DESIGN AND CONSTRUCTION OF A CRADLE SLIPWAY JACKUP JETTY, LOADING BAY WITH CAISSON PILING

CLIENT: 

EL-TOTUOMA INT'L SERVICES LTD

APPROVAL:

EL-TOTUOMA ENGINEER

GEO - STRUCTURAL DESIGN:

Engr. Femi OLOMOLA & Team

SUPERVISION:  (Ongoing)

WEFOS PROJECT 

Soil test

Stages of work

  1. Site visit and dilapidation survey
  2. Estimation of service load
  3. Hydrological and topographic survey
  4. Soil testing [borehole, CPT, SPT, Lab]
  5. Structural design [steel and concrete]
  6. Prefabrication of precaste beams panel
  7. Prefabrication of underwater steel jacket
  8. Geotechnical design and analysis
  9. Bond wall formation
  10. Installing precast beam
  11. driven caisson pile
  12. underwater welding, cutting and alignment
  13. Installing underwater steel jacket at slope gradient.
  14. installing cradle steel track
  15. Concreting and installing concrete ramp floor and shore protection wall
  16. Errection of cradle steel structure
  17. installing pulley block and sling @1000m
  18. Installing electrical powered winch
  19. Launching of marine vessel
  20. Hand over

PROJECT TECHNICAL DATA

  1.  Propose marine vessel size = 45m LOA
  2.  Propose marine vessel hull type = deep V
  3.  Propose vessel weight and dead load = 250 ton (Gross)
  4.  Cradle vessel carrier SWL = 3000 KN 
  5.  Concrete slipway ramp SWL = 6 KN/m2 @66m2
  6.  Steel cradle weight and dead load = 80 ton
  7.  Support roller 1 SWL = 300 KN (Gross)
  8.  Support roller 2 SWL = 200 KN (Gross) 
  9.   Single line pulley force SWL = 150 KN (Gross) 
  10.  Steel caisson axial capacity SWL = 250KN 
  11.  Concrete grade = C20/25/ C30/35 N/mm2 
  12.  Steel grade = S230 
  13.  Slipway gradient = 1:12 & 1:15 
  14.  Underwater operation draft at <5m 
  15.  Safe bearing pressure of foundation soil = 200 - 300 KN/m2

Objective:

The objective of this project is to buide a structurally stable slipway platform where marine vessel or ship can be serviced and docked for maintanace activities even with minimal resources that will effect an optimum value.  

Graphics and Images design by WEFOS PROJECT PUBLISHING

BRIEF SNAPSHOT OF PROJECT REPORT
This report covers the geotechnical investigations, geotechnical characterization and modeling of the "significant volume" for the designed project, and the investigation on the soil-structure interaction to correctly design the propose foundations. This was prepared by the engineer on the basis of data from a testing campaign and/or laboratory tests. 

The project involve massive concrete and steel construction works. it is a cradle slipway meant for dry docking of marine vessle within safe sevice load of the vessel self weight and gross tonnage. 

The slipway structure is service by an electrical powered winch capable of launching the 7,000 tonnage vessle by the pulley block with optimum water draft and gradient.

The following finite element analysis programme has been used for plotting, accurate data acquisition and to perfectly simulate horizontal and vertical member loadings and reactions, please see a short summary of the design approach below: 

All member design and analysis has been from first principle theory, anchoring on the ultimate and serviceability limit state loading with bias for proper load factoring to allow for longer life span of the structure ensuring that all loaded structure are in equilibrium of forces without any undue external effect. 

The loading on the concrete slipway platform has been properly simulated with a moving load at interval of one meter which is coming from the support roller of the cradle compartment or carrier. 


The vertical reactions and the resolve component force was used for axial support consideration while the horizontal reactions has been applied against the winch foundation structure and are free due to sliding effect by the pulling force from the winch. 

The moving load is applied over the entire lenght of the concrete slipway which is directed at the support strip foundation beam and is equally distributed over the foundation plate and subsoil. 

The same moving load magnitude had been applied on the steel beam extending into the river but only at the region within the creek as this is the region receiving full cradle support load because upthrust or bouyancy effect acting on vessel has been lost. 

Every other region along the cradle rail line under the river is receiving the full upthrust load on the vessel which will equally cancel out the effect of the gravity load on the cradle. Hence, the entire cradle slipway structure was analyse and properly simulated by the help of the below listed finite element analysis programme.

1. Dlubal - Structural and Foundation design analysis programme
2. GEO5 - Geotechnical Analysis programme
3. NoVoLab & Labsuite - Geotechnical Laboratory programme 

All design, also had been carried out by the European code of practise as enshrined in the following: 

1. EN1990 - Member loading
2. Eurocode 2 - Concrete design
3. Eurocode 3 - Steel design
4. Eurocode 7 - Foundation design