Structure design: Basic, types, design and importance

When designing a large structure such as a bridge, dam, or skyscraper, nothing is more important than structural integrity.

The last thing you want is a flaw that could endanger human lives if the system fails. Structural design is the discipline of calculating the various load requirements of various structures and designing a structure capable of withstanding worst-case scenarios, such as a 100-year storm.

See also: Combined footing: Design considerations and types

What is structural design?

Structural design is a method to identify safe and economical specifications of a structure sufficient to carry the load. It involves finding out cross-sectional dimension, amount of reinforcement, grade of material, etc. required to withstand internal forces identified from structural analysis.

Structure design: Basic principles

Structures must be able to withstand loads efficiently.

Environmental loads, live loads, and dead loads are the three major types of loads studied by structural engineers. Engineers discovered that the Tacoma Narrows Bridge’s design had overlooked a critical environmental load factor not long after it collapsed.

Smart structural design necessitates smart material selection.

A civil engineer uses materials as building blocks. Material strength and longevity, on the other hand, vary greatly. Furthermore, the structural design must account for the weight of each material as well as how it relates forces to other materials once in place.

Structure design: Types of structural design

There are various types of structural design based on the use case, materials, and structure type.

The two most common types are:

1. A rigid frame is a structure that is supported by a framework with welded joints. Beams and columns, in this case, can withstand a certain amount of bending moment, shear load, and axial load.
2. A concrete shell is a building that lacks internal columns and buttresses in favour of an oval-shaped concrete shell.

The loads and forces you must calculate vary depending on the type of building you design.

A variety of factors must be considered by the structural design engineer. Some examples are:

1. Shear stress is caused by different parts of the structure moving in opposite directions. The most extreme cases happen during an earthquake.
2. Tensile stress: This is essentially a pulling force on any part, such as a cord or beam, that can elongate or break it.
3. Compressive stress: This pressure pushes down on the structure, such as its normal weight and the weight of the entire interior plus everyone inside.

Some structural engineers also specialise in designing structures to withstand specific risks, such as storms or earthquakes. Among the most common are:

1. Wind design: In areas with extremely strong winds, wind-resistant designs may be prioritised.
2. Earthquake design, also known as seismic design, is the process of creating structures that can withstand earthquakes. Focusing on building with an even centre of mass to reduce torsion and incorporating unique elements to improve damping — vibration absorption — are two examples.

Structure design: Requirements of structural design

• Stability to prevent the structure or parts of it from sliding, overturning, or buckling underneath the action of environmental and live loads.
• The ability to safely withstand the stresses induced by loads in various structural members. The structure should not collapse under its own weight.
• Serviceability is the ability to perform satisfactorily under service load conditions. This entails providing sufficient stiffness and reinforcements to keep deformations, crack spacing, and vibrations within reasonable parameters.
• Depending on the project, aesthetics, looks, and a visible internal structure may also be a priority.
• Due to the economy, meeting requirements within the budget is critical. An understanding of various materials, their prices, and their applications is required here.

see also about structure desgin

Structure design: Importance

Engineers need structural design to help them at every stage of their projects. Structural design plays a significant role in meeting safe operations, pragmatic functioning, and government budgeting. This is done through rigorous structural testing, evaluations, and inspections.

In civil engineering, structural design is crucial because it aids in ensuring that the structure is secure. In order to ensure that any structures meet all safety requirements, the structural design provides all the essential information regarding foundations, floors, walls, beams, roof types, and the quality of materials.

Structural design codes and standard

In Structural Engineering, code references and standards are the factors required to make the design structurally safe and sound. There are various Indian Standard (IS) codes meant for all aspect of civil engineering.

Some of the codes are mentioned below:

• IS 456-2000: Plain and Reinforced Concrete – Code of Practice
• IS 800-2000: General Construction in Steel – Code of Practice
• IS 801-1975: Cold-Formed Light Gauge Steel Structural
• IS 808-1989: Dimensions for hot rolled steel beam, column, channel and angle sections
• IS 813-1986: Scheme of symbols for welding
• IS 875-1: Dead Loads
• IS 875-2: Live Loads
• IS 875-3: Wind Loads
• IS 875-3: Wind Loads_2015 Commentary
• IS 875-4: Snow Loads
• IS 875-5: Special loads and combinations
• IS 962-1989: Code of practice for architectural and building drawings
• IS 1608-2005: (ISO 6892-1998)_Metallic materials – tensile testing at ambient temperature
• IS 1852-1985: Rolling and cutting tolerances for hot-rolled steel products
• IS 2062-2011: Hot rolled medium and high tensile structural steel – specification
• IS 2911-1-1-2010: Design and construction of pile foundations – code of practice
• IS 2911-1-2-2010: Design and construction of pile foundations – code of practice
• IS 4326-1993: Earthquake resistant design and construction of buildings
• IS 8000-1985_1_Geometrical tolerating on technical drawings
• IS 8000-1992 – 2: Technical drawings – geometrical tolerancing
• IS 8000-1992_3: Technical drawings – geometrical tolerancing
• IS 8000-1976_4: Tolerances of form and of position for engineering drawings
• IS 8976-1978: Preparation and arrangement of sets of drawings and parts lists
• IS 7557-1982: Specification for steel wire (up to 20 mm) for the manufacture of cold-forged rivets (weights)

Importance of detailing in structural design

Detailed structural design comprises investigation of the stability, strength, and rigidity of the structure to be constructed, depending upon the physical requirements and an analysis of the structural performance, the materials and geometries used. The aim is to produce an efficient structural system that can resist the applied loads without failure during its intended lifecycle. The design helps in determining the most suitable proportions, dimensions and details of the structural elements and connections.

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