Construction Technology of Steel Grid Frame for Gymnasium Roof

1 Pr

stadium roof

oject overview

 The Yinglong Middle School Gymnasium has a total of 1 floors, and the height from the ground to the roof is about 14.9m. The roof of the gymnasium adopts steel space frame  construction technology, with arching on both sides, bolt ball joints, positive quadrangular pyramid space frame , multi-point support on the upper chord, the maximum installation height is 12m, the maximum span is 29.1m, the sag height is 2.188m, and the area reaches 1260 ㎡, the total weight is about 54t. The main components of the space frame  frame are mostly made of Q235B material, and the steel pipe material is high-frequency welded pipe. The steel space frame  bulk unit consists of 1 screw ball and 3 to 5 rods and weighs about 60 kg. The roof material is a composite thermal insulation roof, and the roof adopts the primary and secondary purlin structure. Together with the steel space frame  structure, it forms the slope slope for organized drainage, and steel plate gutters are set up on both sides of the arch.

2 Construction preparations

Preparations must be made before construction. The first is the selection of construction personnel. Professional construction personnel with skilled and rich experience should be selected. Among them, construction personnel in special positions such as welders should be certified to work, and other construction personnel should also be different. degree of training. When preparing materials, be sure to select materials strictly according to the design requirements. Repeated testing for the quality of materials must meet the design requirements. For materials that are easily damaged and damp, such as thermal insulation cotton and roof panels, it is necessary to use color strips or prepare a suitable material site for protection to avoid repeated handling and rain. Construction equipment plays an important role in the construction of steel space frame s. Sufficient and good special equipment and tools must be configured in advance, such as electric welding machines, grinding wheel cutting machines, air pumps, electric riveting guns, etc., and repeated maintenance and debugging must be carried out to ensure The equipment can be used accurately, safely and reliably. For the design of drawings, designers need to check the size of the site, and prepare in advance for the conversion of processing technology drawings and construction drawings, including various positioning drawings, installation drawings, large-scale drawings, etc., to achieve 1:1 Stake out. When checking the drawings, it is necessary to correct and improve the errors of the drawings through careful measurement of the on-site conditions, and negotiate with each unit to formulate the interspersed operation plan, and prepare the data forms and technical documents required for the project. . It should be noted that since the steel space frame  construction technology needs to use cranes for hoisting construction, in order to avoid hoisting problems in the subsequent construction and affect the construction progress, the cranes can be organized in the design stage, and the on-site measurement is carried out to determine the need for cranes. Station and tonnage, as well as the lifting points that clearly need to be hoisted. Before hoisting, remove obstacles on site to ensure the safety of hoisting.

