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 Rebar refers to steel used for reinforced concrete and prestressed reinforced concrete, and its cross section is round, sometimes square with rounded corners。包括光圆钢筋、带肋钢筋、扭转钢筋。

The steel bar for reinforced concrete refers to the straight bar or disc bar steel used for reinforced concrete reinforcement, and its shape is divided into two kinds of round steel bar and deformed steel bar, and the delivery status is straight bar and disc round two kinds。
光圆钢筋实际上就是普通低碳钢的小圆钢和盘圆。Deformed bars are bars with ribbed surfaces, usually with two longitudinal ribs and transverse ribs evenly distributed along the length。横肋的外形为螺旋形、人字形、月牙形3种。用公称直径的毫米数表示。The nominal diameter of a deformed bar is equivalent to that of a circular bar of equal cross-section。The nominal diameter of the steel bar is 8-50 mm, and the recommended diameters are 8, 12, 16, 20, 25, 32, 40 mm。Steel grade: 20MnSi, 20MnV, 25MnSi, BS20MnSi。钢筋在混凝土中主要承受拉应力。Due to the action of the rib, the deformed steel bar has greater bonding capacity with the concrete, so it can better withstand the action of external forces。钢筋广泛用于各种建筑结构。特别是大型、重型、轻型薄壁和高层建筑结构。
There are many types of steel bars, usually classified by chemical composition, production process, rolled shape, supply form, diameter size, and use in the structure:
Steel wire (diameter 3~5mm), fine steel bar (diameter 6~10mm), thick steel bar (diameter greater than 22m
Grade I steel (grade 235/420);Grade II steel (335/455);Grade III (400/540) and Grade IV (500/630)
Hot rolled, cold rolled, cold drawn steel bars, as well as Ⅳ grade steel by heat treatment of heat treatment of steel bars, the strength is higher than the former。
The steel bar configured in the reinforced concrete structure can be divided into the following types according to its role:
2.Stirrup - Subjected to a portion of the diagonal tension and fixed the position of the reinforcement, commonly used in beams and columns。
4.Distribution rib - Used in the roof panel and floor, vertical arrangement with the stress reinforcement of the plate, the weight of the load is evenly transmitted to the stress reinforcement, and the position of the stress reinforcement is fixed, and the temperature deformation caused by thermal expansion and contraction is resisted。
① Smooth steel bars: Grade I steel bars (Q300 steel bars) are rolled for smooth circular cross-section, the supply form is disk circle, the diameter is not more than 10mm, the length is 6m~12m。
② Ribbed steel: there are spiral, herringbone and crescent shape three, generally Ⅱ, Ⅲ grade steel rolled into adult shape, Ⅳ grade steel rolled into spiral and crescent shape。
Steel wire (diameter 3~5mm), fine steel bar (diameter 6~10mm), thick steel bar (diameter greater than 22mm)。
Rebar is now widely used in any building, for human progress has made better evidence, but also today's inspection of the quality of rebar members according to the minimum reinforcement rate of reinforcement, according to the principle of (equal area) replacement of rebar。
(2) Steel for reinforced concrete - Part 2: Hot rolled ribbed steel GB1499.2-2007
The inspection of steel bars must first check the label number and quality certificate of steel bars;Secondly, we should do a visual inspection,从每批钢筋中抽取5% ,检查其表面不得有裂纹、创伤和叠层,钢筋表面的凸块不得超过横肋的高度,缺陷的深度和高度不得大于所在部位的允许和偏差,钢筋每一米弯曲度不应大于四米;接下来力学性能试验,每批若小于60吨则从中抽取2根,每根截取两段,分别做拉伸和冷弯试验。When intercepting the specimen, the steel bar should be removed at both ends of 100-500MM, and the corresponding steel bar should be taken when the specimen is larger than 60 tons。If the results of one test do not meet the requirements, a double number of samples are taken from the same batch for each test。If there is still a sample unqualified, the batch of steel bars is unqualified, hot rolled steel bars in the process of brittle fracture, poor welding performance or significant abnormal mechanical properties and other phenomena, should be carried out chemical composition analysis and other special inspection。
Waste heat treatment of steel bars: immediately after hot rolling through water, surface control cooling, and then use the core waste heat itself to complete the finished steel bars obtained by tempering treatment。
Ribbed steel bar: Steel bar with a surface usually having two longitudinal ribs and transverse ribs evenly distributed along the length。
Relative rib area of a ribbed bar: the ratio of the projected area of the transverse rib in the vertical plane with the axis of the bar to the product of the nominal perimeter of the bar and the distance between the transverse ribs。
螺纹连接,绑扎仍为钢筋连接的主要手段之一。 钢筋绑扎时,钢筋交叉点用铁丝扎牢;板和墙的钢筋网,除外围两行钢筋的相交点全部扎牢外,中间部分交叉点可相隔交错扎牢,Ensure that the position of the loaded steel bar does not deviate;The stirrups of beams and columns shall be arranged perpendicular to the bearing bars,弯钩叠合处应沿受力钢筋方向错开设置。The lap length and position of the joint of tension reinforcement and compression reinforcement are in accordance with the construction and acceptance specifications。
