Original link: https://ekp.zt17.cn/km/imissive/km_imissive_send_main/kmImissiveSendMain.do?method=view&fdId=17cede15790f8627f8b7a9f46e081340
petal-shaped Grand Theater's special-shaped wind-resistant truss three-dimensional space measurement and positioning technology improvement
China Railway No. 17th Bureau Group Construction Engineering Co., Ltd. Li Bin
. Project Overview
Jincheng City Culture and Art Center project is located on the north side of Fengtai East Street and the east side of Wenhua Road. The total construction area is 45,818 square meters, the above-ground construction area is 30,057.1 square meters, and the underground construction area is 15,760.9 square meters. The north-south structure forms are: primary and secondary bidirectional plane trusses, circular space three-dimensional trusses, facade space wind-resistant trusses, and a structural system composed of horizontal support and tie rods. The truss is inverted ladder-shaped as a whole. The cantilever end of the truss horizontal section is raised, the elevation of the highest point of the upward rise is 28.5m, and the total length of the truss is about 39.6m; the lower truss has a total of 12 cups, the elevation of the highest point is 27.32m, and the total length of the truss is about 24.57m. The upper side truss and the lower vertical truss consist of three main chords with specifications of Φ159×8mm, and a spatial truss system with specifications of Φ89×4mm, Φ76×4mm, and a spatial truss system. The upper central truss consists of two main chords of Φ219×7mm and a single row truss system with specifications of Φ114×5 mm, Φ89×4mm, Φ76×4mm, and Φ76×4mm. Comprehensively considering the selection of 260 tons, 130.75 and 25 tons of car cranes for coordinated installation. The BIM effect is shown in Figure 1.
2. Traditional construction technology
The traditional construction method is: use a vertical instrument to guide and measure the axis control point on the ground to the operating platform, and control the installation of the main truss at the axis elevation control point on the operating platform. The upper and lower end points of the secondary truss can be determined after the installation of the main truss. After the truss is installed in place, it should be corrected for straightness and verticality, erect the theodolite on the elastic ink line, rotate the telescope of the theodolite to correct the straightness and verticality of the truss to the allowable range of the specification. The elevation control is controlled using the leveling method of leveling and vertical distance measuring of steel tape measure. The elevation is measured on the bottom floor to a vertical and barrier-free facade. The 50m steel tape measure is measured, and the elevation is guided to the top of the support. Then, the leveling method is used to level the lower end of the truss to control the elevation at the lower end of the truss. The elevation at the upper end of the secondary truss is determined based on the actual elevation of the main truss.
. Innovation points of this technology
The difficulty of this technology is: the truss structure is tilted outward and the upper part is suspended. It is necessary to establish a high-precision elevation plane control system on the roof, which is difficult to position and measure; the internal calculation of the truss positioning coordinates is large, and it is necessary to convert with the field measurement data to provide reference for on-site construction; the construction environment is complex and changes are large, especially the roof, construction environment and the ground. The difference is large, and the wind is generally 1-2 levels larger than the lower part. Due to the influence of sunshine temperature difference, favorable observation conditions and observation time should be selected. Generally, it is early in the morning or evening to reduce the impact of sunlight on observation. The visibility of rainy weather is low, which has a great impact on the aerial measurement accuracy. The construction period is tight, and the measurement project must be fast and accurate. It cannot cause idle work or rework due to inaccurate or delayed measurement data. During construction, measurement managers with rich construction measurement experience are selected for control. At the same time, relevant experts are appointed to provide on-site guidance to ensure the final accuracy of the aerial positioning measurement control of the entire truss.
The main innovations of this technology: ① Use the ground projection line of the characteristic points of the truss to be scattered by the total station, set up assembled mounts according to the projection line, and lift the truss chord belly rod according to the scattered point, and temporarily fix it. Forced assembly shall not be carried out during the installation of the chord. ② The coordinates are extracted using a three-dimensional model. During the truss assembly process, the deviation of the installation axis and the elevation can be monitored at any time and adjusted at any time until the design and specification requirements are reviewed. ③ Deflection measurement is carried out during construction to provide a basis for construction and discuss and resolve problems in a timely manner when they are found. ④A set of technologies ranging from internal data calculation to external field aerial three-dimensional spatial coordinate positioning measurement.
