WHAT IS STRUCTURAL INTEGRITY AND WHY IS IT IMPORTANT?
Structural integrity is an engineering area that helps ensure that, under normal operating conditions, either a structure or structural part is fit for purpose and is secure even if conditions exceed that of the original design. This means supporting its own weight, striving to avoid deformation, breakage, and catastrophic failure during its predicted lifetime.
Integrity is not only a case of good design; for the life of a structure, it needs to be maintained. At periodic intervals, this includes building inspection and repair. Engineers ensure that structures are secure, reliable and perform their intended purpose throughout their entire lifetime.
What are the Causes of Structural Failure?
Structural failure can occur from a range of different sources. The type of failure is often associated with the industry, environment and application of the structure. The primary reasons for failure are as follows:
- Weak structures: The structure is not strong enough to withstand the load to which it is subject. This is usually due to inappropriate geometric design or material choice.
- Structural deterioration: The structure deteriorates due to corrosion, fatigue, wear, rot or creep. Fatigue failures often begin when cracks form at regions of high stress. These cracks grow when subject to cyclic loading, resulting in sudden failure. This is usually due to inappropriate geometric design, material choice or maintenance.
- Manufacturing errors: This includes using the wrong materials or not following manufacturing procedures or standards. It can also result from poor workmanship or components being out of tolerance, etc.
- Defective material: The materials don’t conform to standards, resulting in a lower load-bearing capacity than designed.
- Improper environmental considerations: Engineers may neglect mitigating features for specific environmental conditions, such as natural disasters.
- Unacceptable operational conditions: The structure is not used for its intended purpose.
At What Temperature Does Steel Lose Structural Integrity?
In most large construction projects, such as buildings and bridges, structural steel is used in the form of girders, etc. To maintain the required integrity, the performance of steel is vital. High temperatures are known to weaken steel, softening at around 425°C and losing about half of its strength at 650°C. At these temperatures, the steel will start to buckle and twist if subject to high loads, which will impede structural integrity.
Consequently, engineers must consider the environmental temperature range that a structure will be subject to over its life span.
How to Calculate the Integrity of Structures
In the design process, engineers combine different considerations, such as the performance of materials, stress analysis and fracture mechanics.
To maintain its integrity, all construction/buildings will need inspection and maintenance. To do this, an engineer might:
- Carry out inspections to identify damage. This might involve the use of non-destructive testing (NDT)
- Check that a structure has been built according to the appropriate designs, procedures and standards.
- Check that a structure is being used appropriately for the environment designed for
- Recommend and design modifications to address areas of concern