Strong shear and weak bending design. When the beam is reinforced, the support reinforcement should

Plastic hinges will occur in bending failure of concrete structures, which is a ductile failure, which is a more ideal situation, while shear failure is brittle failure, which is a situation to be avoided.

Our design is a small earthquake design, that is, according to the result of the calculated reinforcement, it is "not bad" under the ** force of a small earthquake (lower than the seismic fortification standard). In the event of a moderate or even large earthquake, plastic hinges may appear in the structure.

According to the principle of stress concentration, plastic hinges must appear in weak links. According to this principle, we can artificially control the position of the weak link, so as to control the sequence of plastic hinges, and rely on plastic hinges to complete the stress redistribution and fully achieve the purpose of energy consumption.

The reinforcement is just enough to meet the calculation, then in the case of a medium and large earthquake, a plastic hinge will occur. If, on the other hand, it is greater than the calculated value and the flexural performance reserve is increased, then the plastic hinge does not necessarily appear here, or it may not appear here in the first place.

The shear force of the frame beam is transmitted from the column, and the support is the part with the largest shear force. Once a plastic hinge is formed at the support, the shear force is consumed by the plastic hinge and no longer burdens the beam. Therefore, our ideal situation is to form a plastic hinge at the support first, and not let the beam be destroyed by shear force before the plastic hinge appears, which is the purpose of "strong shear and weak bending".

As for why the mid-span is enlarged, if the mid-span reinforcement does not have a bending reserve, but there is a small reserve at the support, then it is possible that a plastic hinge will be formed in the mid-span before the shear failure. Once a plastic hinge is formed in the middle of the span, the beam bending moment will be dissipated but the shear force will not, and there is still a risk of shear failure. So avoid this as well.

In fact, these three principles, in the final analysis, are to control the position and order of the appearance of plastic hinges, which can be understood by thinking about it from this perspective.

This is because, the support reinforcement is not amplified, and is balanced according to the bending moment, and the bending moment in the span needs to be amplified, so that it can be ensured that when the beam is stressed, the hinge first appears in the support and does not appear in the middle of the span (the hinge appears in the support, but the superstatically determined structure becomes a statically determined structure, and the transient system becomes in the middle of the span).

Because the reinforcement joint should be arranged at the place where the stress is smaller, and the span normal bending moment of the beam is the largest, and the shear force at the support is the largest (and there is a negative bending moment at the support), so the joint of the lower reinforcement (resisting the normal bending moment in the span) must not be in the span, is located in the range of the beam end span (in fact, because the end shear force is the largest, the stirrups need to be encrypted, and the joint should also avoid the stirrup encryption area mm of the beam end). The reinforcement of the upper part of the concrete mainly resists the negative bending moment of the beam end, so the joint position should be located in the middle of the span. According to the position of the floor slab, the main beam, the secondary beam determines the arrangement of the reinforcement at the intersection, it is obvious that the reinforcement of the slab is on the top, the reinforcement of the secondary beam is centered, and the reinforcement of the main beam is below.

When there is a ring beam or pad beam, the reinforcement of the main beam is on the reinforcement of the ring beam or cushion beam. According to the normal load transfer sequence, the load should be transmitted to the secondary beam through the floor slab, the secondary beam is transmitted to the main beam, and the main beam is transmitted to the columns at both ends, but if the beam is bent and deformed, the load can not be evenly transmitted down in the normal way, and a pad beam is added under the beam at this time, so that the load can be better transmitted downward. The spacing of the upper main reinforcement is too dense, and the spacing of mm that can not meet the requirements of the specification leads to the inability to pour and vibrate smoothly, and will eventually cause the frame beam, the column joint to reach the design strength after pouring the concrete to remove the bottom mold, and the bottom appears serious honeycomb surface and hole phenomenon.

Electromechanical [Date: [Test Center Display] Technical Points for the Installation of Power Station Steam Turbines Cylinders and Bearing Seats Installation The low-pressure cylinders of general power station steam turbines arrive in sections and need to be assembled on site; For the high and medium pressure cylinders of the steam turbine, they are supplied as a whole and do not need to be reassembled on site; For steam turbine medium and medium pressure cylinders assembled in the factory and then dispersed to the site, on-site assembly is required, and the assembly data needs to be measured and adjusted. The bearing seat is installed according to the requirements of the shafting center and the spacing of each bearing, and the center and elevation are measured and adjusted, so that the bearing seat meets the technical requirements of the manufacturer.

The lower part of the beam reinforcement is generally required to be penetrated, and it can also be partially penetrated, and part of it is bent at the support to bear the negative bending moment of the support. For continuous beams, the bending moment of the support under the action of vertical load can be adjusted by amplitude, and the amplitude modulation coefficient is not less than, and the bending moment in the middle of the span should be increased accordingly.

Combine the lower beams in different directions. Poof, lay the line. Except to earn it. Stick figures. How do you think it should be matched?

When designing the cross-section of small eccentric tension members with asymmetric reinforcement of reinforced concrete, ()a, the yield strength is finally reached, and there is a compression area on the cross-section.

b.The final tension does not yield, and there is no compression zone on the cross-section.

c., the yield strength is finally reached, and there is no compression area on the cross-section.

d.Finally succumbed to tension with a compression zone on the cross-section.

