Technical scheme of reinforcement construction in teaching building?

The technical scheme of reinforcement construction in school buildings is very important. Sharp tools make good work. Only by making a detailed and perfect plan before construction can the quality be guaranteed in construction. Zhong Da Consulting will explain the construction technical scheme of the school building reinforcement project for you.

The key points of reinforcement construction in this project include reinforcement entry acceptance, reinforcement sampling, processing, connection and installation, etc. At the same time, our company decided to adopt a new technology of electroslag pressure welding for vertical thick steel bars, and now the key contents of each construction are described as follows.

A, reinforced in acceptance and storage

(a) reinforced raw materials according to the material plan unified organization comes into play, in reinforced must have the factory quality certificate. When steel bars enter the site, they shall be inspected and accepted in batches. Each batch consists of steel bars of the same brand, same heat number, same specification and same delivery status, and the weight does not exceed 60 tons.

(1). Appearance inspection: 5% of each batch of steel bars shall be taken for appearance inspection, and there shall be no cracks, scars and folds on the surface of steel bars. Protrusions are allowed on the surface of steel bars, but they shall not exceed the height of transverse ribs. The depth and height of other defects on the surface of steel bar shall not be greater than the allowable deviation of the size of this part. The bending degree of steel bar should be greater than 4mm per kloc-0/m.

(2) Mechanical property test: two samples are taken from each batch of steel bars, and two samples from each steel bar are taken for tensile test and cold bending test respectively.

If one test does not meet the requirements, another double sample is taken from the same batch for each test. If one sample is still unqualified, the batch of steel bars is unqualified.

Unqualified raw materials are definitely not allowed to enter the market. And strictly witness the inspection and supervise the sampling, and can only be used after meeting the requirements of mechanical properties.

(2) When the steel bars are stored in the yard, the steel bars with different grades and diameters should be piled up separately and clearly marked with signs, which are written with specifications, models, manufacturers, quantities to be delivered, and inspection and test conditions. When stacking, sleepers or rolled channel steel must be laid, the height from the ground shall not be less than 150mm, and the spacing between sleepers or channel steel shall not be more than 2m.

Second, the reinforced double sample

(1). Calculation of steel bar blanking length

The length of steel bar will change due to bending or hook, so it can't be laid out directly according to the design drawing when batching. It is necessary to understand the provisions of concrete protective layer, steel bar bending and hook, and then calculate its blanking length according to the dimensions in the drawing. The blanking length of various steel bars is calculated as follows:

Cutting length of straight steel bar; Member length-protective layer thickness+hook increase length;

Blanking length of bending rib; Straight segment length+inclined segment length-bending adjustment value+hook increase length;

Stirrup blanking length: stirrup circumference+stirrup adjustment value.

(1) Bending adjustment value: The characteristics of steel bars after bending are as follows: firstly, at the bend, the inner skin layer contracts, the outer skin layer elongates, and the axial length remains unchanged; The second is to form an arc at the bend. The measurement method of steel bars is to measure the outsourcing size along a straight line, so the measurement size of bending steel bars is larger than the outsourcing size, and the difference between them is called bending adjustment value, as shown in the following table:

The bending angle of reinforcement is 30 45 60 90 135.

The adjustment value of steel bar bending is 0.35d0.5d0.85d2d2.5d

The measurement method of reinforcement is shown in the following figure:

②. Hook length is increased.

There are three hook forms of steel bars: semi-circular hook, straight hook and inclined hook. Among them, the semicircular hook is the most commonly used hook; Straight hook is only used for additional reinforcement; Inclined hooks are only used for steel bars with smaller diameters.

According to the calculation diagram shown in the following figure (the diameter of the bending center is 2.5d, and the straight part is 10d), the calculated values are: 13.25d for the semi-circular hook, 10.5d for the straight hook and1.9d for the oblique hook.

③. Stirrup adjustment value

The adjustment value of stirrups is the difference or sum of the increase length of hooks and the adjustment value of bending, which depends on the external or internal package size of stirrups.

