Concrete is one of the most widely used materials. Every year around 5 billion cubic yards of concrete are produced worldwide to build everything from driveways to dams and nuclear reactor plants. Although concrete is a strong durable material, concrete structures can fail under extreme loads or if there were mistakes in the design. It is therefore important to understand how and why concrete structures may fail.
Video of the Day
Concrete is particularly resistant to compressive or vertical loads, which is why it is used widely in foundations. However, if the force falling on a concrete structure exceeds its maximum load, also known as critical force, it will cause the concrete to buckle under the weight. The critical load of a concrete column or structure is determined by its cross-section, the elasticity of the materials that compose it and the area over which the load is distributed.
Concrete may be good at withstanding vertical loads but it is comparatively vulnerable to lateral loads. That is why concrete structures are often reinforced with steel, which has complementary characteristics: weak on vertical loads, strong on lateral forces. If a concrete structure receives an extra lateral or horizontal load, it could buckle. This occurs often during earthquakes, which inflict huge lateral forces on buildings.
Changes in Heat
Materials expand and contract with heat and cold. That is why engineers design concrete structures with expansion joints that allow the structure to expand and contract without buckling. However, if expansion joints are not inserted, or if these expansion joints get filled in with foreign material, it could cause the concrete structure to buckle when the temperature increases. This often happens with concrete paving during the hot summer months.
If a concrete structure is not protected from the erosive effects of the elements, such as water and acids, its structural integrity could be compromised, causing the entire structure to buckle and fall. This occurs in areas such as basements and foundations, where excessive water or moisture accumulates. Salt water is particularly dangerous to concrete buildings because it can also corrode the concrete's reinforcement bars.