What is Lumbar Tendon? How to see the waist tendon on the beam?

Waist tendons are also structural ribs.

g: Structural reinforcement.

n: torsional reinforcement.

The specification stipulates that when the beam height exceeds 700mm, a waist bar with a diameter of not less than 10mm should be arranged every 300-400mm along both sides of the beam, and the two waist bars are connected with the same stirrup diameter as the tension bar, and the spacing of the tension is 2 times of the stirrup spacing.

1. Increase the stiffness of the beam skeleton: when the concrete beam is very high, the tall steel frame should bear the load of the steel bar self-weight and the construction machinery and personnel in the construction, which may cause the displacement of the steel bar skeleton and lead to the inaccurate size of the steel bar, which will affect the adhesion between the steel bar and the concrete, and will also affect the durability of the beam.

2. Shrinkage cracks of constrained concrete: In the construction stage, concrete will harden in the air and shrink in volume. Due to the change in temperature, the temperature difference between the inside and outside of the beam will occur, which will cause irregular cracks in the beam.

Because the upper and lower parts of the beam are equipped with steel bars, it can play a role in restraining and preventing the formation and development of cracks. As a result, cracks appear in the middle of the beam and extend to all sides, affecting the appearance of the beam.

3. Reduce the development of cracks in the tension zone. When the beam is subjected to load, the concrete in the tension zone of the beam will crack, and with the increase of load, these cracks will extend to the upper part of the beam, thus affecting the concrete force performance of the beam in the compression zone. At this time, if the waist bar is set, the development of these root cracks can be constrained, and the bearing capacity of the beam can be improved.

From here, I think of a problem, that is, the research work I am engaged in today, the problem of continuous collapse of the structure, I have carried out a quasi-static test of the frame and the continuous rapid loading experiment of the two beam-column nodes, the experiments are carried out until the lower layer of the tensile steel bar is pulled off, through the test data found that the bearing capacity of the beam after the strengthening stage of the suspension stage, as the lower layer of the tensile steel bar is pulled off after the large deformation of the beam, the bearing capacity decreases rapidly, and then begins to rise sharply, Imagine that if there is a waist bar in the middle of the beam at this time, the bearing capacity of the beam will not be almost reduced to zero due to the fracture of the lower steel bar, and then the upper steel bar begins to be tensile because of the sharp deformation so that the bearing capacity rises, but after the lower steel bar is broken, the waist bar bears an excessive cushioning effect, so that the beam with the waist bar is advantageous for anti-collapse, and the impact effect of the beam is slowed down by the fracture of the lower steel bar. In other words, the curve above can be made smoother.

The waist bar is the anti-torsion bar set at intervals of 200mm when the beam height is greater than 400mm; Reinforcement is the inserted reinforcement set up when ladder columns, structural columns, column variable sections, steeplechase plates, filling masonry structural tie knots, or construction is difficult.

g: Structural reinforcement.

n: torsional reinforcement.

There are two kinds of waist tendons: structural waist tendons and torsional waist tendons, the difference is that the role is different, the construction of waist tendons is headed by G, and the anti-torsion waist tendons are headed by N.

When the web height of the beam is 450mm, the two sides of the beam should be configured along the height of the longitudinal structural reinforcement, and the cross-sectional area of the longitudinal structural reinforcement on each side (excluding the beam upper and lower stressed reinforcement and erection reinforcement) should not be less than the web cross-sectional area BHW, and its spacing should not be greater than 200mm. Here, the web height hw is taken according to the provisions of Article 1 of this specification.

Article rectangular, T-shaped and I-shaped cross-section of flexural members, its shear section shall meet the following conditions:

When HW B 4.

v (when hw b 6.)

v (When 4 hw b 6, determine by linear interpolation.)

where. v--The maximum shear design value on the oblique section of the member;

C--Concrete strength influence coefficient: when the concrete strength grade does not exceed C50, take C=; When the concrete strength grade is C80, take C=; The interval is determined by linear interpolation;

fc--design value of axial compressive strength of concrete, adopted according to this specification table;

b - width of rectangular section, width of web of t-section or i-section;

h0 - the effective height of the cross-section;

hw - web height of cross-section: for rectangular cross-section, take the effective height; For T-shaped sections, take the effective height minus the flange height; For the I-shaped section, take the net height of the web.

Note: 1 For simply supported flexural members of T-shaped or I-shaped cross-sections, when there is practical experience, the coefficient in the formula ( can be used instead;

2. For the members with inclined tension edges, when there is practical experience, the control conditions of the shear section can be appropriately relaxed.

The drawing you see is a plane notation method, where G4 represents four structural reinforcements and N4 represents four torsional reinforcements. As for what you said about the section.

It's just a view, and there's nothing easy to say.

First, the main reinforcement on the beam and the main reinforcement under the beam are expressed at the same time

3 22 3 20 The upper reinforcement is 3 22, and the lower reinforcement is 3 20.

2 12 3 18 The upper rebar is 2 12, and the lower rebar is 3 18.

4 25 4 25 The upper rebar is 4 25, and the lower rebar is 4 25.

6 25 8 25 The upper rebar is 6 25, and the lower rebar is 8 25.

The representation of the front is above, the representation of the back is below, and the second, the upper reinforcement of the beam is represented by the method: (marked at the support on the beam).

2 20 represents two 20 steel bars, arranged in length, for double limb hoops.

