Architecture: Computing and Design

1
Architecture Computing and Design

• Current Architectural practice
• Hugh Whitehead
• The laws of form

2
Introduction

• Foster and Partners is a practice well known for
  its many completed buildings, but this chapter
  will focus more on the process of design, which
  is less often described, and in particular on the
  work of the Specialist Modelling Group.

• The Specialist Modelling Group (SMG) was
  established in 1998 and, to date, has been
  involved in 63 projects. We have had the
  opportunity to see many of them progress from
  concept design through to fabrication and on-site
  construction.

3
Introduction

• Analytical studies, on the other hand, are
  becoming an increasingly important part of our
  work. This discussion features two projects, City
  Hall (l998-2002), London, and the Chesa Futura
  (2000- 03), St Moritz, in both of which
  analytical studies have had a profound effect on
  our methodology.

Chesa Futura (2000- 03), St Moritz
City Hall (l998-2002), London
4
City Hall, London

• Location
• A strategic position on the south bank of the
  River Thames adjacent to Tower Bridge and
  directly opposite the Tower of London - a World
  Heritage Site.

5
Design Studies
City Hall, London

• The inspiration
• as the team started work on the project one of
  the partners was heard to say, "We are doing
  something by the river. I think it is a pebble."
  We took up the idea and attempted to create a
  "parametric pebble."

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Design Studies
City Hall, London

• Design Concept
• the concept was to create a large "lens" looking
  out over the river, with a set of floor plates
  attached at the back in a serrated profile, which
  resulted in a "pine cone" glazing effect.

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Design Studies
City Hall, London

• The problem we faced was how to formulate a
  "pebble" in descriptive geometry. Our first
  thoughts were to start with a sphere, which has a
  minimal ratio of surface area to volume, and then
  explore how it could be transformed. This could
  have been achieved using the Microstation.

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Design Studies
City Hall, London

• Having first derived a "minimal control polygon"
  for a sphere, we connected it to a parametric
  control, so that the form could be adjusted by
  using proportional relationships.

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Design Studies
City Hall, London

• The pebble-like form, created in this way for
  City Hall, had some remarkable properties. If the
  main axis is oriented towards the midday sun, the
  form presents a minimal surface area for solar
  gain. The side elevations were also curved,
  presenting a minimal area to the east and west,
  where the facades face a low sun angle.

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Design Studies
City Hall, London

• By slicing the solid model with horizontal planes
  a set of floor plates which revealed further
  interesting characteristics of the form.

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The Energy Case
City Hall, London

• Arup's engineers did a solar study of the
  proposed design, and produced a remarkable image
  in which they colour-coded the surface according
  to the total amount of energy that each cladding
  panel would receive during one year.

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The Energy Case
City Hall, London

• it was immediately clear that the south facade
  was performing as expected - it was selfshading,
  as shown in the image by the blue overhang areas.
  The east and west surfaces were green, indicating
  that the oblique angles of incidence were indeed
  limiting solar gain. But to the north, where the
  atrium glazing would be, there was only a thin
  strip of light blue. The protected area
  was not large enough for the "lens" that
  had been envisioned there was a
  conflict between the design and the
  outcome of the energy
  analysis.

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The Energy Case
City Hall, London

• The final solution required a radical change, so
  that the design of the glazing system would
  literally fit the energy analysis produced by
  Arup. The geometric solution was to
  post-rationalize the surface into a stack of
  sheared cones. We then developed a software macro
  that enabled programmatic generation of the
  glazing solution using this technique.

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The Energy Case
City Hall, London

• The result produced a dynamic visual effect as
  the frames for the glazing fan backwards with the
  rake of the building. To estimate the cost of
  such a solution, the original macro was extended
  to Jay out the glazing panels in a flat pattern,
  automatically scheduling all areas of the facade,
  and listing panel node coordinates.

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The internal glazing
City Hall, London

• A further important element of the City Hall was
  the internal glazing to the atrium, which
  separates the offices from the public space. The
  shape of this surface resembles a glass chemical
  flask, with the debating chamber at the base.

• The form of the "flask" needed to have an equally
  strong rationale for its definition,
  construction, and performance.

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The internal glazing
City Hall, London

• A digital model was created so that the shape of
  the flask could be transformed through a morphing
  sequence, allowing the team to explore the
  spatial requirements for the chamber.
• The morphing sequence was produced by "key
  framing" the three different transformations, so
  that they could be executed in parallel to
  produce a wide range of alternatives.

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Acoustic analysis
City Hall, London

• Arup's engineers performed an acoustic analysis
  of the proposed geometry of the debating chamber,
  and determined that this dramatic shape would be
  difficult to treat acoustically because all the
  sound reflected straight back towards the
  speaker.

• spiral ramp was wrapped around the "flask" and,
  as a consequence, the glazing leaned outward,
  causing the sound to reflect in a totally
  different way.

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The Energy Case
City Hall, London

• spiral ramp was wrapped around the "flask" and,
  as a consequence, the glazing leaned outward,
  causing the sound to reflect in a totally
  different way. The sound-performed as required it
  was scattered and reflected up the neck 'of the
  "flask." It could also easily be dampened by
  applying a sound-absorbing surface to the soffit
  of the ramp.

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Design Rationalization
City Hall, London

• Before a building such as the City Hall could
  progress to construction, the design process had
  to be taken apart and reassembled as a sequence
  of procedures. This meant that the whole building
  was reanalyzed as a set of construction
  components. There is a concrete core, a steel
  structure, the ramp, the atrium, the entrance
  glazing, the front diagrid, and the
  office side cladding,
  resulting
  in a complete component model.

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Geometry Method Statement
City Hall, London

• in order to coordinate construction, we had to
  assist the contractors in understanding the
  building's geometry. A further analysis of the
  form was undertaken as a post-rationalization of
  the geometry, referred to by the team as "Nine
  Steps ,to Heaven". The final form was described
  as a sequence of nine dependent stages, using
  only rational curves for all the setting out, and
  this was issued as a Geometry Method Statement.

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Geometry Method Statement
City Hall, London
22
Geometry Method Statement
City Hall, London

• It may seem counter intuitive that in order to
  build a complex form, originally generated as a
  free-form surface, we embarked on a long and
  difficult process of post-rationalizing the
  design to arc-based geometry. However, the real
  benefits lay in achieving reliable data transfer
  between independent digital systems. By following
  the Geometry Method Statement issued to
  contractors, we were able to describe the City
  Hall geometry in terms of basic trigonometry.

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Tolerance Management
City Hall, London

• The construction sequence Had to be ordered in a
  very specific way. Because the structure of the
  building leans backwards, it progressively
  deflects as it becomes loaded with additional
  floors. This transformation could not be
  predicted reliably and, therefore, it had to be
  monitored and measured on site.

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Tolerance Management
City Hall, London

• In order to control positioning during
  construction, the contractor marked every piece
  of steel structure with holographic targets in
  the factory. By recording coordinates for each
  target in a database, they were able to track
  every piece from the factory to its installation
  on-site.