What is structural engineering, and how does it affect the quality of a project? The following article will provide you with the most general knowledge about structural engineering. If you are a newly graduated construction engineer, you should carefully refer to this article; I believe it will be very helpful for your future work.
1. What is structural engineering
Structure is a collection of parts of a house or building that are connected to each other to perform the task of receiving, distributing, and transferring vertical and horizontal loads of the structure to the foundation, and protecting the structure against environmental impacts such as temperature, atmospheric corrosion, etc. Structural engineering is the mechanics of construction components.
The Sino-Vietnamese word 'Kết' (結) means to tie a knot or connect, and 'cấu' (構) means to make, create, or a work of art. Structure or statics (English: statics, German: Statik) in ancient Greek is 'statike (techne)', which means (the art of) balance, or 'statikos', which means bringing about a state of equilibrium. Structural engineering serves the calculation and design of structures in the construction industry. It is a tool for construction design and, together with modeling theory and component theory, it forms the theory of structures.
Its content includes calculating support forces, internal forces, and deformations due to the impact of external forces on a load-bearing system of a construction project. Besides static forces, there are other impacts: temperature changes, moisture shrinkage, creep, and support deformation. The theory of material strength (e.g., elasticity theory, plastic flow theory) also belongs to structural engineering. Structural engineering is the basis for designing structures in the ultra limit states (ULS) and serviceability limit states (SLS).
The history of structural development is linked to the history of human society. From simple structures made of brick, stone, wood, and bamboo to modern reinforced concrete, steel, and composite material structures... humans have traveled a long path over many millennia. Over time, with advancements in materials and construction techniques, the size of structures has also grown larger.
2. Limitations and concepts of structural engineering
The concepts of Statics, Mechanics, or Structural Mechanics are often used interchangeably and associated with mathematics and theoretical physics, while Structural Engineering or Construction Structural Mechanics aims to apply mechanics or structural mechanics to the construction industry. Therefore, creating the load-bearing system of a structure and designing components (determining required dimensions, cross-sections, amount of reinforcement, etc.) are prioritized.
A structural engineer or construction designer – usually a Civil Engineer rather than an Architect – is responsible for construction design work.
The final result of construction design is the structural calculations and reports proving that the chosen load-bearing system meets mandatory construction standards.
The most important basic requirement of structural engineering as well as structural mechanics is that the load-bearing system must be in a state of stable equilibrium. An important part of structural engineering is modeling the sample load-bearing system from a complex construction project (industry terminology is also called 'structural decomposition') so that it can be calculated within reasonable economic and effort limits.
The structural calculation process continues with determining external forces (Note: the author uses the term [external actions] instead of loads or external forces because, besides force agents – gravity, wind, earthquakes, etc. – there may be other non-force agents such as heat, forced deformation, etc.). From there, internal forces in the components can be calculated. The applied force will be transmitted through the components down to the foundation of the structure.
Load-bearing system – Structural engineering is divided into two groups of load-bearing systems
Bar systems and Truss systems (Bars, Beams, Columns, Frames)
Surface load-bearing systems, including Plates, Slabs, Shells, and Membranes
External actions (external forces, loads) of a load-bearing system in structural engineering must include:
Gravity
Traffic loads
Wind load
Live load
Hydrostatic load
Earth pressure
Earthquake
Thermal
Forced
Etc.
Dynamic loads (impact, vibration, oscillation, earthquake, etc.) are usually converted into a static load before being used for construction calculations.
Classification of construction structures
By construction materials
Construction structures can be classified by construction materials, which also involve different calculation methods and design processes:
– Masonry structures (brick and stone structures)
– Wood and bamboo structures (timber structures)
– Cast-in-place concrete and reinforced concrete structures
– Steel and other metal structures
– Composite material structures
– Foundation structures: soil, rock
– Glass
– Etc.
By load-bearing scheme
– Statically determinate structures
– Statically indeterminate structures
– Planar structures
– Spatial structures
By construction method
– Monolithic, cast-in-place structures
– Prefabricated and semi-prefabricated structures
By structure type:
Building structures: low-rise buildings, high-rise buildings, factory buildings, etc.
Bridge structures: simple bridges, cable-stayed bridges, suspension bridges, etc.
Tunnel structures: pedestrian tunnels, mountain tunnels, metro, etc.
3. Construction structure calculation
Calculation theories for structures are based on approximate hypotheses, among which the first-order, second-order, and third-order theories are important.
First-order theory: calculates forces on a non-deforming load-bearing system. This means that geometric changes of the load-bearing system due to applied loads are ignored. This is only acceptable when small deformations do not affect the calculation results. When the stability of the load-bearing system is at risk, the calculation of geometric changes in the deforming load-bearing system must be prioritized. In addition, in general, unintended deviations of the load-bearing system from the design geometry (e.g., column inclination) and initial deformations of components (e.g., curvature of compression members) need to be considered.
Second-order theory: the rotation of a component is small enough to be ignored. From this hypothesis, it is possible to approximate sin φ = φ and cos φ = 1.
Third-order theory: calculation that takes into account the rotation of the load-bearing system.
When considering the stability of the load-bearing system, especially when calculating for slender materials like steel, aluminum, etc., the calculator must apply special standards for this type of failure deformation.
Calculation methods
Basic calculation methods:
Force method
Displacement method
Classical displacement method
Computational method (Finite Element Method – FEM)
