What are the characteristics of the failure of reinforced concrete beams with suitable reinforcement

Answer] The failure mode of the normal section of the beam is related to the reinforcement ratio, concrete strength grade, cross-section form, etc., and the reinforcement ratio has the greatest impact. With the difference of longitudinal tensile reinforcement ratio, the positive section of reinforced concrete beam may appear the failure of three different properties such as suitable reinforcement, over-reinforcement, less reinforcement. The failure of suitable reinforcement is plastic failure, and the reinforcement and concrete of suitable reinforcement beam can be fully utilized, which is both safe and economical, and is the basis for the ultimate state calculation of the bearing capacity of the positive section of the flexural member.

Both over-rib failure and under-rib failure are brittle failures, which are both unsafe and uneconomical.

Example] About the failure characteristics of reinforced concrete over-reinforced beams, suitable reinforcement beams, and less reinforced beams, (is correct.) a The super-reinforced beam is a plastic failure.

b. The beam is plastically damaged.

c Beams with few reinforcements are plastic failures.

d are all plastic failures.

Analysis] The failure of the suitable reinforcement beam is that the tensile and compressive steel bar first reaches the yield strength, and then the concrete in the compression area is crushed at the same time, which belongs to plastic failure. Whereas, both low-rib and over-reinforced beams are brittle failures. Therefore, the correct answer to this question is b

When the less-reinforced beam fails, the strength of the concrete has not been fully exerted, and the failure starts from the steel bar, and in the whole loading process, the steel bar has the characteristics of plastic failure from elasticity to elastoplasticity, plasticity, strengthening and finally fracture. When the super-reinforced beam fails, the strength of the reinforcement is not fully exerted, and the failure starts from the concrete, because the concrete is a brittle material, its failure is characterized by brittle failure, and it will collapse suddenly without any precursor. When the suitable reinforcement beam fails, the steel bar and the concrete are theoretically reaching its bearing limit at the same time, and the destruction at the same time does not waste the material, and shows the characteristics of plastic failure, which is the ideal realm pursued by the designer, in fact, it cannot be done, the actual situation is, either over-reinforcement, or less reinforcement, as long as there is not too much deviation on it.

The main factors that determine the failure form of the beam positive section are the internal force condition and reinforcement ratio of the beam.

Component cross-section, concrete strength. Relate.

The failure of the reinforcement beam is that the tensile and compressive steel bar first reaches the yield strength, and then the concrete in the compression area is crushed at the same time, which belongs to plastic failure. Whereas, both low-rib and over-reinforced beams are brittle failures.

When the reinforcement beam is overloaded and failed, the concrete in the compression area is crushed at the same time, and the stress of the longitudinal tensile steel bar basically reaches yield, which is characterized by a precursor and belongs to ductile failure. When the over-reinforced beam is overloaded, the concrete in the compression zone is first instantly fragmented and unstable, which is a brittle failure.

Suitable reinforcement beams belong to plastic failure, while less reinforcement and super-reinforcement are brittle failures and should not be used.

Over-reinforcement is when the reinforcement exceeds the allowable reinforcement ratio, so that the concrete has been crushed before the reinforcement reaches the design strength.

Less reinforcement is that the cross-sectional height does not meet the requirements, and the stressed reinforcement is too few, and these two kinds of damage are sudden, and there is no precursor to failure. Suitable reinforcement is in the state between the excess reinforcement and the less reinforcement, when the reinforcement is in the state of failure, the concrete also begins to develop cracks, from the force exceeds the standard to destroy the complete structure is completely broken, there is a process of development and change.

Over-reinforcement refers to the fact that the reinforcement exceeds the allowable reinforcement ratio, so that the concrete has been crushed before the reinforcement reaches the design strength.

Less reinforcement is that the cross-sectional height does not meet the requirements, and the stressed reinforcement is too few, and these two kinds of damage are sudden, and there is no precursor to failure. Suitable reinforcement is in the state between the excess reinforcement and the less reinforcement, when the reinforcement is in the state of failure, the concrete also begins to develop cracks, from the force exceeds the standard to destroy the complete structure is completely broken, there is a process of development and change.

