shaping the integrated floating stage · 2019. 12. 16. · 01_floatingstage_fa.fh11 24/4/08 2:41 pm...

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Integrated Floating Stage at Marina Bay


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ABSTRACT

This paper presents the challenges faced and the systems

engineering solutions implemented in developing a large

floating steel platform at the Marina Bay of Singapore. The

floating platform is designed to be a multi-purpose facility on

the bay for mass spectator events, sporting activities and

cultural performances, as well as be a re-configurable “pier”

for water sports and boat shows. This floating stage, the

world’s largest floating performance stage on water, hosted

the National Day Parade 2007, its first big show. Since then,

the stage and its seating gallery have been used as the venue

for lifestyle events, extreme sports, the Singapore Fireworks

Festival, the WaterFest as well as the finishing point for the

Singapore Bay Run, the biggest mass run organised in Singapore.

Building the floating platform for all these events involved

complex engineering and many considerations had to be taken

into account in the systems development.

Dr Koh Hock Seng

Lim Yoke Beng


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Figure 1. National Day Parade held on the floating performance stage on 9 August 2007

INTRODUCTION

Pontoon-type, very large floating structuresare rare in the world (Suzuki, 2005). This verylarge floating structure (VLFS) technologyprovides an alternative solution to thetraditional land reclamation method forcreating large usable space on water.Singapore’s first application of the floatingstructure technology is the construction of thefloating performance stage at the Marina Bay(Koh et al., 2007a and 2007b).

The Marina floating stage measures 120m x83m x 1.2m and was constructed by assemblingmultiple steel pontoons on water at the site.The floating stage hosted Singapore’s NationalDay 2007 Parade in August 2007 (see Figure1). It is the largest floating stage in the worldfor performances on water. An artificial turf,when laid on its large surface, turns the floatingstage into a temporary sports field. As thefloating platform is a multi-purpose facility formass spectator events including concerts, mega

festivities and water activities like boat shows,the connecting system that interlocks themultiple steel pontoons is designed such thatthe floating platform can be dismantled andreassembled.

A 27,000 seating capacity gallery, which facesthe floating platform allows the spectators onshore to view various events on the stage aswell as on the water against the backdrop ofthe Singapore city skyline. The floatingplatform on the edge of the water of theMarina Bay is located in the new downtownarea, opposite the location of the Marina BaySands Integrated Resort as shownin Figure 2.

ENGINEERINGCHALLENGES

DSTA was approached to study the technicalfeasibility of staging the National Day Paradeon a floating structure and to work out thedesign specifications. The main challenge was


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to design a large-scale floating platform tocarry a high load comprising 9,000 people, 200tons of stage props and three 30-ton vehicles.The solution needed to incorporate floodlightmasts and an artificial turf to create a floatingsports field.

The Marina floating stage is one of the mosttechnically challenging floating platforms ofher size, in view of the many uniqueconsiderations and the innovative design. Asfar as we know, VLFS applications reported byWatanabe et al. (2004a) have been designedas a “single piece”. The Marina floatingplatform had to be versatile, movable and ofmodular design for re-configuration intovarious shapes and sizes to meet differentevent requirements.

With a modular design, one of the greatestchallenges was connecting all these multiplefloating modules into one single platform tocreate the large working surface. It was alsoimportant to keep the motions of thisconnected platform within the allowable limitsfor its intended purposes. The platform hadto be stable and unaffected by waves, windsand tidal currents and at the same time besafe for holding mass performances on it. Themajor challenge was the design of theconnecting system for the functionality androbustness of the integral platform. To holdthe floating platform in position againstcurrents and waves, dolphins were used forthe mooring system. However, these dolphinsare detachable at the bottom of the seabed

Figure 2. Location of the floating platform at Marina Bay (courtesy of URA)

Floating Platform

to allow an unobstructed water surface forsea-sporting activities at the bay.

To allow large numbers of performers andvehicles weighing up to 30 tons to go ontothe platform, access bridges were constructedto connect the floating platform to the landand the seating gallery.

