Element, system and structure. I believe that there is no architecture without a sound structural system, be it expressed or hidden from sight. For the seasoned professional, this statement seems self-evident, but for neophytes and young architectural students, the concept of architecture is often thought of as merely the creation of spaces, or the expression of a list of functions, or worse, the design of beautiful objects.
As a young architecture student, I was taught that there were three important concepts that defined a structural system. That was some time ago and, while structures are dramatically more complex now through the creation of new ways of spanning spaces, I’m confident that the following three concepts remain valid as a first foundation to understand structure.
Element
Image 1: comparison between Le Corbusier’s domino plan and Alvar Aalto’s stool
The first component of a structure is an ELEMENT. It is typically vertical and expressed as a wall or a column (the latter being round, square, pier, or a cross). Any of these elements is considered to be part of a structural system, but not a structure in itself. This means that an element has only the capacity to support its own weight as well as any load that is applied to it. In physics, loads are either punctual or linear, and are symbolized through the letter F (force). Any force has a point of action, a direction, and a magnitude.
The above left diagram shows a wall and four types of columns accompanied by the symbol F; in this case a gravitational force. For the ease of comprehension, I chose two famous examples to illustrate the definition of each concept: the 1914-15 Dom-ino structural system by famed Swiss architect Le Corbusier, and the bent wood stool by Finnish architect Alvar Aalto. In both examples, I have highlighted in green one ELEMENT in the overall design.
System
Image 2: comparison between Le Corbusier’s domino plan and Alvar Aalto’s stool
Pairing an element with another or multiple elements, creates what is called a SYSTEM. In the example of Le Corbusier’s diagram, having one column is an element, including several columns makes it a system. Similarly, all four legs of the stool are now colored in green, thus forming a system. It is important to note that to be called a system, one needs only a minimum of two elements. Building on our first concept of an element being either a column or a wall, we now can define an architectural structural system as either (above left diagram):
- a wall system
- a columnar system
- a mixed system (formed by both columns and walls)
Also, the random setting of columns or legs does not constitute a sound structural system. Architects and engineers tend to organize columns and walls into patterns that makes sense depending on the desired function of the space and the strength and properties of the elements. Again, like for an element, any system is considered to be part of a structural system, but not yet a structure in itself.
Structure
Image 3: comparison between Le Corbusier’s domino plan and Alvar Aalto’s stool
To create a STRUCTURE, we need to introduce at least one horizontal element (beam or slab) or several horizontal elements (series of beams, which is considered to be a sytem in itself because it includes more than one element). In other words, it is the combination of both a vertical system (formed by a minimum of two elements) and either a horizontal element or a horizontal system, that defines a structure. In the example of Le Corbusier’s diagram, the structure is formed by six columns and two slabs (omitting the base slab and footers). Similarly, in Aalto’s stool, all four legs and the seat form a unity that is a structure.
All loads applied on the roof (i.e. wind and snow) or floor slabs (i.e., people, furniture, walls, mechanical systems and facades), or a person sitting on the stool, can easily be transmitted to the ground, thus creating a STRUCTURE. It is also important to note, that the choice of either a slab, beam or more complex structures such as a truss, arch, vault, or dome to name a few, depend on the span between elements and should be dimensioned appropriately.
For additional images, visit Structures and choose any of the sub-tabs (i.e., columns)