PRACTICAL METHOD FOR CALCULATION OF MONOLITHIC FLOOR SLABS STRENGTHENING WITH STEEL BEAMS
DOI:
https://doi.org/10.31650/2786-6696-2025-14-46-58Keywords:
floor slab, strengthening beam, model, calculation.Abstract
The method of strengthening of monolithic reinforced concrete slabs with steel beams in the lower zone is considered. From the late 1990s to the present, residential and civil construction in our country has been based on monolithic frame technology, where flat slabs are mainly used. Slabs often need to be strengthening as a result of damage caused by various reasons or when architectural and planning solutions are changed. Strengthening of such slabs with steel beams is used quite often in construction practice, especially in cases where it is not possible to fully unload the slab structure. The technical solutions for this method of strengthening have been developed for a long time and have many variations. However, if we analyse the building codes in the field of reconstruction and strengthening, we can identify a certain lack of calculation methods for the analysis of strengthening structures. A slab in a monolithic frame system is a repeatedly statically indeterminate structure, so its adequate calculation without the use of modern software systems is hardly possible.
A review of the current building codes in the field of reconstruction and strengthening is carried out. A number of publications in professional journals devoted to this topic and calculation approaches in the design of strengthening are considered. The structural features of strengthening with unloading beams are analysed. A practical methodology for calculating monolithic slabs strengthening with beams in the lower zone using the LIRA-SAPR software package is proposed. The methodology is based on taking into account the initial deformed state of the floor slab. The calculation is carried out by a step-iterative method, taking into account the physical-nonlinear properties of reinforced concrete and the life cycle of the structure. Particular attention is paid to the method of modelling the contact zone "slab-strengthening beam". The contact zone is modelled by means of one-sided connection, which perceives only compression forces.
The presented calculation algorithm has been tested by the author in the design of many facilities that have been implemented and successfully operated for a long time.
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