allows to extract an autogenerative and intrinsic

Two special construction procedures for the

erection of the big communication towers of

Collserola and Valencia

J. Martinez-CalzonMC-2 Estudio de Ingenieria, Victor de la Serna 27,

28016 Madrid, Spain

Abstract

There is a presentation of two constructive processes not only of highcomplexity but also of maximum guarantee and security, for two largestructures of towers. The concepts and ideas described in their developmentcould be employed in any other important constructions as the matter of the factthat they are based on the deep understanding and profit of the structuralsubsystems capacity that every work has.

1 Introduction

The main objectives of the building process in any work, and especially in thecase of the large constructions are aimed to achieve: - Minimum cost and timeof performance. - Maximum guarantee to keep the time limit. - Maximumsecurity in all the process.

These proposals, in the particular cases of the two great towers oftelecommunications in Collserola and Valencia, are obtained through the use ofspecial procedures whose gist is going to be described here.

The main rule followed to obtain the objectives aforementioned was in bothcases to refer to a basic and very deep -close to philosophy- understanding ofthe intrinsic possibilities that implied the structural typology of the architectonicproject. Nevertheless, this occurs not under the global structural systemperspective chosen for the finished construction but from the point of view ofthe combination and mackle of the subsystems, which appear to be hidden in

the final result.In both cases -and all in all in every great work- the specific and internal

analysis of these subsystems shows operative, strong and constructive capacitieswhich at the beginning are not perceptible but whose use in a proper way

Transactions on the Built Environment vol 21, © 1996 WIT Press, www.witpress.com, ISSN 1743-3509

338 Mobile and Rapidly Assembled Structures

allows to extract an autogenerative and intrinsic additional impulse from thestructure itself which leads to produce the best in the execution of the work.

In addition, this determines an extra intensity which is added to the whole,so that the constructive fact itself goes from being a necessary but usually roughstage, to become an important conforming and sustaining phase of the globalspirit of the work, by moving every mean of the project.

It could be said that with this way of searching inherent contributions of thesystem itself, the own true of the building is reached in its highest intensity,getting that pursued eagerness of adequation between intellect and the thing.

2 Collserola Tower. Architect: Sir Norman Foster

The global elevation of the main building, completed by the double telescopingof the mast, used as the general method adopted appears from the idea of takingadvantage, thoroughly and determiningly, of the important nuclear concreteshaft placed in the centre of the building to conceive the creation of a truearchimedium point, or of the maximum impulsion capacity, being based on thereal existence in the space of the point which forms the crowning of that shaft.The final form of the rest of the project is completed from this point in aelegant and perfect way, till to shape the final structural scheme which italready included exciting novelties.

The main structure of the building is formed by four well differentiatedstructural subsystems (fig. 1):1) A cylindrical concrete shaft of 205.5 m. height, with 3 m. internal hollowdiameter and wall thickness of 0.75 m. which first is reduced to 0.5 and thento 0.30 m. in the upper areas.2) A great steel and composite structure, with an annular curvilinear triangleshaped plant which is joined to the concrete shaft and situated at great heightaround it and holds the functional units of the tower.3) A set of three families of prestressed cables of great strength which fixes thetwo aforementioned systems to the ground.4) A steel mast of 82.5 height that crowns the tower over the concrete shaft. Itslower side is formed by a tubular section of 270 m. diameter in one zone and220 in the other one. The upper side is made of a lattice structure with a squaresection of 1.50 m/side in lower section and 0.90 m. in the upper one.

The mast is finished with a small automatic crane with an arm of 0.75,usually vertically placed.

All these systems are interconnected in a structural hybrid solution in whicha combination of different materials is used: reinforced and prestressed concrete,steel ad composite structures and steel and organic fiber cables, in order tobuild a construction where shape, function and structure are interlaced in anoriginal outcome.

The structural concept of the tower could be summed up as follows:The concrete shaft receives and then transfers to the ground all the

functional and gravitational loads together with the vertical components of the


Mobile and Rapidly Assembled Structures 339

cables due to two circumstances: the first one because of the prestressing andthe second one as a consequence or the work facing the horizontal loadingscaused by the winds.

The steel structure of the building, with its own internal stiffness, isassembled to the shaft to transmit the vertical loads and those resulting from theaction of the cables. This join provides the shaft with a high stability by actingitself as a corset of great rigidity.

