How to inspect cold rolled ribbed steel bars 15

On-site re-inspection content: tensile strength, elongation, bending test, repeated bending.

The prestressed steel bars of CRB650 grade and above shall be formed into a disc**, and the rebar of the rebar shall be composed of one per disc and shall not have welded joints.

CRB550 grade steel bars should be bundled into straight strips**, and can also be formed into plates**; The length of the rebar in the bundle can be determined according to the needs of the project.

The cold-rolled ribbed steel bars entering the factory (field) should be according to the steel number. Level. The specifications are stacked and used separately, and should be clearly marked, and should not be stored outdoors for a long time.

The cold-rolled ribbed steel bars entering the factory (field) shall be inspected and accepted according to the following provisions:

1. The reinforcement should be accepted in batches. Each batch should be made by the same manufacturer. Same specification. The composition of steel bars rolled by the same raw material ** and the same production process is not more than 60t per batch. Each batch of steel bars should have a factory quality certificate, and each reel or bundle should have a sign.

2 5% of each batch (but not less than 5 trays or 5 bundles) is inspected for external dimensions, surface quality and weight deviation. The results of the examination should meet the requirements; When one of the reels or bundles is unqualified, the batch of steel bars should be inspected one by one or bundle.

3. The tensile strength and elongation of the steel bars of the strength level 650 and above should be tested one by one, and a sample should be taken after cutting off 500mm from either end of each plate for tensile test. When the inspection results do not meet the requirements of the table in Appendix B of this regulation, the disc steel bar is judged to be unqualified. Repeated bending performance is tested by batch sampling, and two samples are taken from each batch, and if one sample does not meet the requirements, the test results should be carried out one by one.

If the test result does not meet the requirements of the sample, the disc steel bar is judged to be unqualified.

4. The mechanical properties and process properties of the 550-grade steel bars in bundles should be sampled and inspected in batches. In accordance with the provisions of paragraph 1 of this article, the steel bar shall not be more than 10t as a batch, and two samples shall be randomly selected from each batch of steel bars, one for tensile test and one for bending test. When one of the indicators of the inspection results does not meet the requirements, double the number of samples should be taken from the batch of steel bars for re-inspection; If there is still a sample that is unqualified in the re-inspection, the batch of steel bars should be judged to be unqualified.

1. Tensile test.

a) Specimens in tensile and flexure tests are not allowed to be turned.

b) The tensile test should be carried out in accordance with GB T228, and the nominal cross-sectional area should be used to calculate the strength of the reinforcement.

c) For the determination of the total elongation of the larger force, in addition to the relevant test methods of GB T228 according to the regulations. The method of Appendix A could also be used.

2. Stress relaxation test.

a) During the test, the temperature of the sample should be kept at 20 2.

b) The specimen can be mechanically straightened, but shall not be subjected to any heat treatment and other cold work.

c) The initial test force added to the specimen is 70 of the nominal tensile strength of the specimen multiplied by the nominal cross-sectional area of the specimen.

d) The loading speed is 200MPa min 50MPa min, the initial load should be completed in 3min 5min, and the relaxation value should be recorded after 2min of loading.

e) The length of the specimen shall not be less than 60 times the nominal diameter.

f) It is allowed to extrapolate the relaxation rate value of 1000h from at least 120h of test data.

3. Dimensional measurement.

a) The height of the transverse rib is measured by measuring the height of each column of the same cross-section, taking its average value; The spacing between the ribs is measured when the average spacing is used. That is, the distance between the same column and 1 rib is measured by 10, and the average distance between the ribs is measured.

b) The accuracy of dimensional measurement should be accurate.

Fourth, the measurement of weight deviation.

a) When measuring the weight deviation of the steel bar, the length of the sample should not be less than 500mm, the length measurement should be accurate to 1mm, and the weight measurement should be accurate to 1g.

b) The weight deviation (%) of the reinforcement is calculated according to equation (1):

Actual total weight of the specimen - (total length of the specimen, theoretical weight).

The main test items include: stress relaxation performance of steel bar, standard size of steel bar, weight deviation, surface quality.

CRB650 and above grade prestressed steel bars should be made into a plate, and each plate of steel bars should be composed of one and there should be no welded joints. CRB550 grade steel bars should be bundled into straight strips**, and can also be formed into plates**; Bundles of steel.

Summary. Hello dear, happy to answer for you. Look at the product quality certificate presented by the steel manufacturer, and check in detail whether there is a corresponding tag on each bundle of steel bar materials.

Then take a detailed look at the appearance of the rebar material to see if it is straight and whether there is any damage. And check in detail whether the surface of the steel bar material is cracked, oily, granular, and rusty in some places.

How to fill in the hot-rolled steel bar detection basis.

Hello dear, happy to answer for you. Rebar raw material inspection or sock remaining: with a list of materials, a factory certificate and the original manufacturer's test report, and a re-inspection report of the testing center.

