Reasons and Reinforcement Measures for Steel Space Frame Structure Damage (Part 2)

1、At present, the main methods of reinforcing the steel space frame structure are: load reduction (dynamic and static load), changing the structural calculation graphics, increasing the cross-section and connection strength of the original structural members, and stopping the expansion of cracks and other measures.

（1）Redesign and change of structural calculation graphics

Space frame structure generally uses computer for structural analysis, can not blindly trust the computer output results, ignore the calculation of the results of the verification; because the general span of the space frame structure, roof slope is small, easy to occur water and serious snow phenomenon; space frame structure whether in the calculation of theoretical or construction techniques have a certain degree of difficulty, requiring designers and welding, installation personnel of high quality, so the design of a slight negligence, steel space frame structure is very easy to happen quality accidents. The work of redesigning and changing the structure calculation figure is generally operated by the original design and construction unit together, and the user is generally not allowed to change the stress state of the steel space structure, such as increasing the load of the roof of the space frame at will, hanging loads at will in the lower part of the space frame, etc. Design and change the structural calculation graphics of the reinforcement method refers to the use of changing the load distribution status, force transmission path, node nature and boundary conditions, additional additional bars and supports, the application of prestressing, consideration of space co-working and other measures to strengthen the structure.

(2) The traditional reinforcement method of changing the calculation graph of steel space frame structure by redesign calculation

The following methods of increasing the stiffness of the structure or members can be used to add circumference to the steel space frame structure, increasing the support to form a space structure and test it according to the space structure, adding support to increase the stiffness of the structure, or adjusting the self-vibration frequency of the structure to increase the structural bearing capacity and improve the structural dynamic characteristics. Additional support or auxiliary bars to reduce the length of the structure to improve its stability, in the row frame structure focus on strengthening the stiffness of a column, so that it can withstand most of the horizontal force to reduce the load of other columns, in the tower and other structures set up tie rods or moderate tensioning of the cable to strengthen the stiffness of the structure.

The following methods of changing the internal force of its cross section can be used to strengthen the space steel structure subjected to bending, changing the distribution of the load, such as converting a concentrated load into multiple concentrated loads; changing the end support situation, such as changing the hinge into a rigid junction; increasing the intermediate support or connecting the end of the simply supported structure into a continuous structure, adjusting the position of the support of the continuous structure; changing the structure into a propped structure and applying prestress. Diagonal reinforcement:Diagonal reinforcement is used to connect the nodes of a frame by means of diagonal lines to increase the overall stiffness of the frame, reduce the risk of buckling and increase the overall strength of the frame Ying; shear reinforcement, shear bars are used to increase the overall stiffness of the frame by connecting the nodes of the frame in a shear pattern. This helps to reduce the risk of buckling and increase the overall strength of the frame.

The trusses of steel space frame structure can be strengthened by the following methods of changing the internal forces of its bars: adding props to change the trusses into a propped structure and adding prestressing ties.

Reinforcement by increasing the cross-section of space steel space members: When reinforcing steel members by increasing the cross-section, the selected cross-section form should be conducive to the technical requirements of reinforcement and consider the condition of existing defects and damages.

The reinforcement of the steel space frame connection and the connection of the reinforcement: steel connection methods, i.e. welding, riveting, ordinary bolts and high-strength bolts connection methods should be selected according to the reasons why the structure needs to be reinforced, the purpose, force conditions, construction and construction conditions, and considering the original connection method of the structure to determine. Steel space frame structure reinforcement is generally appropriate to use welded seam connection, friction-type high-strength bolt connection, when there is a basis for the use of welded seam and friction-type high-strength bolts mixed connection. When using the weld connection, the welding process and connection materials should be approved by the assessment, and should be cautious when using the weld connection for the bolt ball node. 45″ steel needs to be heated up when welding, and after welding, heat preservation measures should be taken according to the specification, and then gradually cool down.

Steel space frame crack repair and reinforcement: steel space frame structure due to repeated effects of load and material selection, construction, manufacturing, construction and installation of improper, etc. with the tendency to expand or brittle fracture crack damage, should try to repair. Before repair, the causes of cracks and the severity of their impact must be analyzed, targeted measures to improve the actual work of the structure or reinforcement, the components that are not suitable for repair and reinforcement, should be removed and replaced.

Steel space frame structure due to design, construction, snow, wind, earthquake, fire, dynamic load impact and other reasons will cause various forms of damage, must be based on the reliability analysis of the space frame structure, combined with the steel space frame structure manufacturing and design unit calculations, the proposed reinforcement treatment should be used, the reinforcement of the space frame construction in addition to reference to the above traditional construction methods, but also the strict implementation of the relevant regulations, norms and In addition to the above-mentioned traditional construction methods, the reinforcement work of steel space frame structure should be carried out by strictly implementing the relevant regulations, codes and standards.