Seven don't wear a tie:
1, rebar is not allowed to be bound until the laitance of the poured concrete is cleaned-it refers to the rebar cage of the cast-in-place pile or column;
2, steel pollution removal is not clean are not allowed to tie steel;
3, the line of control didn't play well are not allowed to tie steel;
4, steel deviation is not checked, correction is unqualified are not allowed to tie steel;
5, steel joint itself quality inspection qualified are not allowed to tie steel;
6, technical disclosure does not reach the designated position are not allowed to tie steel;
7, steel processing failed to pass the acceptance are not allowed to tie steel.
Five don't test:
1, reinforcement is not completed and not accepted;
2, steel positioning measures do not reach the designated position not acceptance;
3, reinforced protective layer pad is unqualified, can not meet the acceptance requirements;
4, steel rectification acceptance is unqualified;
5, steel binding is not strictly in accordance with the technical disclosure of construction acceptance.
What is the selection principle of reinforcement? 1, steel varieties, grades and specifications should meet the design requirements. (If there is no design, please refer to GB 500 10-20 10 standard 4.2).
2. The quality of the selected steel bars shall meet the relevant product standards. (Re-examination qualified)
3, steel bar should be straight without damage, the surface can not have cracks, oil, granular or flaky old rust.
See GB50204-2002 standard.
What is the arrangement principle of steel bars in beams? Arrangement principle of reinforcement in beam:
1. Diameter of longitudinal reinforcement of beam: when the beam height h≥300mm, it should not be less than10mm; ; When the beam height h < 300mm, it should not be less than 8mm.
2. Net spacing of longitudinal reinforcement of horizontal beam: for upper reinforcement, it should not be less than 30mm, 1.5d(d is the maximum diameter of reinforcement); For the lower reinforcement should not be less than 25mm and D. When there are more than two layers of longitudinal reinforcement at the lower part of the beam, the horizontal middle distance of more than two layers of reinforcement should be doubled than that of the lower two layers. The net spacing between each layer of steel bars should not be less than 25mm and d.
3. The anchorage length las of the lower longitudinal reinforcement of simply supported beam and continuous beam whose simply supported end extends into the bearing shall meet the following requirements: las≥5d； when the concrete in the beam can bear all the shear force; ; When the shear force at the beam end is greater than the bearing capacity of concrete, las≥ 12d for ribbed steel bars and las≥ 15d for round steel bars.
When the lower longitudinal reinforcement is not enough to reach the beam end, effective anchoring measures should be taken, such as adding anchoring steel plates to the reinforcement or welding the reinforcement to the embedded parts at the beam end.
4. The upper longitudinal reinforcement of frame beam or continuous beam should pass through the range of intermediate node or intermediate bearing. The cutting position where the edge of steel bar joint or bearing extends to the middle of span shall meet the requirements of bending bearing capacity and anchorage.
The lower longitudinal reinforcement of frame beam or continuous beam shall meet the following anchorage requirements at intermediate nodes or intermediate supports:
(1) When the strength of steel bar is not used in the calculation, the anchorage length of steel bar extending into the node or bearing is las≥ 12d (ribbed steel bar) and 15d (round steel bar);
(2) When the tensile strength of steel bars is fully utilized in the calculation, the lower longitudinal steel bars should be anchored at nodes or supports, and linear anchorage can be adopted at this time, and the anchorage length should not be less than LA; 90 elbow can also be used for anchorage, and the anchorage length should not be less than 0.41a; ; The lower longitudinal reinforcement can also extend beyond the range of nodes or bearings, and lap joints should be set at the places with small bending moment in the beam, and the lap length should not be less than ll.
(a) Linear anchorage in joints; (b) Bending anchorage in joints; (c) Lapping outside the range of nodes or bearings
5. When linear anchorage is adopted, the anchorage length of the longitudinal reinforcement in the upper part of the frame beam extending into the end node of the middle layer should not be less than la and not less than 5d(d is the diameter of the longitudinal reinforcement in the upper part of the beam). When the column section size is insufficient, the longitudinal reinforcement at the upper part of the beam should extend to the opposite side of the joint and bend downward. The horizontal projection length of curve segment should not be less than 0.4la, and the vertical projection length of curve segment should be 15d.
