1. Theme content and scope of application
This technical requirement specifies the technical requirements during the manufacturing, installation and inspection process of high-strength bolted secondary connectors of steel structures for mobile machinery and equipment. Contents not specified in this technical requirement shall be implemented in accordance with relevant national standards.
This technical requirement applies to mobile mechanical steel structures that require high-strength bolt connections. This technical requirement applies to quality control and construction methods both within the manufacturing plant and during on-site installation.
2. Joint surface treatment
2.1 Friction-type high-strength bolt connections require that the joint surfaces at the joints are in close contact and have sufficient friction coefficients. When the design drawing does not stipulate the processing requirements for the joint surface, the processing shall be carried out according to the following provisions: Sandblast or shot blast the high-strength bolt joint surface to remove rust, oil and other impurities on the surface to meet the Sa2.5 level standard , the roughness is 50~75um, and its friction coefficient shall not be less than 0.40. If there are provisions in the drawings, the provisions in the drawings shall be followed.
2.2 Protective measures should be taken to prevent the friction surface of the treated high-strength bolt connection from being contaminated with dirt and oil. It is strictly prohibited to make any marks on the friction surfaces of high-strength bolt connections. Special care must be taken to prevent contamination of the connecting surfaces during storage in the factory, transportation, and storage at the installation site. The installation unit should pay special attention to protecting the cleanliness and friction surface characteristics of the connecting plate and mother body of the high-strength bolts. It is not allowed to use a grinder to grind the connecting surface of the connecting plate and the connecting surface of the mother body.
3. Inspection of anti-slip coefficient of friction surface of high-strength bolts
The anti-slip coefficient inspection should be based on the steel structure manufacturing batch. Every 2000t of a single project is regarded as a manufacturing batch, and any less than 2000t is regarded as a batch. When the friction surface of the component of a single project uses two or more surface treatment processes, Each surface treatment process needs to be inspected. There are three groups of test specimens in each batch. If the connection is spread to external enterprises, each enterprise should conduct an anti-slip coefficient test.
3.1 The test piece used for the anti-slip coefficient test should be processed in the factory or by a diffusion enterprise. The test piece and the steel structural component it represents should be of the same material, made in the same batch, use the same friction surface treatment process and have the same surface condition. And use high-strength bolt connection pairs of the same batch and performance level and store them under the same environmental conditions. The anti-slip coefficient test was carried out according to the test method of GB50205 "Construction Quality Acceptance Code for Steel Structure Engineering".
3.2 The minimum value of the anti-slip coefficient test must be equal to or greater than the design specified value. When the above specified values are not met, the friction surface of the component should be reprocessed. The friction surface of the treated component is re-inspected.
4. Connection and installation of friction-type high-strength bolts for steel structures
4.1 Preparations before installation
4.2 Select qualified bolts, nuts and washers. The guarantee period of the torque coefficient of its connecting pair is six months from the date of shipment.
4.3 Bolts, nuts, and washers with the following conditions are considered unqualified and are prohibited from use.
a. The source (manufacturer) is unknown;
b. Those whose mechanical properties are unknown;
c. The torque coefficient k is unknown;
d. Those with cracks, scratches, burrs, bends, rust, thread wear, oil stains, being wetted by water, or defects;
e. There is no performance test report attached;
f. Mixed with other batch numbers of bolts;
g. Bolts that are not long enough, that is, the bolt head does not expose the end face of the nut after tightening. Generally, the length extending out of the end face of the nut is 2 to 3 threads.
h. The torque coefficient of the connecting pair exceeds the warranty period.
Pay special attention to waterproofing during transportation and storage.
4.4 Before the construction of large hexagonal head high-strength bolts, the torque coefficient of the high-strength bolt connection pair should be re-inspected according to the factory approval. Each batch of 8 sets should be re-inspected. The average torque coefficient of the 8 sets should be within the range of 0.110 to 0.150, and its standard deviation should be Less than or equal to 0.010. The re-inspection method of the torque coefficient is carried out in accordance with the provisions of GB50205 "Code for Acceptance of Construction Quality of Steel Structure Engineering". High-strength bolts should be installed within a short period of time after the test.