The other key challenges faced in the designof such a large floating platform includedhaving to contend with the environmentalconditions and developments in the downtownMarina Bay. The shallow water at the sitelimits the platform depth while the changingtides put constraints on both the positioningof the platform with respect to the shore andthe gradient of the access bridges that link theplatform structure to the land. As the floatingperformance stage is relatively flexible due toits low profile in relation to the lengthdimensions, it exhibits elastic behaviour similarto a thin plate when subjected to wave actions.Hence there was a need to perform hydroelasticanalyses (Watanabe et al., 2004b) of the stageunder the action of waves found in the MarinaBay. The design also had to address the non-existence of established design rules andstandards for connecting multiple floatingpontoons rigidly as an integral platform.

As safety is of paramount importance in theengineering aspects of the integrated floatingstage, stringent safety requirements have beenadopted in the design.

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SYSTEMS ENGINEERING SOLUTIONS

The floating stage design was conceived as apontoon-type VLFS to support variousrequirements such as hosting the National DayParade, and to serve as a re-configurable “pier”for water sports and boat shows.

Various concepts were assessed technically andalso in terms of schedule risk as suchrequirements had not been implemented andtested on floating structures before. Marketresearch and engineering feasibility studies ofthe static and dynamic behaviour of a thinflexible floating structural system had to beperformed. These included the parametricstudy of the platform freeboard and draft, theforces at the connection of the floatingpontoons and study of suitable mooring system

and access bridges. Environmental conditionssuch as tidal variation, waves, water currentsand wind speeds were also considered in thedesign of the floating platform.

The final solution was to create 15 identicalpontoons of dimensions 40m x 16.6m x 1.2meach, to form the 120m x 83m floating platform(see Figure 3). Figure 4 shows the completedfloating stage including the access bridges.Each pontoon is a box-type structure based onlongitudinal and transverse bulkheads orgirders. In view of the shallow water depthand the need to carry heavy live loads, thefloating structure is made of steel as thematerial is strong and lighter than concrete ofsimilar strength. These pontoons are connectedby mechanical connectors, but the structuraldesign provides flexibility for the pontoons tobe customised into smaller platforms, to bere-located and re-configured for differentpurposes. The design of the rigid connectoris the key component for the functionality androbustness of the integral system. The rigidconnector was thoroughly evaluated to ensurethat the whole platform was safe and thedowntime that might result during productionand testing was minimised.

Model tank tests were performed to study thebehaviour of the floating platform in water.Several combinations of parameters wereinvestigated, including loading conditions, tidalvariations, wave heights and water speeds.Measurement data concerning the motionsand mooring loads in both operational andextreme environmental conditions were

Figure 4. Floating performance stage at Marina Bay

Figure 3. Plan View of floating platformconsisting of 15 pontoons (each measuring

40m x 16.6m x 1.2m) and three access bridges

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collected for the engineering analysis.Figure 5 shows the hydrodynamic model testto examine the performance of the floatingplatform.

Three access bridges (of eight metres to 10metres wide) connect the floating platform toshore for vehicle access and the mass movementof people. In order for the access bridges tohave gentle gradients, a two-segment bridgewas developed. The first segment is a fixedbridge supported by piles. The second segmentis a gangway, articulated at one end while theother end moves horizontally on the platform.The change in the gradient of the gangwayallows unaffected access at all times despitethe tidal variations. Besides ensuring that thebridge system was designed with adequatestrength, deflection and vibration (resultingfrom human movement) analyses wereperformed to study the structural stiffness.

The method of mooring the floating platformin the Marina Bay also required a speciallycustomised solution. The water depth in themiddle of the Bay varies between one metreand seven metres while the water channelbetween the floating platform and theopposite embankment is about 100 metres.Hence the depth and space constraints do notpermit the conventional anchoring system tobe deployed properly and effectively. Aninnovative piling method was devised wherethe dolphins are designed to be detachablejust above the seabed as this solution allowsthe freeing of the sea space area for sea sports.