2.The steel mesh of the plate and the wall must also be fastened at the intersection point of the middle part with staggered intervals, but it must be ensured that the stressed steel bars do not shift。双向受力钢筋网片,须全部扎牢;
4.At the intersection of the plate, the secondary beam and the main beam, the steel bar of the plate is on the top, the steel bar of the secondary beam is in the middle, and the steel bar of the main beam is on the bottom;When there are ring beams or cushion beams, the steel bars of the main beam are on top。
钢筋表面不得允许有裂纹、结疤和折叠。The surface of the steel bar is allowed to have a convex block, but it must not exceed the height of the transverse rib, and the depth and height of other defects on the surface of the steel bar must not be greater than the allowable deviation of the size of the location。
The nominal diameter of the steel bar ranges from 6 to 25mm, and the standard recommended nominal diameter of the steel bar is 6, 8, 10, 12, 16, 20, 25, 32, 40, 50mm。
The Angle β between the transverse rib and the axis of the steel plate should not be less than 45 degrees, and when the Angle is not greater than 70 degrees, the direction of the steel bar should be opposite to the two upper transverse ribs;
The sum of the gap (including the width of the longitudinal rib) between the ends of the two upper transverse ribs of the steel bar should not be greater than 20% of the nominal perimeter of the steel bar;
当钢筋公称直径不大于12mm时,相对肋面积不应小于0.055; The nominal diameter is 14mm and 16mm, and the relative rib area should not be less than 0.060;公称直径大于16mm时,相对肋面积不应小于0.065。
a, length: the steel bar is usually delivered according to the fixed length, the specific delivery length should be indicated in the contract; When rebar is delivered in reels, each rebar shall be one rebar and 5% of  reels (or two if less than two reels) of each lot shall be allowed to consist of two rebars。其盘重及盘径由供需双方协商规定。
b, length allowable deviation: steel bar according to the length of delivery allowable deviation shall not be greater than +50mm。
c, bending degree and end: the bending deformation of the straight bar does not affect the normal use, the total bending degree is not greater than 0 of the total length of the bar.4%;钢筋端部应剪切正直,局部变形应不影响使用。
Steel bar processing generally goes through four processes: steel rust removal;Steel bar straightening;Steel bar cutting;Steel bar forming。
When the bar joint is connected with straight thread or taper thread, it is necessary to increase the upsetting and threading process of the bar end。钢筋配料与代换钢筋代换
(1) When replacing the steel bar specified in the design document with a steel bar of another steel number or diameter, the following provisions shall be observed:
It should be carried out according to the principle that the design value of the bearing capacity of the steel bar is equal, and the structural requirements such as the spacing of the steel bar, the anchoring length and the minimum diameter of the steel bar should be met after the replacement。
When replacing lower grade steel bars with higher grade steel bars, it is advisable to change the diameter of steel bars rather than the number of steel bars to reduce the cross-sectional area of steel bars。
(2) When a steel bar of the same diameter is used to replace a steel bar of another diameter, the diameter change range should not exceed 4mm, and the ratio of the total section area of the steel bar after the change to the section area specified in the design document should not be less than 98% or more than 103%。
(3) When the design main reinforcement is replaced with the same steel number, the spacing should be kept unchanged, and two types of reinforcement spacing configurations with diameters larger and smaller than the diameter of the design reinforcement can be replaced。
我国自八十年代后期起,开始引进冷轧带肋钢筋生产设备。Nanjing, Suzhou, Shanghai, Qingdao, Cangzhou, Kunming and other places have introduced 11 sets of equipment from Germany, Italy and other countries。In the mid-1990s, there were joint ventures or wholly foreign-owned enterprises in Anhui, Guangdong, Jiangsu and other provinces, and several production lines were introduced from abroad。与此同时。国内有些科研单位和企业着手研制或仿制冷轧设备。So far, more than 10 units have been producing and selling a complete set of cold-rolled steel bar equipment, distributed in Beijing, Liaoning, Jiangsu, Hebei, Tianjin and other places。There are also some equipment manufacturers, in the past few years of fierce market competition, due to poor product performance or poor quality was eliminated。
So far, China has built more than 400 cold-rolled ribbed steel production lines, with an annual production capacity of 2 million tons, distributed in 26 provinces and cities。
