Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
The plate used for the portal steel frame of the coal shed space frame is very thin, which can be as thin as 4 mm. For the blanking of multi-thin sheets, the cutting method should be selected and flame cutting should be avoided. Because cutting with flame will cause great wave deformation on the edge of the board. At present, most manufacturers of H-beam welding use submerged arc automatic welding or semi-automatic welding. If the control is not good, it is easy to cause welding deformation, which will bend or twist the components.
1.Problems with embedded parts (anchor bolts): overall or layout deviation; wrong elevation; no protection measures for the thread. It directly causes the bolt holes of the steel column bottom plate to be out of position, resulting in insufficient thread length.
Measures: The coal shed space frame steel structure construction unit cooperates with the civil construction unit to complete the pre-embedded parts work, before the concrete is poured. Relevant dimensions and firmness must be reviewed.
2.The phenomenon of anchor bolts not being vertical: the level of the bottom plate of the frame column and column foot is poor, the anchor bolts are not vertical, and the horizontal error of the pre-embedded anchor bolts after foundation construction is too large. After installation, the pillars are not in a straight line, and they are crooked, which makes the appearance of the building unsightly, brings errors to the installation of the steel pillars, affects the structural force, and does not meet the requirements of the construction acceptance specification.
Measures: The anchor bolt installation should insist on first leveling the bottom plate with the lower adjusting bolt, and then filling it with non-shrinkage mortar secondary grouting. This method is used abroad. Therefore, during the construction of anchor bolts, steel bars or angle steel can be used to fix the anchor bolts. Weld into a cage shape, improve the support, or take some other measures to avoid displacement of the anchor bolts when pouring the foundation concrete.
3.The phenomenon of anchor bolt connection: the column foot anchor bolt is not tightened, the backing plate is not welded with the bottom plate; some anchor bolts with 2 to 3 threads are not exposed.
Measures: Welding bolts and nuts should be adopted; on the outside of chemical anchors, fire-retardant coatings and heat insulation should be thickened to prevent the anchoring performance from being affected in case of fire; the observation data of foundation settlement should be supplemented.
1.High-strength bolt connection
（1）The mounting surface of the bolts does not meet the requirements, resulting in difficult installation of the bolts, or the degree of tightening of the bolts does not meet the design requirements.
Cause Analysis:
①There are impurities such as floating rust and oil stains on the surface, and there are burrs and welding flashes on the wall of the bolt hole；
②The bolt mounting surface is still lacking even after treatment.
Solution:
①The surface rust, oil stains and bolt hole wall problems of high-strength bolts should be cleaned up one by one. It must be treated with anti-rust before use, so that the bolts used for assembly should not be used in formal assembly. Bolts should be kept and issued by special personnel；
②When handling the assembly surface, the sequence of construction and installation should be taken into consideration to prevent repetition, and should be handled before hoisting as much as possible.
（2）The screw thread of the bolt is damaged, and the screw cannot be screwed into the nut, which affects the assembly of the bolt.
Cause analysis: The thread is severely corroded.
Solution:
①The bolts should be selected before use, and pre-configured after cleaning and derusting；
②The bolts with damaged thread can not be used as temporary bolts, and it is strictly forbidden to force the screw holes；
③The pre-selected bolt assemblies should be stored in sets and should not be interchanged during use.
2.On-site welding seam phenomenon of coal shed space frame: the quality is difficult to guarantee; the design requires full penetration of the primary and secondary welds without flaw detection; the main beams and columns of the building are not welded; arc strike plates are not used for welding.
Solution: Before welding the steel structure, check the qualification certificate of the welding rod, select the welding rod according to the design requirements, and use the welding rod according to the requirements of the instructions and operating procedures. There shall be no pores, slag inclusions, arc crater cracks, and the welds shall not have defects such as undercuts and under-welding. The primary and secondary welds shall be subject to non-destructive testing as required, and the welder’s steel stamp shall be checked at the specified welds and locations. Unqualified welds shall not be processed without authorization, and shall be processed after the modification process is determined. The number of weld repairs on the same part should not exceed two times.