Answer]: The failure of B suitable reinforcement is that the tensile and compressive steel bars first reach the yield strength, and then the concrete in the Zhengmeng area is crushed or at the same time under compression, which belongs to the failure of plastic shouting wide bridges. Whereas, both low-rib and over-reinforced beams are brittle failures. Clever socks choose B.

Answer]: C The amount of potato reinforcement of the beam is clearly stipulated in the specification, and it is not allowed to be designed as a beam with more than one or less reinforcement, and there are dispersion limits for the maximum and minimum reinforcement ratios, and their failure is brittle failure without warning.

1) Less-tendon failure pattern.

The component will break down without warning, which is "brittle failure". Failure to make full use of the compressive strength of concrete.

2) Failure form of suitable reinforcement.

The tensile steel bar yields first, and the concrete in the compression area is crushed later, and there is an obvious warning before the failure - cracks and deformation develop sharply, which is "plastic failure".

3) Super-rib failure patterns.

The concrete in the compression area is crushed first, the steel bar does not yield, and there is no obvious warning before the failure, which is "brittle slag failure". The tensile strength of the rebar is not fully utilized.

The suitable reinforcement beam is calculated according to the load force of the suspect, when the force is damaged, the force is transmitted to the concrete and then to the steel bar, and the force is evenly stressed together, and then the concrete is broken, the steel bar is bent and deformed, and the whole beam is also deformed.

The over-reinforced beam is a steel bar greater than the force, and the steel bar can withstand the damage force when damaged, while the concrete is not good and cracks.

Less reinforcement beam is not calculated according to the load force, most of the self-built houses in the countryside have such a problem, the destructive force destroys the steel bar, concrete, concrete cracks, steel bending.

The main feature of the failure is that cracks appear in the concrete in the tension zone first, then the tension reinforcement reaches the yield strength, and finally the concrete in the compression zone is crushed, and the component is destroyed.

Before the failure of this kind of beam defense and verification, the steel bar undergoes a large plastic elongation, so that the collapse causes the more obvious deformation and crack development process of the component, and the failure process is relatively slow, and there is an obvious omen before the failure, which is plastic failure.

Because the strength of the material can be fully exerted, the force is reasonable, and there is a warning before the failure, the reinforced concrete beam should be designed as a suitable reinforcement beam in the actual project.

What is the difference in the bearing capacity of less-reinforced beams, moderately reinforced beams, and over-reinforced beams, and why?

Dear, hello, let you wait for a long time, I am happy to answer for you, less reinforced beams, suitable reinforcement beams and super-reinforced beams refer to the ratio between the cross-sectional reinforcement area of the concrete beam and the maximum bearing capacity. This ratio is known as the reinforcement ratio of the tensile reinforcement. The reinforcement ratio of the less reinforced beam is less than the specified value, the reinforcement ratio of the suitable reinforcement beam is equal to the specified value, and the reinforcement ratio of the over-reinforced beam is greater than the specified value.

The bearing capacity of these three types of beams is different for the following reasons:1Less reinforced beams:

Due to the small reinforcement ratio of the less-reinforced beam, the mechanical capacity of its reinforcement is not enough to resist the bending failure under the load, so its bearing capacity is small. 2.Suitable reinforcement beam:

The reinforcement ratio of the reinforcement beam conforms to the specified value, and can give full play to the stress capacity of the steel bar, so its bearing capacity is relatively large. 3.Super-Reinforced Beams:

The reinforcement ratio of the over-reinforced beam is larger, although theoretically it can bear a larger load, but in fact, too much reinforcement will increase the self-weight of the beam block, and also increase the difficulty and cost of construction, so the over-reinforced beam does not necessarily have a greater bearing capacity than the well-reinforced beam. It should be noted that the bearing capacity of concrete beams is also affected by many other factors, such as the strength of the concrete, the cross-sectional size, the way the force is applied, etc. Therefore, in the actual project, it is necessary to carry out detailed structural calculation and design to ensure the safety and stability of the concrete structure.