Stuttgart Airport Structural Case Study
Background
Stuttgart International Airport is a public airport located in Germany that was first constructed to be a German Airbase in 1938 replacing an existing air strip. After World War ll, the Airport was seized by the US Army until 1948.
In the 1990s, the original terminal was demolished and then replaced with four new interconnected terminals featuring a spacious floor plan and efficient transportation layout to manage a maximum of 12 million passengers yearly. Designed by Architecture group Gerkan, Mag and Partners, each of the four terminals have separate check-in and bagging stations creating small transport networks for both people and luggage to be in close proximity with one of the eight jet bridges. After being dropped off, the path to boarding the plane is very straight forward and linear, making navigation through this international hot spot simple to understand.
What makes this airport unique is that for a relatively small airport, the use of bio-mimicry in the light weight structural members creates a powerful blend with the built and natural environment giving the entire building an open and inspiring vibe. The concept of Biomimicry, considered as the science and philosophy of learning from nature , is a source of architectural design inspiration with different approaches undertaken by architects and engineers.
Structural Design
The Stuttgart Airport uses Tree-like Support Structures in the entry terminals to create an ascending open warehouse-like space. From walking through the main entrance to checking in bags to approaching the gates, the height of the roof increases providing the subtle ease of orientation smooth flow as the guest prepares for take off. The entire roof is divided into twelve sections partitioned by skylights, erected as a two-way slabs. Each of these areas are supported by the steel tree-like structures. These "columns" gather all the loads passing down through the branches which are translated into the trunk and then down to the foundation.
One single support contains four attached tubular poles (that form the trunk of the tree) and spread into three different levels (forms into the branches). They are distributed to carry the roof loads in compression with minimal bending moments. The branches direct the forces into smaller resultant points and then transfer into the four tubular poles that acts as one. The advantage of using this Tree-like structure systems is that the distances between the loading points and the support system is minimized.
While the column structure is termed as “tree-like”, it would be more correct to refer to the structure as an umbel systems, where the total load is distributed to one point and from there transmit the total load via a single member to a support point, the point of application of the reaction force providing total equilibrium. A pin-jointed connection between the support point and the roof structure it is holding prevents movement between these two componets and enforces stability.
Umbel structures start to split and divide loads that meet at nodes. There are many variations to these structures that can be determined by the number of tiers and number of nodes needed for support.
Underlying Principles
Trees in nature have inspired many forms of architecture and without a doubt, they have influenced the construction of the Stuttgart Airport. However, the inspiration ends at its appearance because these "branching" structures cannot be compared with that of a natural tree. In nature, tree branches are subject to mending forces which would negatively impact constructed tree-like structures. The main underlying principle is the focus of reducing the mass of structural materials while increasing efficiency. This concept of "lightweight" structure requires less material, introducing optimal calculations to determine structural strength. In simple terms, the basic rules to follow when designing with light weight members is to...
- Avoid bending stresses and moments.
- Only carry compression forces over short distances to minimize the chance for stability problems and unnecessary added mass.
- Contain and incorporate compression forces over long distances into self stablizing systems.
Structurally speaking, what makes the tree-like support branches holding up the roof so unique is how large of a span the column holds in comparison to its footprint at ground level. This is a product of the open-ground concept that can only really be achieced with "branching" structure systems.
Building Significance
This building effectively showcases a visible structural system that is vital toward the expression of the building. What truly makes this building is that un-like real trees, the smaller, outermost branches of this structure system is able to carry relatively heavy loads. This all comes down to calculations that optimize direct load performance and reduce bending moments. The whole system is built to act like one unit. This umbel system creates large unobstructed areas close to the foundation while providing closely spaced supports at the roof level. Structurally speaking, what makes the tree-like support branches holding up the roof so unique is how large of a span the column holds in comparison to its footprint at ground level.
Inspirational Take-aways
With so many ways to create impact architecture, bio-mimicry holds a powerful connection to the importance of natural intuition. Airports especially have an importance role in architecture in regards to a national expression. Being the first contact with visitors from all over the world, airport designs should have an attractive and vibrant appearance to welcome all visitors.
The shapes of trees are complex and fractal-like, and they have a set of physical, mechanical and biological functions. The relation between them always draws attention of human beings throughout history and, focusing on the relation between shape and structural strength, architects have designed a number of treelike structures, referred as dendriforms. The replication and adoption of the treelike patterns for constructing architectural structures have been varied in different time periods based on the existing and advanced knowledge and available technologies.