Steel structure testing

1. General regulations

1.1 This chapter applies to the inspection of the quality or performance of steel structure and steel components.

1.2 The detection of steel structure can be divided into the performance of steel structural materials, joints, dimensions and deviations of components, deformation and damage, construction and painting, etc. If necessary, physical load test or structural dynamics of structure or component performance can be performed test

2. Materials

2.1 The mechanical properties of structural steel members can be divided into yield point, tensile strength, elongation, cold bending and impact force.

2.2 When the project still has the same batch of steel as the structure, it can be processed into test pieces to test the mechanical properties of the steel; when the project does not have the same batch of steel as the structure, the sample can be taken on the component, but the structure should be ensured. The safety of the components. The sampling quantity, sampling method, test method and evaluation standard of steel mechanical property test specimens shall comply with the following table.

Material mechanical property test items and methods

2.3 When the yield point or tensile strength of the tested steel does not meet the requirements, the sample shall be supplemented for tensile test. In the supplementary test, the steel of the same specification and the same specification shall be classified into one batch, and each batch shall be sampled by three.

2.4 The analysis of the chemical composition of steel can be carried out by component analysis or principal component analysis as needed. Analysis of chemical composition of steel A sample of each batch of steel may be taken. Sampling and testing shall be carried out according to the "Sampling method for chemical analysis of steel and the allowable deviation of chemical composition of finished products" GB 222 and "Chemical analysis method for steel and alloys" GB 223 And should be assessed according to the corresponding product standards.

2.5 The tensile strength of existing steel structural steel can be detected by the method of surface hardness. When using the surface hardness method to detect the tensile strength of steel structural steel, it should be verified by sampling and testing the tensile strength of the steel.

2.6 Corroded steel or the mechanical properties of the steel affected by fire, etc., can be tested by sampling method; the test operation and evaluation of the sample can be carried out according to the provisions of the corresponding steel product standards, and the application of the test results should be clearly stated in the test repor.

3. Connection

3.1 The connection quality and performance of the steel structure can be divided into welding connection, welding nail (stud) connection, bolt connection, high-strength bolt connection and other items.

3.2 For the quality of the first and second welds that require full penetration and the strength of the welds, such as steel, which are not required in design, the quality of the welds shall be tested by ultrasonic flaw detection. The test shall meet the following requirements:

3.2.1 For the quality of steel structure engineering, it shall be tested in accordance with the provisions of GB50205 "Code for Construction Quality Acceptance of Steel Structure Engineering";

3.2.2 For the performance of existing steel structures, sampling ultrasonic testing may be adopted;

3.2.3 The classification of weld defects shall be determined in accordance with the "Method for Manual Ultrasonic Testing of Steel Welds and Quality Grading Method" GB11345;

3.3 All welds of steel structure engineering shall be visually inspected; for the inspection of existing steel structures, the method of sampling and testing the appearance quality of welds may be adopted, or the method of spot check according to the scope specified by the client may be adopted. The method for measuring the dimensions and appearance defects of welds and the evaluation criteria shall be determined in accordance with the Code for Construction Quality Acceptance of Steel Structure Engineering GB50205.

3.4 The mechanical properties of the welded joints may be checked by means of intercepting the specimens, but measures shall be taken to ensure safety. The test of mechanical properties of welded joints is divided into stretching, face bending and back bending, and each test item can take two samples. Sampling and inspection methods for welded joints shall be determined in accordance with "Sampling Method for Mechanical Properties of Welded Joints" GB 2649, "Standard Test Method for Welded Joints" GB 2651 and "Test Methods for Bending and Flattening of Welded Joints" GB 2653. The weld joint weld strength shall not be less than the minimum guaranteed value of the base metal strength.

3.5 When testing the quality of steel structure engineering, the bending test after welding of the welding nail can be sampled; the testing method and evaluation standard, hammering the welding head to bend it to 30°, the weld and heat affected zone are not visible to the naked eye. The crack can be judged as qualified.