3 Construction technology of steel space frame  structure

3.1 Key points and difficulties of construction

In the construction of this project, the steel space frame structure technology has a crucial impact on the success of the project construction. Therefore, the key and difficult problems that need to be solved in the process of engineering construction are also concentrated in the construction process of steel space frame  structure. A key construction technology in the construction of steel space frame  structure is the use of high-altitude bulk method. Due to the large area and span of the space frame  frame in this project, the cost is relatively high if the full hall frame is used. However, because the site is relatively narrow and the location of the crane is not easy to choose, the high-altitude bulk method is used in this project to carry out the space frame  frame. Structural construction. The main method of the high-altitude bulk method is to complete the assembly of each unit on the ground, then install it in the order from the middle to the two sides, and finally lift and install it by a 70t crane. In this process, how to control the unit Structure becomes one of the difficulties. Another difficulty is that, due to the relatively high installation height of the engineering space frame  structure, it is necessary to ensure the safety of the construction personnel when installing the roof panel and then applying the anti-rust paint. 3.2 Fabrication and painting of steel mesh frame components The steel mesh frame structural components mainly include rods, bolt ball joints, hexagonal sleeves, sealing plates and cone heads, set screws, high-strength bolts and supports. The steel pipe is unloaded on a special pipe cutting machine, and then welded with the sealing plate and the cone head. Before welding, it is necessary to determine the length, and control the distance between the two ends, the coaxiality and verticality of the steel pipe. The error of the length of the rod should be controlled within 1mm, and the vertical error of the two ends of the sealing plate and the cone head facing the axis of the steel pipe should be controlled within 0.2mm. The finished rods should be derusted before entering the anti-corrosion workshop for primer spraying. In the production of bolt ball joints, the roundness, diameter, over-burning and crack inspection of the blank ball are firstly carried out, and then rust removal treatment is carried out. Finally, it enters the finishing workshop to process each chord hole and each web hole. After the machining is completed, use the angle ruler, angle disc and mandrel to check the angle to ensure that the included angle error of each threaded hole is within +30'. The size of the hexagonal sleeve is precision cast below M30, and can be forged with a 150Kg air hammer above. After finishing on the CA6140 lathe, the parallelism deviation of the two end faces of the hexagonal sleeve should not be greater than 0.5mm. The cone head and sealing plate are made of Q235-B steel, and the blank is forged by a 150Kg air hammer and a 300T friction press. After finishing by the CA6140 lathe, the deviation of the parallelism of the two ends should not exceed 0.3mm. The production accuracy of the set screw should meet the requirements of "Ordinary Thread Tolerance and Fit", and use high-quality high-strength steel wire. High-strength bolts need to be supplied by Jiangdu High-strength Bolt Factory, a professional manufacturer. The factory products must be accompanied by a factory test report and a certificate of conformity. The crack and hardness test must meet the specified test standards. The support should be a reinforced rib support, and the base plate of the support should be polished before welding with the ball to ensure that the edges are neat. The height of the support should be ensured that the deviation is not more than +1mm, the deviation of the slope is not more than 2mm, and the deviation of the center offset is not more than 3mm. When welding, firstly spot-weld the fixed position on the positioning fixture, and then perform rotary welding. For the painting of steel mesh frame parts, it is necessary to paint the finished supports, rods and supports. For the painting of hexagonal sockets and bolted ball joints, it is necessary to carry out anti-rust and fire-proof painting after the installation of the mesh frame. For set screws and high-strength bolts, no descaling coating is required. In the rust removal of supports, supports and rods, the oxide layer on the outer wall of the steel pipe should be removed first. At the same time, the concave surface formed by the impact of the high-speed steel shot on the outer wall of the steel pipe can effectively increase the paint contact area and improve the paint adhesion. Focus on improving the anti-corrosion effect. Coating should also pay attention to the influence of weather changes. When the temperature of the steel surface is 300C lower than the air temperature, coating should not be carried out. For the use of paint, it must be stirred evenly before use. The paint is generally used up on the same day, and diluent cannot be added at will. For local paint film damage, it should be repainted according to the original coating process to ensure that the color of the steel component surface is consistent, and no wrinkles, bubbles and sags appear, and to ensure the good adhesion of the paint.

3.3 Steel space frame  installation

During the construction of the steel space frame structure of this project, by considering all aspects of the project, the space frame  structure was divided into seven large pieces, of which the heaviest structure weighed about 10t, and was lifted and installed by two 25t cranes. Compared with other solutions, this solution can effectively reduce costs and speed up the construction progress. At the same time, it can better control the installation deflection of the space frame , reduce the waste of manpower and materials, and ensure the safety of construction workers. Before installation, it is necessary to determine the position and height of the support, check the component materials, and confirm that the material specification number is correct. Do a good job of the technical requirements of the spreader, ensure that you are familiar with the work site and tasks, and be sure to remove surrounding obstacles before starting construction to avoid safety and quality accidents.

3.3.1 Assembly preparation

The trial assembly work can further ensure the smooth construction of the project. In the process of assembling small units, according to the order of drawings, the rods and balls are assembled on the ground into a small unit as a whole, and it is determined that the quality of the components meets the technological standards, and the assembly effect meets the installation requirements. Check the quality of the sleeves and high-strength bolts, and be sure to remove debris such as rust and iron sand on the threads. After the overall trial assembly of the small unit is completed, the sub-bureau can test the assembly situation and determine the specific assembly plan. In this project, the amount of steel space frame  structure shows off the sloping structure, which forms a rectangle as a whole, and the direction of force is very symmetrical and clear. The starting installation should be determined according to the support situation and installation difficulty. After forming, it should be installed on both sides to ensure the balance of the installation process. When assembling on the ground, pay attention to hardening the site and tamping the foundation to ensure that the site is flat and drained. Usually, the bearing capacity of the foundation cannot be less than 100kPa. Before assembling, the construction site should be measured and positioned to control the installation accuracy.

3.3.2 High-altitude bulk packing of bolted ball space frame 

The high-altitude bulk method is widely used in the construction technology of roofing steel structures. Before installation, the installation components need to be classified and arranged, such as rods and bolt balls, which need to be arranged according to their size and number type, so as to facilitate the installation. can be successfully searched and used. It is also possible to assemble small units on the ground, allocate bolt balls and corresponding rods in advance, and perform combined installation to form a triangular cone. After re-checking the assembly quality during construction, it can be lifted and installed, which greatly speeds up construction progress. The installation of the space frame  should start from the low end, first install the support, then install the lower chord to make a space frame , and then install the web and upper chord. During the installation process, also pay attention to the measurement and positioning to ensure the accuracy of the installation. Assembly of the top chord: The installation sequence is transmitted from the inside to the outside. When tightening the connection between the top chord and the ball, pay attention to tightening the web rod and the bottom chord in sequence. Assembly of the web rod and the top chord ball: After the web rod and the top chord ball are assembled, a downward quadrangular cone is formed. It should be noted that the connection between the web rod and the top chord ball must be tightened at one time, so that the top chord rod can be installed loosely. Assembly of the chord and the ball: According to the number in the installation drawing, firstly cushion the plane of the lower chord ball, and tighten it in place at one time when assembling the lower chord and the ball.

