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    2022-01-13 17:49

    How to improve plant installation accuracy?

    In the construction industry, with the increasing popularity of the use of steel structure workshops, the production, transportation and installation technologies of steel structure workshops have received more and more attention, and have also been rapidly developed and continuously improved. How to further improve the production and installation accuracy of the steel structure factory and reduce the cost is a topic faced by the factory leasing industry in Beijing. At present, relevant specifications and industry standards have made many provisions in this regard, requiring every step from part blanking to completion.

    In consideration of improving the installation accuracy of the steel structure workshop, some problems and specific control methods that must be paid great attention to in the main links of production, transportation and installation are analyzed and summarized. Now let's talk with our colleagues.

    First of all, the manufacturing and transportation control of steel structures is the basic and prerequisite to ensure the overall structure size and the smooth installation of steel structure plants. Therefore, it is necessary to accurately grasp the straightness and distortion of the steel column, the distance between the connection hole of the column and the column base plate, the processing accuracy of the connection hole itself, the straightness of the roof beam and the processing accuracy of the column beam connection plate, the position and size of the tie rod or support connection plate on the beam column and the beam column itself, and the position and size of the purlin support plate.

    At present, the columns of the steel structure plant are processed from purchased H steel or assembled from plates. If the ready-made H-section steel is processed, the production accuracy of the column is easy to control; If it is assembled from plates, pay attention to the shaping of the steel column after assembly and welding to ensure the straightness of the steel column and prevent distortion. Roof beams are mostly herringbone structures, usually composed of two or four assemblies. Roof beams are generally assembled by manufacturers' plates, and the webs of beams are often irregular quadrangles. Manufacturers with strong technical ability can master the setting out and blanking of the web, while manufacturers with weak technical ability often deviate from the setting out size of the web. Since the shape and size of roof beams are related to the tightness of the connection between beams and columns, the size of web directly affects the shape and size of beams, so it is particularly important. In the design of general steel structure factory buildings, roof beams often have certain camber requirements, whose purpose is to offset the lower deflection caused by the beam body itself and roof load after the overall installation, so as to achieve the installation size. The height of arching is determined by the design. In order to ensure the camber, the shape and size of roof beams should be adjusted to a certain extent, and the manufacturing difficulty of beams is far greater than that of columns. During on-site inspection, the shape of the beam and the tightness of the beam end shall be ensured.

    We have found that in this case, there is a solid gap between the beam and the column after installation. At this time, the large hexagon bolt has lost the main function proposed in the original design, only bearing the supporting role, and there is no friction between the beam and the column. In order to eliminate this hidden danger, we later added shear keys on each column near the lower side of the beam connecting plate to improve the supporting capacity of the roof system. Practice has proved that the effect is very good. In actual construction, due to various factors, beams and columns can not be closely combined, some of which seem to be combined, but in fact they can not meet the requirements, resulting in relatively weak friction between the joint surfaces. In view of this, we hope that in the design of the steel structure plant, it is recommended to add shear keys on the column panel near the lower edge of the beam connecting plate to ensure the support capacity of the column to the roof. Although the shear key is small, it has great effect.

    In order to avoid and reduce the deformation of column, beam, rod and other connectors during transportation, the transportation company must add more support points in the full length range when binding members. The parts should be padded with wood as much as possible, and the peripheral binding should be firm to minimize the deformation of members caused by vibration or heavy pressure during transportation; Two point lifting shall be used during loading and unloading. If the component is too long, the carrying pole can be used and the lifting point can be appropriately increased; When stacking components on the installation site, the number of stacking layers shall be minimized, generally not more than 3 layers. At the same time, support points shall be appropriately increased to prevent members from being compressed and deformed. Don't loosen the control of transportation, hoisting, stacking and other links. Otherwise, even if the components of the steel structure plant are produced again, problems will occur due to transportation and other links, which will bring great trouble to the installation of the steel structure plant.

