Separate combination of bolt and butterfly valve nut is not allowed
2. For door type seismic support, if double-sided splicing of C-shaped channel steel is required due to stress calculation, in order to ensure the overall stress performance of double-sided channel steel, it is required that the splicing process should adopt back hole punching connection or integrated laser welding process, instead of discontinuous spot welding connection. 3. For electromechanical seismic support, The inner edge of the curling edge of C-shaped channel steel needs to be provided with heat treatment teeth with a depth of not less than 0.9mm. At the same time, the matching connecting fasteners should also be provided with dents of the same depth, so as to ensure that the connection can achieve ductile failure when the occluding connection mode encounters a large horizontal load