In the construction industry, with the use of steel structure workshop more and more popular, the manufacturing, transportation and installation technology of steel structure workshop is paid more and more attention, and it also gets rapid development and continuous improvement.How to further improve the manufacturing and installation accuracy of steel structure workshop and reduce the cost is a topic in front of steel structure workshop industry.At present, the relevant national standards and industry standards have made a lot of provisions in this respect, and put forward requirements for every step from parts preparation to completion.

In order to improve the installation accuracy of steel structure workshop, the paper analyzes and summarizes some problems and specific control methods that must be paid great attention to in the main links of production, transportation and installation.Now, I’d like to talk with colleagues.

1、 Manufacturing and transportation control of steel structure workshop

The accuracy of the manufacturing size of the steel structure workshop is the basic and prerequisite to ensure the accuracy of the overall structure size and the smooth installation of the steel structure workshop. Therefore, it is necessary to accurately grasp 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 connection hole itself, the straightness of the roof beam and the processing precision of the column beam connecting plate, and the system on the beam and column.The position size of the bar or support connecting plate relative to the beam column itself, the position size of purlin supporting plate, etc.

     At present, the middle column of steel structure workshop is made of purchased H steel or plate assembly. If the H-shaped steel is ready-made, the production accuracy of the column is easy to control; if it is assembled by plate, the steel column should be reshaped after assembly and welding to ensure the straightness of steel column and prevent distortion.Most of the roof beams are herringbone structure, usually composed of 2 or 4 beams.The roof beam is usually assembled by the manufacturer with plates, and the web of the beam is often irregular quadrilateral. The manufacturers with strong technical ability can accurately grasp the lofting and blanking of the web, while the manufacturers with weak technical ability sometimes have deviation in the lofting size of the web.Because the overall dimension of roof beam is related to the tightness of beam and column connection, the size of web directly affects the overall dimension of beam, so it is particularly important.In the design of general steel structure workshop, there are some arch requirements for the roof beam. The purpose is to offset the down deflection of the beam due to its own and roof load after the overall installation, so as to achieve the installation size.The height of camber is determined by design.In order to ensure the camber, the overall dimensions of roof beams should be adjusted. From this point of view, the manufacturing difficulty of beams is far greater than that of columns.During the on-site inspection, the overall dimension of the beam and the connecting plate at the end of the beam are the key inspection items. The purpose is to ensure the overall effect after installation and ensure the tightness between the beam and the column.

     We have found that after installation, there is a wedge-shaped gap between the beam and the column. At this time, the large hexagon head bolt has lost the most important role proposed in the original design, and only plays the supporting role. There is no friction force between the beam and the column.In order to eliminate this hidden danger, we added shear key on each column close to the lower side of beam connecting plate to improve the support capacity of roof system. Practice has proved that the effect is very good.In the actual construction, due to a variety of factors, the beam and column often can not be closely combined, some seem to be combined, but in fact can not meet the requirements, resulting in the friction between the joint surface is relatively weakened.In view of this, we hope that in the design of the steel structure workshop, it is suggested to add shear key on the column panel close to the lower edge of the beam connecting plate, so as to ensure the support capacity of the column to the roof.Although the shear bond is small, it has a great effect.

In order to avoid and reduce the deformation of columns, beams, tie bars and other connectors during transportation, the transportation company should add more supporting points in the whole length range when binding components, and the parts should be padded with wood as much as possible, and the peripheral binding should be firm to minimize the deformation of components due to vibration or heavy pressure during transportation. Two point crane should be used during loading and unloading,In addition, the number of bearing points should not be increased when the load is over 3, and the number of lifting points should not be increased when the load is over 3.Do not relax the control of transportation, lifting and unloading, stacking and other links, otherwise, even if the steel structure workshop components are manufactured accurately, there will be problems in the transportation and other links, leading to the installation of steel structure workshop.