Another important area of focus is to turn theseating gallery (for the spectators on shore toview performances on the floating stage) intoan integrated facility by taking intoconsideration the viewing angle, distance,lighting effect and mass movement ofperformers. While maximising the seatingcapacity, the architectural design had to takeinto consideration the orientation of thespectator seats and the steepness of the seatinggallery, and to ensure that the comfort of thespectators was not compromised. Many factorssuch as the tidal variation of some three metresto four metres on site were taken into account

Figure 5. Hydrodynamic model testing

in the facility design. This tidal variation affectsthe distance of the floating platform from theseating gallery as the floating platform has tobe located further away in the bay because ofthe shallow seabed near shore.

The need to comply with environmentalspecifications for a reservoir also complicatedthe design as typical corrosion preventionmeasures are prohibited.

With the floating platform sited in downtownMarina Bay, the integrated floating stage hasbeen designed to be aesthetically pleasing.The aesthetic requirements were achievedthrough the treatment of the platformstructures and careful selection of fittings suchas railings and lighting so that the architecturaldesign blends well with the surroundingdevelopment in the Marina area.

STRUCTURAL DESIGN

The floating platform has been designedaccording to the American Bureau of Shipping(ABS) Rules for Building and Classing SteelVessels for Service on Rivers and Intra-coastalWaterways, as well as applicable industrystandards and codes.

In the case of conventional ships, the globalresponse is dominated by rigid body motionswhereas in VLFS, the global response isdetermined by elastic response, either


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For the dynamic analysis, hydroelastic analysiswas performed to estimate the structure andconnector loads when the floating platformwas exposed to wave loading. The waveloading applied to the global finite elementwas calibrated based on experimental resultsobtained from the hydrodynamic model tanktest.

The stresses were checked against strengthrequirements while the vertical deflectionswere checked against serviceabil ityrequirements. Figure 7 shows the verticaldeflection contours of a load case.

CONNECTING SYSTEM

The connecting system ensures adequatestrength and rigid connection to the floatingplatform when the pontoons are inter-locked.These pontoons are joined at the corners usinga floating corner connector and along themating edges with side connectors (five alongthe long edge and two along the short edge).These are designed to withstand dynamic forcesresulting from personnel movement and wavemotion. The corner connecting system consistsof a male member at the corner of eachpontoon and a female member at each of thefour sides of the corner connector (seeFigure 8). The coupling members come intoengagement via detachable locking pins. Thepontoons are connected adjacently using blade-

Figure 6. Finite element model offloating platform

dynamically or statically (Fujikubo, 2005). Asthere were no established rules for the designof such thin flexible plated structures, a first-principles approach was adopted for thestructural design and this requires extensivefinite element analysis and hydroelasticcomputations to predict structural responses.

The response of the global platform to a givenloading scenario was analysed using a 3D finiteelement model of the complete platformconsisting of 15 pontoons, connectors and thethree access bridges. Figure 6 shows thecomputer model used for the engineeringanalysis. Supporting the platform model arelinear springs that simulate the buoyancy force.

For the static analysis, the floating platformunder static dead weight and different liveloads scenarios including eccentric loads wasstudied to determine the stress distributionsand deflection of the platform as well as themaximum loads at the connecting system.

Figure 7. Plots of Vertical Deflections

Figure 8.Joining thepontoonsusing the

cornerconnector

Pontoon


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type engagement tobear the tensions andbending momentbetween adjacent

pontoons (see Figure 9). These side connectorslock the top and bottom of the adjacentpontoons together to form a rigid connection.

From the results of the global response analysis,the local stress response at the connectorsunder combined loading was evaluated usingdetailed structural modelling and static analysis.Figure 10 shows the local structural model forthe analysis of the stress response of the sideconnector with its housing. Figure 11 showsthe results of the finite element analysis of thecorner and side connector in terms ofVon-Mises stresses.

