Understanding Structural Design in Civil Engineering: Definition, Principles, and Types

For a structure to remain stable, it must handle loads and resist external factors like wind over time. That is where you need a structural design. None of us want our buildings to collapse like the Tacoma Narrows Bridge, right? 

What is structural design?

A structural design is what makes a building sturdy enough to work through internal and external loads, stay intact and also resist forces such as strong winds and earthquakes which can otherwise leave a building damaged.

It provides the civil engineers with the tools and methods they need to make a project both functional and safe. Hiring a structural design service will ensure your structure undertakes different loads without its integrity being compromised. 

Principles of Structural Design 

Structural design in civil engineering involves analyzing and creating frameworks that ensure stability, strength, and safety for a building or structure. By efficiently transferring loads—dead, live, and environmental – to the ground, structural design prevents failure and prolongs the lifespan of structures. 

Below are the key principles a structural engineer needs to keep in mind while working on a structure to life – 

1. Load Efficiently –  A structure must bear load efficiently. Below are the three common types of loads one has to consider while creating a structural design –  

• Dead load – Dead load consists of all the components a structure comprises, like the beams, trusses, columns, walls, etc. 

All the elements combined have their own weight, which the building must resist and stand still even when external forces, such as winds, exert pressure on them. 

• Environmental Load – Wind, snowfall, rain, and other weather phenomena can also produce load over a building.

As per the geography where the structure is to be installed, a building can experience different environmental loads. One of the reasons that Tacoma Narrows Bridge failed was that the architects did not consider environmental loads.

• Live Load – Live load consists of the furniture, people, vehicles,etc. which are not a part of its structure but will be accommodated in the building. 

When a natural calamity arises, the live load gets damaged the most. This is why maximum load quantity is considered during the construction process rather than considering the actual live load the building will be bearing.

2. Structural Stability – Structural elements must remain stationary despite the forces acting on them. For a structure to remain stable, it must efficiently transfer the loads from the building to the ground. This distribution of forces ensures the stability of the structure, prevents failures, and protects its occupants.
   
3. Smart Material Choices – The structural engineers select a material that will fulfill the purpose of a member in the construction. Below are the deciding factors that help them make the optimal choice. 

• Strength – The material has to bear all loads without giving in, which is defined as strength. 
• Toughness – refers to a material’s ability to absorb energy and deform without fracturing under stress. It combines strength and ductility, indicating how much energy a material can absorb before breaking.
• Plasticity – When a condition arises, a material should stretch beyond its actual shape; this form of deformation is called plasticity in construction. Metals, for instance, have greater plastic deformation, which is why steel reinforcement bars work so well in structural detailing.  

Using the right material ensures the construction process offers the best performance and increases the durability and longevity of the building. An ideal material will protect against corrosion, wear and tear, and weathering that the buildings are prone to with time.  

How to do structural design of a building?

Structural design of a building involves a systematic process of creating a stable, safe, and functional structure. It involves the below seven stages – 

1. Modeling – At the initial stage, we need a model that mimics the structure. A model is created with all the structure details, including foundations, columns, beams, and other elements. This architectural model will help the client visualize how the structure will look. However, it is unfit for load-bearing calculation. So, when the calculations are done, the drawing is simplified, eliminating unnecessary details. The process is called schematization or creating a mechanical model.
2. Load Analysis – The next step is to analyze all the loads and their collective effect on the building. Load analysis ensures that the building is designed to endure the worst-case scenarios.
3. Structural Analysis – It determines what will happen to the building when different loads act upon it. Different design codes and building standards must be followed, which require using standards software to determine whether the design will sustain the forces. We use advanced structural design and analysis software to ensure the final draft does not require any changes. 
4. System Design – When the structural analysis is done, the next step is to determine the dimensions of every part and ensure all of them function well together. This is what the system design does. 
5. Element Detailing – This section contains the detailed design and specification of the elements, such as materials, dimensions, member sizes, and reinforcements forming the structure. The structural design patterns are applied to streamline the design and specification of individual elements, ensuring consistency, safety, and efficiency throughout the structure.
6. Iterative Design and Drafting – The engineers use this method for prototyping, checking, and refining the product until they reach a point where no changes are needed. In structural designing it helps in improving the quality and functionality of the design.
7. Construction Administration – Structural contractors must ensure that construction aligns with shop drawings to guarantee a structurally sound building. Effective construction administration includes reviewing RFIs, managing deferred submittals, obtaining code approvals, and developing schedules to ensure compliance and smooth project execution.

