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Our BatchGeo world MAP shows the locations of green architecture, green building and renewable energy projects featured on Solaripedia.

Project

Hannover Pavilion Soars in Wood (Germany)

Credits: ©2012 Robin Rogers / Solaripedia

Wood is a renewable construction material and it possesses almost limitless structural possibilities. German architect Thomas Herzog put it to the test in 2000; for the World Expo 2000 in Hannover, Germany, he designed a giant wooden structural “umbrella” roof that protects a central piazza consisting of a stage area for musicians and artists, small reconfigurable pavilions and restaurants, and spectators taking time out between events. Mimicking a forest, this giant roof’s columns represent the vertical structure of tree trunks while the lattice shells represent the tree canopy that allows daylight to penetrate below. This artificial forest of trees and buildings, in which private and public spaces, organic and non-organic forms are integrated, covers more than 172,000 square feet (16,000 square meters), with four individual pavilions ranging in size from 10,000 t0 15,000 sq. ft. (975 to 1,430 square meters). Each pavilion contains a small gallery as well as corresponding service areas so that each building can be used separately. (For additional resources, scroll to bottom.)

 

Hannover Pavilion Roof Construction

A giant structural wood roof in Hannover, Germany, was designed by German architects Herzog & Partner for Expo 2000. It uses steel joinery to help support the 172,000-sq.ft. undulating sustainable wood lattice surface. ©2012 Julius Natterer

The Wood Canopy
The wooden canopy is comprised of ten modular elements, each measuring 120 feet by 120 feet (40m x 40m) and installed at a height of 60 feet (20m) above the ground. The elements are timber double-curved lattice shells, each supported on a central structure. Designed by German architecture firm Herzog & Partner, the roof shells cantilever out on all sides from a central “trunk”, and are covered by a pre-stressed translucent membrane. Each square, modular element is made up of four wedge-shaped pre-fabricated sections (leaves) that utilize a compound slope downward towards the lower center of the square; rainwater naturally runs downhill to the hollow central support columns where it is collected and brought to the ground. These supports are each cut from a single tree trunk, from the classic silver fir of the Black Forest. Seventy trees 150 feet (50m) tall were selected. The bark was stripped with high-pressure water jets and the trunks were cut in half lengthwise, to form each of the four corner columns. l

Munich-based architects Herzog + Partner are specialists in timber research and experimentation.

The World Expo 2000 theme was 'Man, Nature, Technology,’ and the architects considered their organic wood roof structure to be the perfect construction to embody a natural material grown from sustainable sources. However, they also applied conventional engineering standards and modern building codes, according to project structural engineer Julius Natterer.

Each of the ten upturned umbrellas consists of a central four-legged tapering pylon of timber and steel supporting a 40 x 40m square crown, which is further divided into four identical square leaves. At the base of each pylon, steel feet are anchored in a 45-foot (15m) deep concrete ring foundation. The leaves of the crown are double-curved surfaces made up of a skeletal net of laminated timber struts clad in a weatherproof membrane. Rainwater is conducted to the center of each umbrella, down a rainwater pipe in the center of each pylon, and feeds into a grid of 15-foot (5m) wide canals on the piazza which complement the roof geometry. Changing daylight, the aspect of the sun and sky color, is filtered through the thin, fireproof translucent roofing membrane which is self-cleaning and recyclable.

The timber originated in the Black Forest in southwest Germany where the largest concentration of ancient white oaks in Western Europe exists. The oaks chosen for the Expo Roof columns were up to 150 feet (50m) long with a typical diameter of approximately four feet (1.4m), and some trees were up to 250 years old (Editor's Note: this seems like a dubious sustainable practice, although selective culling of "weak" trees is sometimes considered acceptable for old growth forest systems). Suitable trees were selected using ultrasonic equipment that could reveal internal structural weaknesses.

Architect Thomas Herzog has said that his design goal was to reflect the solidity of a tree with its structural strength visible in the progression from a large supporting trunk to the smaller branches and twigs. Computer technology made precision possible and even saved trees from unnecessary felling thereby saving time and resources. The double-curved roof deck and supporting structure were coordinated using a computer program that guided robot cutting machines in the manufacture of factory-made sections that were small enough for highway transport, to be assembled on site.

Specialists on the project carefully studied vibration, wind and snow loads, lighting and daylighting, membrane and color. The design process included collaboration among the architect, engineers and contractors who tested structure and construction feasibility using real models and computer simulations, wind tunnel and loading tests. Steel shafts were incorporate at critical points but this project is considered by some to have been the first time that timber alone, in the form of large area plate collars, solid and laminated sections, was used for structural wind bracing.

It is one of the few Expo 2000 structures remaining on Hannover’s extensive Deutche Messe fairgrounds - the largest fairgrounds in the world as of November 2012.


Documents

  Hannover Pavilion Expo Dach Structural White Paper 2000 (594 kb)

  Hannover Pavilion Structural Engineering Article 2000 (798 kb)


Resources

Herzog and Partner Architects (Germany)