Structural design is a methodical investigation to get the economical specification of a structure or a structural element to carry the predicted load safely.

The goal of structural design is to produce structures that can resist applied loads such as wind loads, snow loads, earthquake loads, and permanent or stationary loads.

While architects are tasked with the look of the building, structural designers deal with the strength, stability, and rigidity of structures. Their job is to make sure the structure is safe and that the architected design is built according to safety standards with minimum costs.

What are design codes?

Design codes specify the guidelines and regulations covering the design of different types of structures e.g. steel, concrete, timber, masonry, or aluminum. Design codes ensure that the material in use is safe and will react to outside forces as expected.

Because of environmental conditions, building materials, economical condition, and similar factors, different countries typically have different specification codes.

What is the difference between structural design and structural engineering?

Structural engineering is a subset of civil engineering. Civil engineering encompasses many kinds of constructions such as roads, bridges, dams, highways, railways, airports, pipelines, sewage, and drainage systems while structural engineering primarily deals with buildings, bridges, towers, lighthouses, and tunnels.

Structural design is a subset of structural engineering. Structural design solely focuses on the design of the structure with respect to codes, whereas structural engineering ranges from material science to the analysis, design, construction, and maintenance of structures that reinforce or counteract loads.

What are the different loads that are applied to a structure?

The most important loads that are applied on a structure are dead loads, live loads (or imposed loads), wind loads, snow loads, and earthquake loads. There are also a number of other loads such as foundation movements, vibration, fatigue, erection loads and soil and fluid pressure (sometimes referred to as “special loads”).

The dead load is the permanent or stationary vertical load applied to the building. The dead load is primarily caused by the weight of the structure.

On the contrary, live loads are caused by moving assets or people. Unlike dead loads, live loads change from time to time, and the structural designer must suitably assume them.

Each load has three properties, which structural designers must take into consideration:

  1. Magnitude: The size of the force that is applied to the structure.
  2. Direction: The direction of the force. For instance, wind loads put pressure against the side of the building, while dead and live loads put a downwards pressure.
  3. Position: The position where the force acts on, i.e. is the pressure mostly affecting a certain wall more than others? The building must not only be evaluated as a whole, rather each area of the building must be measured separately as well.

How to ensure the stability of a construction

When building a structure, developing a solid foundation is crucial to ensure the building is stable and can resist external forces. Therefore, ensuring that the soil beneath the building offers a solid foundation for construction is a vital step. The building must be able to absorb external loads.

Selecting appropriate building materials is the next step. The material determines the durability of the building as well as the costs and what can actually be built. Materials are measured on several properties:

  1. Strength: how well can a material resist applied stress or load.
  2. Toughness: how much energy will make a material crack.
  3. Elasticity: how much can a material be stretched without losing its ability to return to its original shape.
  4. Plasticity: how easily can the material be shaped or molded.

The structural design process

A structural design project generally consists of three phases: planning, design, and construction. In the planning phase, the designer must determine the type of structure. The primary consideration is the function of the structure. Secondary considerations include aesthetics, sociology, law, economics, and the environment.

During the design phase, the proposed solutions in the planning phase are evaluated to find the most suitable proportions, dimensions, and details of the structural elements and connections.

In the construction phase, the actual building starts. There may be some redesign required if unpredicted problems occur, which would need the designer to re-engage and propose a solution to remedy the difficulties.