The cable system develops a double function:1. In first place, the two lower steel groups, one of them formed by six cablesand the other by three, act as fixing elements of three vertices of the lowerplane of the building to the ground, bestowing it a horizontal immobility withthe exception of the displacement due to the original cables deformability.Under these circumstances the cables dimensions are carried out in order tokeep the turnings and swayings of the building below the established limitsrequired by the conditions of the broadcast system of the tower. The six cablesof the external group are anchored to the ground by means of gravity anddeadmen of about 2000 t., and auxiliary components of passive pressure andfriction; the three cables of the internal group are anchored to the base of theshaft.2. On the other hand, the upper group formed by three cables of twaron, anorganic fiber of polyamide, sets the upper point of the concrete shaft to theground of the building, offering thus a great immobility with the sameaforementioned limitations accordingly to the natural alteration of the cables.

The explanation of making use of organic fiber and not steel cables is foundin the fact that, in that way, the video images distortions are avoided as well aseliminating the heat that would be provoked by the induced currents in thecables. Finally, the steel mast appears acting in cantilever built-in at the top ofthe concrete shaft.

The building process was developed as follow, once the operation of slipforming the concrete shaft was completed and inside of which, in the right time,the upper mast was introduced subdivided in two phases or heights. Theconstructive process was organized in this way:- Setting on the shaft crowning a special piece called "cup" (fig. 2) which isbasic to carry out from that point the series of the subsequent sequences.- Complete fulfilment of the main building on the ground level.- Elevation of the mast through the interior of the shaft to leave it suspendedin the upper zone and release the internal hollow of the shaft.- The complete lifting (84 m.) by jacks placed on the cup of the great mainbuilding finished, with a total weight of 2700 t. Special systems of rollingwheels for guiding and counterbalance, as well as particular temporary fixingframes, were included.- Transference and connection of the building to the concrete shaft by meansof joints and starpieces, both especially designed.- Disposition and tightening of the three cable system.- Double telescoping of the steel mast and its final fixing to the shaft.



All the construction process is described in figure 3 and photos.

FIG. 1 COLLSEROLA TOWER - GENERAL DESCRIPTION

TEMPORARY BRACEMENT DURING

FIG. 2 - SPECIAL "CUP SHAPED" PIECE AT THE TOP OF CONCRETE SHAFT



PHASE 1 PHASE 2

PHASE 7 PHASE 8

FIG. 3 - CONSTRUCTION PROCESS



Assembling of the steel membersof the main buildings

4T»̂ _IHtttJIW

Erection of the main buildingon the ground

Lifting process of themain building

Bottom view along the concrete shaft Tower completed



3 Valencia Tower. Architect: Santiago Calatrava

On this occasion, due to the more complex structural scheme of fixing the mastor "needle" (fig. 4), it was essential to divide the construction process in twowell differentiated phases, apart from the "traditional" previous execution of thethree supporting great columns or legs that form each of the office buildings.

The first phase consisted of the complete fulfilment of the system needle +tripod (N + T) to the ground level, with a total height of 263 m. To attainedthis it is used a variation in the method of launching employed in bridges, butin vertical direction and with slight changes both for the tripod and for theneedle.

The second phase carries out the complete lifting of system (N + T)absolutely finished, with a weight of 7200 t. from the ground to the finalposition (erection of 132 m.) by a triple set of lifting jacks placed on the crownof the three columns, in a similar way as the one followed in Collserola, thoughthis time with the very important incidence of the wind effect over the hugesystem (N + T) during all the lifting.

The system of lifting jacks is used in both phases in similar circumstancesbut locating them in different places.

Phase 1. Execution of the set (N + T)The process associates as unique auxiliary elements, apart from the cables andjacks already mentioned, an auxiliary lower ring and a tubular lattice systemthat connects that auxiliary ring with the upper ring included in the greatstarpiece that close on the top the suspension tripod of the needle.

The construction process can be divided in three subprocesses:a) Execution of the tripod by gradual compassed lifting, including the auxiliaryring and tubular system.b) Execution of the needle by vertical launching or lifting of the system formedby the subsequents segments that are welded on the ground following an inverseorder to their position in height.c) Placement of the lining of the needle, at the time that it arises from the upperring included in the tripod, employing an auxiliary platform leant on thestarpiece of the tripod.