From the understanding of the provincial situation, under the strong promotion of the Ministry of Construction and the provincial and municipal construction committees, the promotion of cold-rolled ribbed steel has made great progress。Some provinces have made outstanding achievements, among which Jiangsu and Liaoning provinces have the largest promotion surface, and cold-drawn low carbon steel wire has been eliminated in prefabricated components;In situ concrete structure also has a large number of applications, Sichuan, Fujian Province in this area of the promotion work is very successful。In addition, Beijing, Hebei, Hunan, Anhui, Shanxi, Shandong, Guangdong, Zhejiang, Shanghai and other provinces and cities have also begun to promote the application。据不完全统计。仅1998年全国的推广量已超过60万吨。用于城乡住宅及公共建设的建筑面积达1.5亿平方米,今后还将有较大的增长。
在生产和应用技术方面,我国在引进的基础上有了发展,For example, the tensile strength of cold-rolled ribbed steel has been developed from one strength level abroad to three levels: CRB550, CRB650 and CRB800;The application range is also expanded from non-prestressed concrete structural members abroad to prestressed concrete members。In order to promote the application of steel bars, the competent departments of the state and some provinces and cities have organized the compilation of relevant standards and atlas。The national standard "cold-rolled ribbed Steel Bar" GB13788-2008 has been implemented。The industry standard "Technical Specification for Reinforced Concrete Structures" JGJ95-2011 has been implemented since April 1, 2012。
国家科委已将钢筋列入国家重点推广的项目。The Ministry of Construction included it as one of the 10 new technologies focused on promotion in the construction industry during the "Ninth Five-Year Plan" and "Tenth Five-Year Plan" period (included in the "high-efficiency steel bar and prestressed concrete technology" project)。
When the steel bar is processed, it is necessary to review the steel bar processing table and the design drawing, check whether there are errors and omissions in the cutting table, and press down on each steel bar
Check whether the material table meets the requirements, after these two checks, and then release the real sample according to the material table, the trial production can be made in batches, and the processed steel bars should be stacked neatly and orderly。
If the replacement of steel bars is required in construction, it is necessary to fully understand the design intent and the performance of the replacement material, strictly comply with the various provisions of the current reinforced concrete design code, and it is not possible to replace low-strength steel bars with high-strength steel bars of equal area。The replacement of steel bars in important parts shall be agreed by Party A and the design unit, and shall be replaced with a written notice。
(1) The surface of the steel bar should be clean, the adhesive oil, soil, floating rust must be cleaned before use, and can be combined with the cold drawing process to remove rust。
(2)钢筋调直,可用机械或人工调直。The straightened steel bar should not have local bending, dead bending, small waves, and its surface scars should not reduce the cross-section of the steel bar by 5%。
(3) The steel bar should be cut according to the steel bar number, diameter, length and quantity, the length of the match, the first cut the long material after the short material, as far as possible to reduce and shorten the short head of the steel bar, in order to save steel。
①钢筋弯钩。形式有三种,分别为半圆弯钩、直弯钩及斜弯钩。After the bending of the steel bar, the inner wall of the bending area shrinks, the outer skin extends, the axis length remains unchanged, and the bending area forms an arc. The bending size is larger than the cutting size, and the bending adjustment value should be considered。钢筋弯心直径为2.5d,平直部分为3d。钢筋弯钩增加长度的理论计算值:对转半圆弯钩为6.5d,对直弯钩为3.5d,对斜弯钩为4.9d。
③箍筋。箍筋的末端应作弯钩,弯钩形式应符合设计要求。Stirrup adjustment, that is, the difference or sum of the increased length of the hook and the bending adjustment value, depending on the size of the stirrup outside or inside。
④ The cutting length of the steel bar should be comprehensively considered according to the size of the member, the thickness of the concrete protective layer, the bending adjustment value of the steel bar and the length of the bending hook。 
a. 直钢筋下料长度=构件长度-保护层厚度+弯钩增加长度,
b. Bending bar cutting length = straight section length + oblique bending length - bending adjustment value + bending hook increase length,
c. 箍筋下料长度=箍筋内周长+箍筋调整值+弯钩增加长度。
Before binding, carefully familiarize yourself with the drawings, check whether the ingredients list is different from the drawings and designs, and carefully check whether the finished product size and heart are consistent
下料表相符。核对无误后方可进行绑扎。20# wire is used to bind steel bars with a diameter of more than 12, and 22# wire is used to bind steel bars with a diameter of less than 10。
When double-layer steel mesh is used, a brace (hook) should be set between the two layers of steel bars to fix the spacing of steel bars。
(4) In order to ensure the correct position of the rebar, tie a horizontal reinforcement or stirrup outside the vertical reinforcement, and spot weld it with the vertical reinforcement to fix the position of the wall and column reinforcement, and correct it with a line hammer when spot welding is fixed。
