INSTALLATION OF METAL CONSTRUCTIONS. TECHNOLOGICAL FEATURES. 2. Installation of columns

Metal columns installed on solid concrete foundations can be supported:

■ on anchor bolts with gravy pre-embedded in the foundations at the joints of the cement slurry after aligning the installed column along two mutually perpendicular axes;

■ directly on the surface of the foundations raised to the design mark of the milled column bottom without subsequent dressing with cement mortar;

■ on pre-installed, adjusted (with a layer of cement mortar if necessary) steel base plates with an upper planed surface (non-calibrating installation).

In preparing the columns for installation, they are subjected to the following risks: the longitudinal axis of the column at the level of the bottom of the column and the top of the foundation.

The columns installed on the foundations provide only anchor bolts if the column has wide shoes and with a height of up to 10 m. Higher columns with narrow shoes, apart from fastening on bolts, mourn in the plane of least rigidity on both sides. The braces are fixed on the upper part of the column before it is lifted, and during installation they are fastened to anchors or nearby foundations. After tensioning the braces, the lines can be removed from the column.

You can remove braces only after fixing the columns with permanent elements. The stability of the columns in the direction of the axis of the building provide crane girders and connections established after the installation of the first pair of columns and connecting crane girders.

Metal columns mounted on foundations are fixed in the process of installation with anchor bolts (Fig. 17.1). If metal gaskets are enclosed under the base of the column, they must be welded. The columns of the upper tiers (for example, in the built-in bookcase) are fastened with high-strength bolts or welded.

Alignment of frame structures, especially columns, is labor-intensive. The use of a non-calibrating installation method allows to improve the quality of work while reducing the construction time of the structure.

Day of over-mounting is necessary for the appropriate preparation of structures at the factory and at the construction site. Increased accuracy of manufacturing structures is provided by the following:

■ construction of the shoe of the columns and the base plate of the shoe is manufactured and delivered to the object separately;

■ the ends of the two branches of the columns must be milled;

■ Base plates are made planed.

4 strips with threaded holes for bolts should be welded to each base plate; axial hazards should be applied to the branches of the columns.

In the non-calibrating method of installation, steel columns are supported on a steel plate. In this case, the surface of the foundations is concreted below the design mark by 50 ... 60 mm and, after exact installation, the plates are poured with cement mortar. The base plate is set with adjusting bolts on the support strips, which must be concreted into the foundation flush with its surface as embedded parts. The supporting plane of the plate is set by adjusting the nuts of the set screws on the level. The value of the actual mark of the base plate should not differ from the design by more than 1.5 mm.

When installing the column, axial risks on its branches are combined with the risks applied on the support plates, which ensures the design position of the column, and it can be fixed with anchor bolts. Additional displacement of the column for alignment along the axes and height is not required in this case. After installing the braces to the mounted structures of the columns and their tension begin to mount crane girders. Crane beams installed on axial risks do not require additional alignment. After fixing them on the bolts, the braces are removed.