Steel Column Installation
1. Types of steel columns: single-layer, multi-layer steel columns; there are long and short steel columns; cross-sectional forms include: mouth, work, O, II, III shapes.
2. Selection of lifting points: The position of the lifting points should be determined based on the shape, end face, length, and lifting performance of the steel column. ① General steel columns have good elasticity and rigidity. The lifting point adopts a single point vertical lift, the lifting ear is placed at the top of the column, the column body is vertical and easy to align. Through the position of the column’s center of gravity, subject to the length limit of the crane boom, the lifting point can also be placed at 1/3 of the column length, the lifting point is obliquely lifted, and it is difficult to align due to the inclination of the steel column. ② For slender steel columns, two or three points can be used to prevent the steel column from deforming. ③ If you do not use welded lifting ears, you should pay attention to two points when directly tying the steel wire rope on the steel column itself. The first one: the four corners of the steel column (mouth, I-beam) are made of corner angles (angle steel ∟ is clamped in the semi-circular steel pipe) to prevent the steel wire rope from being cut off; the second one: at the binding point, to prevent the I-beam steel column from being locally squeezed and destroyed, a reinforcing rib can be added, a grid column is lifted, and a support rod is added at the binding point.
3. Lifting methods: For large and long steel columns in heavy industrial plants, depending on the equipment of the crane and the site conditions, single-machine, two-machine, and three-machine lifting can be used. ① Rotation method: The steel column is transported to the site, and the crane rotates while lifting the hook to make the column rotate around the column foot and lift the steel column. ② Sliding method: The single or double machine lifts the steel column, the crane only lifts the hook, and the method of lifting the steel column by sliding the steel column foot is used. To reduce the friction between the steel column foot and the ground, a sliding path should be laid under the column foot. ③ Delivery method: Double machine or three machine lifts, to reduce the friction between the steel column foot and the ground, one of them is the auxiliary machine, the lifting point is selected under the steel column, when lifting the column, cooperate with the main machine to lift the hook, as the main machine lifts, the auxiliary machine needs to walk or rotate, during the delivery process, the auxiliary machine bears part of the load, and the steel column foot is delivered to the foundation, the auxiliary machine unloads the hook, unloads the load, and the main machine is fully loaded at this moment. ④ Precautions for double machine or multi-machine lifting: a. Try to choose the same type of crane. b. Distribute the load of the lifting point according to the capacity of the crane. c. The load of each crane should not exceed 80% of its corresponding lifting capacity. d. Multi-machine lifting, during the operation, cooperate with each other, coordinate actions, use iron flat carry to lift, try to keep the iron flat carry balanced, the tilt angle is small, to prevent one crane from losing weight and causing the other crane to overload, causing safety accidents. e. Signal command, the division command must obey the general command.
4. Installation of light steel structure columns ① Light steel structures generally refer to portal frame columns. Since these columns are all variable cross-sections, the column roots are small, the column tops are large, the heads are heavy and the feet are light, and the center of gravity is eccentric. After installation and fixation, temporary support must be added when necessary to prevent tipping. ② The anchor bolts of the column foot should be positioned by a reliable method. In addition to measuring the length of the right angle side, the length of the diagonal should also be measured. Before and after the concrete is poured and before the steel structure is installed, the position of the anchor bolts should be checked to ensure that the plane size and elevation of the foundation meet the design size requirements. ③ The adjustment of the elevation, the alignment of the longitudinal and transverse cross lines, the verticality and the installation method, refer to the general steel column installation process. ④ The allowable deviation of the installation of the portal frame lightweight building steel structure can be executed according to the relevant provisions of the national standard “Quality Acceptance Specification for Steel Structure Engineering” GB50205—2001.
5. Steel column correction includes column base elevation adjustment, alignment of longitudinal and transverse cross lines, and column body vertical deviation. ① Single-layer structure steel column correction a. Adjustment of the base elevation of the column. According to the actual length of the steel column, the flatness of the column bottom, and the distance from the top of the steel bull leg to the bottom of the column, the key is to ensure the elevation value of the top of the steel bull leg to determine the adjustment coefficient of the foundation elevation. The specific methods are: when installing the first floor column, an adjusting nut can be added to the anchor bolt under the column bottom plate, and the elevation of the upper surface of the nut is adjusted to be flush with the elevation of the column bottom plate. After putting on the column, use the nut under the bottom plate to control the elevation of the column, and the accuracy can reach within ±1mm. The gap reserved under the column bottom plate can be filled with non-shrinkage mortar by the kneading method. When using this method, the strength and rigidity of the anchor bolts should be calculated. b. Longitudinal and transverse cross lines: When the steel column bottom is made, on the side of the column bottom plate, use a steel punch to punch out four mutually perpendicular faces, one point on each face, use three points to align with the foundation surface cross line, strive to achieve point-line coincidence, if there is a deviation, you can borrow a line. Line method; when the crane does not unhook, slowly lower the three-sided line to the elevation position. To prevent the pre-embedded bolt from deviating from the hole in the column bottom plate, consider the deviation value in the design, appropriately enlarge the hole, and solve it by welding the upper pressure cover plate. c. Column body vertical deviation correction: Use cable correction method, use two theodolites at 90o to find vertical, continuously adjust the nut under the column bottom plate during the correction process, until the correction is completed, screw on the 2 nuts on the column bottom plate, the cable is loosened and not stressed, the column body is in a free state, then use the theodolite to recheck, if there is a deviation, adjust the lower nut, if there is no error, tighten the upper nut. The tightening force of the anchor bolt generally has a design specification, see Table 1 for the tightening force of the anchor bolt. The nut of the anchor bolt can generally use double nuts, or after the nut is tightened, the nut and the screw rod can be welded.
