2003-2 an oval design. a new proposal and a new methodology

8/6/2019 2003-2 An Oval Design. a New Proposal and a New Methodology

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Tubu lar St ruc tu res X - Jaurrleta, Alonso & Chica (Eds.)e2003 Swets & Zeitllnger, Usse, ISBN 90 5809 5525An oval design. A new proposal and a new methodologyF . Escrig & J . SanchezS ch oo l o f A rc hite ctu re o f S ev illa ; Spain

ABSTRACT: This paper .is concerned with the design and construction of a 14,000 sqm, roof supported 01 1four piers. The way in which the space structure has been designed, the efficiency of the girders and the generalaspect make this building a good example of how this particular design helps to overcome many problems thatother well experimented solutions h av e b ee n u na ble to do.

1 GENERAL CONCEPTSAs a professional commitment, we were asked tocover an uncovered pavilion with an oval structure.The Velodrome de Dos Herrnanas, 145m. X 114m.with seating for 3,000 and a cycle track. The innerspace of the track ring is on the whole used for multi-purpose activities but up tallow has been made littleuse of ow ing to the conditions offered by the building.The City COUllCi! decided after a Iotofconsidera-lion to invest ina project to completely cover the enclo-

sure thus guaranteeing greater use and functionality.Technical solutions were then required to start workan the covering structure.Inflated structures such as those used in the

Geiger-Berguer could not be used as we were dealingwith a covering and not an enclosure. Many s olu ti on sw er e n ot c on sid er ed a pp lic ab le , a s they re qu ir ed a g oo ddeal of maintenance. Tensed material membranes,which are very spectacular.also came under consid-eration but we preferred a softer image and besides

Figure 1. Preliminary design,

the cLient discarded both, the inflated and the tensedstructures.The preliminary design presented by our team wasselected (Figure 1) and we began to develop the proj-ect. All oval structure is complex, one of th e master-pieces being th e Roman Coliseum. While the sphericallayers develop some very equally distributed forces.the elliptic layers undergo b ig variations making useof different hollow sections necessary.We eventually agreed on the use of steel hollow

sections. Our team has always rejected th e use of lat-tice structures owing to the high price of the weldedjo in ts . We have b ee n ab le to d em on stra te th at th e p ri.c elsqm, of space structures with pre-fabricatedapbericaljoints is more expensive than that of w elded rigidjoints. The problem is the assembly difflculty whenusing r ig id jo in t s for a large span roof.A n oth er o tu sta nd in g a sp ec t of the p ro je ct th at inter-e ste d u s w as th e to ta l in de pe nd en ce between th e coverand the existing building. Wedid not w ant to becomein v olv ed i n 8 . f l imsy construction. As the surface around


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91m.

Figure 2. Geometric layout of the perimeter.

F ig ure 3. Intersection. o f'th e tw o cylinders.

the building was very scarce, we could not extend itsperimeter as was done by Schlaich in Stuttgart. Wealso wanted to give a floating aspect to the coverthat had not been achieved using the Schlaich solution.We decided to build four big external supports withvery thin heads, located on the vertexes of a91 m, x 91 ID. square and to support the roof on them(Figure 2). We thus discarded the possible use of anellipsoid shape and decided on the shape consistingof intersection of two cylindrical surfaces, the mainone with a radius of 99 ..6m. and the secondary onewith a radius of 173 ID. (Figure 3).TIns provided us with a roof covering all theVelodrome (Figure 3) and which could be perfectlyadjusted to the existing perimeter. The external girdersplaced on the perimeter of the space stru ctu re w ou ld n otbe submitted to stress due to the bend of the s p ac e s tr uc -ture. Stress transmissions are indicated in Figure 4.

Figure 4.. Forces lines.

Figure 5. Internal and border box girders.