3.6 Material properties and torque coefficient of high-strength large hexagon bolt connection pairs, inspection methods and inspection rules shall be in accordance with "Technical conditions for high-strength large hexagon bolts, large hexagon nuts and washers for steel structures" GB/T 1231, "Steel structure JGJ 82 is determined by the G50205 and the Code for Design, Construction and Acceptance of High-strength Bolt Connections for Steel Structures.

3.7 Inspection of material properties and pre-tension of torsion-shear type high-strength bolting joints, inspection methods and inspection rules shall be in accordance with "Technical conditions for torsion-shearing high-strength bolts for steel structures" GB/T 3633 and "Steel structure construction" The quality acceptance specification is determined by GB50205.

3.8 For the quality of the torsion-shear high-strength bolt connection, check whether the plum head at the end of the bolt has been screwed off. Except for the structural reasons, the bolt of the plum head cannot be unscrewed in the final screw. The number should not be greater than 5% of the number of bolts in the node.

3.9 For the inspection of high-strength bolt connection quality, the exposed thread buckle can be inspected, and the thread buckle should be exposed to 2 to 3 buckles. Allow 10% of the bolt thread to expose 1 button or 4 button.

4. Size and deviation

4.1 The inspection of steel component dimensions shall comply with the following requirements:

4.1.1 The number of sampling inspection components can be determined according to the specific circumstances, but should not be less than the minimum sample capacity of the corresponding corresponding detection category;

4.1.2 The scope of the dimension inspection shall be to detect the full dimensions of the sampled components. Each dimension is measured at three parts of the component, and the average of the three test values is taken as the representative value of the dimension;

4.1.3 The method of measuring the size can be measured according to the provisions of the relevant product standards, wherein the thickness of the steel can be measured by an ultrasonic thickness gauge;

4.1.4 The evaluation index of component dimensional deviation shall be determined according to the corresponding product standard;

4.1.5 For the important dimensions and general dimensions of the test batch components, the test shall be qualified according to the standard.

4.1.6 In special parts or special cases, the parts that have a great influence on the safety of the components or the parts that are representative of the damage should be selected for testing.

4.2 Dimensional deviation of steel members shall be calculated based on the dimensions specified in the design drawings; the allowable value of deviation shall be determined in accordance with GB50205 "Code for Acceptance of Construction Quality of Steel Structure Engineering".

4.3 The testing items and testing methods for the installation deviation of steel components shall be determined in accordance with the Code for Construction Quality Acceptance of Steel Structure Engineering GB 50205.

5. Defects, damage and deformation

5.1 The inspection of the appearance quality of steel can be divided into uniformity, whether there are interlayers, cracks, non-metallic inclusions and obvious segregation. When there is doubt about the quality of steel, mechanical properties or chemical composition analysis of steel raw materials should be carried out.

5.2 The detection of steel structure damage can be divided into cracks, local deformation, corrosion and other items.

5.3 Steel cracks can be detected by observation and penetration. When using the infiltration method, the grinding wheel and sandpaper shall be used to polish the surface of the inspection part and the surrounding area within 20 mm. There shall be no oxide scale, welding slag, splash, dirt, etc.; the surface of the polishing surface is cleaned with a cleaning agent, and the surface is sprayed after drying. Agent, the infiltration time should not be less than 10min; then use the cleaning agent to remove the excess penetrant on the surface; finally spray the indicator, stay for 10min~30min, observe whether there is crack display.

5.4 Deformation of the bending deformation of the member and the unevenness of the plate can be detected by the method of observation and measurement, and the degree of deformation can be measured. The deformation evaluation should be carried out according to the current "Code for the Acceptance of Construction Quality of Steel Structure Engineering" GB50205.

5.5 Loose or broken bolts and rivets can be detected by observation or hammering.

5.6 Corrosion of structural members may be determined according to the corrosion degree and rust removal grade of steel surface before painting. GB 8923 determines the corrosion grade. For grade D corrosion, the thickness of the steel plate shall be measured.