⑤ It is strictly forbidden to open holes after the external wall is poured. All the embedded parts and buried pipes of the entrance should be reserved. The reinforcement of the hole side is detailed in the construction drawing。墙、柱内预留钢筋做防雷接地引线,应焊成通路。Its location, quantity and practice are detailed in the installation and construction drawings. Qualified welders should be selected to carry out welding work, and the structural reinforcement should not be damaged. The pre-burial of hydropower installation must be coordinated with civil construction, and the wrong burial and leakage burial should not be allowed。
(1) When the longitudinal loaded steel bars are arranged in double or multiple layers, a short steel bar with a diameter of 15mm should be placed between the two rows of steel bars. If the diameter of the longitudinal steel bar is greater than 25mm, the diameter specification of the short steel bar is the same as that of the longitudinal steel bar。
② The joint of the stirrup should be staggered and tied with two standing ribs, the cantilever beam is the stirrup joint under, the rest of the practice is the same as the column。梁主筋外角处与箍筋应满扎,其余可梅花点绑扎。
③板的钢筋网绑扎与基础相同,双向板钢筋交叉点应满绑。It should be noted that the negative steel bar (face reinforcement) on the upper part of the board should be prevented from being stepped on;In particular, awning, overhanging eaves, balconies and other cantilever plates should strictly control the position and height of the negative reinforcement。
④ At the intersection of the plate, the secondary beam and the main beam, the steel bar of the plate is on the top, the steel bar of the secondary beam is in the middle layer, and the steel bar of the main beam is on the bottom, when there is a ring beam or a cushion beam, the main beam is on the top。
⑤ The bending starting point of the floor steel bar, such as the processing plant (field) in the processing of no bending, the design drawings and no special note, can bend the steel bar according to the following provisions, the side span support of the plate according to the span 1/10L as the bending starting point。板的中跨及连续多跨可按支座中线1/6L为弯起点。
When the reinforcement at the joint of the frame beam is very dense, it should be noted that the net spacing between the main reinforcement of the top surface of the beam should be left 30mm to facilitate the need for concrete。
1) The end of the lap length from the bending of the steel bar shall not be less than 10 times the diameter of the steel bar, and the joint shall not be located at the maximum bending moment of the member。
2) In the tension area, the end of the binding joint of the grade I steel bar should be bent, and the grade II steel bar should not be bent。
6) Before strapping, the strapping should be performed according to the spacing required by the design drawing, and the strapping should be performed according to the line to control the quality。
7) In order to ensure the correct position of the steel bar, according to the design requirements, the steel bar is supported by the steel horse stool @600。
According to the design requirements, the steel bar with diameter ≥18 in this project is preferentially lengthened by mechanical extension and sleeve extrusion connection technology, and the rest of the steel bar is lengthened and horizontal reinforcement
钢筋焊接分为压焊和熔焊两种形式。Pressure welding includes flash butt welding, resistance spot welding and gas pressure welding;Fusion welding includes arc welding and electroslag pressure welding。In addition, the welding of the steel bar and the T-shaped joint of the embedded part should use submerged arc pressure welding, arc welding or perforated plug welding, but the welding current should not be large to prevent the burn of the steel bar。
闪光对焊广泛用于钢筋连接及预应力钢筋与螺丝端杆的焊接。热轧钢筋的焊接宜优先用闪光对焊。Flash butt welding of steel bar (is the use of butt welding machine to make two sections of steel bar contact, through a low voltage strong current, after the steel bar is heated to a certain temperature and becomes soft, the axial pressure top forging is carried out to form a butt welding joint。The common techniques of flash butt welding are continuous flash welding, preheat flash welding and flash-preheat flash welding。对Ⅳ级钢筋有时在焊接后还进行通电热处理。
Arc welding is the use of arc welding machine to produce high temperature between the welding rod and the welding parts, arc melting of the welding rod and the welding parts within the arc burning range, to be solidified to form a weld or joint, arc welding is widely used in steel bar joints, steel bar skeleton welding, prefabricated structural joint welding, steel bar and steel plate welding and various steel structure welding。The joint forms of steel bar arc welding are: lap welding head (single side weld or double side weld), side welding head (single side weld or double side weld), split welding head (flat welding or vertical welding) and groove side welding head。
焊接接头质量检查除外观外,亦需抽样作拉伸试验。If there are doubts about the quality of welding or abnormal conditions are found, non-damage inspection can also be carried out (X-ray, gamma ray, ultrasonic inspection, etc.)。