The space structure has the biggest stress in themain arches, intersection of the two cylinders. Theperipheral arches support less compression (Figure 5).The design of the arch should be in agreement withthe acting forces but for aesthetic and structural rea-sons we decided to use the same section for al l thearches: a box girder of2.5 m, by 2.0m. (Figure 6). Wewould perhaps have been able to maintain the imageof the preliminary design without borde:r girder. Butthe final design was the best solution for finishing offthe roof and for integrating the guttering. Andbesides, the effect of the wind on borders with thinedges is much greater than in the finally built spacestructure ..As an intuitive option more than for preliminary

dimensioning and without any lattice beams, we chosea double layer space structure of continuous hollowsection profiles and a depth of 250 cm. between thetwo layers (Figure 7). To build it with reduced mod-ules we designed appropriate construction devices:flanges, telescopic joints, half pipes etc. (Figure 8).Owing to the low rise profile of cylindrical sur-

faces, the horizontal stresses ac e very big and there-fore the four supports must be designed accordingly.The horizontal forces applied to the support headscreate a moment in the base of about 20,000 tons X m.The weight of supports bas been used to help todiminish stress in the foundation.However , the area of

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182..4f!0.0, 40.0 ,42.0 I 40.0 ,20.0, f O o o r 40.0 I 80.0 I 40.0 ,20.q

CARA 'NTER~.R. IXI \I \I \/ \I \

Figure6. Transversal section of the internal box girders (a) and of border box girders (b).

Figure7. Connection of space structure with box girders.

Figure 8. View of the connection of the space structurewith tbe box girders.

the heads of the support may be less than that of thebase, because the vertical loads and shear forces ofthe roof can be easily absorbed. Therefore, we decideto use pyramidal piers (Figure 9).The foundation was made up of eight pilots of

150 em. and 20 m, of depth. Although the stress onth e foundation was mainly balanced by the compres-sion created by the selfweight of the piers, itwas nee-essary to use pilots to absorb the remaining stress(Figure. 10).. Figure 9. Aspect of one of the four supports.


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Figure 10. Detail of the foundation piles.

2 CONSTRUCTIVE SOLUTIONSUp to now, all the details have been schematicallydescribed. Wewill DOW explain them in greater detail.We placed a steel sheet panel sandwich on top ofthe space structure as shown in Figure 11. The devas-

tating effect of wind on cover sheets with thin bordersis a great worry as the pulling out forces are up to tentimes the force of the wind on the rest of the surface.We decided to anchor them separately on the externaledge of the structure as much as possible. On the otherhand, the quantity of rainwater to be drained is suchthat we needed gutters of large dimensions. We optedto integrate the gutters in the structural shape of thesection and thus give it the shape shown in Figure 6..The advantages are the following:

(a) We increased the area to distribute forces.(b) We diminished the buckled surfaces that wewillnow be analyzed keeping in the shape in mind.

(c) We created a dynamic appearance which wouldotherwise seem very heavy.

(d) We formed the gutter,The heads of the supports are on the lower points ofthe roof where all forces will concentrate and this isalso where all the rainwater will converge and at thesame time gives access to the pedestrian way Jnsidethe girders. The design of the head of the support isshown in Figure 12. Some 20 mm, thick sheets havebeen welded to the supports to reinforce them and tomake easier to connect the three box girders to thefaces of the support (Figure 9).

Figure II. View of the covering sheet over th e gutter.

Figure 12. Meeting point of gutters and supports.

The gutter section of the boxgirders continuesdown the external face of the supports so that thewater will slide down it to the ground where collec-tors will be located. The support would have appearedenormous ifwe bad 110t used the warped shapes thatgive them a volatile aspect. The drainage gutter lookslike two leaves that open as wings. The final result isshown in Figure 12.Circular openings have been located in the girder

faces seen from tile interior of the pavilion to lightentheir aspect and make the walk through the long tun-nels less oppressive and for maintenance purposes.andfor installing machinery. It is interesting to keep inmind the fact that theses boxes are prepared in such. away that they can be visited (Figure 13). Through theseperforations the whole space structure may be visitedwithout the need of any special elevators.(Figure 14).

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Figu re 1 3.. Pedestrian way inside of the box girders.

Figure 14. View oftbe box girders from inside the pavilion.

Figure 15 . Jacks placed at the base of tile t empor ar y s up po rt s ..

3 BUfLDING AND ERECTION OF THESTRUCTURE

In our proj ect, we included an assembly sequence thatwas accepted by the buikiing company. lt consisted ofa series of different stages for erecting parts of thestructure and for joining the big modules on site.