In addition to numerical computer simulations,verification using prototype testing of thecorner and side connectors was sought(see Figure 12). The stresses and elasticdeformation were measured and the resultswere compared with the finite element analysisof the localised model.

MOORING SYSTEM

In the development of the mooring system,various environmental constraints such asshallow water and tides were key factors forconsideration. Conventional mooring systemsinvolving cables and chains were not suitablefor the floating platform because the tidalrange was relatively large when compared tothe shallow depth of the platform. The heavyframe guide dolphin mooring system andcaisson-type mooring system were also notsuitable because the floating platform has to

Pontoon in water

Corner Connector

Side Connector

Figure 11. Plots of Von-Mises Stress

Figure 10. Boundary conditions forlocalised finite element model of side

connector and its housing

Figure 9. Joining the pontoons using the side connector


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be moved to another site from time to time.Therefore, a detachable dolphin mooringsystem with the aim of easing the process ofinstallation, keeping the floating platform inposition and preventing the structure fromdrifting away was devised and implemented.The detachable dolphin mooring system alsohas the advantage of having its componentsdetachable and reusable.

The detachable mooring system comprises fourcomponents, namely the dolphin column, theplatform anchor, the casing pile and the fenderrollers (see Figure 13). The casing pile is

Figure 12. Full-scale prototype load testing

rammed deep into the seabed and protrudesslightly above the seabed to provide a securefooting where the dolphin column is bolted,and the top of the dolphin is locked using theplatform anchor attached to the sides of thefloating platform. The dolphin mooring systemmoors the floating platform from lateralmovement and prevents it from drifting awaywith the current.

For the design of the mooring dolphin columns,an extreme scenario where conditions such aswaves, currents and wind acting simultaneouslyon the floating structure was simulated. Thelayout of the dolphin columns is such that thehorizontal displacement is adequatelycontrolled and the mooring forces areappropriately distributed.

SAFETYCONSIDERATIONS

Safety is a primary consideration in theengineering aspects of the floating stagedesign, specifically safety against structuraldamage and personnel safety. This is supportedby conducting system safety assessment wherepotential hazards are identified and mitigatedthrough technical solutions or procedures.

The design of the pontoons and the floatingplatform meets the International MaritimeOrganisation standards for intact and damagedstability, with each pontoon having at leasttwo-compartment subdivision status. Thefloating platform has been designed as a rigid

Figure 13. Detachable dolphin mooring system

Platform Anchor

Dolphin ColumnFender Roller


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platform in which the connectors hold thepontoons securely. Due to the large horizontaldimensions of the floating platform, stabilityof the structure is not a problem, even in theevent of few compartments suffering damage.

The types of marine craft in the vicinity consistmainly of small cruise boats or sports craft.The probability of these marine craft cominginto close proximity with the floating platformis very low and highly unlikely. For accidentalcontact, it is expected that most of the damagewill be borne by the striking craft and not thefloating platform or mooring piles.

The connecting system is designed to hold thepontoons together with the expected loadingon the platform and has been certified by ABSConsulting. The designed loading capacitydistribution is documented and allowableoperating parameters are established.

In contrast to the mooring lines system, thedolphin mooring system prevents free driftingof the floating platform and averts damageto the surrounding facilities. The design is incompliance with the technical conditionsimposed by the Building and ConstructionAuthority of Singapore.

The heaving effect of the floating platformon the performers was investigated todetermine the translational accelerations ofthe structure as a large number of personnelare expected to remain on the stage forprolonged durations. The computed frequency-weighted accelerations were analysed to bewithin the established human tolerance limitsfor motion sickness and endurance orproficiency level for an eight-hour duration.

In addition, the response of the floatingplatform to participants’ simultaneous jumpingwas studied. This human response analysisprovided the assurance that the floating stageis suitable for mass performance and sportingactivities.

For better protection against lightning, two40m-high masts on each side of the seatinggallery and six 30m-high masts on the floatingplatform have been erected to serve aslightning masts with an overhead wirespanning between two pairs of masts.