Electroslag pressure welding is usually used for the welding length of vertical or oblique (inclination in the range of 4:1) steel bars in cast-in-place concrete structural members。电渣压力焊有自动和手工电渣压力焊两类。Compared with arc welding, it has high efficiency, low cost and can be vertically connected, so it is widely used in engineering。进行电渣压力焊宜用合适焊接变压器。The fixture must be dexterous, the upper and lower jaws are concentric, and the maximum deviation of the axis of the upper and lower steel bars must not be greater than 0.1d,同时也不得大于2mm。
When welding, first remove the rust within about 120mm of the end of the steel bar, clamp the clamp on the lower steel bar, and straighten the upper steel bar in the moving electrode。自动电渣压力焊时还在上下钢筋间放置引弧用的钢丝圈等。Then fill the pill box, fill the flux, turn on the circuit, and use the handle to ignite the arc.。Then stabilize for a certain time to form a slag pool and melt the steel bar (stable arc), with the melting of the steel bar, use the handle to slowly lower the upper steel bar。When the arc stabilization reaches the specified time, the handle is used for pressurized upforging (upforging) at the same time of power failure to eliminate slag inclusion and bubbles to form a joint。After cooling for a certain period of time, the pill box is removed, the welding flux is recovered, the fixture is removed and the welding slag is removed。引弧、稳弧、顶锻三个过程连续进行。
Resistance spot welding is mainly used for the cross connection of small diameter steel bars, such as for welding steel mesh, steel skeleton and so on。它的生产效率高、节约材料,应用广泛。The working principle of resistance spot welding is that when the steel bar is cross-spot welding, the contact point is only one point, and the contact resistance is large, at the moment of contact, all the heat generated by the current is concentrated on one point, so that the metal is heated and melted, and the welding spot metal is welded under the electrode pressure。
When resistance spot welding steel bars of different diameters, such as the diameter of smaller steel bars is less than 10mm, the diameter ratio of large and small steel bars should not be greater than 3;If the diameter of the smaller steel bar is 12mm or 14mm, the ratio of the diameter of the size of the steel bar should not be greater than 2。应根据较小直径的钢筋选择焊接工艺参数。
Gas pressure welding steel bar is the use of acetylene - oxygen mixed gas combustion of high temperature flame to heat the initial pressure of the two steel bar end joint, so that the end of the steel bar plastic deformation, and promote the metal atoms of the steel bar end to spread each other, when the steel bar is heated to about 1250~1350℃ (equivalent to the melting point of steel 0.80~0.90倍)时进行加压顶锻,使钢筋焊接在一起。
钢筋气压焊接属于热压焊。在焊接加热过程中,加热温度只为钢材熔点的0.8~0.9倍,且加热时间较短,所以不会出现钢筋材质劣化倾向。In addition, it is lightweight, flexible, efficient, energy saving, low welding cost, and can be used in all directions (vertical, horizontal and diagonal) welding。所以在我国逐步得到推广。
加热系统中加热能源是氧和乙炔。The flow meter is used to control the input of oxygen and acetylene, and the welding of steel bars with different diameters requires different flow rates。After the heater is used to mix oxygen and acetylene, the flame is emitted from the nozzle to heat the steel bar, and the flame is required to heat the steel bar evenly, have sufficient temperature and power, and be safe and reliable。
加压系统中的压力源为电动油泵,使加压顶锻的压力平稳。The crimper is one of the main equipment of gas pressure welding, which is required to accurately and conveniently fix two steel bars on the same axis, and evenly transfer the pressure generated by the oil pump to the steel bar for welding purposes。
The steel bar of air pressure welding should be cut off by the grinding wheel cutting machine, and the end face should be perpendicular to the axis of the steel bar。Before welding, the end face of the steel bar should be polished, the oxidation layer and dirt should be removed, so that it shows a metallic luster, and a thin layer of welding activator should be sprayed to protect the end face from oxidation。
Steel bar process performance includes many items, according to the characteristics of different products can be put forward different requirements, such as ordinary steel bar requirements for bending and reverse bending (reverse bending) test, some prestressed steel is required to carry out repeated bending, torsion, winding test。
The forms of all these tests simulate, to varying degrees, the processes that may be involved in the actual use of the material,如普通钢筋需要弯钩或弯曲成型,预应力钢丝有时需缠绕等,而其目的就是考核材料对这些特定塑性变形的极限承受能力,因而工艺性能也是对材料的塑性要求,且与上述延性(伸长率)要求是相通的,一般来说伸长率大的钢材,其工艺性能好。
然而与拉伸时的单向受力状态相比,工艺性能试验的受力状态就复杂得多,试样变形类型与大小则各向(轴向、径向)不同,The microstructure, grain size, harmful residual element content of the steel, especially any internal and surface defects that affect continuous deformation such as cracks, inclusions, etc., may affect and cause the test to fail。So in a sense, for assessing the quality of steel, it can be said that the process performance test is more stringent。
