GENERAL DESCRIPTION
The introduction presents a general description of the work, substantiates the relevance of the dissertation research topic, discloses the connection of the work with scientific programs, plans and themes, formulates the purpose, objectives, object and subject of the dissertation research, indicates the scientific novelty and practical significance of the obtained results, defines the personal contribution of the applicant, provides data on approbation, publications, structure and scope of the work.
The first chapter analyzes modern approaches to fire resistance assessment of steel-reinforced concrete slabs, particularly those with profiled steel sheeting. Both experimental and calculation methods used in Ukraine and abroad have been studied. Problems related to accuracy, complexity and cost of existing methodologies are outlined. The need to improve approaches to determining fire resistance limits taking into account the features of actual structures, fire conditions and the influence of mechanical loading has been identified. The purpose and objectives of the dissertation research are formulated.
The second chapter investigates thermal processes occurring in steel-reinforced concrete slabs with profiled steel sheeting during fire exposure. Computational fluid dynamics (CFD) software was employed for this purpose. The specifics of computational mesh construction, selection of boundary conditions and model configuration are analyzed in detail. Temperature exposure modeling was performed for various scenarios, which allowed determining temperature distribution patterns in slab cross-sections and drawing conclusions about their thermal behavior.
The third chapter develops an experimental methodology for fire testing of steel-reinforced concrete slab specimens in a specially designed small-scale fire testing furnace. Requirements for furnace parameters, heating configuration, sensor characteristics and specimen mounting methods are determined. The process of specimen fabrication, conditioning under normal conditions and subsequent heating is described. The experimental procedure and results are presented. Temperature values were recorded at control points in the cross-section, which became the basis for subsequent calculations. The obtained data confirmed the feasibility of using a simplified testing model for fire resistance research.
The fourth chapter presents an improved methodology for fire resistance assessment of steel-reinforced concrete slabs, which involves temperature field reconstruction based on point measurements in a small-scale fire furnace. The proposed approach allows accounting for slab profile features and non-uniform heating without full-scale testing. Compliance of the temperature regime with the standard fire curve, negligible influence of slab orientation on results, and 30% reduction in measurement equipment requirements were confirmed. The fire resistance limit according to the load-bearing capacity criterion (239 minutes) was determined, validated by numerical analysis and consistent with data from scientific sources, which allows recommending the methodology for practical application.
The fifth chapter develops a step-by-step algorithm consisting of 9 stages for assessing the fire resistance limit of steel-reinforced concrete slabs with profiled steel sheeting, combining experimental and numerical methods. An improved implementation scheme for the methodology using a small-scale fire furnace is presented, accounting for specimen structural features and thermal conditions. Optimal parameters for specimen dimensions, installation configuration, burner placement and sealing requirements for air-tightness are substantiated. Post-fire residual load-bearing capacity calculation was performed, confirming the approach effectiveness. The list of mandatory experimental data for calculations is determined, and the use of Fisher's F-criterion for result verification is recommended.
Practical significance of the obtained results
Consists in developing an effective experimental-computational methodology for fire resistance limit assessment of steel-reinforced concrete slabs with profiled steel sheeting, which allows reducing full-scale fire testing volumes through the use of small-scale fire testing installations without loss of assessment accuracy; adapting the method to various slab types with steel profile rib heights up to 52 mm, accounting for actual reinforcement, geometry and thermal loading conditions; improving accuracy of temperature field and structural element strength calculations during fire exposure; integrating the proposed methodology into engineering calculation practice using Mathcad and ANSYS software, which facilitates automation of the fire resistance limit determination process; improving the regulatory and technical framework for testing and design of reinforced concrete structures for fire resistance.
