Types of failures experienced in different structure is greatly influenced by the type of construction material used. The resisting capability of steel structure to a particular load action is not similar to that of a concrete structure for the same load conditions.
Types of failures experienced by different construction material in a structure, their causes and details are discussed in this article.
Types of Failures Experienced by Different Construction Materials
Failure Caused by Steel as a Construction Material
The different features of steel material i.e. the chemical composition, heat treatments, rolling processes and other manufacture techniques employed govern the mechanical properties of steel. Steel of same grade may show different values or results which is dependent on the rate of loading of the steel specimen, the temperature at which the test is carried out, the geometry of the specimen and the condition of the specimen.
Easy study of different failures observed in steel material can be done by classifying the same into:
- High Strength Steels
- High strength low alloy steels
- Tempered alloy steels
- Quenched alloy steels
ASTM designations are provided for each of the above-mentioned steel types. These designations are provided for light gauge cold form members, rivets, weld filler material, wire, strand, rope, cable, forgings, castings, bolts.
Common failure observed in steel rolled shapes or sections that are fabricated are:
- Failure caused in the welded areas
- Buckling or web crippling of the sections
- No design considerations for torsion effects result in great issues
- Support points lacks rotational restraints
- Columns lack lateral supports
- The compression flanges of the beams lacking lateral supports will result in the failure of the structure
- Ignoring the effect of member stability to consider the overall stability of the structure
Brittle fracture is a sudden failure occurring in steel structures that will result in sudden collapse of the whole system. The main causes of brittle fracture found in steel structures are:
- The loading rate on the structure is very rapid in nature
- Corrosion of steel materials – (Mostly in the critical sections, joints, and corners where the stresses are higher)
- The loading will we provided in repeated cycles
- The welded connections of the steel structure will be highly restrained
- The tensile stress might be higher
- Higher carbon content in the steel structure
- Having flaws or notches
Failures Caused by Concrete as a Construction Material
The concrete gain mechanical properties which is dependent on the:
- Chemical Composition of the cement
- Grading of the cement and aggregates
- Quality of water
- The mixing method and quality
- Proper placing
- Finishing of the concrete
- Proper curing conditions
- Small and large quality aggregates
- The environmental conditions to which concrete is exposed
The process of hydration bonds the various components together. This helps in increasing the mechanical properties of the concrete. More permeable the concrete more it attracts the moisture and other chemicals. This affects the internal structure of the concrete and the durability is affected extremely.
The distress in concrete are caused due to the following reasons:
- The concrete being subjected to repeated cycles of freezing and thawing
- The concrete components subjected to extensive shrinkage and expansion
- The chemical attack of chlorides and sulfates results in change of volume.
- Presence of high content of alumina result in the degradation of the strength.
- Chlorides penetrates the concrete that results in the corrosion of the concrete reinforcement.
- The concrete void spaces may have bacterial fermentation which results in the bursting and the disintegration.
Failures Caused by Masonry as a Construction Material
Increase in the moisture content makes the masonry structure to expand and lesser moisture content makes it to contract. This is the case with brick masonry and this deformation is not reversible in nature. In the case of concrete masonry units, shrinkage is a major issue.
Failures observed in the masonry units are resulted from the following problems:
- Freezing of the water present in the joints results in the cracking.
- The metal ties and the structural steel members are subjected to corrosion
- Cracking due to settlement issues
- Shrinkage and bending process result in the curling of the concrete floor.
- Movement of the masonry units induces cracks extremely
- Thermal expansion of the masonry units will result in the tension in the masonry. This will lead to cracks.
- The wall that is running in the same direction may undergo shortening and resulting in cracking of the walls.
Most of the issues mentioned is due to the lack of proper consideration of design and detailing of the expansion and the control joint.
Failures in Wood as a Construction Material
Wood is a unique construction material which is mainly composed of organic cellular grained structure. Wood is hence an anisotropic material. But wood material is assumed as orthotropic material, along three principal elasticity directions along radial, tangential and longitudinal directions of the material.
The elastic properties of this material are thus studied by finding the Young’s modulus. Poisson ratio and shear moduli. Most important elastic property that is used in the design is the modulus of elasticity.
Most of the failures found in this material is associated with the:
- Moisture content
Other failures experienced by the wood material is due to the deterioration and the degradation of their properties mainly due to the following reasons:
- Simultaneous saturation and drying repeatedly
- Attack of different fungi species which will result in the degradation and decomposition
- Termite and beetle attack
- Wood exposure to heat and fire
The failures observed in sizable timber structures are due to the volume changes of the wood with the varying levels of drying shrinkage, or due to inefficiency in the connection details. Improper maintenance of connections result in failure problems. Alternate wetting and drying too results in the failure.