Hot-rolled ribbed steel bars for reinforced concrete" (GB 1499-1998), concrete structure engineering construction quality acceptance specification (GB50204-2011 revised edition).

Hello dear, very high leather to answer for you. Look at the product quality certificate presented by the steel manufacturer, and check in detail whether there is a corresponding tag on each bundle of steel bar materials. Then take a detailed look at the appearance of the rebar material to see if it is straight and whether there is any damage.

And check in detail whether the surface of the steel bar is burned to see if there are cracks, oil stains, granularity, and rust in some places.

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1. Hot drawn disc rods and hot drawn straight strips are directly measured with vernier calipers, and direct readings can be done.

2. When the hot tie ribbed steel bar is measured with vernier caliper, one end of the caliper should be stuck on the rib and one end should be stuck on the smooth surface under the rib.

If both ends are stuck in the ribs or on the smooth surface under the ribs, it is not right.

The common name of hot-rolled ribbed steel bar is rebar, which is divided into three grades: HRB335 (the old brand is 20MNSI), HRB400 (the old brand is 20MNSIV, 20MNSB, 20MNTTI), and HRB500, which are widely used in the construction of civil engineering such as houses, bridges, and roads.

Use the factory nominal diameter. If you want an actual value, you can use a vernier caliper to measure it.

Typically, the tool used to measure the diameter is a vernier caliper.

The user only needs to use the two measuring jaws of the vernier caliper to clamp the ribbed side of the ribbed steel bar and the non-ribbed (smooth round side) respectively, and the value that appears at this time is the diameter of the cold-rolled ribbed steel bar.

Matters that should be paid attention to when using vernier calipers to measure the cold width of the rolled ribbed steel bar:

1. The two measuring claws of the vernier caliper must always be in a vertical state when they are stuck on two different measuring surfaces of the ribbed steel bar;

2. When measuring, the fastening screws should be tightened first, and the moving vernier should not be too forceful. The contact between the two claws and the object to be measured should not be too tight. Do not make the clamped object move in the mega claw.

3. When reading, the line of sight should be perpendicular to the ruler surface. If the reading needs to be fixed, the vernier can be fixed to the ruler body with a fastening screw to prevent sliding.

Dimensions, shape, weight and allowable deviations.

There are two standards for hot-rolled steel bars: "Steel for Reinforced Concrete Part 1 - Hot Rolled Round Steel Bars (GB" and "Steel for Reinforced Concrete Part 2 - Hot Rolled Ribbed Steel Bars (GB) Which inspection is of course subject to the two standards. Inspection Regulations:

Dimensions, shape, weight and allowable deviations. Provisions of technical requirements: provisions on chemical formation analysis, mechanical properties and process performance test methods of steel bars.

Cold-rolled ribbed steel bars (GBL3788-1992).

1) Size specifications.

Three-sided ribbed reinforcement.

a-transverse rib bevel angle - the angle between the transverse rib and the axis a-transverse rib height.

b-cross rib top width, c-cross rib spacing.

Ribbed reinforcement on both sides.

a-transverse rib bevel angle a-cross rib and axis angle, a-transverse rib height.

b, the width of the top of the transverse rib, c, the spacing of the transverse ribs, d, the inner diameter of the reinforcement.

Dimensions and specifications of three-sided ribbed reinforcement.

Nominal diameter mm Nominal cross-sectional area mm Theoretical mass (kg m) Rib midpoint height rib 1 4 height na mm rib top width b mm rib distance relative rib area r

a Allowable deviation c mm Allowable deviation ( ).

mm(4) +15

2.The angle between the rib and the reinforcement shaft is 40°-60°. The bevel angle between the two sides of the rib and the surface of the reinforcement is greater than or equal to 45°. The sum of the intercostal spaces should not be greater than 20 of the nominal circumference.

3.The allowable deviation of the theoretical mass is not greater than 4.

Dimensions and specifications of the ribbed reinforcement on both sides.

Nominal diameter mm Inner diameter d rrnn Nominal cross-sectional area mm Theoretical mass (kg m) Rib midpoint height rib 1 4 height mm rib top width b mm rib distance relative rib area r

Standard Size Allowable Deviation A Allowable Deviation C Allowable Deviation

mm5 ± 15

891012 Note: 1The allowable deviation of the theoretical mass is not greater than 4.

2.Longitudinal ribs with a height of no greater than are allowed.

What is the permissible deviation of the diameter of the rebar? Are you talking about the deviation of the rebar when it leaves the factory or the deviation when the rebar is lashed?

"Code for Acceptance of Construction Quality of Concrete Structure Engineering" GB 50204-2002 (2011 Edition) Article: When the steel bar enters the site, the specimen should be extracted for mechanical properties and weight deviation inspection in accordance with the provisions of the current national standards, and the inspection results must comply with the provisions of the relevant standards. The weight deviation index of cold-rolled ribbed steel bars is 4% in the GB13788-2008 standard of cold-rolled ribbed steel bars.