Lytvyn O. Interaction of high-rise buildings with the soil base under dynamic influences.

The dissertation by O.V. Lytvyn, "Interaction of High-Rise Buildings with Soil Foundations under Dynamic Impacts", is dedicated to the study of the stress-strain state of foundation structures in high-rise construction under the influence of dynamic loads, including seismic and blast effects. The primary goal of the research is the development and enhancement of mathematical models and methodologies that improve the accuracy of predicting the interaction of the "foundation–soil–building" system and optimize structural solutions to enhance the stability of buildings. The study analyzes soil compaction mechanisms beneath foundations, assesses the impact of soil compressibility on load-bearing capacity, and develops numerical modeling algorithms using the finite element method (FEM) implemented in the Abaqus software. A new mathematical model has been proposed, incorporating changes in porosity coefficient and deformation modulus of soil as a function of pressure, allowing for more accurate prediction of settlements and uneven compaction. The research examines the effects of seismic waves and blast loads on high-rise buildings, focusing on their impact on resonance frequencies, torsional oscillations, and the non-uniform distribution of stresses in load-bearing structures. Numerical methods were applied to analyze the dynamic behavior of buildings, including direct time integration methods, the CONWEP algorithm for modeling blast loads, and the normal mode method for assessing seismic wave impact. The study revealed that insufficient width of expansion joints in multi-section buildings could lead to increased impact loads and damage in critical areas. Methods for reducing dynamic response have been proposed, including the introduction of beam systems, which adjust the spatial rigidity of structures, modify resonance frequencies, and ensure a more uniform distribution of stresses. These methods help to reduce vibration amplitudes by 20–30%, thereby preventing progressive structural failure. The practical significance of the research is confirmed by its implementation in the design of building foundations for a real construction project in Kyiv, leading to a reduction in pile foundation length and reinforcement requirements by up to 30%, while maintaining permissible settlement values. The obtained results can be applied in the development of regulatory frameworks for high-rise construction in seismically active regions and in the design of foundation structures under complex geotechnical conditions.