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Reasons and Reinforcement Measures for Steel Space Frame Structure Damage (Part 1)

The development and application of steel space frame structure has become quite popular. Because of the advantages of prefabricated main parts in the factory, on-site installation, convenient construction and labor saving, the steel space frame structure is widely used in large and medium-sized public buildings such as stadiums, waiting halls, exhibition halls, banquet halls, workshops, rain shelters, markets, etc. Space frame structure is widely used for its light weight, high spatial rigidity, good seismic performance, economic material, convenient construction, beautiful shape and other advantages. However, due to natural disasters, design, construction and use, accidents of the space frame frame structure also occur from time to time. In this paper, according to the reasons for the formation of damage to steel space frame frame structure, a simple scheme of reliability identification and reinforcement is proposed for the development and popularization of steel space frame structure.

1、Steel space frame structure quality accidents and defects analysis

A comprehensive review of the design and processing of the space frame structure, installation documents: check the drawings, calculations, design modifications and other information of the space frame structure and its related substructure, pay attention to its support conditions, load conditions, working conditions and the necessary calculations are correct. Check the production and testing records of the parts of the space frame structure, the quality certificate and test report of the materials, the product qualification certificate and test report of the parts, the quality of the welding seam and the inspection data of the parts, etc., whether they meet the requirements of the relevant national standards. Check the construction records and inspection and acceptance documents of the space frame structure installation, including the longitudinal and transverse side length deviation, center deviation of the support points, height deviation and deflection records after the space frame is in place.

Conduct a comprehensive survey on the actual condition of the space frame structure: investigate the actual condition of the tree frame, including the total plane size, space frame size, space frame height, support condition, load, seismic intensity, base t category, use environment, etc. Check the quality of the structural parts and welds of the space frame. Check the installation quality of the space frame frame, which includes the size of the installation deviation. To detect the use status of the space frame structure, such as space frame deflection, rod bending, etc.

Perform the necessary verification and review of the space frame structure: first review the original design, that is, based on the original design conditions, the original rod cross-section is calibrated to see if there are super strength design value rods. When the original design has unsafe rod for, according to the actual support condition, load and use condition, with the code allows the strength design value to review, to see whether it is safe. When the original design has changed, such as additional rods and a large number of cross-section substitution, increase the larger holes, then the actual structural condition should be reviewed.

2、The causes of damage and deformation formation of steel space frame structure

Steel space frame structure (limit state): the whole structure or part of the structure beyond a specific state can not meet the design requirements of the function, this specific state is called the limit state. Generally can be divided into the following two limit state: (1) bearing capacity limit state: for the structure will lose its stability, collapse or significant damage results of the state; (2) normal use limit state: the structure or members to normal use or durability of a specified limit in the state called the normal use limit state. Such as: affect the normal use or appearance of deformation: affect the normal use or durability of local damage (including cracks); affect the normal use of vibration; affect the normal use of other specific state.

3、The root cause of the space frame (limit state)

Permanent load action: its value is fixed during the design reference period, or its change is very little compared with the average value. For example, the self-weight of the main structure. Variable load action: The value is variable during the design reference period, and its change has a certain degree of variation compared with the average value. For example, the live load and its dynamic effect on the roof of steel space frame structure, wind load, temperature change, snow load, etc. Incidental load effect: the probability of this effect in the design reference period is very low, but the results should be paid attention to. For example, earthquake, explosion, impact caused by traffic accidents, flooding and fire, etc. The steel grid structure (limit state) will be generated under the combined action of the above three types of loads, so it needs to be strengthened.