The overall synchronous lifting of the large steel truss canopy

1 Overview

As one of the windows of Guigang City, the expressway Xingliu Interchange Guigang Toll Station, with the implementation of the first-level connection traffic improvement project, the clear height of the toll station has been difficult to meet the requirements, and the steel pipe truss ceiling of the existing toll station needs to be the main body. The overall structure is upgraded by 3m. The overall shape of the steel pipe truss of the toll station canopy is symmetrically distributed with the middle high and the two ends low. The entire canopy is 90m long, 37m wide, 1.6m high, 2.25m spaced between trusses, 52m spaced between supporting columns, and the whole building highs 25m, The truss is suspended on 4 large steel columns through 8 groups of 32 stay cables. At the same time, the steel columns also serve as the main tower of the cables, carrying the overall weight of the steel tube truss canopy, and the total weight of the entire steel structure is 650t. According to the requirements, in the process of lifting construction, it is necessary to ensure the normal use of some lanes of the toll station, and at the same time avoid excessive changes in the structural stress of the steel pipe truss roof under the normal use state, which will cause irreversible deformation of the roof and affect the safety of the existing structure, the overall hydraulic synchronous jacking scheme is selected for this purpose.

Figure 1 Effect diagram of toll station after lifting

2 Difficulties in project implementation

Before lifting the steel pipe truss canopy, the four large steel columns of the original main support structure need to be separated from the base structure, and then the next construction can be carried out after separation. The main difficulties in the implementation of this project are as follows:

(1) The steel pipe truss canopy is large in size and high in tonnage. It is an existing structure that has been used for many years. It is difficult to evaluate the performance changes of the main structural components of the ceiling. It is necessary to avoid changing the steel truss during jacking construction. The focus point of the structure changes the normal working conditions of the ceiling structure, and the lifting construction is difficult; 

(2) During the construction of the steel pipe truss, it is necessary to ensure that the use of some lanes of the toll station is not affected. The truss structure has a high center of gravity, and when the structural support column is separated from the foundation, unfavorable working conditions such as unevenness or structural overturning are prone to occur. high requirements;

(3) The jacking construction involves multiple sets of jacks and multi-point synchronous jacking. Improper synchronization control will easily cause the roof to tilt, causing uneven stress on the roof structure and irreversible deformation. In severe cases, it may even overturn and cause major safety accidents. High requirements for lifting control;

(4)After the roof is lifted into place, it is necessary to lengthen the original four large-scale supporting steel columns, and connect them with the original embedded bolts, and docking accuracy is required. In view of the above implementation difficulties, it is necessary to properly reinforce the overall structure before the construction of the steel pipe truss, and set up corresponding limit control measures to meet the safety and precision control requirements during the lifting process.

In order to ensure the overall safety of the roof structure during the lifting process, the lifting construction adopts the synchronous lifting control scheme of “balanced oil pressure at the jacking point, structural attitude adjustment, and displacement synchronous control”, using the YT-1 intelligent computer synchronous control system. According to the control strategy and specific algorithm, the system can realize the real-time control of the lifting attitude and load situation of the steel structure.