. Key technologies
.1 Construction sequence
Establishing a tire frame → first-hand main truss installation, positioning and temporary fixing on the support frame → install 4 main trusses and secondary trusses to install the supporting frame → install the peripheral annular inverted triangle truss, temporary support frame positioning, temporary fixing → form a reference unit, and use this as the basis to install steel columns and steel beams in turn. → Install the roof steel columns and steel beams → Unload the truss membrane
The temporary operation platform of this project is used for a large amount, and it cannot be recycled between the lifting units. Therefore, 426*8mm spiral pipe is used as temporary support. The temporary support platform is arranged at the top of the column at the intersection of the axis. H300X150X6.5X9 steel is installed on the top of the support. Experience calculation and on-site truss position confirmation, and two temporary support channels are required for the upper horizontal truss. See Figure 2.
spiral tubes are 9m, 8m, and 7m per section, and the 4 support lengths are about 110m, and a total of 12 spiral tubes are needed. First, the 426*8mm standard spiral pipe transported to the site of the processing plant will be discharged according to the actual situation on site. Use a total station to locate the temporary bracket placement position and accurately locate the temporary bracket at the stress balance point of the three main trusses.
Assembly spiral pipe: The discharged spiral pipe is assembled into a single 21.74m long spiral pipe, and the spiral pipe is assembled into a whole through I-shaped steel. Because the single row of spiral pipes is upright 21.74m long and thin ratio does not meet the requirements, the column foot area is increased by welding 8m east-west length and one 6m north-south direction at the bottom of the circular tube; the column foot is increased by adding shears (I-shaped steel) to achieve the increase of stability of the column foot; 300*200*20 hanging lugs are welded at 12 meters of the spiral pipe, and 14 steel wire ropes are used to pull the cable wind ropes.
top is 300mm I-shaped steel, the upper I-shaped steel cantilevered out 3m, and a stiffener is added at the 2.5m support position to prevent the steel pipe from deforming due to too much load on the upper part. A I-shaped steel is installed every 4m in the middle of the steel pipe. Four support channels are pulled at the same stand at the elevation of 22.00m to increase the stability of the upper part, add cable wind ropes to the middle of the support, and increase the stability of the lower part by increasing the column feet at the bottom. The trusses assembled through the on-site tire frame are placed on a 260-ton car crane to the pre-made support, and the cantilevered trusses are temporarily supported. The I-steel is welded on the upper part of the temporary support. The I-steel ends are pulled into oblique braces through the I-steel and the temporary support to achieve the weight bearing of both ends of the upper I-steel. The upper truss elevation is adjusted by adjusting the jack. The three-claw main truss is a unit body, which is fully lifted to the truss support and temporary bracket. The other three-claw main trusses are the same as the above truss hoisting scheme, so that they can be carried out.
Set up temporary support at the upper side truss of the wind-resistant truss column to install the truss in sequence; after the installation is completed, the wind-resistant truss columns are connected in sequence through a 130-ton car crane; the remaining trusses are installed in sequence in sequence according to the above method. The following key technologies below
are temporarily kept confidential. Since you want to continue to report the award, please understand.
.23D positioning measurement
.2.1 Establishing a three-dimensional control network
.2.2 Displacement correction of inclined trusses
4.2.3 Truss assembly measurement
.2.4 Truss installation positioning and deflection measurement
Figure 3 Observation point location layout diagram
5. Actual effect
5.1 Economic benefits
Jincheng Culture and Art Center project uses three-dimensional spatial positioning measurement and control technology to ensure the installation accuracy of each node of the wind-resistant truss, making the top truss aerial three-dimensional installation and closing process perfectly connected, and the overall installation effect of the truss is significant. Due to quality assurance, the rework and the construction period is advanced to 20 days, saving 100,000 yuan in direct and indirect costs.
5.2 Social benefits
This technology is simple to use, has high installation accuracy and reliability, improves installation efficiency, and ensures the smooth construction of the corresponding subsequent processes of the peripheral curtain wall.Thanks to the adoption of this technology, not only good quality and construction cost have been achieved, but also good socio-economic benefits have been generated, providing reference experience for future wind-resistant truss construction.
6. Conclusion
Jincheng Cultural and Art Center project is petal-shaped. It is another major landmark building in Jincheng City. It adopts truss structures in the north and south, and the construction is difficult and the overall air is suspended. It analyzes its installation focus and difficulties, and proposes to adopt a three-dimensional spatial positioning control and measurement method to finally achieve the high-precision requirements required for installation, and has achieved good results in construction quality, construction period and cost, leaving valuable experience for future similar construction.