Correct answer: c

1. According to: axial.

The position of tensile force, whether there is a compression zone in the cross-section, the development process of cracks and the failure mechanism of components. 2. Small eccentric tension members(1) When the longitudinal axial force acts within the steel bars on both sides, the cross-section is tensile on the side close to the longitudinal tensile force, and the side away from the longitudinal tensile force may be tensile or compressed. (2) When the eccentricity is small, the whole section is tensile and the stress on the side close to the longitudinal force is larger, and the stress on the side away from the longitudinal force is smaller; When the eccentricity is large, it is close to the longitudinal reinforcement.

One side is in tension, and the side away from the longitudinal reinforcement is compressed. (3) With the increase of longitudinal tensile force, the cross-section stress also gradually increases, and when the concrete on the side with greater tensile stress reaches its tensile limit, the cross-section cracks. (4) For the case that the eccentric lap distance is small, the concrete crack will be quickly penetrated after cracking; For the case of large eccentricity, due to the withdrawal of the concrete from the crack in the tension zone, according to the equilibrium condition of the force on the cross-section, the compressive stress in the nip zone also disappears, and is converted into tensile stress, and then the crack penetrates.

(5) After the small eccentric tensile member forms a through crack, the full-section concrete withdraws from the work, and the tensile force is all borne by the steel bar, when the steel bar stress reaches its yield strength.

, the component reaches the ultimate bearing capacity of the positive section and fails. 3. Large eccentric tension members(1) When the longitudinal tensile force acts on the side of the steel bar on both sides, the section is tensile on the side close to the longitudinal tensile force, and the side away from the longitudinal tensile force is compressed. (2) With the increase of axial force, the tensile stress of the concrete on the tensile side gradually increases, and the strain reaches its limit tensile strain cracking, although the cross-section is cracked, there is always a compression area, otherwise the external force can not be balanced.

After the concrete is cracked, the crack does not penetrate the entire section. (3) When the reinforcement of the tensile side is moderate, with the increase of the longitudinal axial force, the tensile rebar yields first, the crack is further developed, the compressive area decreases, and the compressive stress increases, until the concrete at the edge of the compression reaches the ultimate compressive strain, and finally the compressive steel bar yields and the concrete is crushed. (4) When the tension side of the head reinforcement configuration is too much, it is possible that the concrete on the compression side is crushed first, and the tension side reinforcement is always unyielding, and its failure is brittle failure, which should be avoided in the design.

At the height variable section of the foundation girder, the upper and lower steel bars should reach the length of the anchorage to reach the anchorage length value of mutual anchorage, the lower steel bar ends, and the upper steel bar is inserted into the lower beam.

Wherein the main beam is directly rested on the column, the secondary beam is rested on the main beam, and sometimes a section of the beam is rested on the column, and one end is rested on the other beam, and this is also regarded as the secondary beam.

Stress support of foundation beam:

1. The main beam of the foundation is supported by an independent foundation or cushion cap.

2. The foundation secondary beam is supported by the foundation main beam.

3. There are also marks on the construction drawings, JZL represents the foundation beam, and the cross-section is large and the reinforcement is large. JCL stands for foundation secondary beam, with small cross-section and small reinforcement.

To reach the anchorage length value, the lower reinforcement is closed, and the upper reinforcement is inserted into the lower beam.

Summary. The height difference of the beam section is not more than 100 and the reinforcement of the bottom reinforcement of the beam is the same, and it can be set according to 1 6 bending through.

If the height difference of the beam section is not more than 100 and the reinforcement of the bottom reinforcement of the beam is the same, can it be set according to 1 6 bending through?

The height difference of the beam section is not more than 100 and the reinforcement of the bottom reinforcement of the beam is the same, and it can be set according to 1 6 bending through.

Under normal circumstances, the height difference of the plate beam section is not more than 100mm, and when the reinforcement of the bottom reinforcement of the beam is the same, it can be set according to 1 6 bending through. However, in practical application, the reinforcement and other parameters of the large reinforcement at the bottom of the beam may be different due to the different cross-sectional area of the beam, so reasonable reinforcement should be carried out according to the actual parameters of the beam to ensure the safety of the beam.

Summary. 1.The ultimate limit state of the bearing capacity of the reinforced concrete flexural member is the failure stage of the component. 2.

In the design of reinforced concrete flexural members, the strength calculation determines the design size, material, reinforcement amount and reinforcement arrangement of the components, so as to ensure that the bearing capacity of the section is greater than the load effect. The calculation method is divided into two methods: cross-section design and cross-section review. 3.The strength calculation of the reinforced concrete flexural member must meet:

Load effect MJ = cross-section bearing capacity mu, where load effect MJ is the effect value of the load combination coefficient as described in Chapter 2, and the bearing capacity mu should also consider material safety.

What values should be applied to the strength of the reinforcement used in the design calculation of flexural member reinforcement?

Generally, the design value of axial compressive strength fc is used for concrete; The tensile strength design value FY is used for the reinforcement, and its value can be referred to Chapter 4 of the Code for Design of Concrete Structures (GB50010-2010), which can be analyzed for specific problems.

1.The ultimate limit state of the bearing capacity of the reinforced concrete flexural member is the failure stage of the component. 2.In the design of reinforced concrete flexural members, the strength calculation determines the design size, material, reinforcement amount and reinforcement arrangement of the components, so as to ensure that the bearing capacity of the section is greater than the load effect. The calculation method is divided into two methods: cross-section design and cross-section review.

3.The strength calculation of the reinforced concrete flexural member must satisfy: load effect MJ = cross-section bearing capacity mu, where the load effect MJ is the effect value of the load combination coefficient as described in Chapter 2, and the bearing capacity mu should also consider material safety.