Engineering 101: Structural Design and Structural Analysis

Structural engineers ensure that structures such as buildings, tunnels and bridges can withstand the various pressures and stresses placed upon them, as a result of human use and external factors such as the weather and natural disasters.

To ensure the stability and strength of a structure, structural engineers rely on a number of methods, in particular structural design and structural analysis.

Structural design and structural analysis help engineers determine how a structure will cope when subjected to a range of forces.  This insight has a direct impact on the materials selected for each individual component and how they fit together.

Let’s take a look at each discipline in more detail.

Structural design

Simply put, structural design is the careful consideration of the strength and stability of structures.  The aim of structural design is the production of a structure that is capable of withstanding the loads placed upon it throughout its lifetime.

There are 3 distinct phases:

• Planning (i.e. conceptual design);
• Design (i.e. detailed structural design)
• Construction

Planning

During the planning stage, the initial concept for the structure is drawn up.  Integral to the planning stage is the consideration of the various factors that would impact upon the structure’s overall design and construction, usually resulting in a range of viable alternatives to choose from.

The most important thing to consider at this stage is the structure’s function (i.e. how it will be used).  A range of secondary factors may also be taken into account.  These include, but are not limited to:

• Aesthetics – what will the structure look like? Will it fit in well with its surroundings?
• Sociology – how will the structure impact on the development and function of society?
• Law – will any laws be broken during and after construction?
• Environment – what effect will the structure have on the environment?
• Structural limitations – anything that may adversely affect the structure’s design and subsequent construction

Design

With a firm concept in place, a detailed structural design is required.  The completed design will describe the various different elements of the structure and how they will fit together.

The overall strength, stability and rigidity of the structure is of utmost importance.  The aim is therefore the design and development of a structure that will resist the various loads it will be subjected to over time, without risk of failure or collapse.

Construction

With the design of the structure complete, the next stage is construction.  Generally speaking, structural engineers are not involved in the construction of a building and take more of an advisory role.

During the build, it may come to light that some elements of the structure may need to re-designed.  This may be due to material availability or if there’s a problem with the foundations.  In these instances, the original designs will need to be re-visited and adjusted accordingly.

Structural Analysis

Structural engineers analysing structural design plans

Structural analysis determines how a structure will behave when subjected to various loads and plays a key role in structural design.

As mentioned in our previous blog on beam design, load simply refers to the various forces a structure will be subjected to.

For instance, loads that are applied vertically (i.e. vertical load) include the collective weight of the materials a structure is made from, the impact of people, furniture and equipment, even accumulated rain and snow.

Loads that act upon a structure horizontally (i.e. horizontal loads) are also taken into account.  These forces tend to be weather related, such as strong winds.  The impact of natural disasters, such as earthquakes, are also considered.

The data accumulated from the analysis of the impact of various loads feeds directly into structural design.  In other words, structural analysis is a forecasting tool, used to determine the type and size of structural elements and the materials they should be made from.

Structural analysis should ensure that structures not only withstand various loads, but also maintain shape and resist deformation.