Overview
Zurich zoo's elephants have a new home, a compound of some 22,000 m2 with a 6,800 m2 shelter under a wooden free form cupola spanning 80 m. The park is named after the Thaï Kaeng Krachan wildlife reserve where the Zurich Zoo sponsors and maintains a longterm protection program.
The compound comprises an extensive outside area with man made rocks, water pools and landscaping designed to suit the elephants' lifestyle.
The building housed under the wooden cupola provides bull stables, healthcare and quarantine quarters, all technical resources including HVC equipment, offices, and a visitors' gallery and restaurant "lodge" on the first floor.
An underground underwater observation facility allows visitors to view the elephants swimming, while elevated pathways allow interior and exterior views.
The interior is climate controlled and maintains year round tropical temperature to support the growth of vegetation similar to that of the animals' natural environment.
The sloping grounds with unstable geological strata over solid rock required special foundations, that also house the rainwater cisterns. A ring foundation links the four foundations and the reinforced concrete building set into the hillside rockface. The interior playground area has a compacted soil/sand flooring.
The wooden cupola is a relatively lightweight solution and can be thought of as a completed wooden formwork that stayed in place rather than serving as a temporary form for a reinforced concrete shell that would have been nearly three times heavier.
The complexity of the project called for integrated parametric programming, providing solutions throughout the design process, structural decisions, manufacturing (including automatic generation of single element drawings and programs for CNC machining), logistics for prefabrication, transport and assembly.
Parametric Programming
Integrated parametric modelisation and programming does what it says : it provides information technology solutions to the complex and often contradictory parameters of a building through design, structural concept, simulation and verification, project revisions and through to production planning, single element generation and CNC programming, transport and site assembly sequences.
A free form project such as this is can neither be planned nor build by traditional methods. This would generate thousands of design, calculation, drawing and manufacturing details of the complex shape and its layers - and all would have to be redone every time one parameter was varied, as every changes affects the rest of the structure.
The complex continuous form is created through a mathematical simulation of its geometry (NURBS : non-uniform rational basis splines). Developed by the French motor industry in the '70s to efficiently produce ever changing car bodies, this method is today integrated in software such as Rhino, design tools that architects use to create complex continuous forms.
Kaulquappe, a provider of IT solutions in variuous fields, in charge of the parametric programming, has integrated programming facilities allowing architects to handle design options with changing parameters. They also allow structural engineers to conceive and verify structural options and solutions. Kaulquappe then provided solutions for the automatic generation of single element representations in the whole form and in detail along with CNC programs for their prefab production.
Parametric programming first searches for an abstract level on which to consider the multitude of parameters needing integration for management solutions.
See parametric modelling of the entire building here.
See FEM validation here.
See the tension ring details here.
Structure
The free form, wide span dome is a unique wooden structure combining six distinct functional strata.
The complex build is a combination of three layers of triple-layered CLT (Leno from Merk Timber) crossed at 30° each, strapped by glulam rays and belted by a tension ring of preconstrained reinforced concrete.
The weak shear force resistance of wood in the primary CLT panels made the secondary glulam structure necessary, following the structural rays and nodes. These and the simple statics of nail connections between the panel layers made for easy calculations, as long as the CLT panels were not connected edge to edge.
Wooden edge beams and spacer blocks form the support of a thermal insulation level closed by a structural layer of Kerto on which sits a network of technical distribution channels onto which the ETFE cushion frames are attached. The frames hold the waterproof FPO felt layers, topped with an outside Kerto layer (with a preventive autoclave treatment), serving as accessible support for maintenance.
The roof's undulating edge sits partly on the rear wall of the technical building tract set into the hard rock of the sloping grounds and partly on those of the 276 angular concrete/wood columns that meet the lower edges of the dome. Set downhill on the closed concrete ring foundation they transfer their loads into four structural bases that rest on solid rock through a series of concrete piles. These bases also house four rainwater cisterns.
The complexity of the often contradictory parameters of design and structural elements required that static appreciation, material, production down to the programming of CNC machining of the wood elements and to the transport and assembly constraints had to be solved by integrated parametric programming. It would have been otherwise impossible to generate all details through the various stages of planning, revisions, calculations and manufacturing.
Exterior
The cupola's structure and its organic appearance allow for unfiltered daylight through the skylights set into the shell and gives the impression of a rain forest canopy with its play of light and shade.
The exterior landscape connects with the interior through pathways for the elephants and views through the peripheral file of columns for visitors. The elephants can wander freely in and out in the reserved zones and are meant to spend time in search for food and feeding from a range of available sources. The visitors follow paths that provide open views to the outer park and into the hall under the dome and continue onto an interior first floor gallery cum restaurant above the hall's open zone.
The dome's column façade is complete with wood/glass elements made to measure by Merk Timber (Germany).
Special zones allow the visitor to visually assist training sessions and healthcare, and there is an underwater view facility under the indoor pool.
The hall is thermally and hydgrometrically regulated to enable the vegetation to mirror that of the Thaï Kaeng Krachan Wildlife Park.
The wood structure is completely weather protected. A crossed double layer of Sarnafil FPO felt protects the outside face of the dome. The wooden part of the angular concrete/wood columns is protected by the roof's overlap. The maintenance access to the roof is provided by autoclave impregnated Kerto.
Interior
Under the dome, the facilities include offices, technical management, quarantine quarters, bull pens, mixed quarters, health care areas and a pool with view from underwater.
A regulated climate (humidity and temperature controlled environment) maintains the tropical vegetation of the park all year. The vast interior playground comprises rocks and sand pools, water basins and feeding arrangements that stimulate the animals.
The wooden canopy with its 271 skylights (a total of 2100 m2 = 35 %) complements te admission of daylight through the peripheral column façades.
See a 360 degree panoramic view here.