The anchorage requirements of the longitudinal reinforcement at the lower part of the frame beam at the end node are the same as those at the middle node.
6. In the cantilever beam, at least two upper steel bars should extend to the outer end of the cantilever beam and bend down at least12d; ; The rest of the steel bars should not be cut off at the upper part of the beam, but should be bent down according to the specified bending starting point position and anchored at the lower part of the beam.
7. When the beam end is actually partially restrained, but calculated as simply supported, the longitudinal structural reinforcement should be set in the upper part of the supporting area, and its cross-sectional area should not be less than 1/4 of the cross-sectional area required for the calculation of the longitudinal stressed reinforcement in the middle and lower part of the beam span, and should not be less than two, and the length of the longitudinal structural reinforcement extending inward from the supporting edge should not be less than 0.2l0(l0 is the calculation span).
8. The spacing of the twisted longitudinal reinforcement arranged along the periphery of the beam section should not be greater than 200mm, and should not be greater than the short side length of the beam section; In addition to setting torsional longitudinal bars at the four corners of the beam section, other torsional longitudinal bars should be evenly and symmetrically arranged along the periphery of the section. Torsional reinforcement should be anchored in the bearing according to tensile reinforcement.
What is the principle of steel bar substitution? Equal area substitution and equal strength substitution.
The reinforcement of members controlled by the minimum reinforcement ratio is replaced by equal area, and that controlled by strength calculation is replaced by equal strength.
How to replace steel bars? What is the principle of steel bar substitution? (1) Equal-section substitution: generally, it refers to the substitution of original design steel bars with the same material (design strength) but different diameters, and its calculation formula is:
Distance between replacement steel bars = (theoretical weight of replacement steel bars/theoretical weight of original design steel bars) * original design distance
[Example] A design uses 10 round steel bars with a spacing of 180 mm, but it is planned to be replaced by 8 round steel bars because of the shortage of 10 round steel bars. What should be the spacing between steel bars?
The spacing of replacement reinforcement = 0.395/0.617 *180 =115 (mm).
(2) Replacing the number of steel bars according to the theoretical weight: it is suitable for the reinforcement of the number of steel bars, and the calculation formula is:
The quantity of replacement steel bars is greater than or equal to the theoretical weight of original design steel bars/theoretical weight of replacement steel bars * original design quantity.
[Example] The reinforcement of a design is 10 turns, and it is proposed to replace it with 8 turns. How much should it be after replacement?
Replacement quantity of steel bars = 0.617/0.395 *10 =15.62, and 16.
When using root substitution, we must pay attention to the structural requirements.
(3) Equal strength substitution: generally speaking, it refers to the substitution of original design steel bars with the same or different specifications (diameters) but different materials (design strength), and its calculation formula is:
Substitution reinforcement spacing = (theoretical weight of substitution reinforcement * strength coefficient of substitution reinforcement)/(theoretical weight of original design reinforcement * strength coefficient of original design reinforcement) * original design spacing (mm)
[Example] The original design circle 10 spacing180 mm (grade I steel) is now replaced by circle 8 (grade II steel). What should be the spacing between steel bars?
The spacing of replacement reinforcement = (0.395 * 3.4)/(0.617 * 2.4) *180 =163 (mm).
(4) Substituting reinforcement quantity according to strength: it is suitable for reinforcement design based on reinforcement quantity, and the calculation formula is as follows:
Number of replacement steel bars ≥ (original design steel bar theoretical weight * original design steel bar strength coefficient)/(original design steel bar theoretical weight * replacement steel bar strength coefficient) * original design steel bar number.
[Example] The original design used four circles 25 (grade I steel). If 22 circles (secondary steel) are used instead of steel bars, how much is needed?
Quantity of replacement reinforcement =(3.85*2.4)/(2.98*3.4)*4=3.65, and 4 is taken.