Our seven steps structural design process blog contains a detailed breakdown of the essential steps in structural design. Refer to our in-depth blog to understand the stages better.

Factors to Consider for Creating Structural Design 

A structural design aims to deliver durable, efficient, cost-effective solutions prioritizing functionality and safety, laying the foundation for long-lasting infrastructure. By considering the factors below, engineers create designs capable of withstanding environmental and dynamic forces. 

• Material Selection – The engineers must choose the correct specification for every material for the design to translate into a successfully executed project. Every material has different strengths, such as plasticity and toughness. Your structure will deliver the best experience and attain greater longevity when you choose it right. 

• Load Assessment – The loads involved and how the building will respond when under their influence must be considered. Only if they can be sustained can the draft be executed.   

• Structural Geometry – The shape of a structure’s elements determines precisely how the stress will be distributed. Complicated geometries can sometimes collect stress in higher quantities in one place. If this is the case, uniformly disturbing the stress becomes necessary to eliminate potential risks and failures.  

• Safety Factor – Safety margins should be included in the design plan to ensure the team can deal with unexpected construction variations. With a safety margin, fluctuations in materials and load projections are easy to manage, making the structure strong enough to withstand unexpected loads and errors. 

Types Of Structural Analysis

The three main types of structural analysis. Each type ensures the structure’s safety and efficiency throughout its lifecycle. These examine stability, material behavior, and deformation under different conditions – 

Static Analysis – It is used to identify how the structure will react to constant load.  It helps determine the structure’s response, stress distribution, deformation, etc. Engineers use static analysis to understand how gravity, wind, damping, and seismic activities will affect the structure.  

Dynamic Analysis – It analyzes how the structures behave towards the dynamic loads positioned over them, such as vibrations, oscillations, etc. 

Finite Element Analysis – FEA  is a revolutionary technology that allows the structural engineer to divide a complicated structure into smaller elements and calculate their load. Combining them to calculate the collective loads provides an accurate picture. 

To learn more about how these calculations are done, read our structural load calculations blog. 

Linear Analysis – Linear analysis is done when a structure is expected to behave linearly. We assume that the structure’s geometry, material, and equilibrium will remain unaffected by the applied load for quick computations. 

Nonlinear Analysis – Nonlinear analysis is used when a structure’s behavior doesn’t proportionally respond to applied loads. It considers material changes (e.g., plasticity), large deformations, and boundary conditions. Unlike linear analysis, the stiffness matrix evolves during loading, requiring advanced techniques for modeling real-world scenarios with complex behaviors.

FAQs

What is Structural design in Civil Engineering?

It is the process of designing structures that provide safety, stability, and longevity. To ensure a structural design is fully proof, the engineers need to do load analysis and structural analysis and also choose suitable materials for reinforcements and building the structure. 

Can structural engineers design houses?

The structural engineers help the architect execute their plan by providing a precise design for the structure to hold the materials. Yes, they can design houses as well. They can also help with structures such as stadiums, bridges, tunnels, etc. 

What is factored load in structural design?

Factored load is the load acting on a structure multiplied by the load factor. It helps assess the strength of the structure and is a vital factor in designing the reinforced concrete members.

Conclusion

Structural design is a pivotal factor in ensuring the safety and resilience of construction projects. Engineers create frameworks that withstand both routine use and extreme conditions by evaluating how structures respond to various forces. This blog has explored structural analysis principles, methodologies, and the structural design process that play an important role in developing robust and efficient engineering solutions.