The steel structure space frame is a new type of structure that has been widely used in the past ten years. It is composed of bolt ball connection points and seamless steel pipe components. It is a statically indeterminate structure based on high-strength bolts or welded connections, which has the advantages of low steel consumption and easy engineering construction. With the rapid development trend of the world economy and society, more and more steel structure space frame structures have been used in sports venues, airport waiting rooms, train station waiting halls, gas stations, large and medium-sized warehouses in factories, etc. span engineering projects.
The bolted ball space frame is a large-span steel structure space frame, which is relatively common in the construction of large and medium-sized construction projects. The use of the spherical space frame to carry out long-span engineering construction can effectively reduce the operation time, the construction technology is relatively simple, and the labor amount of electric welding and welding on the construction site can be reduced, and the welding deviation of electric welding is small and very easy to adjust. However, with the popularization of the bolted ball space frame structure in housing construction in recent years, the collapse of the steel structure space frame often occurs. Therefore, controlling the quality of the bolted ball space frame has a vital effect on the stability and safety of the application of the bolted ball space frame.
The compressive strength of the high-strength bolts in the steel structure space frame of the bolt ball connection point is the main factor affecting the bearing capacity of the connection point. The hardness is related to the surface hardness. The surface hardness test of high-strength bolts can ensure the quality of the bolts.
During installation and construction, the thread length of the high-strength bolts screwed into the bolt ball has been hidden, so it is impossible to measure accurately, and it is impossible to judge the length of the screwed-in bolts. If the screwed-in length is not enough, there will be potential safety hazards, which will directly affect the strength and stiffness of the space frame connection.
If the diameter, roundness, unbalanced milling surface and thread of the bolt balls are too large, the installation of the space frame will exceed the allowable deviation, so that the dimensions and axes of the space frame will not meet the design requirements, affecting the mechanical performance of the space frame and reducing the bearing capacity, causing a safety hazard.
Common quality problems and hazards: The deviation of the processing length of the space frame member, the verticality of the section to the pipe axis and the axis of the nozzle exceeds the allowable regulations of the specification, which will make the space frame frame assembly and installation difficult. Assembly and installation can not be installed or reluctantly installed, resulting in large deviation of geometric dimensions and rod axis, which do not meet the design requirements, affect the mechanical performance of the space frame, and reduce the structural bearing capacity.
After the total assembly of the bolted ball space frame is completed, the connection between the high-strength bolts and the ball joints is not fastened, there is a gap, looseness, and no tightening, and the overall deflection of the space frame exceeds the specification (ie, exceeds the design value by 1.15 times). It will reduce the overall strength and rigidity of the space frame structure and affect the safety of use.
After the installation of the space frame structure is completed, the additional hanging load during use will cause the deflection to increase, even exceeding the design value specified in the specification by 1.15 times, causing serious safety hazards. The surface of the space frame has serious coating peeling, corrosion and other phenomena in about 5 to 10 years, resulting in poor appearance and threatening the safety of the space frame structure.