Structures and Material Properties

Structures

• A structure is a set of elements that receives and transmits loads
• It is composed of different united and organized elements, designed to sustain specific loads
• When designing a structure, it is necessary to foresee the forces that will act on it and determine its dimensions to withstand them
• Structures can be natural or artificial
• A structure is in equilibrium when the sum of loads equals the sum of tensions

Material Properties

• Choosing appropriate materials is important when constructing a structure, requiring knowledge of their properties
• Load is the external force acting on elements, which can be static, dynamic, cyclic, or alternating
• Tension is the reaction produced in a material when a load is applied, having the same magnitude as the applied load but in the opposite direction
• Elasticity is a mechanical property where certain materials undergo reversible deformations when an external force is applied, allowing them to recover their original shape once the force is removed
• Plasticity is a mechanical property in which certain materials experience irreversible deformations when an external force is applied, preventing them from recovering their original shape
• Deformation, also known as elongation, occurs when a material is subjected to a load, causing tension and deformation, which can be elastic or plastic
• Resistance is a material's property to withstand a force, even with deformation
• Rigidity is a material's capacity to withstand a force without deforming
• Hardness is a material's property offering resistance to scratching or penetration
• Slenderness is an object's quality relating its length or height to a transverse dimension

Elastic, Plastic Zones, and Breaking Tension

• Elastic Zone materials deform slightly upon load application and recover their initial shape when unloaded
• Plastic Zone materials undergo irreversible elongation or deformation when a load is applied
• Breaking Tension occurs when the plastic zone is surpassed, and the material breaks

Forces and Stresses

• Analyzing the stresses caused by the structure's own forces or external forces from the natural environment is necessary to create a sketch or outline for the future construction of furniture, a building, or a machine
• A force is an external action that can cause deformation in a body or modify its original state, whether at rest or in motion
• Stress is the force applied to a body in a specific area, causing it to stretch, compress, or shear
• Stress is defined as the result of applying various forces at one or more points in a particular direction

Types of Stresses

• Compression is the stress that tends to decrease the length of a material due to the presence of two opposing forces
• Traction is the stress that tends to increase the length of a material due to the presence of two forces moving away from each other
• Flexion is the combination of traction and compression stresses that leads to bending and is the stress that tends to bend a material due to a perpendicular force and one or more opposing forces applied at different points; in structures, flexion mainly affects horizontal elements such as beams
• Buckling is the bending that occurs as a consequence of the slenderness of an element undergoing compression; while a column is subjected to compression, it can buckle and bend slightly in the center if it is too slender

Structural Elements

• Structures consist of different types of elements designed to transmit the loads they support to the ground; these elements are classified as vertical, horizontal, or inclined, such as stair slabs
• The elements forming a floor structure include beams, joists, vaulted ceilings, wire mesh, and a compression layer
• Pillars with a square or rectangular section receive loads and transmit them vertically and point-wise towards the foundations
• Columns share the same structural purpose as pillars but are distinguished by their section, with columns having a circular section
• Load-bearing walls transmit the load vertically and linearly towards the ground with these elements mainly working under compression
• Beams are linear elements that transmit loads horizontally, usually made of reinforced concrete or steel, but can also be found in wood
• Joists are small beams
• Vaulted ceilings are not structural elements in themselves but are essential for covering the surface between joists and lightening the floor structure; they can be either lost formwork (integrated into the floor structure) or reusable removed once the compression layer is finished; materials can be ceramic, plastic, expanded polystyrene, or concrete
• Compression Layer is a 4-5 cm layer of concrete with a wire mesh that provides homogeneity to the floor structure and helps distribute loads horizontally towards the joists

Foundations

• Foundations constitute the base of a building and are located underground, receiving and transmitting all the loads to the ground
• Their design depends on whether the construction is made with load-bearing walls, pillars, or if it is buried
• Footing is an isolated foundation that receives loads from pillars or columns and connects with other footings, and when it receives a load-bearing wall, it is called a continuous footing
• Foundation slab is a footing surface needed is so large that it ends up being the entire floor structure when the ground is very sandy or has low resistance
• Retaining walls are vertical elements designed to withstand horizontal thrusts, which commonly appear during excavation, requiring the earth to be supported to prevent collapse
• Arches are flat structural elements that mainly work under compression and transmit horizontal stresses to the ground; they can be constructed with small pieces called voussoirs, with the central piece being the keystone
• Vaults and domes are created when arches are formed in three dimensions; with vaults being created by extruding an arch and domes are made from the revolution of an arch