3.3.3 Steel space frame  

hoisting scheme Before hoisting, the site facilities should be leveled and hardened with C15 concrete, and the thickness should not be less than 100mm. For crane equipment, a 70-ton truck crane is used for unit hoisting for high-altitude bulk loading. The length of the main arm of the truck crane should reach more than 19.2m, the working range should be within the range of 18m, and the allowable hoisting weight should be 4.8 tons, which can meet the construction requirements of the steel space frame  structure of this project. To ensure the smooth progress of the hoisting construction, complete the overhaul of the hoisting equipment and ensure that the hoisting equipment is in good condition. When hoisting the roof space frame , the hoisting and installation procedures are: ground in place→inspection→air hoisting→support connection (temporary)→inspection→vertical support, tie rod, air-conditioning boom hoisting and installation→calibration inspection→support fixing . The hoisting adopts the overall hoisting of a single space frame  frame, so in order to ensure the stability of the hoisting, when determining the hoisting point, the position close to the center is usually selected. When hoisting, it should be slow to prevent the single frame from rotating under control. To further ensure stability, the cables can also be manually tightened from four directions to prevent sideways shaking of the space frame . When the space frame  is placed in place, it should also be carried out slowly, and the support bolts should be accurately aligned to ensure that the hoisting is in place. Temporary fixing method can be used to perform initial screwing, and then hoist the second space frame  frame, connect and tighten with the first space frame  frame, and so on to complete the installation. After the installation is completed, the space frame  frame should be calibrated, and the tightening condition should be checked again, and the final fixing work should be done. The weight of the purlin is relatively light and the cross-section is relatively small, so when hoisting, the method of hoisting with one hook or multiple pieces is often used. During the hoisting process, care must be taken not to collide with the original building. During the hoisting process, if the paint surface of the component is scratched, it must be cleaned and repainted in time. After the hoisting is completed, the inspection is carried out, and the qualified steel components can be top-painted.

 4 Roof installation and construction technology

4.1 Quality Standards

The materials used in the construction of the project belong to the composite thermal insulation roof, which mainly consists of 0.45mm bottom plate + 100mm thermal insulation cotton + 0.6mm thick panel. The purlins are made of primary and secondary purlins, and the gutter steel plate is made of 2.0mm galvanized steel gutter cold-rolled.

4.2 Specific installation method

When installing the primary and secondary purlins and drainage gutters of the space frame  frame, first install the support on the bolt ball of the upper chord of the space frame  frame according to the installation drawing. The installation and fixation of the gutter bracket must pay attention to keeping the level flush. Since the steel plate gutter is relatively thin, it is easy to deform when it is welded with other components. The main purlin and the gutter bracket can be welded first, which can effectively control the occurrence of gutter deformation and keep the gutter level and straight. It is more conducive to waterproof treatment and roof installation. When the purlin is installed and welded, the main purlin and the center of the support are first welded, and then the secondary purlins are arranged on the main purlin according to the spacing required by the design and then welded. The space frame  roof panel needs to be installed after the primary and secondary purlins are installed. Install the base plate first, then lay the insulation on the base plate. When installing the panel, the panel with the same orientation as the secondary purlin should add a fixed flat iron to ensure that it is perpendicular to the purlin. The roof panel is suspended on the gutter longitudinally, and attention should be paid to the complete engagement with the center rib and bottom rib of each fixed seat. Use the arrows to mark the laying direction, and the anchors are secured with two suitable self-tapping screws. When the second steel plate is placed on the second row of fixed seats, ensure that the inner rib is superimposed on the outer rib of the first or previous steel plate, and the center rib must be on the upright edge of the overtime center rib. When interlocking the fixing seat, the interlocking rib of the fixing seat should ensure that it fully engages with the central rib of the roof panel. When pressing the concave shoulder embedded in the inner rib along the convex shoulder of the outer rib, a clear "click" should be heard if it is fully pressed in. The rear panels use the same mounting method.

5 Conclusion

Through the above analysis, the construction technology of the steel space frame  structure of the stadium roof is very complicated. Therefore, in the construction and application of the stadium, in order to ensure the smooth progress of the project, it is necessary to make preparations for the construction, fully understand the site conditions, and formulate a scientific and feasible construction plan. , to ensure the accuracy and stability of the construction process, so as to better ensure the quality and safety of the project construction.