ASSEMBLY AND VERIFICATION TESTING

The 15 pontoons were transported individuallyby tugboats from the shipyard in Jurong wherethey were fabricated, to the Marina Bay (seeFigure 14). The journey included a passagethrough the Marina Barrage at the mouth ofthe Singapore River (see Figure 15). Once atthe site, the pontoons were fully assembledusing the connecting system to form the

Figure 14. Pontoons being towed to Marina Bay by tugboats

Figure 15. Passage through the Marina Barrage


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floating platform, which was then secured tothe mooring piles (see Figure 16).

Extensive full-scale load tests were conductedon the platform at the site to validate thefloating platform design and to ensure thatthe stage could withstand the large loads ofperformers, vehicles and stage displays (seeFigure 17).

CONCLUSION

Besides hosting the National Day Parade, thefloating platform also provides a wonderfulopportunity for all kinds of activities such as

concerts, sports events and activities on andaround the water. The integrated floatingstage is now a landmark in the Singaporecityscape and adds to the vibrancy of theMarina Bay.

It also opens up new possibilities in spacecreation - the offshore space - and in theprocess generates economic value in land-scarce Singapore. It serves to complementother space creation initiatives such as landreclamation, construction of high-rise buildingsor the development of underground caverns.

The Marina floating platform has created muchawareness of the technical viability of large-scale floating platforms and will inspire thebuilding of more floating structures such asfloating storage facilities for processedpetrochemicals, mobile offshore bases, floatingairports, floating houses / community andfloating industrial facilities in the future.

Figure 16. Assembly of floating pontoons on-site

Figure 17. Load Testing of floating platform

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BIOGRAPHY

Dr Koh Hock Seng is Senior Principal Engineer and Senior Programme Manager(Naval Systems). He has extensive experience in the conception, planning,systems engineering and project management of large-scale systems such asthe Landing Ship Tanks and the Stealth Frigates. Hock Seng led the DSTA teamin the effort to develop the mega floating platform at the Marina Bay. Hegraduated from the University of Hamburg (Germany) with a degree in NavalArchitecture and obtained his PhD in 1991. Currently, he serves in theGermanischer Lloyd’s Technical Committee for Naval Ships. His awards includethe Defence Technology Prize (in 1996, 2001 and 2007), the SAF Good ServiceMedal (in 2003) and the National Day Award (in 2001).

Lim Yoke Beng is Senior Principal Engineer and Programme Manager (LandSystems). He has extensive experience in military vehicles and bridges-relatedprojects and was involved in the mega floating platform at the Marina Bay.He obtained his Bachelor of Mechanical Engineering from the University ofNewcastle (Australia) in 1988. In 1995, he obtained a Master of Science inMilitary Vehicle Technology from the Royal Military College of Science, UK.

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REFERENCES

Fujikubo, M. (2005). Structural Analysis forthe Design of VLFS. Marine Structures, 18,pp. 201-226.

Koh, H.S. and Lim, Y.B. (2007a). IntegratedFloating Platform. Proceedings of the 11thNaval Platform Technology Seminar, Singapore.

Koh, H.S. and Lim, Y.B. (2007b). The FloatingPlatform at Marina Bay: The Challenges,Proceedings of IStructE Asia-Pacific Forum onStructural Engineering: Innovations in StructuralEngineering, Singapore.

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Suzuki, H. (2005). Overview of Megafloat:Concept, design criteria, analysis and design,Marine Structures, 18, pp. 111-132.

Watanabe, E., Utsunomiya, T., Wang, C.M. andMoan, T (2004a). Very Large Floating Structures:Applications, Analysis and Design, Core ReportNo. 2004-2, National University of Singapore,Singapore.

Watanabe, E., Utsunomiya, T. and Wang, C.M.(2004b). Hydroelastic analysis of pontoon-typeVLFS: A literature survey, EngineeringStructures, 26, pp. 245-256.

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