf, respectively. Both words seem to refer to the Duke of Alba (1507–82), who was not very popular among the French and Dutch during this period. There are several plausible reasons why people started using this corruption as a synonym for dolphins [1.3]:

• The duke was as rigid and unbending as a multiple-pile berthing structure.
• The duke attached his opponents or insurgents, the Watergeuzen (‘Sea beggars’), to these types of berthing structures at low tide and they were drowned when the tide came in [2.3].
• The duke introduced these types of structures in France and the Netherlands.
• The mooring lines attached to the berthing structure represent a death by hanging – a rope around the neck of the duke.
• Due to the movement of the water, the piles look like diving dolphins – representing the Duke of Alba avoiding crucial battles.
• To humiliate the duke, because from a distance the dolphin looked like the slender head of the duke with a coat. The people would like to use the driving on the head of the duke.

Pile berthing structures were frequently installed adjacent to docks, locks and waterways. The terms d'alba and dalf in the words duc-d'albe or dukdalf seem to refer to the word dolphin and the term duc or duk was most likely related to the words ‘dock’ or ‘docking of vessels’. Therefore the name of the duke was used (or rather, misused) to denominate breasting dolphins for docking vessels. Later in Holland, the berthing piles were also called Konginspalen, which means piles for a king.

1.2 Guidance for the reader

Breasting and mooring dolphins are installed in inland waterways, adjacent to jetties and waiting facilities, for shipto-ship transhipment or as crash barriers in commercial port areas. These marine structures were originally constructed on the basis of trial and error and mainly consisted of wooden piles. Around 1900 it was possible to perform fairly simple calculations in order to estimate the strength and deformation characteristics of dolphins. In 1930, Dr Hermann Blum developed a more advanced method for the design of horizontally loaded piles. This method has been used ever since, although alternative design models are available, such as p-y curves and finite element methods. The use of steel as a construction material was also introduced around 1930. However, up until the 1950s, wood remained the main construction material in the design of dolphins. In the Netherlands, flexible dolphins realized since the 1950s are predominantly laterally loaded steel tubular piles with large pile diameters and high ductility in order to achieve economy of design.

The line loads of moored ships cause static lateral loads at the top of a dolphin's pile head. Dolphin piles are defined as flexible dolphins because of the contribution of the pile deflection to the absorption of berthing energy. Breasting dolphins are often installed with a fender system or a wooden timber structure to reduce hull pressure during the landing procedure of a vessel, as well as to protect dolphins and the structure directly behind them, which can be a jetty, bridge, lock or storm-surge barrier. The different types of dolphins are described and discussed in chapter 2.

Although a dolphin's structure is rather simple, its design is relatively complex since the structure needs to provide both support (minimum deflection) and energy absorption (through flexibility). The latter results in the uncommon condition that high soil strength becomes unfavourable, which is not common for geotechnical structures. At present, the diameters of thin-walled steel tubular piles are increasing, as are their D/t ratios. This has a positive effect on the mobilized passive soil wedge, but a negative effect on ductility, the capacity of cross sections and drivability. A sudden collapse due to local buckling before large deformations develop should be avoided because no warnings are received before failure. The most important design aspects are discussed in chapter 3, which presents the state of the art of the available knowledge with regard to essential design aspects and methods presently available in the industry. In the Netherlands, flexible dolphins are classified as geotechnical structures and they have to comply with the Eurocodes. Unfortunately, clear guidelines for dolphins have not been implemented in the Eurocodes and detailed design guidance is lacking. This often results in a fairly conservative design compared to existing flexible dolphins. Although code compliance is important, existing dolphins are performing quite well and the asset portfolio of flexible dolphins in the Netherlands is in good condition, which does not logically support the need for more conservative designs. Hence, chapter 4 presents four case studies that were used to compare the available design models and safety philosophies and techniques for dolphins. The theoretical background to existing design methods was based on a limited amount of prototype testing. To increase reliability and safety, more insight was obtained by performing a full-scale field test in the Port of Rotterdam (see appendix A1) that investigated in detail not only geotechnical failure but also the effects of local buckling and excessive yielding. To derive reliable conclusions concerning the actual performance and failure modes, test piles were loaded until a structural failure or an impending collapse occurred. The more advance design aspects – such as piles in slopes, drained and undrained soil behaviour, and repetitive loading – are discussed in detail in chapter 5. The main objective of this guideline is to provide engineers, asset managers, suppliers, tender teams, contractors and principals with guidance on the design and construction of flexible dolphins. The results and insights reported in chapters 1–5 were used to develop a design approach for flexible dolphins. The steps in the design approach are described in chapter 6, and the construction is covered in chapter 7. This latter chapter provides quite useful information for the designer with regard to procurement, fabrication, material properties, drivability and decommissioning. Another important aspect is the equipment installed on flexible dolphins – such as fender systems, the platform, bollards, quick release hooks and lighting/illumination – which is described in chapter 8. The lifecycle aspects and sustainability in the design of a flexible dolphin are highlighted in chapter 9. Finally, the lessons learned are presented in chapter 10.