Figure 5 and 6 shown the operative stages sequence of phase 1.1) Assembling the system of starpiece and ring which form the upper part ofthe tripod (fig. 7) and the six diagonal rods; the first segment of the auxiliarytubular lattice and the first part of the auxiliary platform to situate the lining.IE) Elevation of the whole work about 13 m. by means of three jacks placedin the buildings, on temporary girders arranged at 50 m. height over the ground.2) Placement of the first segment of the tripod rods and the second of theauxiliary tubular lattice. The structure of bridges which will connect thebuildings and the needle in the final definitive situation are added. The upperpieces of the tubular mast and lattice are placed on the floor including its

lining.



2E) Elevation of the whole work another 11.5 m.3) Placement of the second segment of rods, the third segment of tubular latticeand the upper piece of transition between the upper mast and the needle.

All the platforms and systems needed for the later effectiveness of thesequential lining of the needle are placed.3E) New elevation around 8 m.4) Placement of the final segment of rods including the lower auxiliary ring.Placement of the final segment of the auxiliary tubular lattice which connectsthe two rings.

Lower joint and welding of what is the first real needle segment.4E) Elevation of 17.5 m. reaching a fix position of the tripod and auxiliaryelements, permits to replace the jacks in the upper ring of the tripod. At thistime the lower bracing between lower ring and concrete legs is situated andtogether with the starpiece, keeps the continuous stability of the needle facingthe wind.5) Placement and welding of needle segment in lower area. Placement of liningin needle areas situated over the upper ring of the tripod.5E) Elevation of the needle with regard to the tripod about 12 m. (making roomin the lower hollow to locate a new segment), by means of the lifting jacksarranged in the upper ring of the tripod. This system will increase the numberof units in proportion of the loads which become higher.6) Placement of fixing lugs to support the needle in the lower ring. Resting ofthe system of needle in that lower ring, to recuperate the stroke of jack wiresof the upper ring. Release the former lugs in the needle and new fixing ofwedges in the provisional support on the auxiliary lower ring.

Placement and welding of the new needle segment in lower area.6E) Elevation of the needle system with regard to the tripod to leave room forthe new segment.

Repetition of the steps 5, 5E, 6 and 6E.19) Placement of the final needle segment which includes the great closingpiece and joint of the tripod with that needle.20) Placement of the lower bracing at the union level needle-connecting rodsof tripod, which remains suspended from the system of horizontal tripod ends.

Elimination of the auxiliary tubular lattice and lower ring.21) Endings of the communication bridges and the rest linings of the needle.Elimination of the auxiliary platform.

Trespassing the whole equipment of lifting jacks to the crown of thebuildings structures to carry on with the following phase of the constructiveprocess.

Phase 2. Elevation of the system (N + T) (fig 8)This phase starts with the preparation of the upper platforms to place the jacksover the great reception pieces that will be welded, at their right time, with thestar points of the tripod to complete this element.

After that, cables are placed and the lifting starts guided by the horizontal



tripod ends placed inside the channels of theelevators and braced against horizontal wind forcesby the double system of star-tripod and horizontalauxiliary bracing, vertically separated between themto a height around 45 m.

Once the final height is reached, the system issupported on fixed points arranged on the near thetop of the buildings and the final great pin-joints arecarried out between the starpiece which has gone upand the reception pieces placed on the buildingscrowning. The next step is to proceed to place thebolt elements and definitive tripod supports.

Finally, the system is softly lifted by means of apower jack system that remains as definitive element,for the eventual changes or repairs; and the previousfixing supports are eliminated so that the structureN + T is taken to its final position. The closing ofbridges and the eliminations of the auxiliaryplatforms and lower bracing are the last steps of theconstructive process.

OFFICE BUILDINGS (LEGS),

FIG. 4 VALENCIA TOWER - GENERAL DESCRIPTION



PHASE 1

CONCRETE .LEGS EDGE

STAGE 4 STAGE 5

FIG. 5



PHASE 1

STAGE 6 STAGE 19

FIG. 6



LOWER RING AND COLUMNS OF THETEMPORARY STRUCTURE BETWEEN RINGS

FIG. 8 CONSTRUCTION PROCESS. PHASE 2


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allows to extract an autogenerative and intrinsic