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Anonymous users2024-02-15The fracture caused by the concrete tension of the beam body is mainly caused by eccentric tension.
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Anonymous users2024-02-14The tensile capacity of concrete is very poor, the amount mainly bears the bending moment, the general beam bottom is tensile and mainly bears the tensile force by the steel bar, the concrete is only the role of protecting the steel bar, if the reinforcement is too little or the position of the reinforcement is not too thick to protect the layer, the beam stress section becomes smaller, which will cause the steel bar to yield, and there will be cracks at the bottom of the beam, which will lead to direct cracking.
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Anonymous users2024-02-13What does it mean, is it a tensile concrete beam?
The cause of the fracture of concrete beams is the development of minor cracks in concrete, the so-called droplet stone penetration. Under normal circumstances, the tensile strength of concrete is far lower than the tensile strength, and if the tensile strength is exceeded, the concrete will crack.
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Anonymous users2024-02-12The tensile strength of the beam itself is exceeded.
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Anonymous users2024-02-11Kiss! Hello, happy to answer your <>
The reasons for the pro-precast beam has not yet been broken in the tensioned concrete are as follows: 1. Which is the abnormality of the concrete hardening wheel. When the concrete is not completely hardened, if it dries too quickly, it will produce shrinkage cracks 2 and temperature change cracks.
When the cement is hardened, the temperature difference between the concrete surface and the interior is large, resulting in a huge change in the temperature of the concrete surface. As a result, a large cooling contraction is generated, which triggers the restraint inside the concrete, and finally cracks appear in the concrete. 3. The design is not thorough.
For example, the cross-section of the reinforced concrete beam is not enough, the span of the beam is too large, the height is too small, or due to calculation errors, etc., these reasons will lead to structural cracks in the concrete beam. 4. Cracks caused by construction quality. Due to the low grade of concrete, the cross-sectional size does not conform to the design, etc., it will also lead to cracks in the concrete beam.
5. Transportation is not compliant. In the process of transportation and hoisting of prefabricated steel concrete beams, due to the unreasonable support and inconsistent position of the lifting point. It will also lead to cracks in the steel concrete beam.
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Anonymous users2024-02-10Kiss! Hello, happy to answer your <>
When the concrete strength of reinforced concrete component does not reach 75 of design strength, prestressed concrete component is out of pit when not carrying out prestress tensioning, will cause quality problems such as beam plate breakage, cracks. (1) Cause analysis 1, when the prefabricated components are out of the pit, the concrete strength is lower than the strength required by the design for hoisting, and the components are broken or seriously cracked during hoisting. 2. Before the prefabricated components are out of the pit, the actual size is not checked, and the position of the embedded steel bars and lifting rings and the quality of the concrete are stretched out, and the shape of the components is incorrect, and the surface is not smooth, resulting in the beam and plate can not be installed properly during installation.
3. If the prefabricated components are not installed with embedded lifting rings or hanging holes and the correct lifting point position is not calculated, it will lead to cracks or fractures in the beam plate. 4. When lifting and stacking plate components, the upper and lower positions are wrong (the position of the fulcrum should be consistent with the position of the lifting point), resulting in the broken beam and plate components, and the special fixed frame and the placement position are not set up when the components are moved, resulting in an accident caused by the overturning of the beam body; When the beam body is placed flat, there is no supporting square timber at the hanging points at both ends, resulting in negative bending moment and short cracks. 5. The site of stacking prefabricated components is uneven, not solid, or there is water accumulation, and the components are stored for a period of time due to the softening and sinking of the ground due to the analysis and damage.
6. The stiffness and stress of the components are not considered when stacking, or the number of storage layers is too large. Generally, large components are stacked horizontally for up to 3 layers, and precast beam stacking is not easy to be more than 4 layers, and if the stacking exceeds the requirements, the components will be damaged. 7. The fulcrum of the two wheels of the component is uneven, and the layer is not separated by a skid, which will also cause damage to the component.
2) Preventive measures to strengthen construction management and strict crane operation procedures. The focus of the lifting and installation work should be on safety, not only to ensure personal safety, but also to ensure the safety of beams and plates. Therefore, before construction, there must be a detailed construction organization design to ensure that the lifting method, the stacking site and the stacking method should be checked for the stress hormone and the bearing capacity of the foundation to prevent problems.
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The strength grade of prestressed concrete should not be lower than C30, and when carbon steel wire, steel strand, and heat-treated steel bars are used as prestressed tendons, the concrete strength grade should not be lower than C40. >>>More
Let's talk about my opinion, 1. If the oil gauge has been calibrated, the corresponding oil gauge reading and stress formula are correct, then the stress value should be no problem;2. There is such a big gap, I think it should be a theoretical elongation miscalculation, which should be the elastic modulus of the steel strand to take whether there is a problem;3. This problem has not been studied, and I personally think that there should be no such thing, and I have encountered a short beam tension that is larger than the design;4. Now more than 20% theoretically it must be put down to re-analyze the reasons and then stretch, in fact, it should not be done, timely grouting and anchor sealing should be no problem, the possible quality impact may be that the anchor backing plate is easy to crack, and the precamber may be too large to cause cracking at the bottom of the beam.
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. >>>More
There are three types of suitable reinforcement failure, super reinforcement failure, and less reinforcement failure. >>>More
As follows:
1. Transverse cracks occur in reinforced concrete columns under compression, which may be due to insufficient mutual anchorage of column or beam longitudinal reinforcement. >>>More