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Structural Crack Treatment Of Concrete Beams(1)
Analysis, Judgment, And Treatment Of Structural Cracks In Concrete Beams
The different stress conditions of the beam can cause different forms of cracks. From the perspective of beam force, horizontal beams mainly bear the load of plates, and sometimes they may also be subjected to concentrated loads. The main effect of beam bearing capacity is bending moment, with more positive bending moments at the mid span of the beam; There are more negative bending moments on the edge of the support, and in some cases, there are also significant shear forces.
Locally concentrated suspended loads may cause tensile cracks. Such cracks are prone to structural damage and should be reinforced promptly.
Due to different load-bearing and constraint conditions, there are two types of vertical cracks generated by beam bending: negative moment cracks at the top of the beam at both ends and positive moment cracks at the bottom of the mid span beam. Occasionally, bending and compression cracks may occur due to concrete fragmentation in the compression zone.
Under conditions such as edge beams and asymmetric loads, they may also be subjected to torsional forces, resulting in various cracks that intersect diagonally with the beam axis.
Concrete components may accumulate restrained tensile stress due to temperature, shrinkage, and other factors, leading to indirect cracks in the middle of the beam. These types of cracks will be perpendicular to the beam axis and sometimes constrained by reinforcement, resulting in jujube shaped cracks at the waist of the beam.
This article takes the location and morphology of cracks in concrete structures as clues, lists the causes, properties, and impact on structures of 14 common cracks, and provides targeted treatment suggestions.
1.
Cross edge beam waist area
Diagonal crack, wide in the middle and narrow at both ends
Reasons for crack formation?
Insufficient concrete strength
Concentrated load action
Section too small
Local defects
Insufficient reinforcement of hoop reinforcement
Crack?
Stress cracks
Abdominal shear crack
The impact of cracks?
Insufficient shear bearing capacity
Easy to cause brittle failure
Affects durability
Crack treatment?
Cover it up
Reinforcement treatment if necessary
2.
Concentrated load to span edge
Diagonal through, the beam is divided into two halves
Reasons for crack formation?
Insufficient concrete strength
Concentrated load at large shear spans
Section too small
Local defects
Insufficient reinforcement of hoop reinforcement
Crack?
Stress cracks
Diagonal opening crack
The impact of cracks?
Insufficient shear bearing capacity
Causing brittle failure
Affects durability
Insecurity
Crack treatment?
Reinforcement treatment
3.
Concentrated load zone at the edge of the beam
Cross edge diagonal serrated cracks
Reasons for crack formation?
Large concentrated load on the edge
Insufficient alkali strength
Section too small
Local defects
Insufficient horizontal bending reinforcement and punching failure
Crack?
Stress cracks
Punch cut crack
The impact of cracks?
Insufficient shear bearing capacity
Causing brittle failure
Affects durability
Insecurity
Crack treatment?
Reinforcement treatment
4.
A beam with a large span to height ratio in the middle span
Multiple diagonal parallel cracks across the middle span
High strength, unidirectional carbon fiber wrap pre-saturated to form a carbon fiber reinforced polymer (CFRP) wrap used to strengthen structural concrete elements.
Language: English