Figures 16 and 17. Connection of the hollow sections andth e box girders.

Figure 18. Transport.

To eliminate the provisional support we bad to fore-see the use of hydraulic jacks that would permit thegradual descent of all of the supports at the same time,controlling the descent and checking to make sure thattheyagree with the calculations ..This is a very decisiveand important stage. Ifeverything goes as planned thediscrepancies with the theoretical calculations will besmall The provisional towers are fixed andjacks placedat the base to be able to saw off the legs of the tempo-rary support and to begin the descent (Figure 15).

4 DEFINlNG THE WORKIn a modular structure the pieces have to adjust withgreat precision. There is no room for percentage toler-ance. However, although it is possible to manufactureabsolutely accurately, thermal changes, handling dur-ing work, deformation f rom 'in te rna l tension and manyother causes, l imit the precision to values impossibleto improve. For 100 m. lengths tolerances of one perthousand imply error of 10 em. Joints must be designedto absorb the tolerances (Figure 16) and the sameapplies to the connection to the box girders (Figure 17).The systematic confirmation of position by a topog-rapher on the site is essential,

5 ASSEMBLY OF TIlE BOX GIRDERARCHESThe arches arrived at the site from Gijrm (Spain)on 25 m . long trucks (Figure 18). Once off th e truckand on the ground, the arches were joined. They were

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Figure 19.. Provisional towers.

Figure 20. Connection of arches.

Figure 21. Aasembl ing the cantilever box girder.then lifted and supported on the provisional. towers(Figure 19) and were p1aced correctly before beingwelded and joined in a continuous arch (Figure 20).We began with the cantilever arches as we wanted

to clear the working area (Figure 21) and then the sameprocedure was carried out with the interior archesplaced on the head support (Figure 22). InFigure 23we can appreciate the lack or excess of welding andput it under review when joining and fixing the archesrigidly to the supports (Figure 24). Once the archesare installed they may be visited (Figure 25).

Figure 22. Assembling of interior box girder.

Figure 23. Gap to be completed with welding.

Figure 24. Difficulties of adjusting the girders to thesupports.The arches of the border of the main facades were

mounted after the others so as not to interfere withthe pieces already hoisted. Infact, they were not eventaken to the work site until itwas time for them to bemounted so as not to get in the way.

r

6 ASSEMBLY OF THE SPACE STRUCTUREAssembly of the space structure is shown in Figures 26,27 and 28. The final appearance of the space structureis shown in Figure 29.


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Figure 25. View from inside the box girders.

Figure 26. Placing the first module of space structure.

Figure 27. Intermediate assembly phase.

7 STEEL ROOF SHEET~ san dw ich sheet injected w ith g lass fibre was put~ntoposition and the inside face was perforated toImprove th e acoustic conditions. A polycarbonatep an el w as p la ce d I . I l th e eeatre to p rov id e n atu ral lig ht.:h~finisbed aspect can be seen i : 1 ) Figure 30 from theUlslde andan aerial view in Figure 31.

Figure 28. Pinal assembly phase.

Figure 29. View of the finished space structure,

Figure 30. Image of the finished interior.

Figure 31. Aerial view of the finished roof.


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Figure 32. . Construction sequence,


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8 CONCLUSIONSA curved roof made from shell parts offers an advan-la ge over otb~r plane surfac.e5 and even bas advan-tages over solid archesand single shells. Great stresscooccnInted on the edges w ill then be reinforced bymeans o f s ol id a rch es o r la rg e g ird ers.W e have been able to support a 14,OOOsqm . w ides pan roof on. four p ie rs and with .a depth o f o nly 2 .5 0 m.

REFERENCESI. Bscri.g, I i ' . & Sanchez 1. "G re at S pa ce Curved Structures

w ith rigid: joists", Theory De-sign and Realization ofShell and Spatial Structures. lASS.agoya 2000.

2. Escrig, 0 : , Sancbez;.l &Va lc ar ce , J P., " Th e Reman Owl" .Fifth fllte matio llaJ C on feren ce o n, p ace S tr uc tu r es , Univof Surrey. UK . Thomas 'Ielford, 2002.

2003-2 an oval design. a new proposal and a new methodology

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