Vessel Impacts with Floating Piers

Transcription

1 Vessel Impacts with Floating Piers October 2017 PIANC

2 The vulnerability of floating piers By necessity piers are the most exposed structures in the river Public spaces that can host 100+ people Berthing operations dramatically increase likelihood of impact Relatively small as a proportion of vessel size compared to other structures Damage is often difficult to repair and highly likely to render the facility inoperable

3 Thames Passenger Piers - Westminster & many others

4 Fixed Walkway Floating Pontoon Restraining Piles Vessel Berth(s)

5 Design Considerations Codes and Standards: BS Guidance on quantifying impact energies. Limited relevance to inland waterways and smaller craft Lloyd s Register Classification of Linkspans No requirement for Pontoon certification (eg. Lloyd s Register) + maintenance General Considerations relating to vessel impact: Quantifying a design energy of an abnormal or accidental impact Protecting passengers- Pontoon should not break free, capsize or sink Linkspans are also vulnerable and intolerant to heavy impacts- should not become detached

6 Design Considerations Potential Impact Energy design events (worst case) Reference Vessel Displacement (t) Speed (knots) Energy (MJ) Baltica Hav 3000 (laden) Tracy Bennett Tug + 3 Barges Thames Clipper

7 Energy Absorption Capacity Elastic energy absorption External fender deflection Pontoon displacement Pontoon mass, drag force, added mass Pontoon/Pile connection system Pile deflection Plastic energy Pile connection failure Pontoon buckling Pile deformation Typical berthing Abnormal berthing Design Accidental Impact Force Elastic Plastic Failure Displacement

8 Energy Absorption Capacity Pontoon/Pile connection systems Courtesy of Houlder Ltd

9 Special Protection Systems

10 Special Protection Systems 12 MJ Protection the London Eye; Main energy absorber pistons capacity of 10.6MJ 3.6MJ absorption in the canting browpontoon connection Floating boom protection to the brow and wheel 12MJ absorbed over 10m

11

12 Special Protection Systems Linkspan Protection Driven by site location and Navigational Risk Assessment Significant consequences Additional design forces to consider Crumple zones and secondary restraint chains Avoid queueing on the linkspan

13 Consequences of Impact and Mitigations Damage Event Consequence and Repair Mitigation Measures Plastic deformation of Fendering Pontoon buckling Pile guide failure Pile deformation/failure Linkspan collision Berth potentially inoperable, or with restrictions Berth inoperable, stability risk. Repair unlikely insitu- Facility closed for ~3 months Risk of pontoon becoming detached and damage to piles. Reduced pile capacity. Heavy marine plant required to rectify- pontoon removed Injury + linkspan failure. Facility inoperable, pending inspection/repair. Fender units to be replaceable insitu Pontoon stability to remain through compartment pontoon design, buoyancy contingency (2 compartments flooded) Pile guides to be replaceable insitu. Redundancy in pile guide placement. Safety chains or secondary restraint Pile guide connection designed to protect piles Assess exposure, consider deterrents or special protection measures,

14 Conclusions Standard floating piers are unlikely to be capable of withstanding the worst case impact An appropriate Design Accidental Impact should be considered Site location is key in defining possible and likely impact scenarios Mitigation measures should be implemented to manage the consequences (upto and beyond the Design Impact case) Energy absorption capacity can be estimated by summation of the F- curves Repairing pontoons is time consuming and expensive New piers in the East exposed to larger vessels with higher energies

15

16

17 Where are we going?

18

19