Table 1 Anchor bolt tightening force
a. Adjustment of the base elevation of the column, correction of the vertical deviation of the first floor column, and the method of correcting the single-layer steel structure column are the same. The difference is that for high-rise and super high-rise steel structures, the basement part of the steel is all rigid steel columns, and the surroundings of the steel columns are full of steel bars. To adjust the elevation and find the vertical line, the steel bars must be combed appropriately to carry out the work. High-rise and super high-rise steel structure column correction: mainly control the horizontal elevation of the steel column, the position of the cross-axis line and the verticality. Measurement is the key process of installation. b. The adjustment of the top elevation and the control of the elevation of other section frame steel columns can use two methods: one is to install according to the relative elevation, and the other is to install according to the design elevation, usually installed according to the relative elevation. After the steel column is hoisted in place, it is fixedly connected with large hexagon high-strength bolts, that is, the upper and lower ear plates, without tightening, through the crane lifting, the crowbar slightly adjusts the column gap. Measure the pre-marked elevation value of the top of the upper and lower columns. After meeting the requirements, drive in the steel wedge and spot weld to restrict the steel column from falling. Considering the shrinkage of the weld and the compression deformation, the elevation deviation is adjusted to within 5mm. After the column is installed, a level is placed on the top of the column, measure the relative elevation, get a reasonable value as the zero point, use the zero point as the standard to convert the top line of each column, control the line during installation, compare the measurement results of the elevation with the pre-inspection length of the top of the next column, and perform comprehensive treatment. If it exceeds 5mm, adjust the top elevation of the column. The adjustment method is to fill in a certain thickness of low-carbon steel plate. c. Correction of the longitudinal and transverse cross lines of the second column. In order not to have a wrong mouth between the upper and lower columns, try to make the cross lines of the upper and lower columns coincide. If there is a deviation, insert a gasket (gasket thickness 0.5-1.0mm) on different sides of the connecting ear plate of the column, tighten the large hexagon high-strength bolt to the rated torque value. Note: The bolt hole of the temporary connection ear plate should be 4.0mm larger than the bolt diameter, and use the sufficient margin of the bolt hole enlargement to adjust the manufacturing error of the steel column -1～＋5mm. d. Correction of the vertical deviation of the second steel column: The correction of the steel column focuses on the pre-inspection of the relevant dimensions of the steel column and the pre-control of the factors affecting the verticality. Methods such as reserving deviation values can be adopted. The vertical correction of the standard column can use three theodolites to track the installation of the steel column and steel beam. The verticality correction of the steel column can be divided into two steps. The first step is to use cable-free wind correction. A steel wedge is driven on one side of the steel column deviation direction or a jack is jacked up. On the premise that the verticality of a single column does not exceed the verticality, the axis line of the column top is controlled to zero, and finally the large hexagon high-strength bolt of the temporary connection ear plate is tightened to the rated torque value. Note: The bolt hole of the temporary connection ear plate should be 4.0mm larger than the bolt diameter, and use the sufficient margin of the bolt hole enlargement to adjust the manufacturing error of the steel column -1～＋5mm. The second step is to install the beam of the standard frame body, first install the upper beam, and then install the middle and lower beams. The process of installing the beam will affect the verticality of the column. It can be carried out using steel wire rope cables (only suitable for columns towards the span), jacks, steel wedges and hand hoists, as shown in the “Manual” P913 page Figure 9-65. The columns of other frames are developed from the standard frame body to the surroundings, and their practices are the same as above. Single-layer, multi-layer steel column external dimensions allowable deviation Installation of steel roof truss
1. The lateral stiffness of the steel roof truss is poor, and it needs to be reinforced before installation. Single-machine lifting (one point or 2~3~4 points plus iron flat carry method) often reinforces the lower chord. Double-machine lifting should reinforce the upper chord.
2. The binding point of the truss must be tied at the node of the truss to prevent the component from bending deformation at the lifting point.
3. After the first truss is hoisted in place, cables should be fixed on both sides of the truss. If there is a wind column at the end, it can be fixed with the wind column after correction. After the second truss is hoisted in place, a truss adjuster is used on each slope to correct the verticality of the truss, fix the two ends of the support, bolt or weld → install vertical braces → horizontal braces → check for errors, become a model room, and so on.
4. In order to reduce high-altitude operations and improve production efficiency, the skylight frame can be pre-assembled on the truss on the ground, and the lifting ropes are tied on both sides, and the skylight frame is clamped in the middle to ensure the stability of the overall installation.
5. Steel truss verticality correction method: Pull a full-length steel wire on one side of the truss lower chord, and at the same time, pop out a ruler of the same distance from the center line of the truss upper chord, and correct it with a plumb bob. You can also use a theodolite, place it on one side of the column top, and move a distance a from the axis line. There is also a point with a distance of a on the opposite column. Pop out a distance a from the center line of the truss, and the three points are on the same line. , The truss can be made vertical. Replace the plumb bob and the full-length steel wire with a theodolite.
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