When the varieties or specifications of steel bars in construction do not meet the design requirements, they can be replaced with reference to the following principles. (1) Equal strength substitution: When the members are controlled by strength, steel bars can be replaced according to the principle of equal strength; That is, the reinforcement of different steel grades is replaced according to the principle of equal strength. That is, the strength after steel bar substitution; Before replacement, it should be greater than or equal to the reinforcement strength RgAg. (2) Equal area replacement: When members are reinforced according to the minimum reinforcement ratio, the reinforcement can be replaced according to the principle of equal area. That is, according to the principle of equal reinforcement area, replace the reinforcement of the same steel grade. (3) When the component is controlled by the crack width or deflection, the crack width or deflection shall be checked after replacement. (4) The replaced steel bars shall meet the structural requirements and special requirements put forward by the design. When replacing steel bars, we must fully understand the design intent and the replacement efficiency of materials, and strictly abide by the provisions of the current design code for concrete structures; The replacement of steel bars in important structures needs the consent of the design unit. 1) for some important components, such as crane beam, thin web beam, string truss, etc. , it is not advisable to use first-class round steel instead of second-class ribbed steel bar. 2) After the steel bar is replaced, it should meet the requirements of steel bar structure, such as minimum diameter, spacing, number of steel bars, anchorage length, etc. 3) In the same cross section, different kinds and diameters of substitution steel bars can be provided at the same time, but the tension difference of each steel bar should not be too large to avoid uneven stress on the members. 4) The longitudinal reinforcement and bent reinforcement of beam should be replaced separately to ensure the strength of normal section and inclined section. 5) When eccentrically compressed members, such as door frame beams, crane workshop columns, upper chords of trusses, etc. ) or eccentric tension members for steel substitution, do not calculate the amount of reinforcement in the whole section, and should be substituted according to the stress surface (compression and tension) respectively. 6) When members are controlled by crack width, if small-diameter steel bars are used instead of large-diameter steel bars and high-strength steel bars are used instead of low-strength steel bars, the calculation of crack width can be omitted. 7) At the natural temperature (40 ") in cold areas, the steel bars in the components are not easy to be brittle because they work together with concrete. Therefore, under the condition of negative temperature, when the mechanical efficiency of steel bars meets the national standard, -4 grade hot-rolled steel bars, cold-rolled steel bars and cold-drawn steel wires can be used in reinforced concrete and prestressed concrete structures in cold areas.
What is the principle of sampling each batch of steel bars?
Answer: See Code for Quality Acceptance of Concrete Structure Engineering (GB 50204-2002) (2011version):
5.2. 1 When the reinforcement comes into play, the test pieces shall be selected according to the current national standards for mechanical efficiency and weight deviation inspection, and the inspection results must meet the relevant standards.
Inspection quantity: determined according to the purchase batch and product sampling inspection scheme.
Inspection method: check the product certificate, ex-factory inspection report and re-inspection report.
Description of terms
Reinforcement is very important to the bearing capacity of concrete structures, and its quality should be strictly required. According to the actual situation of the building steel bar market, this regional revision adds the weight deviation as the requirement of steel bar entry acceptance.
The current national standards related to the efficiency and inspection of hot-rolled round steel, hot-rolled ribbed steel bar, heat-treated steel bar and welded steel bar are: steel for reinforced concrete Part 1: hot-rolled round steel GB 1499. 1, steel for reinforced concrete Part 2: hot-rolled ribbed steel bar GB 1499.2, steel for reinforced concrete. 3065433 International standards related to the efficiency and inspection of cold-worked steel bars include: cold-rolled ribbed steel bars GB 13788, cold-rolled twisted steel bars JG 190, technical specification for cold-rolled ribbed reinforced concrete structures JGJ 95, technical specification for cold-rolled twisted reinforced concrete members JJ115, and technical specification for application of cold-drawn low-carbon steel wires.
