Removal of a monolithic reinforced concrete floor slab damaged by through cracks from an emergency state

The issue of durability and reliability of monolithic reinforced concrete structures is always relevant. Timely technical inspections of structural elements of the building, detection of defects and elimination of the cause of their occurrence make it possible to restore the load-carrying capacity by carrying out repairs and increase the durability of the building. The article highlights the results of the visual-instrumental inspection of the ceiling above the eleventh floor of the unfinished multistory building on the street. Chemists in Ivano-Frankivsk. Conducting a visual-instrumental inspection of the floor slab above the eleventh floor is associated with the need to determine the crack causes on the entire slab surface in the lower and upper zones and establish the condition of technical state and provide proposals for further operation of the floor slab. At the time of the inspection, the building had eleven floors. It is planned to build three more floors and a technical one. Conclusions about its carrying capacity were formed and recommendations for further operation were developed. Destructive and non-destructive methods determined the average grade of concrete of the examined floor slab - C12/15, which does not correspond to the concrete class C20/25. With the help of the Trimble M3 electronic total station, the deflections due to the self-weight of the floor slab were determined, with the help of the MPB-2 microscope (0.05mm division), the maximum crack opening widths and the depth of penetration into the body of the monolithic slab were determined. By mechanical opening and with the help of the "POISK 2.51" ultrasonic device, the number, diameter and class of working fittings in the compressed and stretched zones were checked and recorded. Field tests and verification calculations of the load-carrying capacity showed that in the compressed zone of the floor slab, all excessive cracks are shrinkable. Since the zone of compression of concrete is excluded from the work, the additional load on the slab will cause its destruction. To ensure further safe operation and forces perception in the compressed zone of concrete, it is proposed to increase the working height of the slab, to perform reinforcement of the reinforcement element with main reinforcement in two directions. Schemes of reinforcement and instructions for the order of execution of work when reinforcing the floor slab are proposed.