Stirrup adjustment value

Measurement method of stirrups-stirrup diameter

4~568 10~ 12

Measure the outer packing size. Measure the inner packing size 4080501006012070150 ~170.

(2). Steel cutting table

Steel bar foreman is responsible for the blanking of steel bars. He must fill in the processing material list and apply for processing according to the requirements of design drawings, combined with the requirements of concrete protective layer, steel bar bending, hook, lap joint and anchorage. The list of processing materials includes the quantity, specifications, outline drawings and processing dimensions of steel bars. The cutting table must be approved by the technical team before it can be handed over to the workers for steel processing.

Third, the processing of steel bar

Before reinforcement processing, all kinds of reinforcement processing machinery and equipment shall be overhauled to ensure normal operation and compliance with safety regulations. When processing steel bars, first remove the oil, dirt and floating rust on the surface of steel bars. Straightened reinforcement shall not be bent, completely bent or slightly bent.

When processing, start from the bill of materials first, and then mass production after the trial production is qualified. All processed semi-finished products should be stacked according to specifications, quantity and classification. Steel processing shed has a special person to register the processed semi-finished products and distribute them uniformly. It is strictly forbidden to lack them among outstanding talents. The quality standard of steel bar processing should comply with the relevant design and specification requirements.

Bending forming of steel bar:

(1). Relevant regulations on hook.

(1) The end of grade I steel bar should be hooked at 180, and its arc bending diameter (d) should not be less than 2.5 times the diameter (d) of steel bar, and the length of straight part should be determined according to the design requirements.

(2) When the end of Grade II rebar needs to be bent by 90 or135, the bending diameter (d) should not be less than 4 times of the rebar diameter; The straight part shall be determined according to the design requirements.

(3) The bending diameter (d) in the middle of the bending steel bar should not be less than 5 times the diameter of the steel bar.

(2) Bending of steel bars can be divided into mechanical bending and manual bending. Generally, manual bending can only bend steel bars with smaller diameters. Mechanical bending and manual bending are adopted in this project.

(3) Bending forming process

1. Marking: Before bending, mark the position of the bending point with a pencil according to the size of the bill of materials. When marking, it should be noted that the bending adjustment value is deducted according to different bending angles, and the deduction method is to deduct half from the length of adjacent two paragraphs; When there is a semicircular hook at the end of the steel bar, the length of this section is increased by 0.5d for marking; The marking work shall be carried out from the center line of steel bar to both ends. For example, steel bars with asymmetrical edges can also start from one end. If there is any difference when marking to the other end, it should be readjusted.

(2) Bending of steel

When the steel bar is formed on the bending machine, the diameter of the mandrel should be 2.5 times the diameter of the steel bar, and an eccentric shaft sleeve should be added on the forming shaft to meet the needs of bending steel bars with different diameters. When bending fine steel bars, in order to keep the bent steel bars straight, the iron retaining shaft should be made into a variable retaining frame or a fixed retaining frame (adjusted by adding iron plates). When bending, the strength should be controlled in one step, and secondary reverse bending or repeated bending is not allowed.

(3). The quality requirements of steel processing

The shape of the steel bar is correct after bending, and there is no warping uneven phenomenon on the plane; The clearance diameter of the hook at the end of the steel bar is not less than 2.5 times the diameter of the steel bar; Rebar bending starting point can not have cracks. Therefore, Grade II steel bars cannot be bent over and then bent back; Allowable deviation: total length 10MM, bending point displacement 20mm, bending height 5 mm, stirrup side length 5 mm.

Fourth, the connection of steel bar

The reinforcement connection methods adopted in this project include flash butt welding (horizontal reinforcement), arc welding, electroslag pressure welding, etc.

(1) flash butt welding

Flash butt welding can be divided into three processes: continuous flash welding, preheating flash welding and flash-preheating-flash welding.

In order to obtain a good butt welded joint, welding parameters should be selected reasonably. Includes adjustable length, flash allowance, flash speed, upsetting allowance, upsetting speed, upsetting pressure and transformer stage.

When preheating flash welding is used, there must be parameters such as preheating margin and preheating frequency.