This guideline is intended to obviate extensive discussions during the design and construction stages of projects involving flexible dolphins. It is part of a series of Dutch port infrastructure design recommendations, such as the Quay Walls handbook, the Jetties and Wharfs handbook, and the Banks handbook.

1.3 References

• [1.1] Website: http://historiek.net/dukdalf-een-touw-om-alvas-nek/43108/#.Voz29kb396I.
• [1.2] Website: http://www.constellationsofwords.com/Constellations/Delphinus.html.
• [1.3] Desnerck, R., Devos, M., Lanszweert, W., Termote, T., Van Cauwenberghe, C., Parmentier, J. & Seys, J. (2004). Zeewoorden: een speurtocht naar de naamsverklaring van zandbanken, geulen en andere ‘zeebegrippen’. ‘t Potje; Dukdalf, in: De Grote Rede 11. De Grote Rede: Nieuws over onze Kust en Zee, 11: pp. 14–16 http://www.vliz.be/docs/groterede/GR11_zeewoorden.pdf.

2 Types of Dolphins

A large variety of dolphins have been developed over time. Although this design guideline focusses on the design and execution of flexible dolphins, this chapter describes the main types of dolphins used in practice. The specific characteristics of each type of dolphin are discussed.

2.1 Functions and main types of dolphins

A dolphin is a marine structure that is frequently installed in ports, waterways and other places related to marine traffic. Dolphins are typically located adjacent to waterfront structures such as quay walls, jetties, locks and bridge piers. The function of a dolphin is threefold:

• To allow ships to berth and moor safely and efficiently by:
  • transferring berthing energy to the soil;
  • protecting the hull of vessels;
  • accommodating line pull forces;
  • accommodating loads due to passing vessels;
  • accommodating wind- and current-induced loads.
• To protect waterfront structures by acting as a crash barrier and sacrificial structure.
• To direct and guide marine traffic by acting as a lead-in dolphin and navigation aid.

Breasting and mooring dolphins are the most common types of dolphins. Breasting dolphins are mainly installed to absorb by deflection the kinetic energy of berthing operations. Spring lines may also be attached to bollards or quick release hooks may be installed on the breasting dolphin. Breasting dolphins also accommodate lean-on forces due to wind loads and passing v...

Table of contents

• Cover
• Title Page
• Copyright Page
• Preface
• Contents
• 1 Introduction
• 2 Types of Dolphins
• 3 Design aspects and methods
• 4 Evaluation of Design Methods
• 5 Special design conditions for dolphins
• 6 Design approach for flexible dolphin design
• 7 Construction aspects
• 8 Furnishing flexible dolphins
• 9 Sustainability
• 10 Lessons Learned
• Appendix 1 Full-scale field test of laterally loaded tubular piles
• Appendix 2 Risk based reliability differentiation
• Appendix 3 Design aspects
• Appendix 4 PLAXIS 3D calculations
• Appendix 5 Design procedure for breasting dolphins with fender systems
• Appendix 6 Example calculation methods