What Are the Types of Failures in Beam? . Failure modes in reinforced concrete beams are classified into two major types: flexural failure and shear failure. The former occurs when the imposed load exceeds the flexural capacity of the materials of the beam, while the latter occurs due to deficiency in shear resistance between different materials of the beam.
Read More : Concrete Beams With Openings Analysis And Design
These failure modes are further divided into different kinds of failure; the former is categorized into tension failure, compression failure, and balanced failure whereas shear failure is categorized into tension shear failure and compression shear failure. The nature and mechanism of these failure modes are different.
Some of them are favored in terms of design, but there are others that need to be avoided in order to prevent severe collapses of structures. For instance, the crushing of concrete and shear failure modes are undesired since they occur suddenly without any warning.
What Is A Beam?
A beam is a horizontal structural member that carries vertical load acting on the building frame. Based on the design requirements, different types of beams are used in construction. In this article, we’ll discuss types of failures in beam.
Types Of Failures In Beam
There are mainly two types of failures in beam.
- Shear failure.
- Flexural failure.
Read More : What is an RCC Coupling Beam?
Shear Failure
When the shear stress on an object exceeds the maximum permissible shear stress, then the object undergoes a failure known as shear failure. Shear failure can be defined as a failure that takes place due to insufficiency of shear resistance available between the materials.
Shear strength is the strength of a material or component against the type of yield or structural failure where the material or component fails in shear.
A shear load is a force that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force.
In simple words, shear stress is maximum at 45° in the cross-section of the beam; hence diagonal crack is formed in shear failure, and shear failure occurs at the end of the beam where the beam connects to the column. To avoid this type of failure, stirrups are provided.
Shear failure can be easily determined by checking out the excessive deflection or development of cracks, which gives an advance warning about the probable occurrence of shear failure.
It is difficult to understand the extent to which reinforcement will act along with concrete and predict the actual time of occurrence of shear failure. The figure shown below shows the shear failure in the beam.
Read More : What is the Difference Between Beam and Lintel?
Diagonal Tension Failure
This type of failure begins with development of flexural cracks at the tension of beam due to flexural tensile stress.
Due to further increase in applied load on beam, growth of crack amplifies and cracks grow further wider and lengthy with a slight bend in diagonal direction, towards the load application point.
Shear Compression Failure
This failure occurs due to initiation and further development of cracks to the compression zone in cross-section of beam and compressive strength is compromised.
Shear compression failure results into crushing of concrete at the tip of diagonal crack around the point of load application.
Splitting Shear Failure
It is a common case of shear failure in case of deep beams, as the loads are directly transferred to supports so higher shear stresses are generated.
Anchorage Failure
When the main reinforcement are not adequately anchored, splitting of concrete occurs along the longitudinal reinforcement, due to small diagonal cracks.
Read More : What is a Lintel Beam?
Causes Of Shear Failure
The reasons behind shear failure are :
- It may occur due to insufficient knowledge of the resistance between reinforced steel rods and concrete columns.
- It may occur due to the wrong interpretation of the data made available to the design engineer.
- It may also take place due to insufficient strength of the concrete used for the structure.
- It may even take place due to a mismatch in the positioning of the reinforcement of steel rods.
Read More : Types of RCC Beam
Flexural Failure
Flexural strength, also known as modulus of rupture, bend strength, or fracture strength, is a material property defined as the stress in a material just before it yields in a flexure test.
The flexural strength represents the highest stress experienced within the material at its moment of rupture. It is measured in terms of stress. To overcome this type of failure, main steel is provided at the bottom/top of the beam. Flexural failure occurs at the mid-span of the beam.
Read More : Reinforced Concrete Design To Eurocode 2 7th Edition
Flexural Tension Failure
In this type of failure, the steel reinforcement starts yielding before crushing of concrete. It is also known as ductile failure because it gives enough warning of failure in form of deflection.
This failure is occurs in case of under-reinforced sections i.e., the reinforcement is less than balances section. At the beginning, the cracks are developed at tension side and then the cracks further extend towards compression side.
The cracks so formed are vertical in orientation and lies perpendicular to most tensile fibre of beam. From designer’s point of view, it is the most favourable failure.
Flexural Compression Failure
In this type of failure, the crushing of concrete occurs prior to yielding of reinforcement steel at tension side of beam.
This is also called as brittle failure of structural member as there is no warning in form of deflection, before the structural failure of beam.
This failure predominantly occurs in over-reinforced sections, i.e. reinforcement provided is greater than required in balanced section.
Read More : How to Calculate Land Area at Site?
Frequently Asked Questions (FAQs)
What is the most common type of beam failure?
Flexural failure is the most common, occurring when a beam bends excessively under load.
How can beam failures be detected early?
Regular inspections using visual methods and non-destructive testing can identify potential issues.
What is flexural failure in simple terms?
It’s a type of failure where the beam cracks due to bending stress exceeding its tensile strength.
Why does buckling occur in beams?
Buckling occurs due to axial compressive forces on slender beams without adequate lateral support.
Related Topics
-
What is an RCC Coupling Beam? Types, Benefits, and Applications Explained
-
Why Doubly Reinforced Beams Are Essential for Structural Integrity: A Complete Guide
-
What is the Difference Between Beam and Lintel? | A Comprehensive Guide to Structural Design
-
Top 10 Types of Stirrups in Concrete Beams: Essential Guide for Civil Engineers
