How to improve the installation accuracy of steel structure plant

In the construction industry, with the increasing popularity of the use of steel structure plants, the production, transportation and installation technology of steel structure plants has received more and more attention, and it has also been rapidly developed and continuously improved. How to further improve the production and installation accuracy of steel structure plant and reduce costs is a topic placed in front of the steel structure plant industry. Now the relevant national norms and industry standards have made a lot of provisions in this regard, from the parts to the completion of every step of the requirements.

In order to improve the installation accuracy of steel structure plant, some problems and specific control methods which must be paid great attention to in the main links such as production, transportation and installation are analyzed and summarized.

1, steel structure plant production and transportation control

The accuracy of the production size of the steel structure plant is the basic and prerequisite for ensuring the accuracy of the overall structure size and the smooth installation of the steel structure plant. It is necessary to accurately grasp such as the straightness and distortion of the steel column, the distance between the connecting hole of the column and the beam and the column bottom plate, the processing accuracy of the connecting hole itself, the straightness of the roof beam and the processing accuracy of the connecting plate of the column and the beam, the position size of the tie rod or the supporting connecting plate on the beam and the column itself, and the position size of the purlin support plate.

At present, the column in the steel structure plant is processed by purchased H steel or assembled by the plate. If it is processed by ready-made H steel, the production precision of the column is easy to control; If it is assembled from a sheet, pay attention to shaping the steel column after assembly and welding to ensure the straightness of the steel column and prevent distortion. Most of the roof beams are herringbone structures, often assembled by 2 or 4 trusses.

The roof beam is generally assembled by the manufacturer with the plate, and the web of the beam is often irregular quadriateral, the manufacturer with strong technical ability can accurately grasp the lofting and unloading of the web, while the manufacturer with weak technical ability has deviation in the lofting size of the web.

Because the shape size of the roof beam is related to the tightness of the connection between the beam and the column, the size of the web directly affects the shape size of the beam, so it is particularly important. In the design of the general steel structure plant, there are often certain arch requirements for the roof beam, whose purpose is to offset the downward deflection of the beam body due to its own and roof load after the overall installation, so that it just reaches the installation size.

The height of the arch is determined by the design. In order to ensure the camber degree, the shape and size of the roof beam must be adjusted to a certain extent, from this point of view, the production difficulty of the beam is much greater than the production difficulty of the column. During our on-site inspection, the outline size of the beam and the connecting plate of the beam end are the key inspection items, the purpose of which is to ensure the overall effect after installation and ensure the tightness between the beam and the column.

We have found that when there is a wedge gap between the beam and the column after installation, the large hexagon head bolt has lost the more important role proposed in the original design, and only bears 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 close to the lower side of the beam connection plate to improve the support ability of the roofing system, and the practice proved that the effect was very good. In actual construction, due to a variety of factors between the beam and the column often can not be closely combined, some seem to be combined, but in fact can not meet the requirements, resulting in the relative weakening of the friction between the joint surface. In view of this, we hope that in the design of steel structure factory buildings, it is recommended to add shear keys on the cylinder plate next to the lower edge of the beam connecting plate to ensure the column's supporting ability to the roof. The shear bond is small, but it does a lot.

In order to avoid and reduce the deformation of columns, beams, tie rods and other connectors in the transportation process, the transportation company should be required to increase the support point in the full length range of bundling members, as far as possible between the wood pad, the external bundling should be firm, in order to minimize the deformation of the components due to vibration or heavy pressure during the transportation process; In the loading and unloading to use two points, such as the member is too long, can use the pole and increase the lifting point; When the components are stacked at the installation site, the number of stacked layers should be reduced as far as possible, generally not more than 3 layers, and the supporting points should be appropriately increased to prevent the compression and deformation of the components. Do not relax the control of transportation, lifting, stacking and other links, otherwise, even if the steel structure plant components are more accurate, there will be problems due to transportation and other links, leading to big troubles in the installation of steel structure plants.