2、 Quality control of steel structure workshop installation process

Before the installation of the steel structure workshop, the preliminary work should be done well.For example, before hoisting, the installation personnel should retest the components, and only under the premise that the components are not deformed and the installation dimensions are correct, the hoisting can be carried out.In addition, on the premise of confirming that the strength of foundation concrete meets the specification requirements, the installation personnel shall also inspect the embedded bolts or cup mouth of the steel column foundation. If the position and elevation of the foundation deviate, the position shall be recorded so as to adjust the position of the steel column.

In order to improve the installation accuracy of the whole steel structure workshop, it is better to select the part of the workshop with column support, tie bar and roof support to install first.After the hoisting of this part of steel column, the axis and elevation of the steel column shall be retested first. After correcting the deviation, the steel column shall be temporarily stabilized with cable wind rope, and then the support between columns, roof beam and tie bar between beams shall be installed, which is called rough installation.Before the installation of roof beam, it should be assembled on the ground first, and then hoisted 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 the components are fixed, the axis and elevation of the steel column are retested and corrected again, that is, fine adjustment.The axis of the steel column should be retested from two directions. After the retest is qualified, the bolts of each part should be tightened in turn.The high-strength bolt should be initially screwed. 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 from the beam column contact point to the support and tie bar contact point, and the two ends of the same part should be symmetrically carried out at the same time, so as to reduce the cumulative error of one side.Only in this way can the steel column be installed correctly.If it is found that the installed parts and the installed parts do not match during the process, the installed parts can not be adjusted, but the installed parts or other remedial measures can be taken.For example, if the steel beam and the steel column do not match, the steel column cannot be adjusted, only the steel beam.In the whole process of bent installation, the correct installation of steel column is the necessary condition for all other correct installation. 

In the process of steel structure workshop installation, each independent bent part should form a stable structure as soon as possible.Through the above methods, several other parts can be installed separately in order to make the whole plant have a stable bent structure with interval first. In this way, the accumulated error generated during the installation of the whole plant can be dispersed to each part, and the deformation or falling off or even overturning of the installed steel members due to the influence of natural conditions can be avoided.When the steel columns and beams between other bent frames are installed, they should also be measured and corrected independently, instead of taking the adjacent bent frame as the reference.During the whole installation process of the main structure, after the partial bent structure is installed in place and the deviation is corrected, the final tightening torque value of the high-strength bolt must meet the requirements of the specification, and the inspection personnel shall sample, measure and record.

All temporary fixing bolt holes of components to be welded on site shall be designed with long shaped holes, so as to facilitate installation and adjustment and ensure the overall installation accuracy.The long hole should also be designed for the unilateral connection hole of purlin and other secondary members, of course, the relevant gasket should be increased accordingly.Special attention should be paid to the fact that purlins are all installed at high altitude, and the plate wall is thin. If cutting and spraying at high altitude due to the deviation of installation holes, it will indeed bring a lot of inconvenience and danger, and also affect the appearance.Therefore, it may be more reasonable to design the connection hole between the two ends of purlin and the steel beam and column, or at least one side of the purlin.

When the roof steel frame system is installed, sometimes the installation of roof support and roof purlin often conflicts.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 be hoisted.Our usual practice is to hang the roof purlins on the roof beams in batches and fix them. Purlins in the same span can be divided into 4 or 5 batches. After stacking, they must be fixed.It is very important to let the crane boom extend out of the roof from the gap between the purlins. After the roof supports are hoisted and fixed, the roof purlins can be spread out. This construction sequence is very important.Considering that the installation of enclosure and main structure is often not the same construction unit, it must be under the unified command and coordination of an experienced manager.This can not only avoid the mutual interference between construction units, but also improve the safety of high-altitude operation process.In the above installation process, it should be reminded that if there is a crane beam system in the workshop, and the space distance between the crane beam and the roof is not enough for the crane boom, the crane beam should be installed before the roof support is installed; if the space distance between the crane beam and the roof is large, it can be installed later.Generally speaking, the crane beam should be hoisted as soon as possible, which is also beneficial to the stability of the whole bent.