    The quality control of the installation process of the steel structure plant shall be carried out before the installation of the steel structure plant. For example, before hoisting, the installation personnel shall retest the components, and only when the components are not deformed and the installation dimensions are correct can they be hoisted. In addition, on the premise of confirming that the strength of the foundation concrete meets the requirements of the specification, the installer should also detect the embedded bolts or cup openings of the steel column foundation. If the foundation position and elevation dimension deviation are found, the position shall be recorded to adjust the steel column position.

    In order to improve the installation accuracy of the whole steel structure plant, it is better to select the parts in the plant with inter column support, tie bar and roof support for installation. After hoisting this part of steel column, first retest the axis and elevation of the steel column, correct the deviation, temporarily stabilize the steel column with cable and wind rope, and then install the support between columns, roof beams and tie rods between beams, which is the so-called rough installation. Before installing the roof beam, it shall be assembled on the ground and hoisted after passing the measurement. After the beam is in place, it shall be connected with high-strength bolts, and other parts shall be fixed with corresponding bolts, but various bolts shall not be locked. After each component is fixed, the axis and elevation of the steel column shall be retested and corrected, that is, fine adjustment. The steel column axis shall be retested from two directions. After the retest is qualified, the bolts of each component shall be tightened in sequence. High strength bolts shall be tightened first. During tightening, the axis of steel column shall be dynamically tracked. If the axis changes beyond the allowable value, it shall be adjusted immediately. The whole tightening process shall be from the beam column joint to the support. The two ends of the same component shall be symmetrical to reduce the accumulated error on one side. Only in this way can the correct installation of the steel column be ensured. If it is found that the installation parts and the installation parts cannot match during the installation process, the steel column or other installation parts cannot be adjusted.

    During the installation of the steel structure plant, each independent bent part shall form a stable structure as soon as possible. Through the above method, other parts can be installed in sequence, so that the whole plant has a bent structure with stable spacing, so as to disperse the accumulated errors generated in the installation process of the whole plant to all parts, and avoid deformation, falling off or even overturning of the installed steel members due to natural conditions. When installing steel columns and beams between other bent frames, the deviation shall be measured and corrected independently, not based on the bent frame next to it. During the whole installation of the main structure, after the partial bent structure is installed in place and the deviation is corrected, the high-strength bolts shall be finally tightened. The final torque value must meet the requirements of the specification, and the inspector shall sample, measure and record.

    All temporary fixing bolt holes of components requiring on-site welding shall be designed as long holes to facilitate installation and adjustment and ensure overall installation accuracy. Single side connection holes of purlin grade members shall also be designed as long holes. Of course, relevant gaskets should also be increased accordingly. Special attention should be paid to the fact that the purlins are installed at height and the plate wall is thin. If they are cut and sprayed at height due to the deviation of the installation hole, it will indeed bring a lot of inconvenience and danger, and affect the appearance. Therefore, it may be more reasonable to design the connection holes or at least one side growth holes between the two ends of purlin and steel beams and columns.

    When installing the roof steel frame system, sometimes there are contradictions between the installation of roof support and roof purlin. If the roof support is installed first, the roof purlin cannot be hoisted; If the roof purlin is installed first, the roof support is not convenient for hoisting. Our usual practice is to lift the roof purlins in batches and fix the roof beams. Purlins of the same span can be divided into 4 or 5 batches and must be fixed after stacking. It is very important to let the crane boom extend out of the roof from the gap between each batch of purlins, hoist the roof support, and lay the roof purlins after fixation. Considering that the installation of enclosure and main structure is often not the same construction unit, experienced management personnel must be responsible for unified command and coordination. This can not only avoid mutual interference between construction units, but also improve the safety of high-altitude operation. In the above installation process, it should be reminded that if there is a crane beam system in the plant, the space between the crane beam and the roof is not enough, and the crane beam should be installed before installing the roof support; If the space between the crane beam and the roof is large, it can be installed later. Generally speaking, the better installation of the crane beam is also conducive to the stability of the whole crane frame.


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