Quality control in space frame construction

The bolt ball space frame is composed of bolt balls, bolts, steel pipe sleeves, pins, a conical head or sealing plate, and other components. The steel pipe rod and bolt ball are connected by high-strength bolts to form a spatial network structure. The structural load is borne by high-strength bolts and bolt balls. The quality problem of any component will endanger the whole safety of the structure. Below is how to control the quality of various components to make further elaboration.

(1) The quality of the components. It is the most important link to ensure the quality of space frame structure engineering to strictly check the quality of components and eliminate unqualified components before assembling the space frame structure. Check the factory qualification certificate of network frame components when entering the site, check whether the variety, model, specification, and size meet the design requirements, make acceptance records when entering the site, and conduct sampling tests on bolt balls, high-strength bolts, and rods according to the specifications.

(2) Strictly control the quality of the bolt ball. Bolt-ball is the most important component in the whole space frame structure. It plays the role of a stress node in the whole space frame. Its unqualified quality will cause serious harm to the safety of the whole space frame. During the appearance quality inspection of bolt balls entering the field, attention should be paid to the problem of over-burning crack and thread tolerance matching accuracy. When cracks and over-burning defects are found, sorting and inspection should be carried out one by one to remove the bolt balls with defects. Performance test of bolt balls shall be conducted according to different specifications of each batch of 5%, not less than 5 for testing, strictly prohibiting the use of unqualified bolt balls. Where the test found cracks and other hazardous defects, it is recommended to return the whole batch of goods or scrap processing. Because the bolt ball cracks and other defects are generally caused by forging, it not only exists on the surface of the ball, the inner surface of the ball often also exists cracks and other hidden residuals, with the long-term use of the space frame, cracks will gradually expand, and eventually lead to the failure of the bolt ball.

(3) Do a good job of sampling inspection of high-strength bolts. Appearance quality inspection and tensile ultimate bearing capacity test should be carried out for high-strength bolts when entering the site. Batch sampling test for the tensile ultimate bearing capacity test of high-strength bolts should be conducted according to regulations, with 5% of each batch and not less than 5 bolts. Quenching micro-cracks are not allowed in the test, especially transverse cracks, which are the most harmful. The test data show that the quenching crack rate of the high-strength bolt is more than 30%. Therefore, the test found cracks, it is recommended that the whole batch of returns or scrap processing, in order to eliminate hidden dangers. High strength bolt is mainly to the improper heat treatment process of crack, crack not only exists on the surface, it is present in the bolt at the same time surface, with batch sexual problems, and bolt factory is connected to the bar together commonly, set within the bar cone head, the scene not to bolt crack of roots for effective detection, especially after assembling, bolt in completely hidden, It is impossible to reinspect and find problems.

(4) Quality control of rods. The appearance quality inspection should be carried out when the rod enters the site, and the tension test should be carried out on the welding seam of the cone head and steel pipe according to the provisions. The test results should meet the corresponding national standards and design requirements of the specimen steel tube material. Relevant tests show that the quality of the weld is intact, and the rod is prone to crack in the temperature-affected zone of the weld under load. When there are welding process defects in the welding seam and the cross-sectional area of force is reduced to a certain extent, tensile fracture occurs at the welding seam, such as incomplete welding and crack. Therefore, rod inspection and test can not be ignored. It must be used after all the test results meet the requirements.