THE STRUCTURAL DESIGN OF THE HOTEL FOR THEMARQUES DE RISCAL WINERY.

Miles Shephard(p), César Caicoya, Miguel Ángel Frías.

1. INTRODUCTION.

The Marqués de Riscal Winery has commissioned Frank Gehry to design a hotel fortheir facilities in Elciego, in La Rioja, Spain’s principal wine growing region. Gehry’sdesign is for a highly innovative building with titanium and stone cladding. This paperwill describe how the engineers translated the Architect’s ideas into structural workingdrawings. It will also describe the advanced computer techniques used in this process.

The project is now under construction, having commenced in May 2003.

2. DESIGN ASPECTS.

2.1. Architectural Concepts.

The celebrated architect Frank Gehry was commissioned to design a new hotel buildingat the Marqués de Riscal Winery in Elciego, in La Rioja region of Spain. This will bethe architect’s third project in Spain, the most famous being the Guggenheim Museumin Bilbao. IDOM collaborated previously with Gehry on the Guggenheim and in thisproject they are the Architect of Record. Their responsibilities include the detailedarchitectural design, the structural design, the services design and the site supervisionand management.

The hotel for the Marqués de Riscal Winery will be an emblematic building clad instone, glass and titanium. With a built area of approximately 2000 m2, the building itselfis not large but its geometrical complexity makes it one of the most remarkablebuildings of this new millennium. The three floors and one mezzanine of the hotel aresupported above what appears to be a vineyard by three massive columns(‘supercolumns’) and four inclined prisms that support the cantilevers of the endelevations. The main structure is wrapped in a series of flowing coloured titaniumcanopies supported directly off the main structure and from the ground on slender steelsections. These provide shade from the intense Rioja sun.

The hotel reception area is a diaphanous space on the vineyard level. The next floorincorporates 14 bedrooms, the floor above contains the restaurant and the top floorhouses the boardroom for Marques de Riscal. Although the hotel appears to be foundedin a vineyard this is, in fact, a false perception. The vineyard lies on top of a new winestorage cellar and the building’s three ‘super columns’ pass through this slab and arefounded in rock 8 metres below the reception level.

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Figure 1. Building Overview (model)

There are three floors, one mezzanine and the roof above the entrance level. Each floorslab is highly irregular in shape with many peaks and troughs in their outlines. The slabsgradually reduce in size successively giving the building a pyramidal shape. Thecolumns are not visible within the building and all forms of support are hidden withinthe highly irregular internal walls. This has given rise to non-continuous and inclinedcolumns.

Figure 2. Canopy Detail with titanium cladding (model)

The architects made extensive use of physical models when designing the building.Numerous scale models were made and changed in the process of fine tuning theexternal appearance of the hotel. Each physical model was then translated into digitalform and the program CATIA was used for three-dimensional modelling. These CATIAmodels were then translated into various different other programs for structuralcalculations or in order to lay the design down on paper.

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Figure 3. 3D Catia Models. Slabs and Canopies

2.2. Structural Concepts

Three ‘supercolumns’ with a total height of 16.5m start from the foundations below thebottle store and pass through the second floor (the hotel entrance level) rising up to thethird floor. They are founded on large pad footings directly on rock below the bottlestore slab.

The third floor is a massive concrete slab that basically supports the rest of the building.In addition to three concrete lift cores, a forest of small steel section columns hiddenwithin the internal partition walls of the building spring from this slab.

Figure 4. Structural Section.

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The building’s internal spaces governed the positioning of these columns and thereforethey are highly irregular. In addition, the third floor supports the majority of the canopyloads along its edges. The only supports for the slab are the three ‘supercolumns’aligned along the central axis of the slab and four inclined columns, which support thecantilevers at the ends. Transversely there are cantilevers of up to 10m in length. Inaddition the slab is not centred about the longitudinal support axis and therefore the‘supercolumns’ resist a permanent dead load moment.

The slab is of variable depth with a 1300mm section running longitudinally. Thetransverse cantilevers have variable depth between 1300mm to 450mm at the edgeswhile the cantilevers supported by the inclined columns have a constant depth of750mm.

This slab is very highly loaded and the transverse cantilevers are especially sensitive todeflections. In order to counteract these deflections the slab is transversely posttensioned. The irregularity of the slab edges, the amount of supports required at the slabedges for the canopies and the fact that the tensioning must be done in phases in order toprevent cracking under temporary conditions brings added complications to thisprocess.

Another complication for the slab as a whole is that it is supported by the very stiff‘supercolumns’ and there are no movement joints. It is therefore designed to resist thestresses induced by the stiff supports in shrinkage and temperature change. A concretepouring method is defined for the Contractor in order to reduce the shrinkage stresses toa minimum.

