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June 17, 2019

Complex Structures – The Desert Rose

Complex Structures-Qatar-Museum

When I travel I’m always amazed and inspired by the buildings and structures that I see.

And when I arrived in Doha, the world’s richest city, a strange structure caught my eye from the taxi window.

NMoQ (National Museum of Qatar)

Hungry for information as to what it was, I searched on Google and discovered it to be the brand new National Museum of Qatar. I had to go there!

But first I needed to better understand the structure – who designed it, how such an irregular and unusual shaped structure was constructed, and I guess most importantly, what grief the engineers and draftees had to endure to complete the architect’s vision.

I read a number of articles, but for your benefit, here are just the facts:

Architect – French architect Jean Nouvel

The design drew inspiration from the Desert Rose, a crystalline formation found below-ground in saline regions of the desert.

When imagined as a building, the result is a four storey, 300m by 200m sculpture of intersecting disc shapes up to 80m in diameter.

The desert rose

Engineer – Arup Engineering

Main contractor – Hyundai E&C

Cost – $434 million

Proposed opening date – Scheduled for 2016

Actual opening date – 28 March 2019

Design methodology

There are hundreds of interlocking disks that represent the desert rose concept in the walls, ceilings, roofs, and floors; all varied in curvature and diameter.

Rhinoceros is a 3D modeller used to create, edit, analyse, document, render, animate and translate NURBS curves, surfaces, and solids, point clouds, and polygon meshes, according to their website.

The structural team developed a parametric Generative Components script-based tool to automatically create wire-frame geometry in the correct position within the architectural Rhino envelope. The basic wire-frames were further populated with property and loading data using spreadsheet-based automation.

Custom-designed spreadsheet macros were further used to combine separate disc models into larger combined models for structural analysis. Element strength checking was also automated as far as possible, to make practicable the design of the 250,000 separate steel elements.

The analysis models were used as the basis of the production Tekla model, directly translating geometry, section data and also key annotation such as disc-to-disc interface nodes.

The Tekla model was issued to the contractor at tender stage for accurate pricing.

During the construction phase, the contractor adopted and developed this model to a fabrication level of detail.

Also at tender, the Tekla model was used to interrogate concrete volumes in order to produce accurate steel reinforcement figures

Materials of construction

The discs are made of steel truss structures assembled in a hub-and-spoke arrangement, clad in glass fibre reinforced concrete panels.

To achieve the vision, a huge amount of steel has been used, 28,000 tonnes to be exact, which is around four times the amount that was used to construct Paris’ Eiffel Tower.

Specific design challenges

The key challenges for the design resulted from the highly complex geometry of the disc interaction. No two discs are the same; no two discs intersect each other in precisely the same way. The galleries and other key spaces in the building are created by the interstices between the discs; any alteration to the architecture involves moving discs and thereby moving the structure within the discs.

This led to an evolution of systems and processes required to handle, manipulate and develop geometric ideas from the architect, and establish engineering solutions, before communicating them in their most useful form to the wider community.

Complex structural design drawings

Therefore the structural modelling (both analysis and production) needed to address the requirement to:

  • Position elements in the correct place in 3D space within the cladding envelope.
  • Generate and model elements as efficiently and automatically as possible in order to keep up with iterations of architectural arrangement.
  • Facilitate cross-discipline coordination, with the design and 3D modelling team in London, plus the architectural team based in Geneva and Paris and a client in Qatar.

The scheme for the building involves many intersecting steel framed discs and therefore results in numerous connections between discs with largely different geometries. Advice was taken from external steel fabricators and their design teams (who might ordinarily carry out the detailed design of such connections), to establish an effective normalised solution where possible. Though many bespoke connections could not be avoided, a significant number could be based around a connecting CHS which could tolerate a large range of incoming member arrangements and thus standardising the supporting steel arrangement. In order to communicate this to the contractor, a number of connections were designed, detailed and illustrated on drawings with 3D perspectives and 2D sections. The nature of the each connection was such that the geometry and therefore design could not properly be understood without interrogation of the intersecting members in three dimensions, for which Tekla was invaluable.

Within discs, families of connections were defined to cover typical arrangements such as the bracing connection to the chord of a truss. Although more simple than the connections between discs, it was also useful to understand these in 3D to investigate how the subtle changes in geometry between discs changed the nature of the connections. Typical internal connections were again represented by both 3D and 2D information on the drawings with tables of parameters such as plate thickness and the number of bolts defined for a range of section sizes and incoming member angles.

Complex 3D Model of the structure
3D Model of the structure

The project is a fantastic example of the need for the use of technology throughout the process – in communication, in design, in construction.

I would love to have visited the museum. However, it was closed due to Ramadan until the evening – something the taxi driver who took us there would surely have known!

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