HORDIIUK M. Durability and deformation of reinforced-concrete slabs at power and high temperature influences

The dissertation summarizes the current state of the issue and sets the tasks of research, the main prerequisites for the possibility of using reinforced concrete slabs under force and high temperature influences. A methodical approach to the assessment of the stress-strain state of slab structures is presented. The developed technique is based on the prerequisites that are usually accepted when solving similar problems. The exact calculation of reinforced concrete slabs working in two directions is proposed to be performed with the help of special software packages by numerical methods (for example, by the finite element method). Experimental researches of fragments of buildings on fire resistance are carried out. A reinforced concrete fragment was used as an experimental sample, the structural system of which was a spatial structure with monolithic reinforced concrete walls and a room-sized floor slab. Reinforcement of structures, as well as the materials used (concrete, reinforcement), corresponded to those actually used in the construction of residential buildings from monolithic reinforced concrete. The obtained results allowed to establish that the test by the real center essentially differs from tests by model. The heating temperature increases much faster in real hearth tests than in model hearth tests. High-temperature heating and subsequent fire extinguishing with water leads to the destruction of surface layers and weakening of concrete. Conditioning of structures in the fresh air leads to destruction and stratification of the strengthened concrete with exposure and corrosion of armature. Practical methods for determining the limit of fire resistance of slab elements have been developed. To determine the limit of fire resistance in the event of a limit state on the bearing capacity, it is necessary to perform thermal and static parts of the calculation. According to the results of the thermal part of the calculation, the zone of destruction is determined under the conditions of heating by a heat source from below and the temperature distribution along the thickness of the plate. The temperature distribution along the thickness of the plate is determined during the research, but can be taken from the results of previous research. The technique of definition of a technical condition and a residual resource of the operated reinforced concrete plate designs which is used at inspections of designs, designing of elements of strengthening of designs of buildings and constructions is developed. The comparisons of results which are received experimentally and by means of calculations on the methods developed by the author, and also data on practical application of results of the spent researches of designs at definition of their technical condition and a residual resource are resulted.