Introduction. In cities, a large number of buildings are multi-storey. Multi-storey buildings can be public, industrial and residential. Buildings with a height of more than 75 m are called high-rise, with a height of more than 100 m — unique. The frames of multi-storey buildings consist of columns, ties and ceilings. The bearing capacity and rigidity of the building frame is determined by the interaction of all the elements of the frame. The overlaps transfer the load to vertical load-bearing structures, form horizontal hard disks that combine columns with vertical connections, affect horizontal movements and vibrations of the frame. The stress-strain state of the frame is affected by defects and deviations from the design solution. The quality of a construction object depends not only on the quality of design and manufacturing, but also on the quality of construction and installation work. During the installation of building structures, the main objectives are to ensure the spatial position of building elements required by the project, the mutual connection of structures with each other, ensuring the safety of installation work. Installation of building structures is a complex process of assembling buildings from separate, pre-made elements. Increasing the efficiency of installation work is based on the use of progressive methods of work production, increasing the level of automation and mechanization of work. Geometric dimensional tolerances in construction are divided into functional and technological. For a frame structure with rigid interfaces of elements, deviations from the design position lead to the appearance of additional, primarily bending moments, which may cause earlier exhaustion of the bearing capacity. The relevance of the work is to develop a design methodology for steel frames of multi-storey buildings, taking into account fabrication and installation errors.

Materials and methods. The calculation of steel frames can be performed in linear and nonlinear formulation. The linear calculation does not take into account the deformation of the system under the action of the load and the forces accumulated in the frame elements. With the nonlinear approach, the calculation is performed by several methods: Elastic analysis of the second order-Plastic analysis of the second order. The assessment of the impact of initial imperfections was carried out on the example of a frame structure of a 10-storey residential building. When performing the calculation, the finite element model of the core frame is taken into account. The work of a separate flat frame is considered, which takes into account the design features of the frame. LIRA-SAPR 2021 computing complex was used for the calculation. Initial imperfections of the frame were taken in accordance with the current Russian standards. In addition to direct consideration of the distorted geometry, calculations were performed with additional distributed horizontal loads applied on each floor according to Eurocode 1993-1-1. The movements and forces of characteristic points and sections of the frame obtained by different methods were compared with each other. The influence of imperfections on movements and efforts from individual loads was studied. The cross sections of the frame elements were initially selected so that its bearing capacity was ensured under the action of combinations of combinations of design loads. The calculated combination of loads includes constant load, snow load, payload, wind load.

Results. When analyzing the results, it is necessary to take into account that direct accounting of assembly and manufacturing errors in the geometry of the frame is more correct, but requires the formation of more complex calculation schemes that take into account the errors of the geometry of the frame. The displacements and forces obtained by linear calculation of the frame structure differ little from the results of nonlinear calculation, which allows us to recommend a linear calculation method for the frame structure.

Conclusions. Based on calculations of the stress-strain state of the frame of a multi-storey building, it was found that direct accounting of manufacturing and assembly errors in the geometry of the frame allows for a more accurate assessment of the work of the frame. The use of Eurocode technique with additional horizontal loads at the level of each floor using a frame structure leads to excessive movements and efforts compared to the actual ones.