Study on Decision-Making Method of Lifting Space Frame in Maintenance Hangar ( Part 2)

(2)、Analysis of the conditions and advantages and disadvantages of the new point lifting scheme

The universality of the new point lifting scheme is higher than that of the in-situ lifting scheme. In the structural design phase, there is no need to reserve sufficient structural load for the lifting scheme, and there are no application restrictions for super-large spans.

The new point lifting scheme is between the in-situ lifting and the jacking scheme. Its biggest advantage is that the force during the lifting process is completely separated from the original structural system, and there will be no structural safety risks caused by the lifting construction.

Secondly, since the stressed lattice column is newly added, for the lattice column, the stress of the new point lifting scheme is all axial force. The calculation of its construction scheme is relatively simple, and it does not need to consider the eccentric compression caused by elastic deformation during construction. Relatively speaking, the controllability of its construction scheme is the highest among the three schemes. At the same time, since there is no overlap in the process, the newly added lattice columns and the original structure columns of the hangar can be constructed at the same time, which speeds up the construction progress to a certain extent. Compared with the in-situ lifting, the new point lifting has all the lifting lattice columns and the foundation and pile foundation under the lattice columns, so the cost of this scheme is higher.

(3)、Analysis of the conditions and advantages and disadvantages of the space frame lifting scheme

The space frame lifting scheme has relatively no special reserved conditions, and the universality of the scheme is consistent with that of the new point lifting scheme.

The advantage of the space frame lifting scheme is that there are many control links, which can be continuously fine-tuned during the construction process. At the same time, compared with the lifting scheme, the space frame lifting scheme has relatively lower automation requirements on construction equipment.

The disadvantage of the jacking scheme is also that there are too many control links, which can easily generate cumulative errors and lead to overall jacking deviation. In addition, since the jacking frame needs to be installed continuously during the jacking process, it is very difficult to control its strength and levelness.

3.2、Decision-making logic of space frame lifting schemes under different conditions

From the analysis of the advantages and disadvantages of the three lifting schemes, on the premise that the construction plan is controllable, the preferred lifting scheme must be in-situ lifting. Considering that there is still a long construction preparation time and multiple previous construction processes before the space frame is lifted, there is every opportunity to adjust the construction progress. Special attention should be paid to the fact that if in-situ lifting is adopted, the design institute should be notified of the requirements of the construction plan before the overall construction to see if the original design plan needs to be reinforced accordingly.

Correspondingly, if the design unit of the entire project is relatively inexperienced, and the construction team also lacks the experience and ability to upgrade large-span steel structures, you can choose a new point to upgrade. Relatively speaking, the newly added construction cost of adopting new point upgrades is not much compared with the entire project investment, but it does avoid many safety hazards in construction.

Due to the poor controllability of the construction quality and no obvious advantages of the scheme, it is not recommended to use the jacking method for space frame construction in principle.

3.3、Analysis of construction points under different decision-making

If the space frame is constructed with an in-situ lifting scheme, the verticality of the original structural columns must be strictly controlled in the early stage of construction. The deviation value of its verticality should generally be 20% higher than the acceptance specification of the national standard ; secondly, during the lifting process of the network frame, it is necessary to focus on the deformation of the structural column, and control it with reference to the deformation limit requirements of the national standard frame column ; thirdly, the entire During the lifting process, local cracking of the main body of the structure should be strictly prohibited. A high degree of vigilance should be maintained for any tiny gaps generated by the column ; fourth, the distance between the lifting point and the structural column should be precisely controlled to avoid friction between the lifting point and the structural column due to elastic deformation of the structural column; For the construction of the new point lifting scheme, it is necessary to recalculate the strength of the newly-built structural lattice column foundation and floor strength in the early stage of construction to ensure that the force and flatness of the lattice column floor meet the requirements. During the promotion process, the balance and level of each promotion point should be controlled to ensure that the overall promotion is within the preset conditions.

The overall lifting process should pay attention to the influence of wind speed and temperature at any time, so as to avoid uncontrollable changes in the space frame due to changes in natural conditions.

4、Through the practice of different lifting schemes for three maintenance hangar space frames, this paper summarizes and extracts the scope of application and advantages and disadvantages of different hangar space frame lifting schemes, and proposes that the in-situ lifting space frame should be used first under the condition of technical strength. Based on the conclusion of the space frame lifting scheme, and based on the practice of the actual space frame lifting scheme, the main construction control points under different schemes are proposed, hoping to provide a reference for the subsequent space frame lifting cases.