The subsequent floors are designed as flat slabs supported on irregular steel columns.As these columns are hidden in the internal partitions of the building they are highlyirregular. There are inclined columns and non continuous columns and this has led tothe slabs having to resist high point loads from columns being supported directly by theslab at that level. In the majority of cases, the flat slabs are 450 mm thick with 200 mmreduced depth areas in zones of less moment. The result appears like an irregular beamand slab arrangement but functions like a flat slab.

Three cores rise from the ‘supercolumns’ in order to give the structure lateral stability.In order to reduce negative effects produced by shrinkage and temperature differencewith three lateral supports, only the central core provides lateral support in bothdirections. The end cores have walls transversely across the slab only, while the centralcore is a box. Transversely all three cores provide horizontal support, whilelongitudinally only the central core functions.

The canopies are attached to the edges of the main structure. Each canopy is designed asa self-supporting structure with at least three points of support. The upper canopies aresupported directly off the slabs while the lower canopies are supported both from theslabs and from columns rising off pad foundations sitting directly on the bottle storeroof slab.

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2.3. Detailed Design of the Main Structure

Given the highly irregular nature of the supports, loads and shape of the slabs, each slabwas modelled in detail using finite element plates. The program chosen for modellingwas ANSYS due to its flexibility and high calculation capacity.

The most sensitive slab was the third floor. This was the slab with the highest loads as itsupports the rest of the structure and it also has the longest cantilevers, up to 10 metresin places.

Figure 5. 3rd Floor Plan.

Extensive modelling was carried out on this slab in order to check the following loadcases:

• Dead and live loads supported directly on the slab• Dead and live loads from the columns• Dead, live and wind loads from the canopies• Shrinkage loads caused by the three rigid supports• Loads from the post tensioning, including by phased tensioning

The deflections at the ends of the cantilevers were very carefully checked and the posttensioning designed to reduce the deflection to within the building code limits. Phasedtensioning was required in order to remove the possibility of cracking in the soffit of theslab. 55% tendons will be tensioned once the concrete has gained sufficient strength.Once the forth floor has been cast and its formwork removed 25 % more of the cablesshould be tensioned and the remaining 20% should be tensioned once formwork hasbeen removed from the roof slab.

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Reinforcement was designed in both directions with the moment envelopes taken fromthe computer models. Special attention was paid to the local detailing of reinforcementin the irregular cantilever zones and over the ‘super column’ supports.

Figure 6. Model of 3rd Floor.

The remaining slabs were 450mm thick with 200mm thick sections in less stressed areaswith the exception of the mezzanine slab, which had a constant depth of 250mm. Theseslabs were designed in a similar way to the third floor, with detailed models in ANSYS.The irregular columns (non-continuous, sloping, etc) were modelled in order to giveaccurate results for areas that will be locally very highly stressed by column point loads.

2.4. Detailed Design of the Secondary Structure

As much as anything, the design of the secondary structure supporting the canopies wasa geometrical problem. This was done in very close cooperation with the architects andin order to achieve this an engineer was assigned to Gehry’s offices to carry out thisdesign. The whole structure will be visible and therefore aesthetic considerations wereas important as structural requirements.

The concept of each canopy is that it is a determinate structure supported at a minimumof three points. The frames consist of two main beams (I sections), highly deformedabout their minor axis, supporting T sections, 90% of which were straight. These Tsections are supported at a variety of angles along the main beams thus producing a facecurved in two directions without the need for bending beams in two directions. The Tbeams support hat channels that will be bent into shape during erection. Titanium platesare then riveted to these channels.

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Figure 7. Wood Frame Model / New York Mock Up.

The first problem encountered in the design of the canopies was that of estimating theloads. The forms are so irregular that the wind codes could not be directly applied to thestructure. It was therefore decided that a wind tunnel test should be carried out. Using ascale model produced by Gehry, RWDI tested the structure in their wind tunnel inCanada. The data produced included patch loads of varying intensity for each canopy.These were combined with dead loads, access maintenance loads, snow loads andaccumulated snow loads for the gullies, each multiplied by its given partial factordepending on the load combination, to form a loading envelope for each canopy.

The design of the canopies was an iterative process. An initial design was carried out inorder to estimate possible section sizes. The structure was adjusted until the Architectdeemed the initial section size satisfactory.

In order to progress to the next stage of design a wire frame model of the canopies wasrequired. The architects were using CATIA for their three dimensional design. Thisallowed all the building surfaces to be modelled in space. The canopy supportingstructure was added to the surface model and the result was then translated into theRhino 3D modelling programme so that it could be used for the basis of a structuralmodel.

