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What is structural design in civil engineering?

Author: Step Engineering
by Step Engineering
Posted: Jun 09, 2019
structural engineers

The structural design is a highly specialized area of??civil engineering. It can be described as a set of methods or tools that are used to determine safe and economical specifications for a structure, and to ensure that a planned structure is strong enough to carry the expected load. Structural engineers perform a structural analysis to determine what internal and external forces could affect the structure, then design a structure with the appropriate materials and reinforcements to meet the requirements.

There is a strong relationship between the professional disciplines of architecture and structural engineering. While architects usually have the task of designing the visually appealing features of a project, structural engineers focus on strength, durability and safety when designing a building.

Basic principles of structural design

Structural engineers combine the basic principles of structural design with a solid background in physics and materials science to ensure that structures are built to withstand the loads and forces they will encounter during their use.

Civil engineers who design structures for construction projects should be excellent problem solvers. The decisions made by structural engineers during the structural design phase of the project will affect everything from the cost and duration of the project to the maximum safety and viability of the structure.

Below, we highlight some of the most important factors that structural engineers must take into account when designing a building.

Civil engineers use structural analysis to understand how forces impact structures

Structural engineers are mainly concerned with the safety and stability of the structures they design. Structural analysis is the main tool used by structural engineers to ensure that a structure can withstand the different types of forces encountered during normal operation.

A civil engineering designing a subway platform must ensure that the platform does not collapse under the weight of thousands of passengers. A structural engineer designing a rail system must use materials that will not be damaged when a 50,000-pound railway car is used on the tracks.

A structure designer must ensure that the train station they are building does not collapse when snow builds up on their roofs in the winter.

Civil engineers investigate three properties of forces when performing a structural analysis:

Magnitude: the size of the force that is applied to the structure.

Address: The direction of the force. A strong wind would act against the side of the building, while the weight of heavy snow would act downward, in the direction of gravity. Different systems of materials and reinforcements are required to counteract different types of forces.

Position: The position on which the force acts. Structural engineers should evaluate the effects of anticipated forces in each area of??the building, not just the building as a whole.

The structural elements must remain stationary

If you have ever tried to build a rock tower on the beach, you may have found the important structural principle that the elements of a structure must remain stationary to ensure its stability. The first step is to ensure through geotechnical engineering that the ground below the building provides a solid foundation for the construction. A solid foundation helps ensure that the structure itself is immovable and can withstand external forces.

For a structure to remain stationary, the sum of the forces acting on it must always equal zero. However, civil engineers know that external forces will be applied to the structure throughout its operation. These may include live loads as occupants of buildings and furniture or environmental charges such as wind, snow and earthquakes.

In any case, an effective structural design requires civil engineers to ensure that a building can absorb applications of external force, maintaining its own balance. Just as a tree branch that does not bend will break with the wind, a structure that can not absorb external forces is vulnerable to damage and instability.

Structural designers must choose the appropriate materials

The selection of appropriate building materials is one of the key responsibilities of structural design. The ability of a structure to withstand external and internal forces and maintain its own state of equilibrium and stability depends on the properties of the materials from which it is built. Structural engineers choose materials based on a series of measured properties that predict their performance in construction applications:

-Force, a measure of how well a material can withstand a load or applied effort. The opposite of strong is weak.

-The tenacity, a measure of how much energy will cause a given material to crack. The opposite of hard is fragile.

-The elasticity is a measure of how much you can stretch a material and still recover its shape.

-The elasticity measures the capacity of a material for plastic deformation. Plastic deformation occurs when a material is stretched beyond its ability to return to its normal shape. Metals exhibit plastic deformation when they crack, making them stronger than other materials that break, such as glass.

Pulling everything together...

Imagine you are a designer of structures that creates a design for a skyscraper. How will you decide what building materials to use? Because the building is tall and has a face with a high surface area, you know that the greatest risk to your structure is likely to be strong winds. Also, because the building is quite high, you could risk falling into an earthquake.

If you could choose between a concrete and a steel construction, you will want to review the properties of both materials and determine how they would affect the safety of your building. When looking for the specifications for a steel construction, you realize that the steel is more ductile: it can be made of plastic elongated up to 15% before the fracture, while the concrete exhibits very little plasticity and fractures immediately once its stretch stretch threshold is exceeded. It is quite fragile.

You come to the conclusion that a material that does not fracture under stress is a better option, and you correctly choose steel as a construction material.


Structural design plays an important role in construction projects. The structural design is carried out by a structural engineer whose function is to guarantee the safety, stability and performance of the structure. Civil engineers use structural analysis to assess the forces that could act on a structure and to choose materials and reinforcements that will effectively resist those forces.

Structural engineers design buildings, towers, tunnels, bridges and other types of structures through the knowledge and successful application of the principles of physics and material science.

STEP Engineering provides its civil and structural engineering services to support oil and gas facilities, refineries, pipelines, petrochemical plants, water treatment facilities, etc.

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Author: Step Engineering

Step Engineering

Member since: Jul 12, 2018
Published articles: 31

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