Butt welding defects and preventive measures

Preventive measures for abnormal serial number and defect type

The combustion of 1 was too violent, resulting in a strong explosion. The step of transformer slows down the combustion speed.

2. Quickly and unsteadily remove the oxide on the bottom and surface of the electrode.

Improve transformer sequence

Accelerate the combustion speed

There is oxide film, incomplete penetration or slag inclusion in the joint to increase the preheating degree.

Accelerate the melting speed near upsetting.

Ensure the forging process of charged surface.

Accelerated upsetting

Increase upsetting pressure

4. The connector has shrinkage cavity, which reduces the number of transformer stages.

The combustion process is too intense.

Appropriately increase upsetting allowance and forging neck pressure.

5. The welding metal is overheated or the affected area is too small to preheat.

Accelerate the melting speed, shorten the welding time, and avoid too much charged upsetting.

6 Inspection of cracks in the joint area The chemical composition of steel bars should be preheated at low frequency to increase the degree of preheating.

7. Micro-melting and burning shall be carried out on the surface of steel bar to remove rust and oil stain on the clamping parts of steel bar.

Remove the oxide on the inner surface of the electrode.

Improve the shape of electrode gap and increase the contact area.

8 Adjust the electrode position correctly when the connector is bent or the axis is deviated.

Repair the electrode clamp or replace the deformed electrode.

Cut or straighten the elbows of steel bars.

(2) Arc welding: This project can adopt binding welding or lap welding.

(1) Selection of covered electrode for arc welding: According to the design regulations.

(2) Bonding welding and lap welding process

(1) Before welding, the assembly and positioning of steel bars shall meet the following requirements: when binding welding is adopted, the gap between the end faces of two main bars shall be 2 ~ 5mm；; When lap welding is used, the pre-bending and installation of steel bars should ensure that the axes of two steel bars are in a straight line; The tie rod and the main reinforcement are fixed by four-point spot welding; When lap welding, it should be fixed at two points, and the positioning weld should be more than 20mm away from the binding belt or lap end.

(2) When welding, the arc striking should start from one end of the tie bar or lap bar, and the arc closing should be at the end of the tie bar or lap bar, and the arc pit should be filled.

(3). When binding or lap welding is adopted for steel bar joints, the weld length shall not be less than the binding or lap length, and the weld height H shall not be less than h≥0.3d and shall not be less than 4 mm; Weld width h≥0.7d and shall not be less than10mm; ; When steel bars and steel plates are lap welded, the weld height h should be ≥ 0.35d and should not be less than 6mm；; Weld width h≥0.5d, and not less than 8mm；;

Five, steel binding and installation

(1) Preparation before binding

(1) Check whether the steel grade, diameter, shape, size and quantity of finished steel bars are in conformity with the bill of materials, and correct and supplement in time if there are any mistakes and omissions.

(2) ready to tie wire and binding tools. The wire used for binding steel bars can be No.20-No.22, of which No.22 wire is only used for binding steel bars with a diameter below12 mm. ..

(3) Prepare cement mortar pad: the thickness of cement mortar pad should be equal to the thickness of protective layer. When the shim is used in the vertical direction, 20 # iron wire can be buried in the shim.

(4) Draw the position line of steel bar: flat steel bar, and draw a line on the template; Column reinforcement, draw points on two diagonal main reinforcement; For the stirrup of the beam, draw points on the vertical bars. For foundation reinforcement, mark points on one reinforcement in each direction or mark lines on the cushion.

(5) Steel bar transportation: The steel bars in this project are transported by derrick with tie rods, hoisted to the ground, and transported to the binding site manually.

(2) Binding of reinforcement

(1) Binding of foundation reinforcement

Cleaning the cushion layer, the steel bar foreman is responsible for writing the specifications, spacing and joint position of the steel bars used in each area and foundation in a conspicuous position with a brush, and then the operator is responsible for drawing the position line of steel bar binding on the cushion layer with a pencil as required. Note that the short-term reinforcement at the bottom of the foundation must be arranged above the long-term reinforcement.