2 22 + (4 12) means that 2 22 is the length and 4 12 vertical ribs.

For hexa-limb hoops.

6 25 4 2 means that the upper row of reinforcement is 4 25 and the lower row is 2 25.

2 22+ 2 22 means that there is only one row of rebars, two at the corners and two in the middle, evenly arranged.

3. Beam waist tendons.

Representation: G2 12 represents the structural reinforcement on both sides of the beam, one 12 on each side.

G4 12 represents the structural reinforcement on both sides of the beam, and there are two 12s on each side of the beam.

N2 12 represents the torsional reinforcement on both sides of the beam, one 12 on each side.

N4 18 represents the torsional reinforcement on both sides of the beam, two on each side and 18.

The steel bars starting with g and n are waist tendons. There are only these 2 types of waist reinforcements, and the reinforcement is the same, but the length of the deep support is different.

Anchoring. It does not have to be bent, for example, the waist bar is constructed in 15D, and the torsional steel bar (LLE, LAE).

Fourth, the lower part of the beam reinforcement representation method: (marked in the lower part of the beam).

4 25 means that there is only one row of main reinforcements, and 4 25 all extend into the support.

6 25 2 4 means that there are two rows of reinforcement, the upper row of reinforcement is 2 25, and the lower reinforcement is 4 25.

6 25 (-2 ) 4 means that there are two rows of reinforcements, the upper row of reinforcements is 2 25, does not extend into the bearing, and the lower row of reinforcement 4 25 extends into the shed core support.

2 25 + 3 22(-3) 5 25 means that there are two rows of reinforcement and the upper row of reinforcement is 5. 2 25 extends into the support, 3 22, does not extend into the support. Lower rib 5 25, arranged through length.

When the cross-sectional height of the beam minus the plate thickness is greater than or equal to 450mm, the torsional reinforcement, that is, the waist bar, needs to be added to the beam.

The lap of the torsional steel bar is LL or LLE (seismic resistance), and the anchorage length car is the same as the lower longitudinal reinforcement of the frame beam, and the anchorage and lap of the structural steel bar are calculated by 15D, and in 03G101-1, when the web HW of the beam is greater than or equal to (450) mm, the longitudinal structural steel bar must be configured. When the beam width is 350, the diameter of the rib is (8) mm. The tension spacing is (twice the non-encrypted spacing).

The waist bar can be added with a diameter of 10 or 12, and the round steel with a diameter of 10 should be anchored at both ends, and the rebar is not used. Evenly arranged, waist bars are set on the left and right sides of the beam, symmetrical and straight.

Torsional steel bars generally refer to the steel bars arranged on the side of the frame beam when the load on both sides of the frame beam is different and a certain torque is generated on the frame beam. The structural reinforcement and torsional reinforcement are designed by the design institute, and the code of the structural reinforcement is G, and the code of the torsional reinforcement is NThe anchorage length of the structural reinforcement is 15d

The anchorage length of the torsional reinforcement is the same as the anchorage length of the main reinforcement of the beam.

Waist tendons, also known as "mold denan abdominal tendons", are divided into two types: one is torsion tendons, which start with n on the drawing, and the other is structural reinforcement that starts with g. The torsion resistance of the beam belongs to the structural reinforcement in the design, that is, the mechanics does not need to design to calculate the size of the specific force, and this data is checked according to the structural requirements of the national design code.

When the beam height reaches a certain requirement, it is necessary to add waist reinforcement, according to how much, how much to add specifications according to the structural requirements to find out. The anchorage length of the torsional waist bar is set according to the requirements of the code or the atlas stressed reinforcement, and the anchorage length of the structural reinforcement is set according to the requirements of 12d and 150mm. When the height of the beam bucket exceeds 700mm, in order to prevent vertical cracks in the middle of the beam due to temperature deformation and concrete shrinkage, every 300 400mm along the height on both sides of the beam, a longitudinal structural steel bar with a diameter of not less than 10mm should be arranged.

Waist reinforcement: a kind of steel reinforcement structure in the building structure.

Structural reinforcement is a structural reinforcement that meets the structural requirements and is set up for various factors that are not easy to calculate and are not taken into account. (This is to enhance the stiffness of the component and meet the design requirements) Under normal circumstances, when the height of the web of the beam is greater than or equal to 450mm, the longitudinal structural reinforcement should be configured, and the annotation method is to start with the letter G, when the side of the beam needs to be configured with torsional longitudinal reinforcement, it is to: the annotation mode is to start with N.

The torsional longitudinal structural reinforcement should meet the spacing requirements of the longitudinal structural reinforcement on the side of the beam. Note that these are symmetrical configurations.

To put it simply, there are two kinds of waist tendons in the beam. One is the structural reinforcement, the other is the torsion reinforcement (g, n these two can be called waist reinforcement, but their structural performance is also different in structure, so they are generally divided into structural reinforcement and torsion reinforcement, waist reinforcement is their popular name).

1.The waist bar is a structural reinforcement, not calculated, when the beam has a certain height configuration, the torsion bar is to be calculated, to meet the reinforcement ratio, to meet the torsional bearing capacity of the component.

2.The arrangement of waist bars is generally arranged on both sides of the beam, along the height of the beam, and the torsion bar is also used in spiral staircases, at the corners of the section, on the side, on the top surface and other positions.

3.The waist bar is a longitudinal structural steel bar, and the torsion bar is generally composed of two parts: longitudinal stress steel bar and stirrups.