In addition, the reverse bending test of steel bars is essentially a strain aging sensitivity test. This is because the molten steel generally contains a certain amount of free nitrogen (N), also known as residual nitrogen. When the content is too high, the steel can be embrittlement at room temperature after plastic deformation。
由于钢筋常常需弯曲成型以后使用,已经产生了塑性变形,如果材性变脆,The structure will not be able to withstand the external load (such as an earthquake) that causes plastic deformation of the steel bar.,Therefore, the reverse bending test is included in the steel bar standard as an important technical requirement at home and abroad,同时对钢的氮含量予以限制(不超过0.012%)。
研究表明,用于钢的微合金化的一些元素如钒、钛、铌等,特别是钒与氮有较好的亲和力,钢中加入钒可有效结合自由氮,钒与氮的结合还能进一步增强钒对钢的强化效果,So some standards say, "Nitrogen levels can be higher if enough of the nitrogen binding element is present."。
Since the anchoring agent is made of high-strength material as aggregate, gelled material as binder, supplemented by high-flow micro-expansion anti-segregation and other substances, its composition is mainly inorganic materials, organic materials as auxiliary, no corrosion effect on steel bars。因此,能在几小时内产生一定的锚固力。It has the characteristics of fast setting, fast hardening, high strength, no shrinkage, high shear strength, low penetration resistance and so on。The construction method is applicable to all mine roadway, tunnel, water conservancy, slope support and other projects within 3m surrounding rock bolt support。
The mechanical properties of the steel bar are measured by test. The mechanical properties of the steel bar quality standard are yield point, tensile strength, elongation, cold bending performance and other indicators。
When the stress of the steel bar exceeds the yield point, the tension does not increase but the deformation increases significantly, which will produce a large residual deformation, the tension value of the steel bar unit area borne by the tension value divided by the cross-sectional area of the steel bar is the yield point σs°
Tensile strength is the tensile value obtained by dividing the maximum tensile value that can be borne by the steel bar before being pulled apart by the cross-sectional area of the steel bar, and the tensile strength is also known as the ultimate strength。It is the largest stress value in the stress-strain curve, although it has no direct significance in the strength calculation, but it is an essential guarantee item in the mechanical properties of the steel bar。因为:
(1) Tensile strength is the ultimate capacity of the steel bar to withstand static load, which can represent how much strength reserve the steel bar has after reaching the yield point, and is an important indicator of resistance to plastic damage。
(2) The steel bar has defects in the melting and rolling process, as well as the instability of the chemical composition of the steel bar, often reflected in the tensile strength, when the carbon content is too high, the temperature at the end of the rolling is too low, the tensile strength may be high;When the carbon content is small and the non-metallic inclusions in the steel are too much, the tensile strength is low。
(3) The level of tensile strength has a direct impact on the ability of reinforced concrete structures to resist repeated loads。
Elongation is the maximum strain value when the specimen is broken in the stress-strain curve, also known as elongation, which is an indicator to measure the plasticity of the steel bar, and the same as the tensile strength, is also an essential guarantee item in the mechanical properties of the steel bar。
Elongation is calculated as a percentage of the original length of the stretched portion of the steel bar when it breaks under tensile force。When the two sections of the specimen are broken together, the length of the standard distance section L1 after fracture can be measured, and the plastic deformation value can be obtained by subtracting the original length L0 of the standard distance. The ratio between this value and the original length is expressed by δ, that is, the larger the δ value of the elongation, the better the plasticity of the steel。The elongation is related to the standard distance. The standard distance of the hot-rolled steel bar is 10 times the diameter of the specimen as the measurement standard, and the elongation is expressed as δ10。For the steel wire, the length of the marking distance is 100mm as the standard of the most test, expressed by δ100。对于钢绞线则为δ200。
Cold bending performance refers to the resistance of steel bars to cracks when plastic deformation is produced by cold processing (i.e. processing at room temperature)。冷弯试验是测定钢筋在常温下承受弯曲变形能力的试验。The size of the stress should not be considered in the test, and the steel bar specimen with diameter d is bent to 180° or 90° around the bending center of diameter D (D specifies 1d, 3d, 4d, 5d)。Then check the steel bar sample for cracks, scale, fracture and other phenomena to identify whether its quality meets the requirements, cold bending test is a more stringent inspection, can reveal the internal organization of the steel bar uneven defects。
