Mechanisms of structural failure
Contents |
[edit] Introduction
Structural failure refers to defects in which a load bearing component of the building is unable to support and transfer loads to another element. Structural failure develops due to breakdown in the performance of the materials in a structural component may be caused by:
- Erroneous construction: Failure of the engineer to supervise all the construction activities at the site resulting in faults to construction elements which later develop into failure; issues like use of salty sand in making concrete, use of poor grade steel not as specified, improper tightening of torque nuts, bad welds and so on.
- Improper design: Failure of the engineer to account for all the loads the structure is to carry, application of erroneous design theories, use of inaccurate data, not taking account of the impacts of repetitive or impulsive stresses, improper use of materials, misunderstanding of properties and so on.
- Foundation failures: Failure of the ground on which the foundation rests to carry load, causing displacements, altering the stress distribution to the whole structure and so on.
- Overloading: Excess loads that are applied beyond that which had been anticipated, these loads might be due to vibrating earthquake, heavy snow loads, hurricanes, storage, change of use and so on.
- Innovation: New types of structures subject to unexpected failures.
[edit] Compressive and tensile failure
Compressive failure can be sudden and catastrophic, apparent by cross breaks caused by the excessive longitudinal compression or bending. Tensile failure can be detected by stretching in the sizes of the member. These elongations come along with cracks that orient perpendicular to the direction of the tensile forces.
[edit] Bending failure
Bending is the bowing deformation of a beam or other member under load. Bending stress can be slow or sudden depending on the nature of the force applied, whether compressive or tensile forces.
[edit] Shear failure
Shear failure is principally an internal splitting force caused by two forces acting in opposite directions at a distance to one another along the cross section of a structural member. Shear cracks are diagonal, for example, appearing in the web of a beam.
[edit] Buckling failure
Buckling is a creasing failure by crumpling of a longitudinal structural member loaded eccentrically with a compressive force. It occurs to long and slender members subject to axial compressive stress. Buckling load is a compressive load at which a column or strut begins to buckle. Steel columns are more prone to buckling than concrete columns because they are more slender. Also slender beams and floor joists fail due to compressive stresses resulting from the bending.
Buckling Vs. Bending
Buckling | Bending |
Occurs when the load reaches a certain critical value known as Critical load | Occurs under all magnitudes of loads applied to a structural component. |
Buckling takes place abruptly. | May be sudden or gradual, it gives warning signs of failure of the structural component before complete collapse. |
Buckling under load members become unstable, but will generally not fracture | Bending under load member deflects, it may start to develop some cracks. |
Instability caused by buckling in one member can lead to excessive stresses in other members causing progressive collapse of the whole structure. | The defects developed due to bending stress cause less effect to progressive failure of the whole structure. |
Buckling is due to axial stresses applied along the longitudinal axis of the member. | Bending is a combination of tensile and compressive stresses. |
For a member to withstand loads against buckling failure it should be designed to reduce its slenderness by increasing its cross-sectional dimension.
Bracing a member at its intermediate points along its length or height
For economical reasons consider bracing a member as cheaper and easier than increasing its cross sectional dimensions this is uneconomical.
[edit] Conclusion
Compressive, tensile, bending and buckling are the basic types of structural failure for construction elements. These are caused due to faults in design and construction. To mitigate these failures the structural engineer has to properly study properties of the structural materials, loads to be applied and the use of the structure to propose an appropriate material, adequate cross section and a proper structural system.
[edit] Related articles on Designing Buildings
- Biaxial bending.
- Building failure.
- Consolidation.
- Cracking and building movement.
- Defects.
- Defects in brickwork.
- Defects in dot and dab.
- Defects in stonework.
- Failure of cast iron beams.
- Failure to mention asbestos.
- Flat roof defects.
- Flooring defects.
- Force.
- Ground heave.
- Housing defects.
- In Plain Sight: reducing the risk of infrastructure failure.
- Latent defects.
- Patent defects.
- Roofing defects.
- Shear force.
- Smarter systems predicting failure.
- Structural failures.
- Strut.
- The future infrastructure of Scotland.
- Ties.
- Wall tie failure.
Featured articles and news
Registered building inspectors
Building types and conflicts of interest updates explaineed.
Engineering services still struggle with labour shortages
According to latest quarterly services survey of the sector.
Infrastructure that connect the physical and digital domains.
Harnessing robotics and AI in challenging environments
The key to nuclear decommissioning and fusion engineering.
BSRIA announces Lisa Ashworth as new CEO
Tasked with furthering BSRIA’s impressive growth ambitions.
Public buildings get half a million energy efficiency boost
£557 million to switch to cleaner heating and save on energy.
CIOB launches pre-election manifesto
Outlining potential future policies for the next government.
Grenfell Tower Inquiry announcement
Phase 2 hearings come to a close and the final report due in September.
Progress from Parts L, F and O: A whitepaper, one year on.
A replicated study to understand the opinion of practitioners.
ECA announces new president 2024
Electrical engineer and business leader Stuart Smith.
A distinct type of countryside that should be celebrated.
Should Part O be extended to existing buildings?
EAC brands heatwave adaptation a missed opportunity.
Definition of Statutory in workplace and facilities management
Established by IWFM, BESA, CIBSE and BSRIA.
Tackling the transition from traditional heating systems
59% lack the necessary information and confidence to switch.
The general election and the construction industry
As PM, Rishi Sunak announces July 4 date for an election.
Eco apprenticeships continue help grow green workforce
A year after being recognised at the King's coronation.