The program RISA was used for the structural modelling of the canopies for its threedimensional capabilities and its ease of use. The data from the wire frame model wasimported into RISA. The orientation of the members was checked and then a series ofload cases were input to complete the calculation. A large number of different loadcases were used in order to ensure that every possibility had been catered for.

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Figure 8. Wire Frame Model.

A very sensitive part of the design was the connections to the slabs, especially on thethird floor. As previously described the third floor slab is post tensioned. In order toallow access to the cables the highly irregular slab edge cannot be cast until tensioningis complete. Therefore there are a number of important canopy supports that areattached to sections of the slab that are not cast monolithically with the third floor.Continuity of reinforcement to this newly cast edge section of slab will be vital in orderto transmit the forces from the canopies. This is achieved in two ways: threaded bars arespliced onto the previous pour, thus ensuring continuity but leaving the area free forcable tensioning and the canopy connection itself is formed from a fabricated I sectionrunning along the edge of the slab so distributing the loads as much as possible. The Isection is attached to the concrete by way of stud shear connectors.

Figure 9. Canopy/Slab Connection

Canopy connections to the upper floors were simpler as they could be cast in with therest of the slab. For conformity with the third floor connections, Edge I beams wereused with shear studs to tie them to the slab.

One of the most innovative aspects of the canopy design was the way in whichcomputer programs were used in order to visually model the structure. This wasimportant for two reasons: firstly these models highlighted any points where structuralmembers or the cladding might clash with other canopies or the main structure.Secondly, the visual models gave the architects the opportunity to review the connectiondesigns from an aesthetic angle before the design was translated into working drawings.

Full scale tests were carried out on the performance of the cladding for the canopies,testing their reactions to wind pressure, suction, heat and freezing. The plates arescrewed into the structure. As the plates expand and shrink due to temperaturedifference forces will be exerted on those screws. Tensions will be generated due towind forces. These stresses were checked with a full scale mock up of a section of acanopy subjected to conditions in excess of those expected.

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We had the opportunity to test the theory of the designs when three of the canopies wereconstructed at 2/3 scale for an exhibition. The Guggenhiem Museum in New York helda Gehry Retrospective Exhibition and scale models of the Marques de Riscal canopiesformed one of the pieces. This gave us the chance to see exactly how the structure fittedtogether and it gave the architects the opportunity to see how the finished product wouldlook. The fabrication and erection of the structure was not unduly complicated and thevisual aspect of the finished canopies was very much as required by the architects.

Figure 10. Connection in CATIA / Reality in New York.

3. CONSTRUCTION DOCUMENTATION

Given the complexity of the building and its structural calculations it was decided toprovide the Contractor with a high level of detail for each connection type and everyreinforcement detail. While the Contractor must geometrically detail the steelworkconnections, generic details provide the connection type and govern the aestheticqualities of the unions. The reinforcement details of complex areas such as the columnsupports are drawn at scale 1:10 in order to reduce possible errors of interpretation. Thehigh level of detailing in the construction drawings is also coupled with a high level ofsite supervision to ensure that the building is constructed in the exact way intended bythe design team.

The building itself is highly irregular and given the number of different drawings thepossibility of error within the AutoCAD plans is high. During the development of thedesign, all drawings were taken from a CATIA masterplan where all the outlines of thedifferent layers (concrete, steel sections, cladding, etc.) were plotted in threedimensions. It was therefore logical that the setting out of the structure should be basedon the CATIA drawings. Information from the CATIA file takes precedence over anyAutoCAD drawing. The Contractor has the full CATIA file loaded onto a PC on site,which is dedicated to the setting out of the building.

4. CONCLUSIONS

The design of the Marques de Riscal Winery Hotel building has been a greatopportunity for engineers and architects alike to push back the frontiers of what was

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previously thought possible. The extensive use of computer software has been of primeimportance not only in structural calculations but also in aesthetic design and inensuring adequate fit between the different structures and the cladding.

The building is currently in progress on site. While it was never going to be an easystructure to build due to its highly irregular shape, it is hoped that the extensiveplanning and calculation during the design phase will assist the Contractors during theconstruction phase.

Figure 11. Progress on Site. June 2003

ACKNOWLEDGEMENTS.

The author would like to acknowledge the assistance of the following people: ShyamalaDuraisingham and Karl Blette.

REFERENCES.

Duraisingham, S. and Barrett, R. and Blette, K. and Pérez, F. and Caicoya, C. TheStructural Design of the Hotel for the Marques de Riscal Winery, Spain. The StructuralEngineer. 2 July 2002. Volume 80 Number 13. Pages 23-29

CORRESPONDENCE.

Miles ShephardAvda. Lehendakari Aguirre, 348014 BILBAO94 479 76 00miles@bilbao.idom.es

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