When steel bars enter the site, the product certificate and factory inspection report shall be checked, and sampling inspection shall be conducted according to relevant standards. Due to the differences in engineering quantity, transportation conditions and the number of various reinforcing bars, it is difficult to make uniform provisions on the batch size of reinforcing bars entering the site. In the actual inspection, the relevant standards have specific provisions on entry inspection, which should be followed; If the relevant standards only stipulate the ex-factory inspection of products, the batch number shall be determined according to the following conditions when entering the inspection site:
1. For steel bars of the same manufacturer, same brand and same specification, when the number of steel bars entering the site at one time is greater than the factory inspection batch of the product, they should be divided into several factory inspection batches and implemented according to the sampling scheme of the factory inspection;
2. For steel bars of the same manufacturer, brand and specification, when the number of steel bars entering the site at one time is less than or equal to the factory inspection lot of the product, it shall be regarded as an inspection lot, and then it shall be implemented according to the sampling scheme of the factory inspection;
3. For the same batch of steel bars that come into play at different times, when there is a reliable basis, they can be treated as steel bars that come into play at one time.
In this inspection method, the product certificate and factory inspection report are the proof materials of product quality, and the main performance indexes of the product should be listed; When users have special requirements, they should also list some special inspection materials. Sometimes, the product certificate and the factory inspection report can be combined into one. The on-site re-inspection report is the result of on-site sampling inspection, which can be used as a basis for judging whether the material can be used in engineering.
The inspection quantity of each batch of steel bars shall be implemented according to relevant product standards. International standard "Steel for Reinforced Concrete Part 1 Part: Hot Rolled Round Steel" GB 1499. 1— 2008 and Steel for Reinforced Concrete Part 2: Hot-rolled ribbed bars GB 1499. 2— 2007 stipulates that 5 specimens should be taken from each batch, and the weight deviation should be checked first.
In this specification, when it comes to the quantity and method of incoming inspection of raw materials, unless otherwise specified, it should be understood and implemented according to the above instructions.
This article is mandatory and should be strictly implemented.
5.2.2 ? For structures with seismic fortification requirements, the longitudinal reinforcement strength should meet the design requirements; When there are no specific requirements in the design, the frame and brace members (including steps) designed according to the first, second and third levels of earthquake resistance shall adopt HRB335E, HRB400E, HRB500E, HRB335e, HRB400e or HRB500e steel bars, and the measured values of the maximum stress and total elongation shall meet the following requirements:
1 ? The ratio between the measured tensile strength and the measured yield strength of steel bars should not be less than1.25;
2 ? The ratio of the measured yield strength of reinforcement to the standard strength value should not be greater than1.30;
3? The total elongation of reinforcement under the maximum stress should not be less than 9%.
Inspection quantity: determined according to the purchase batch and product sampling inspection scheme.
Inspection method: check the re-inspection report on approach.
Description of terms
According to the newly issued international standard GB500 10 "Code for Design of Concrete Structures" GB500 1 1, this article puts forward the provisions on the strength and elongation of longitudinal reinforcement in some frames and diagonal braces (including treads) in order to ensure the seismic efficiency of important structural members. The ratio of measured tensile strength to measured yield strength in clause 1 of this article is customarily called "strong yield strength ratio" in engineering, the ratio of measured yield strength to standard yield strength in clause 2 is customarily called "super ratio" or "super yield strength ratio" in engineering, and the total elongation under maximum force in clause 3 is customarily called "uniform elongation".
Frames in this article include frame beams, frame columns, frame-supported beams, frame columns and slab-column columns in various concrete structures, and their seismic grade shall be determined by design according to the current national standards. Support members include outrigger trusses and stairs. The seismic grade of supporting members is not specified in relevant standards, and all supporting members shall meet the requirements of this article.
The steel bar marked with "E" brand is specially produced to meet the efficiency requirements of this article, and its surface rolling has special marks.
This article is mandatory and should be strictly implemented.
What are shear wall steel binding and structural steel binding? Shear wall is a vertical structure, which aims to counteract the horizontal and vertical seismic vibration energy waves during earthquakes. General thickness is not less than 140 mm shear wall reinforcement binding is to bind the distribution reinforcement in vertical and horizontal directions, and then hang a retractor. Tractors generally bend to 65438 035 degrees. As for the binding of structural reinforcement, it is nothing more than columns, walls and beams.