Control methods to improve the accuracy of leasing and installation of Beijing plant.
In the construction industry, with the increasing popularity of steel structure workshops, the production, transportation and installation technologies of steel structure workshops have been paid 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 plant and reduce the cost is a topic faced by the steel structure plant industry. At present, the relevant national specifications and industrial standards have formulated many provisions in this regard, and put forward requirements for every step from parts 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.
1、 Control the production and transportation of steel structure workshop.
The accuracy of the production size of the steel structure workshop is the basic and premise to ensure the accuracy of the overall structure size of the steel structure workshop and the smooth installation. Therefore, it is necessary to accurately grasp the straightness and distortion of the steel column, the distance between the column beam connection hole and the column bottom 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 bar 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 in the steel structure workshop are processed with H steel or assembled with plates. If the ready-made H-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 steel columns after assembly and welding to ensure the straightness of steel columns and prevent distortion. Roof beams are mostly herringbone structures, usually assembled from 2 or 4. Roof beams are generally assembled from plates, and the web of the beam is often irregular quadrangle. Manufacturers with strong technical ability can accurately 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 plants, roof beams often have certain camber requirements, whose purpose is to offset the deflection caused by the beam body itself and roof load after the overall installation, so as to achieve the installation size. The camber height is determined by the design. In order to ensure the camber, the shape and size of the roof beam shall be adjusted. In this regard, the production difficulty of beams is far greater than that of columns. During the on-site inspection, the shape and size of the beam shall be mainly inspected to ensure the overall effect after installation and the tightness between beams and columns.
We have found that in this case, there is a continuous gap between the beam and the column after installation. At this time, the large hexagon head bolt has lost the most important role proposed in the original design, only bearing the support role, and there is no friction between beams and columns. In order to eliminate this hidden danger, we later added shear keys 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, the beams and columns can not be closely combined, and some of them 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 workshop, it is recommended to add shear keys near the lower edge of the beam connecting plate to ensure the support capacity of the column to the roof. Although the shear bond is small, the effect is great.
In order to avoid and reduce the deformation of column, beam, rod and other connectors during transportation, the transportation company must increase support points within the whole length. All components shall be padded with wood as far as possible, and the periphery shall be bound firmly to minimize the deformation of components 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 components are stacked on the installation site, the 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 relax the control of transportation, hoisting, stacking and other links, otherwise, even if the components of the steel structure plant are fabricated accurately, problems will occur in transportation and other links, resulting in great trouble in the installation of the steel structure plant.
2、 Quality control of steel structure plant installation process.
Before the installation of the steel structure workshop, all preliminary work shall be done well. For example, before hoisting, the installation personnel shall retest the components, and hoisting can only be carried out on the premise that the components are not deformed and the installation dimensions are correct. 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 there is any deviation between the foundation position and elevation dimension, the part shall be recorded 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 select the inter column support in the plant, and install the tie bar and roof support first. After this part of steel column is hoisted, the axis and elevation of the steel column shall be retested first. After correction, temporarily stabilize the steel column with cables and wind ropes, and then install the support between columns, roof beams and tie bars between beams. This is called rough installation. Before installation of 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 components shall be fixed with corresponding bolts, but various bolts shall not be locked. After all components are fixed, the axis and elevation of the steel column shall be remeasured and corrected again, that is, fine-tuning. The steel column axis shall be retested from two directions. After the retest is qualified, the bolts of each part shall be tightened in sequence. High strength bolts shall be initially 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, and the symmetrical method shall be adopted for both ends of the same component to reduce the accumulated error on one side. Only in this way can the correct installation of the steel column be ensured. In this process, if it is found that the installed parts do not match the installed parts, the installed parts cannot be adjusted, but the installed parts shall be adjusted or other remedial measures shall be taken. For example, if the steel beam and the steel column do not match, the whole steel column can only be adjusted. During the whole bent installation process, the correct installation of steel columns is a necessary condition for all other correct installation.
During the installation of the steel structure workshop, 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 intervals, so that the accumulated errors generated in the installation process of the whole plant can be dispersed to all parts, and the installed steel components can be prevented from deformation, falling off or even overturning due to the influence of natural conditions. When installing steel columns and beams between other bent frames, they should also be measured and corrected independently, rather than based on the bent frame next to them. During the whole installation of the main structure, after the local bent structure is installed in place and corrected, the high-strength bolts shall be finally tightened, and the final tightening torque value must meet the specification requirements. The inspectors shall sample, measure and record.
All temporary fixing bolt holes of components to be welded on site shall be designed as long holes to facilitate installation and adjustment and ensure overall installation accuracy. Single side connection holes of purlins and other secondary members shall also be designed as long holes. Of course, relevant gaskets shall be increased accordingly. Special attention should be paid to the fact that the purlins are installed at high altitude and the plate wall is thin. If they are cut and sprayed at high altitude due to the deviation of the installation holes, it will indeed bring a lot of inconvenience and danger, which will also affect the appearance. Therefore, it may be more reasonable to design the connecting holes between the two ends of the purlin and the steel beams and columns as long holes or at least one side as long holes.
When installing the roof steel frame system, sometimes the installation of roof support and roof purlin will conflict. 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 within 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 purlins of each batch, hoist the roof support, and lay the roof purlins after fixation. Considering that the installation of the enclosure and the main structure is often not the same construction unit, it must be commanded and coordinated by experienced managers. This can not only avoid the mutual interference between the construction units, but also improve the safety of the empty operation process. 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 the roof support is installed; If the distance between the crane beam and the roof space is large, it can be installed later. Generally speaking, it is better to lift the crane beam as soon as possible, which is also conducive to the stability of the whole bent.
Finally, the installation of color plates.
Before installing the color plate, first of all, make a good measurement to determine the standard dimensions of the length and width of the color plate. The purpose is to ensure that the upper edge of the color plate can be matched.