Fundamental Structural Elements and Applied Forces
What Defines a Structure?
A structure is a set of interconnected elements capable of withstanding forces and transmitting them to the support points, ensuring the system is both stable and resistant.
The forces acting upon a structure are referred to as loads.
Resistant and Stable Structures
A structure must possess resistance (the stamina to withstand loads) and stability (the ability not to fall or collapse).
A structure’s resilience is determined by its capacity to safely manage and transmit the applied loads.
Structural Elements for Strength and Stability
Which elements and resources provide inherent strength and stability to a structure? Triangles and Arches.
Triangles
Triangles are the only geometric shapes that cannot be deformed by applying forces on their sides, making them inherently stable and strong.
Arches
Arches add significant strength to a structure, primarily working under compression.
Common Structural Components
The most used elements in a structure are:
- Foundations
- Columns or Pillars
- Beams
- Arches
- Braces
Detailed Structural Components
Foundations
All structures require a resistant base. Foundations are typically located below ground level. They are equivalent to the roots of trees, ensuring stability. Most buildings are constructed on concrete foundations to prevent sinking due to the structure’s weight.
Columns or Pillars
These are vertical elements specifically designed to support compression forces.
Beams
These are horizontal elements designed to support flexion (bending) forces. Beams support the various floors of a building.
Arches
An arch is a curved element used to span a gap between two pillars. It transfers the structural load outward and downward to the ends. (Example: Details of the church of Thira, Greece)
Braces
Braces are wires or bars that primarily support tension (traction) forces. They are often made of steel and serve to increase the overall strength and stability of a structure. (Example: Carlos Fernandez Casado Bridge, Leon)
Types of Structural Stress (Effort)
Structural stress refers to the internal forces that appear within the elements of a structure when subjected to external forces or loads.
Tension (Traction)
An element is subjected to tensile stress when forces act to increase its length (pulling it apart).
Example: The cables or strings used as wind bracing are subject to tension forces.
Compression
An element is subjected to compressive stress when forces act to decrease its length (pushing it together).
Example: The columns of a temple supporting the roof are primarily under compressive stress.
Bending (Flexion)
An element is subjected to bending stress when the forces or loads tend to cause it to curve or deflect.
Shear Stress (Shearing)
An element is subjected to shear stress when forces act parallel to the cross-section, tending to slide one section past another (to cut it).
Torsion
An element is subjected to torsion when forces exist that tend to twist one section relative to another.
Stability in Structures
Stable Structures are those that, when a force is applied, maintain their equilibrium and return to their original position once the force is removed.
Conversely, structures that lose their balance or collapse when a small force is applied are considered unstable.