The technology of installing large-span space frame structure canopy in existing buildings

 1. Project Overview

space truss



The 107th Neighborhood Commercial Building in Shanghai is a large-scale urban complex project. In order to make better use of the space, the engineering design intends to build two steel structure canopy between several buildings and on the roof platform, so as to make the existing open space Development generates commercial land. The steel structure awning project has 2 monomers, namely the center awning and the wedding awning. The structure of the awning is a grid structure, and the rods of the grid space frame are welded rectangular tubes, and the material is Q345B.

1.1 Center awning

The central space frame canopy is located between the 1", 2", 5" commercial buildings and the west tower of the project. The construction site is narrow and the surrounding tower cranes have been dismantled. The site situation is complicated, which brings great difficulties to the structural installation of the project. The unit is diamond-shaped, the eaves height is 24m, the plane size is about 46mx53m, and the total steel consumption is about 500 t. The steel columns supporting the awning of the grid structure are branch-shaped steel columns, and the steel columns are divided into primary columns, secondary columns and tertiary columns. Column, the column adopts the steel pipe column with the cross-sectional dimensions of ф1117 mm x 40 mm, ф 610 mm x 35 mm and ф406 mm x 22 mm, the bifurcated nodes are cast steel parts, and the three-level column lattice space frame is the hinged node. 

1.2Wedding awning

The wedding awning is located on the roof of a 5" commercial building with a roof elevation of 15.50 m. The surrounding tower cranes have been removed. There is a split-level structure such as an elevator machine room under the awning projection. The awning reticulated space frame is a regular hexagonal unit, and the eaves height is about 13m ( Relative to the roof), the plane size is 15mx28m, and the total steel consumption is about 75t. The column is a ф550mm x 14mm (internally filled with C30 concrete) steel tube concrete column, and the cross-section of the reticulated space frame side beam is 350mm x 150mm x 12 mm x 16 mm, the section of the reticulated space frame unit is 350 mm x 150 mm x 6 mm x 12 mm, and the roof space frame is connected to the column through a basin-type rubber bearing. The reticulated space frame model of the wedding awning is shown in Figure 3.

2 Analysis of engineering features and difficulties

1) The reticulated space frame is a welded box section, and the intersection nodes are welded nodes. The on-site welding volume is large, and the welding quality control requirements are relatively high;

2) The on-site construction site is narrow, the tower crane has been dismantled, and large cranes cannot be set up. The methods of ground assembly and hydraulic integral lifting need to be considered;

3) The spatial positioning of the tree-like bifurcated column is difficult, and high measurement accuracy is required;

4) The reticulated space frame is flat, but the facade has a straight slope and a curved slope, which makes it difficult to splicing on site;

5) The central awning has cast steel nodes, and the cast steel components have higher requirements on the production process and installation accuracy;

6) The wedding awning has a basin-type rubber bearing, which requires higher installation technology.

3 Construction technology route

1) According to the structural characteristics of the central awning and the on-site construction conditions, and comprehensively considering the technical and economic factors such as construction period and cost, the installation of the awning is implemented with the construction technology route of ground assembly and hydraulic integral lifting. Specifically, 8 lifting points are erected in the 4 corner areas of the central awning, 2 lattice columns are erected at each lifting point, and lifting beams are erected on them, and hydraulic jacks are used for overall lifting.

2) According to the structural characteristics of the wedding awning and the construction conditions on site, the technical route of assembling on the ground, hoisting it to the floor with a 500kN car, and then hoisting it in blocks with a single-angle mast.

3) The layout of the construction site. Component transportation shall be entered from the 1" gate or 6" gate, and shall be transported along the construction road to the construction area. Due to the narrow site, in order to avoid secondary reverse transportation, the order and quantity of components entering the site can meet the construction speed on site, and a small number of components are in the construction area. Put it aside, no large temporary component storage yard, 250kN truck crane is used for unloading, 250kN truck crane is used for central awning assembly, and 500kN truck crane is used for wedding awning to transport the components upside down to the roof of a 5" commercial building, and then use a separate The corner mast is hoisted in blocks, and the center awning is divided into sections. According to the characteristics and design requirements of the steel structure of this project, and considering the construction conditions on site, the length of a single member cannot exceed 8m, otherwise it will cause transportation difficulties. The first-class steel column is divided into 2 sections, The reticulated space frame is assembled on-site after the reticulated space frame unit is processed in the factory according to the design requirements. The structural arrangement of the central awning reticulated space frame is shown in Figure 5.

4) Wedding awning segment. The wedding awning is located on the roof of a 5" commercial building. Some steel columns are processed in 2 sections and transported to the site, assembled into a whole and then hoisted; longitudinally, the side beams are processed in 4 sections, transported to the site and assembled into 2 sections for hoisting; The space frame is divided into 10 longitudinal strips, each strip is about 14.50m long and 2.80m wide, which is divided into two sections for processing and transported to the site, spliced into strips and then hoisted. 

space frame steel structure

According to the structural characteristics of this project, it was decided to adopt the construction technology of assembling and lifting the grid frame, and the construction technology of assembling and synchronizing the overall lifting within the span was formulated, which solved the problems of the complex surrounding environment of the construction, and also solved the installation of the space steel grid structure. difficult problems, so that the entire construction process can be successfully completed, which not only saves a lot of measures cost, but also achieves good social and economic benefits.

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