Types of Structural Cracks in Concrete Beams | Causes of Cracks in Concrete Beam

In this Article today we will talk about the Types of Structural Cracks in Concrete Beams | Causes of Cracks in Concrete Beam | Concrete beam | Structural Cracks | Fixing Structural Cracks | Concrete Cracks Types | Types of Crack in Concrete | Why Concrete Crack | Shear Cracks in Beam | Flexural Cracks in Beam | Vertical Cracks in Beam | How to Repair Cracks in Concrete Beam

Types of Structural Cracks in Concrete Beams:

Several types of cracks occur in concrete beams due to shear stress called as shear crack, reinforcement corrosion, insufficient rebar cover, bending stress and compression failure.

The occurrence of various crack patterns in the building mostly takes place during construction and/or after completion. A building component develops cracks whenever the stress in the components exceeds its strength. Stress in the building component is caused by externally applied forces/loads.

Almost all the types of cracks in Reinforced Concrete Beams are fundamentally defined by the principle cause or mechanism associated with the function of cracks. Causes of Cracks in Concrete Beam

Types of Concrete Cracks in Beams:

Here we have tried to provide you with an overview of almost all the types of cracks occurred in RCC beams. Fixing Structural Cracks

Flexure word also means “Bending”. Cracking in reinforced concrete beams subjected to bending usually starts in the tensile zone i.e. soffit of the beam. The width of flexural cracks in reinforced concrete beams for short-term may stay narrow from the surface to the steel. However, in long-term under continuous loading, the width of crack may get increased and become more uniform across the member.

Member

• RC Beam Shear Cracks in Beam

Important Characteristics

• Originates in maximum moment region (in above image this region is in centre of the beam, it varies as per support Conditions of beam)
• May be single or in groups
• Maximum width at bottom/top of beam Vertical Cracks in Beam

Causes or Possible Reasons

• Flexural capacity of the beam is inadequate.
• When Cross section of the beam or main reinforcement in beam is insufficient.
• i.e. it is loaded more than defined loads. Vertical Cracks in Beam

02. Shear Cracks in Reinforced Concrete Beams

Shear cracks in reinforced concrete beams occur in hardened stage and it is usually caused by structural (self-weight) loading or movement. These types of cracks are better illustrates as diagonal tension cracks due to combined effects of flexural (bending) & shearing action.

Member

• RC Beam Vertical Cracks in Beam

Important Characteristics

• Originates nearer to supports.
• Maybe single or in groups.
• Maximum width at neutral axis region or at bottom of beam. Flexural Cracks in Beam

Causes or Possible Reasons

• Shear Capacity of the beam is inadequate.
• Cross section or torsional reinforcement insufficient.
• Both here happen due to loading more than designed load.

03. Torsional Cracks in Reinforced Concrete Beams

Usually beams are subjected to torsion along with bending moment and shear force. Bending moment & shear force occurs as loads acts normal to the plane of bending. However, loads away from the bending plane will causes torsional movement.

Member

• RC Beam

Important Characteristics

• Originates nearer to maximum torsion region.
• Single generally uniform width. Appears over the whole periphery in helical form

Causes or Possible Reasons

• Torsional strength of the beam is inadequate.
• Cross-section or torsional reinforcement insufficient.

04. Corrosion Cracks in Reinforced Concrete Beams

Corrosion cracks in reinforced concrete beams runs along the line of reinforcement. It usually separates the concrete from reinforcing bars.  It is mostly manifested by discoloration of paint or stains of rust.

Member

• RC Beam

Important Characteristics

• Runs along the line of reinforcement.
• Uniform width in general

Causes or Possible Reasons

• Bond between reinforcing bars and concrete not satisfactory.
• May be due to corrosion of bars/fire damage.

05. Shrinkage Cracks in Reinforced Concrete Beams

Shrinkage cracks in reinforced concrete beams occur during two stages, which are pre-hardening stage and hardened stage. In pre-hardening stage these types of cracks are called as plastic shrinkage cracks & in hardened stage they are known as drying shrinkage cracks. Shrinkage cracks occur when fresh concrete is subjected to a very rapid loss of moisture.

Member

• RC Beam

Important Characteristics

• No regular pattern or thickness and in general superficial.

Causes or Possible Reasons

• Curing is inadequate or no control over water-cement ratio.
• Usage of an excessively rich mix.
• Shrinkage reinforcement, if any, insufficient.

06. Sliding Cracks in Reinforced Concrete Beams

The diagonal mode of failure by sliding along the critical cracks is known as failure by sliding and usually appears at the edge of the supports of beam. These types of concrete cracks appear if concrete gets disturbed in fresh state.

Causes or Possible Reasons

• Concrete in a beam is disturbed at an early age when adequate strength not realised.
• Maybe due to disturbance of formwork at green stage or early deshuttering.

07. Tension Cracks in Reinforced Concrete Beams

Tension cracks in reinforced concrete beams occur usually due to shrinkage or temperature variations. Tension cracks usually appear in those members where restraint is provided in the longitudinal movements. Usually tension cracks tend to propagate over the full depth of the cross-section of beam.

Member

• Reinforced Concrete Tie Flexural Cracks in Beam

Important Characteristics

• Appear over whole periphery. Generally over the whole length of the member.
• Parallel to each other.
• Uniformly observed

Causes or Possible Reasons

• Capacity of the member in tension is inadequate.
• Tensile reinforcement is insufficient.

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5. Bar Bending Schedule (BBS) | BBS Step by Step Preparation | Excel Sheet

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FAQs:

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What causes a concrete beam to crack?

The main reason of the crack is underestimating the cladding weight. Based on the results, a repair methodology was selected using CFRP sheets to increase the flexural capacity of the beam section with enhancement to its torsional and shear carrying capacity to meet the design demand.

Are cracks in concrete beams normal?

The layered cracks in reinforced concrete beams in compression zone are typical load cracks, which will endanger the safe use of structures when they are serious. Treatment method: under normal circumstances, reinforcement measures are adopted in the compression area by sticking steel reinforcement technology.

How do you reinforce a cracked beam?

Once you ensure that all the jack posts are structurally sound, the support beam's crack can be fixed. A quick way to repair the beam is to use an angle iron underneath the beam's cracked part. This is to make the steel take the load even if the beam cracks fully.

At which point is the beam most likely to crack?

Diagonal tension is the main cause of the crack. Near the supports is where this crack is most likely to be seen. The shear force due to all loads is likely to occur at supports.

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Conclusion:

Full article on Types of Structural Cracks in Concrete Beams | Causes of Cracks in Concrete Beam | Concrete beam | Structural Cracks | Fixing Structural Cracks | Concrete Cracks Types | Types of Crack in Concrete | Why Concrete Crack | Shear Cracks in Beam | Flexural Cracks in Beam | Vertical Cracks in Beam | How to Repair Cracks in Concrete Beam. Thank you for the full reading of this article in “The Civil Engineering” platform in English. If you find this post helpful, then help others by sharing it on social media. If any formula of BBS is missing from this article please tell me in comments.