(1) High strength bolt connection

1) The bolt equipment surface does not meet the requirements, resulting in poor bolt installation, or the degree of bolt tightening does not meet the design requirements.

Analysis of the reasons:

① There are floating rust, oil and other impurities on the surface, burr and weld bead on the wall of bolt hole.

② The bolt mounting surface is still defective after treatment.

resolvent:

① The surface of high-strength bolts shall be cleaned one by one for rust, oil and bolt hole wall defects. Before use, it must be antirust treated, so that the bolts for assembly can not be used in formal assembly. Bolts shall be kept and issued by special personnel.

② The construction and installation sequence shall be taken into account in the treatment of assembly surface to prevent repetition, and the treatment shall be carried out before hoisting as far as possible.

2) The screw thread of the bolt is damaged, and the screw can not screw into the nut freely, which affects the assembly of the bolt.

Cause analysis: the thread was seriously rusted.

resolvent:

① Before use, bolts should be selected, cleaned and pre assembled after rust removal.

② The bolt with damaged thread can not be used as temporary bolt, and it is strictly forbidden to drive into the screw hole by force.

③ Pre selected bolt components shall be stored in sets and shall not be interchanged during use.

(2) On site weld phenomenon: it is difficult to guarantee the quality; ultrasonic flaw detection is not used for the first and second grade weld with full penetration required by the design; the main beam and column of the floor are not welded; arc striking plate is not used for welding.

Solution: before the welding of steel structure, check the qualification certificate of welding rod, select the welding rod according to the design requirements, and use the welding rod according to the instructions and operating procedures. The weld surface shall be free of cracks and overlap, the first and second grade welds shall be free of pores, slag inclusion and crater cracks, the first grade welds shall be free of undercut, incomplete welding and other defects, and the first and second grade welds shall be subject to nondestructive testing according to the requirements The welder's steel seal shall be checked at the specified weld and position. The unqualified weld shall not be treated without authorization, and the process shall be modified before treatment. The weld repair times of the same part shall not exceed two times.