The detection and safety assessment of long-span space frame roof structures is a comprehensive issue, mainly involving different standards, but also involving the actual component cross-section, steel corrosion, actual load conditions, changes in seismic fortification categories, and the durability of the lower support structure. Sexual degradation and degradation of roof structure performance.
The detection of space frame structures and three-dimensional trusses mainly includes structural geometric dimensions, structural deflection, member cross-sections, support settlement differences, compression bar buckling, member corrosion, joint weld quality, etc. The space frame of bolt ball joints needs to be inspected High-strength bolt tightening and sleeve loosening. In addition, it is necessary to check the composition and self-weight of the roof structure, the self-weight of the indoor ceiling and suspension equipment, etc., and check the durability of the roof enclosure structure and the waterproof condition of the roof.
The safety assessment of the roof structure should be based on the original design drawings (geometric dimensions, rod specifications, material strength grade, substructure layout), combined with the measured cross-section and corrosion of the rods, according to the current measured self-weight of the roof structure and the self-weight of the hanging equipment , considering the roof live load and so on to carry out the load combination and carry out the overall structural analysis. Calculate the internal force of the rod, check the bearing capacity and stability of the rod according to the tension and compression rod; calculate the deflection of the structure, check the allowable deflection according to the requirements of the regulations, and compare the calculated deflection with the measured deflection. According to the local seismic fortification intensity, combined with the span of the roof structure, consider whether to carry out the structural seismic analysis and checking calculation (including the roof structure and the lower supporting structure).
In addition to the assessment of the upper roof structure, the safety assessment of the lower support structure is also required. When evaluating the safety performance of the lower support structure, the component size, concrete strength grade, and reinforcement configuration should be measured. The safety assessment according to the current standards should focus on the evaluation of the ultimate bearing capacity of structures and components, and the structural requirements proposed in the current standards can be appropriately relaxed.
During the safety assessment, the review of the ultimate bearing capacity state of the structure, the checking calculation of the limit state of normal service and the checking calculation of the seismic performance of the structure should be carried out according to the original code and the current code respectively.
For structures that can meet the original code and basically meet the current code, it should be evaluated as safe, and structural reinforcement and reconstruction may not be carried out, but normal steel structure members must be treated with antirust on the surface; If the current code is met, but the deflection slightly exceeds the current code, it can also be evaluated as safe, and the structure does not need to be reinforced; not greater than 1.05 times the design strength of the material), it can be assessed as basic safety;
For structures that can meet the original code but not meet the current code (the stress of some members exceeds the design strength, and the stress exceeds 1.05 times the design strength of the member), or can no longer meet the original code, let alone the current code, should assessed as unsafe.
For structures assessed as safe, reinforcement and reconstruction may not be carried out; for structures assessed as basically safe, reinforcement and reconstruction may not be considered, but there are certain restrictions on the use of the structure, and the possible increase in roof loads and hanging loads must be strictly limited For roof gutters, great attention should be paid to the unobstructed drainage to prevent the increase of ponding load caused by poor drainage in the gutters; for structures that are evaluated as unsafe, they should be notified immediately to stop using them, and the structures should be reinforced and reconstructed as soon as possible according to the current specifications , when the comprehensive cost of reinforcement and reconstruction is high, demolition can be considered.