(2) Column rebar binding

The vertical reinforcement of the column in this project is proposed to be connected by binding. When binding the column reinforcement, the vertical reinforcement of the lower column is exposed from the floor and fixed with tools or stirrups to facilitate the extension of the upper column reinforcement. For different parts of the upper and lower columns with different section sizes, the exposed parts of the lower column reinforcement must be collected before binding the beam reinforcement. Column stirrup joints should be staggered vertically, and the intersection of stirrup corner and vertical reinforcement should be fastened.

(3) Beam and plate steel binding

When the longitudinal reinforcement of the beam appears double-layer or multi-layer arrangement, a short reinforcement with a diameter of 25mm is placed between the two rows of reinforcement. The joints of beam stirrups are staggered, and they are bound by two vertical poles. The joint near the continuous beam support is at the bottom, the mid-span joint is at the top, and the stirrup joint is at the cantilever beam at the bottom.

In the cast-in-place slab, the steel bars in the short-span direction are arranged below; Set large-span steel bars on the floor; Negative reinforcement in cast-in-place slab, and reinforcement in short span direction is set on the floor slab; The reinforcement in the long-span direction is arranged below.

The wire buckles of adjacent binding points should be splayed to prevent the mesh from being skewed and deformed, and the steel bars of the steel bar binding joint should be fastened with wires in the middle and at both ends.

The reinforcement of frame beam should be placed in the vertical reinforcement of column.

(4) Measures to ensure the spacing of floor reinforcement

Generally, the diameter of negative reinforcement of floor slab is relatively small, which is easy to be trampled and deformed during construction, deviating from the design position, and prone to cracks during use. Especially the awning, balcony and other cantilever members, if seriously deviated, may also cause structural safety problems, so the position of negative reinforcement should be strictly controlled. This project adopts negative reinforcement of saddle-shaped reinforcement supporting plate. At the same time, it should be noted that the clear distance between the stressed steel bars on the top surface of the beam is 30 mm to facilitate concrete pouring. The supporting steel bar is φ 10 steel bar, one for every 700X 100 meters, and the height of supporting steel bar is H= thickness -20. The schematic diagram of the support rib is as follows.

(5) Anchorage and lap joint of reinforcement

Reinforcement anchorage and lap stagger rate shall be carried out in strict accordance with the design drawings and construction acceptance specifications.

(3) Reinforcement fixation and finished product protection

(1). For members equipped with double-sided reinforcement, support reinforcement and contact reinforcement shall be added according to the design requirements.

(2) The vertical main reinforcement of the column is prone to displacement at the floor, and even causes column deviation in serious cases, so reinforcement measures must be taken to resolutely put an end to column vertical reinforcement deviation. Anti-column vertical reinforcement deviation measures as shown in the figure below:

(3) When the longitudinal reinforcement of the beam is double-layer or multi-layer, the cushion reinforcement between the two layers of reinforcement should be reinforced with a diameter of 25 or more, and meet the requirements of the clear distance of reinforcement in the design drawings. The spacing between pads is 2m, and the upper and lower pads should be staggered. Steel mesh and steel skeleton must be firmly bound to prevent deformation and looseness of steel bars. The second row of steel bars on the beam surface must be hoisted to prevent the steel bars from slipping when pouring concrete.

(4) The negative reinforcement on the board surface is easy to be trampled and deformed, so the negative reinforcement should be bound after the completion of the embedded hydropower pipeline. Set up overhead passage, with reinforced horse stool and upper personnel passage. When pouring concrete, the concrete worker stands on the walkway to pour concrete, and the steel bar worker is on duty to correct deformed steel bars at any time. Schematic diagram of reinforced horse stool is as follows:

(5) After the steel binding is completed, the person responsible for quality inspection and finished product protection and the precautions for finished product protection shall be listed. So as to facilitate the quality control of reinforcement engineering and the smooth development of the next working procedure.

The detailed information of "Technical Scheme for Reinforcement Construction in School Buildings" can be found in the link of Zhong Da Consulting and Design, and all relevant building construction information you want is available.

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