Second, the quality control of steel structure plant installation process

Before the installation of steel structure plant, it is necessary to do a good job of the preliminary work. For example, before lifting, the installation personnel should retest the components, and the lifting can only be carried out on the premise that the components are not deformed and the installation size is correct. In addition, on the premise of confirming that the strength of the foundation concrete meets the requirements of the code, the installation personnel should also test the embedded bolts or cup ends of the steel column foundation. If the position and elevation size of the foundation are found to be deviated, the position should be recorded in order to adjust the position of the steel column.

In order to improve the installation accuracy of the whole steel structure plant, it is better to choose the part of the plant with column support, tie rod and roof support to install first.

After the lifting of this part of the steel column, the axis and elevation of the steel column should be retested first, and the steel column should be stabilized temporarily with the cable wind rope after correction, and then the inter-column support, roof beam and inter-beam tie rod should be installed, which is the so-called coarse installation. Before the roof beam is installed, it should be assembled on the ground first, and then lifted after passing the measurement. After the beam is in place, it is connected with high-strength bolts, and other parts are fixed with corresponding bolts, but all kinds of bolts should not be locked.

After each component is fixed, the axis and elevation of the steel column are re-measured and corrected, that is, fine tuning. The axis of the steel column should be retested in two directions, and after the retest is qualified, the bolts in each part should be tightened in turn. The high-strength bolt should be screwed first. During the tightening process, the axis of the steel column should be dynamically tracked. If the axis change exceeds the allowable value, it should be adjusted immediately.

The whole tightening process should be carried out symmetrically on both ends of the same part from beam-column contacts to support and tie rod contacts to reduce unilateral cumulative errors. This ensures that the steel column is installed correctly.

If the installed component and the installed component do not match, adjust the installed component or take other remedial measures instead of adjusting the installed component.

For example, if the steel beam and the steel column do not match, the steel column cannot be adjusted, but the steel beam can only be adjusted. During the entire rack installation process, the correct installation of the steel column is a necessary condition for the correct installation of everything else.

In the process of installation of steel structure plant, each independent shelving part should form a stable structure as soon as possible. Through the above method, the other parts can be successively installed, so that the entire plant has a stable and spaced structure, so that the cumulative error generated during the installation of the entire plant can be dispersed to each part, and can also avoid the influence of natural conditions, so that the installed steel components deformation or fall off or even overturn.

When installing steel columns and steel beams between other racks, they should also be measured and corrected independently, and cannot be based on the next rack. In the whole main structure installation process, after the local rack structure is installed in place and corrected, the final screw of the high-strength bolt should be made, and the final torque value must meet the requirements of the code, and the inspection personnel should sample measurement and record.

All temporary fixing bolt holes that need to be welded in the field should be designed with long holes, which is easy to install and adjust, and more favorable to ensure the overall installation accuracy.

Purlin and other members of the unilateral connection hole, should also be designed to grow holes, of course, the relevant gasket should also be increased accordingly. Special attention should be paid to the fact that because the purlin installation is high-altitude operation, the panel wall is thinner, if the deviation of the installation hole is cut and sprayed at high altitude, it will indeed bring a lot of inconvenience, but also dangerous, and has an impact on the appearance. Therefore, it may be more reasonable to design the connecting holes of both ends of the purlin and the steel beam and steel column, or at least the single side of the design. Click ☞ Engineering materials to download for free

When installing a roof steel frame system, sometimes the installation of roof supports and roof purlins often contradicts. If the roof support is installed first, the roof purlin cannot be lifted; If the roof purlin is installed first, the roof support is inconvenient to lift. Our usual practice is to first hang the roof purlins on the roof beam in batches, and the purlins in the same span can be divided into 4 batches or 5 batches, and must be fixed after stacking.

Let the crane boom extend out of the roof from the gap between the batch of purlins, lift and fix the roof support, and then lay the roof purlin, this construction sequence is very important. Considering that the installation of the envelope and the main structure is often not the same construction unit, it must be unified by an experienced manager to command and coordinate.

In this way, not only can avoid mutual interference between construction units, but also improve the safety of the high-altitude work process. In the above installation process, it should be reminded that if there is a crane beam system in the plant, and the space distance between the crane beam and the roof is not enough to use the crane boom, the crane beam should be installed before installing the roof support; If the crane beam is far from the roof space, it can be installed later. In general, it is better to lift the crane beam as early as possible, which is also beneficial to the stability of the entire rack.