After bending 180 degrees according to the bending center diameter specified in the following table, the surface of the bending part of the steel bar shall not crack。牌号公称直径a
W (weight, kg) =F (area m2) ×L (length, m) ×ρ (density, g/cm3) ×1/1000
d= Section diameter mm, such as the section diameter of 12mm rebar, weight per meter =0.00617×144=0.888kg
1, steel bar engineering, should distinguish cast-in-place, prefabricated components, different steel types and specifications, respectively according to the design length multiplied by unit weight, calculated in tons。
2, when calculating the amount of steel reinforcement, the design has specified the length of the steel tower, according to the specified length of the tower;If the tower connection length is not specified in the design, it has been included in the loss rate of steel bars, and the tower connection length is not calculated separately。钢筋电渣压力焊接、套筒挤压等接头,以个计算。
3, the pre-tensioned prestressed steel bar, according to the dimensions of the component to calculate the length, the post-tensioned prestressed steel bar according to the design of the prestressed steel reserved hole length, and distinguish different anchorage types, respectively, according to the following provisions:
(1) When screw anchors are used at both ends of low alloy steel bars, the prestressed steel bars are reduced by 0 according to the reserved pore length.35m,螺杆另行计算。
(2) When one end of the low alloy steel bar uses the emblem insert and the other end of the screw anchor, the length of the prestressed steel bar is calculated according to the length of the reserved hole, and the screw is calculated separately。
(3) When one end of the low-alloy steel bar uses the emblem insert and the other end uses the rib anchor, the prestressed steel bar increases by 0.15m,两端采用帮条锚具时预应力钢筋共增加0.3m计算。
(4) When post-tensioned silicon self-anchoring is used for low-alloy steel bars, the length of prestressed steel bars is increased by 0.35m计算。
(5) When JM,XM,QM type anchorage channel length is less than 20m, the length of prestressed steel bar is increased by lm;When the length of the channel is more than 20m, the length of the prestressed steel bar is increased by 1.8m计算。
(6) The carbon steel wire is tapered anchor, and the length of the prestressed steel bar is increased by lm when the channel length is within 20m;When the channel length is more than 20m, the length of the prestressed steel bar is increased by 1.8m.
The thickness of the concrete protective layer of the stressed steel bar should meet the design requirements, and when the design has no specific requirements, it should not be less than the diameter of the stressed steel bar, and should meet the requirements of the following table:
(1) The thickness of the protective layer of the steel bar of light aggregate concrete should comply with the current national standard "Design Rules for Light Aggregate Concrete Structure"。
(2)处于室内正常环境由工厂生产的预制构件,当砼强度等级不低于C20且施工质量有可靠保证时,其保护层厚度可按表中规定减少5mm,However, the thickness of the protective layer of the prestressed reinforcement in the prefabricated member should not be less than 15mm;Prefabricated components in open or indoor environments with high humidity,When the surface is coated with cement mortar and there are reliable quality assurance measures, the protective layer thickness can be used according to the protective layer thickness value of the component in the normal indoor environment in the table。
(3) reinforced concrete flexural members, the thickness of the protective layer of the reinforcement end is generally 10mm;The thickness of the protective layer of the main rib of the prefabricated ribbed plate can be considered according to the beam。
(4) The thickness of the protective layer of steel bars distributed in the plate, wall and shell should not be less than 10mm;The protective layer thickness of stirrup and structural reinforcement in beams and columns should not be less than 15mm。
When the end of the grade I steel bar needs to be bent by 1800, 1350, 900, or hook, the arc bending diameter D should not be less than 2 of the diameter d of the steel bar.5 times, the length of the straight part should not be less than 3 times the diameter of the steel bar d;The inner diameter of HRRB335 and HRB400 steel bars should not be less than 4 times the diameter of the steel bar d, and the length of the straight part of the bend hook should meet the design requirements。
The bending Angle of the steel bar is generally 300, 450, 600 three kinds, and the bending added value refers to the difference between the diagonal length of the steel bar and the horizontal projection length。