6. Construction

6.1 The detection and calculation of the slenderness ratio of steel structural members can be measured according to the provisions of Chapter 4 of this Chapter. The slenderness ratio of the members should be calculated according to the actual size.

6.2 The connection of the steel structure support system may be tested in accordance with the provisions of Chapter 3 of this Chapter; the dimensions of the support system components may be determined in accordance with the provisions of Chapter 4; they shall be verified or assessed according to the design drawings or the corresponding design specifications.

6.3 The width-to-thickness ratio of the cross-section of steel structural members may be measured and calculated according to the provisions of Chapter 4, and shall be assessed according to the design drawings and relevant specifications.

7. Painting

7.1 The quality of steel structure protective coatings shall be tested in accordance with the relevant national product standards for coating quality.

7.2 The descaling grade of the steel surface can be determined by the comparison of the pictures of the current national standard "Corrosion grade and derusting grade of steel surface before painting" GB8923.

7.3 The coating thickness of different types of coatings shall be tested by the following methods:

7.3.1 The thickness of the paint film can be detected by the paint film thickness gauge. The number of sampled components should not be less than the minimum capacity of the standard test sample, and should not be less than 3 pieces; 5 pieces per piece, the value of each place is 3 The average of the dry film thickness of the measuring points at 50 mm apart.

7.3.2 For the coating thickness of thin fire-retardant coatings, the coating thickness tester may be used for testing. The measurement method shall comply with the provisions of CECS24 for the Technical Specifications for Application of Fire-retardant Coatings for Steel Structures.

7.3.3 For the thickness of thick fire-retardant coatings, the stylus and steel ruler shall be used for testing. The measuring method shall comply with the provisions of CECS24 for the Technical Specifications for Application of Fire-retardant Coatings for Steel Structures.

The thickness value and deviation value of the coating shall be assessed in accordance with the provisions of GB50205 for the Acceptance of Construction Quality of Steel Structure Engineering.

7.4 The appearance quality of the coating may be tested and evaluated according to the provisions of GB50205 of the "Quality Acceptance Specification for Steel Structure Engineering" according to different materials.

8. Steel grid

8.1 The detection of steel grid can be divided into the bearing capacity of the joint, the weld, the size and deviation, the unevenness of the rod and the deflection of the steel grid.

8.2 The test of the bearing capacity of the welded ball joints and bolt ball joints of the steel grid shall be carried out in accordance with the requirements of JGJ78 of the "Quality Inspection and Evaluation Standard for Grid Structure Engineering". For the existing bolt ball node grid, the node can be taken out from the structure to test the ultimate bearing capacity of the node. When intercepting the bolt ball node, measures should be taken to ensure the structure is safe.

8.3 Welds in steel grids may be tested by ultrasonic flaw detection. The inspection operation and assessment shall be in accordance with JG/T3034.1 or "bolt ball joint steel mesh" of "welding ball joint steel grid weld seam ultrasonic flaw detection and quality classification method" Ultrasonic flaw detection and quality classification method for frame welds are carried out according to the requirements of JG/T3034.2.

8.4 The appearance quality of welds in steel grids shall be tested in accordance with the requirements of GB50205 for the Acceptance of Construction Quality of Steel Structures.

8.5 Welding ball, bolt ball, high-strength bolt and rod deviation detection, detection method and deviation allowable value shall be carried out in accordance with the provisions of JGJ78 of "Grid Structure Engineering Quality Inspection and Evaluation Standard".

8.6 The wall thickness of steel mesh steel pipe members can be detected by ultrasonic thickness gauge. The finish layer should be removed before testing.

8.7 The unevenness of the axis of the rod in the steel grid frame can be detected by the method of pulling wire, and the unevenness should not exceed one thousandth of the length of the rod.

8.8 The deflection of the steel grid can be detected by laser range finder or level gauge. The number of points in each half span should not be less than 3, and there should be 1 measuring point in the span. The end measuring point should not be larger than the end bearing 1m.