The mechanical properties of steel bars are measured by experiments. The mechanical properties of steel bars are measured by yield point, tensile strength, elongation and cold bending performance. Then, the following is the analysis of the key points of quality supervision and control of reinforced engineering that I have compiled for you. Welcome to read and browse.

1. Quality control and acceptance of raw materials

1) When the reinforcement comes into the site, the on-site civil supervision engineer shall require the construction unit to provide the ex-factory certificate and test report of the reinforcement. Pay attention to each bundle of steel bars with iron plate, and also pay attention to whether the number on the factory certificate and test report is greater than the number of entry, otherwise it should not enter the site, and should be accepted and piled up in batches. 2) Check the appearance quality of steel bars. Steel bars shall be straight and undamaged, and the surface shall be free of cracks, oil stains, granular or flaky old rust. 3) After steel bars enter the site, a batch shall be selected according to the same brand, the same heat number and the same specification, and the weight of each batch shall generally not exceed 60 tons ... Random sampling shall be conducted under the witness of qualified supervisors. Two bending tests and two tensile tests should be done for each batch of steel bars. For the part exceeding 60 tons, 1 bending sample and 1 tensile sample will be added for each additional 40 tons (or the remaining part less than 40 tons). Only after the test results are qualified can they be used in engineering; For the unqualified steel bars, the construction unit shall be immediately notified to evacuate the site.

2. Control of steel processing

1) the end of hpb235 steel bar should be 180? The inner diameter of the hook should not be less than 2.5 times the diameter of the steel bar, and the length of the straight part of the hook should not be less than 3 times the diameter of the steel bar. 2) When the design requires the terminal to be 135? When the hook is bent, the bending inner diameter of HRB335 and HRB400 steel bars should not be less than 4 times the diameter of steel bars, and the length of the straight part after the hook is bent should meet the design requirements. 3) The reinforcement shall not be greater than 90? When bending, the inner diameter of the bending arc at the bend should not be less than 5 times the diameter of the steel bar. 4) In addition to welding closed-loop stirrups, the ends of stirrups should be hooked, and the hook form should meet the design requirements. When the design has no requirements, it shall comply with relevant regulations.

3. Control of steel bar connection

3. 1 steel welding process control

1) sample guide. Before the formal welding of the welding project, the welders involved in the welding shall conduct trial welding under field conditions, and only after passing the test can they be formally produced as welding samples. The test results shall meet the requirements of quality inspection and acceptance. 2) Attention should be paid when welding the indwelling position of the joint: a. The joint of the steel bar should be set in a place with less stress. It is not advisable to set two or more joints for the same longitudinal reinforcement. The distance from the end of the joint to the bending starting point of the steel bar should not be less than 10 times the diameter of the steel bar. The joints in the same component should be staggered. In the same connection section, the percentage of joint area of longitudinal reinforced bar should meet the design requirements; When the design has no specific requirements, it shall comply with relevant regulations.

3.2 Control of welding operation

1) arc welding, attention should be paid to: a. According to the brand, diameter, joint form and welding position of steel bar, correctly select covered electrode, welding technology and welding parameters, especially the selection of covered electrode; B. During welding, the main reinforcement shall not be burned; C welding ground wire should be in close contact with steel bar; D, selecting welding current according to the diameter of steel bar and covered electrode; E. check whether the lap length and batten length meet the specification requirements; F. Check whether the length and height of the weld meet the design requirements; G. When welding, the welding slag shall be removed in time, the surface of the weld shall be smooth, the residual height of the weld shall be smooth and the arc pit shall be filled; H. Check whether the weldment has defects such as slag inclusion and bubbles; A, lap welding, surfacing welding, seam welding joint in addition to the appearance quality inspection, also need to take samples for tensile test; J. If you have doubts about the welding quality or find abnormal conditions, you can also carry out nondestructive testing methods (X-ray, X-ray, X-ray, X-ray). X-ray, ultrasonic inspection, etc. ) check. 2) Electroslag pressure welding, attention should be paid to: a. Electroslag pressure welding is only applicable to the connection of vertical or diagonal steel bars with a diameter of 14 mm~40 mm in cast-in-place concrete structures, and it shall not be used as horizontal steel bars in beams, plates and other components after vertical welding. This may be due to the fact that after electroslag pressure welding of columns or shear walls in some parts, the steel bars need to be replaced due to design changes, and the field workers will use the welded steel bars as beams and slabs. The supervision engineer should pay special attention to this situation, which is not allowed to be used in the project; B, selecting an ordinary AC welding machine, selecting the welding machine capacity according to the diameter of the welded steel bar, and adjusting the current; C. The welding parameters of electroslag pressure welding are controlled current, welding voltage and electrifying time, which should be selected according to the diameter of steel bar, which is the key to successful welding; D. During welding, the axes of upper and lower steel bars should be consistent as far as possible, with the maximum deviation not exceeding 0. 1d(d is the diameter of steel bars) and not exceeding 2mm；; E. Check that the height of the welding ladle protruding from the surface of surrounding steel bars shall not be less than 4 mm, or rework; F. supervise the welder to conduct self-inspection during the welding process. When welding defects such as eccentricity, bending and burn are found, find out the reasons and take timely measures to eliminate them; G. The appearance quality of the joint should also be checked, and the tensile test of the sample should be carried out according to the method specified in the specification.

3.3 Welding inspection

In the process of welding, if the welding performance is found to be poor, the supervision engineer should pay special attention to it, and ask for chemical composition inspection or other special inspection of this batch of steel bars.

3.4 steel binding lap connection mode

Joints shall be implemented according to the current national standards GB 50204 Code for Acceptance of Construction Quality of Concrete Structures and GB 500 10 Code for Design of Concrete Members, in which it should be noted that: 1) The binding lap joints of adjacent longitudinal reinforcement in the same member shall be staggered. The transverse clear distance of the rebar in the binding lap joint should not be less than the rebar diameter and not less than 25 mm. 2) The length of the connection section of the rebar binding lap joint is 1.2L 1(L 1 is the lap length). In the same connection section, the area percentage of lap joint of longitudinal tensile reinforcement should meet the design requirements; When the design has no specific requirements, it shall comply with relevant regulations. 3) Within the overlapping length of longitudinal reinforcement of beam and column members, stirrups shall be set according to the design requirements. When the design has no specific requirements, it shall comply with relevant regulations.

4. Control of steel bar installation

1) According to the design drawings, check the variety, grade, specification, quantity and length of reinforcement must meet the design requirements, and pay special attention to the position of negative reinforcement. If Ф 22 misuses Ф 20, the length of the main reinforcement of the balcony cantilever beam into the beam does not meet the specification requirements, and the reinforcement leakage device is constructed in the higher beam, with the negative reinforcement on the beam support less than L/3 and the second row less than L/4; 2) When the variety, grade or specification of steel bars need to be changed, design change documents shall be handled; 3) Check whether the joint position, lap length and anchorage length of steel bar meet the specified requirements, and construct it in strict accordance with the atlas specified in the design; 4) Check whether the concrete protective layer meets the requirements. If the thickness of the protective layer of steel bars does not meet the requirements, it may affect the bearing capacity and durability of structural members; 5) Check whether the steel binding is firm, and whether there is looseness or deformation; 6) Oil stain, paint stain and granular (flaky) rust are not allowed on the steel bar surface; 7) The allowable deviation of steel bar installation should not be greater than the specification requirements.

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