箍筋的末端应作弯钩,弯钩形式应符合设计要求。When the design does not have specific requirements, the stirrup made of grade I steel or low carbon steel wire, the bending diameter of the bending hook D should not be greater than the diameter of the stressed steel bar, and not less than 2 of the diameter of the stirrup.5 times;The length of the straight part of the hook, of the general structure, should not be less than 5 times the diameter of the stirrup;The length of the straight part of the stirrup hook of the structural member with seismic requirements should not be less than 10 times the diameter of the stirrup。
The anchoring length of steel bars refers to the length of each other's steel bars at the intersection of various components。If the design drawing clearly stipulates, the anchorage length of the steel bar shall be calculated according to the drawing;When the design has no specific requirements, it is calculated according to the provisions of the "Code for the Design of Concrete Structures"。
The GB50010-2002 code stipulates: (1) the anchoring length of the tensile steel bar (2) the anchoring length of the steel bar of the ring beam and the structural column
When calculating the amount of reinforcement, it is also necessary to pay attention to the reinforcement not drawn and not clearly indicated in the design drawings, such as the additional distribution bars of the upper negative bending moment of the double reinforcement bars in the floor, the horse stool used to support the double reinforcement of the base plate in the construction of the reinforced concrete wall and the tension bars used in the construction。这些都应按规范要求计算,并入其钢筋用量中。
LAW series microcomputer controlled electro-hydraulic servo horizontal tensile testing machine adopts the frame integral steel plate welded frame structure,单出杆双作用活塞缸施加试验力,圆柱销插装试样,负荷传感器测力,根据试样规格长度可有级调整拉伸空间,计算机屏幕控制并显示试验力及试验曲线,按试验方法的要求自动处理试验数据,This machine is a special equipment for lifting belt, chain and rope products one by one tensile test,用于吊装带类产品的逐个拉伸负荷,破坏等试验,要求操作灵活方便,加载缓慢平稳,机体承载能力强等优点。
1 主机:
1.1 The whole frame adopts steel plate welding frame structure, and the main structure of the system is composed of front and rear chuck seat, oil cylinder and front beam;
1.3 The shape of the main machine is designed on the basis of meeting the technical requirements of the horizontal test equipment. The shape is simple and bright, the proportion is coordinated, and the color is reasonable, so that the stability, safety and beauty of the test equipment are unified。
2 油源系统(泵站):
2.1 A set of 10l/min,30MPa constant pressure pump set: the use of domestic well-known brand motor, imported low noise high pressure gear pump。
2.2 The motor is equipped with a vibration damping device (select a vibration damping pad) to reduce vibration and noise;
2.3 Oil tank: fully enclosed standard oil tank, volume 80 liters, equipped with oil temperature gauge, oil level gauge, precision pressure filter, air filter, etc., and with oil temperature, liquid level, oil resistance protection and indication device, according to the use of the oil circuit with the corresponding high-precision oil filter device。
2.4 With temperature limit, oil filter blockage, low liquid level automatic shutdown or alarm function;
2.5 Pipeline system: the hydraulic pipeline of the main cylinder loader and the chuck actuator is connected by high pressure hose。
3 控制系统:
3.1 Dual-channel control board all adopt digital circuit, the structure is consistent, improve the interchangeability of each channel;
3.2 Computer screen to complete the integrated data control display and test curve display functions;
3.3 数据存储功能完善,可进行历史数据再现与图形显示;



⑴ φ10@100/200(2) indicates that the stirrup is φ10, the spacing of the encrypted area is 100, and the spacing of the non-encrypted area is 200, all of which are double leg stirrup。
  ⑵ φ10@100/200(4) indicates that the stirrup is φ10, the spacing of the encrypted area is 100, and the spacing of the non-encrypted area is 200, all of which are the limbs。
  (3) φ8@200(2) indicates that the stirrup is φ8, the spacing is 200, and the double leg hoop。
  ⑷ φ8@100(4)/150(2) indicates that the stirrup is φ8, the spacing of the encrypted area is 100, and the band is four limbs, and the spacing of the non-encrypted area is 150, and the band is two limbs。
(1) 3Φ 22,3 Φ20 means that the upper steel bar is 3Φ22, the lower steel bar is 3Φ20。
  (2Φ 12,3 Φ18 indicates that the upper steel bar is 2φ12, the lower steel bar is 3Φ18。
  (4Φ 25,4 Φ25 indicates that the upper bar is 4Φ25, the lower bar is 4Φ25。
  (4) 3Φ25, 5Φ25 means that the upper steel bar is 3Φ25, the lower steel bar is 5φ 25。
  (1) 2Φ20 means two bars of Φ20, arranged through the length for double leg hoops。
  (2Φ22+ (4Φ12) means that 2Φ22 is the pass length, 4φ12 vertical ribs for six leg hoops。
  (3) 6Φ 254/2 indicates that the upper row of the upper steel bar is 4Φ25, and the lower row is 2Φ25。
  (4) 2Φ22+ 2Φ22 means that there is only one row of steel bars, two in the corner, two in the middle, evenly arranged。
⑴ G2φ12 表示梁两侧的构造钢筋,每侧一根φ12。
  ⑵ G4Φ14 表示梁两侧的构造钢筋,每侧两根Φ14。
  ⑶ N2Φ22 表示梁两侧的抗扭钢筋,每侧一根Φ22。
  ⑷ N4Φ18 表示梁两侧的抗扭钢筋,每侧两根Φ18。


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