The effect of (1) initial imperfections and (2) material degradation of reinforced concrete columns on their safety in emergency situations was investigated. The research was limited to low- and medium-flexibility columns. Numerical modeling and proven regulatory methods of analysis were applied to determine the ultimate bearing capacity, taking into account supplementary dynamic loading by a longitudinal force and a bending moment in case of emergency. The numerical model, describing the column structure, has 3D elements simulating concrete, and rebars simulating reinforcement frames (cages). Imperfections are simulated by (1) the physical loss of elements, (2) unzip of nodal elements, and (3) unzip and further zip using nonlinear elements simulating gaps and cohesion between concrete and reinforcement. Implicit dynamics and an incremental method were employed to make computations. Within the framework of this computational scheme, a nonlinear problem was solved using the Newton–Raphson method with nodal forces convergence. The effect of imperfections, such as geometrical deviations and deterioration of mechanical characteristics, on the bearing capacity of compressed bending elements was identified under emergency actions. Risks of mechanical safety loss were analyzed to find that columns in the frame structures of highly hazardous, technically complex, and unique buildings and structures, subjected to supplementary loading, need an additional safety margin in the range of 3–21%. Rectangular cross-sections of columns are the most effective in terms of the safety criterion.

Alternative approaches to the estimation of corrosion-damaged beams stiffness with regard for localization of corrosion focus and distribution of corrosion damages in concrete on the basis of layered model are considered. The following methods of determining displacements in corrosion-damaged reinforced concrete beams of rectangular cross-section have been considered. In the first one, the stiffness of the beam in determining the deflection is considered constant. In this case, the corrosion-damaged deflections values may be underestimated due to failure to take into account the actual work of reinforced concrete. In the second, the deflection is calculated considering the height of the concrete compression zone that varies along the length of the beam. For these approaches, stiffness reduction in the beam sections in the presence of corrosion damage to the concrete of the compressed zone is modeled. It is shown that in the presence of corrosion damage, the deflections of the structure can significantly increase, which requires mandatory consideration in the life cycle of load-bearing structures of structures when assessing their mechanical safety. The necessity of obligatory registration of corrosion damages in the implementation of algorithms of optimal design of reinforced concrete structures has been revealed.

Method of searching for rational shapes of skeletal structures based on the use of Delaunay tetrahedron partition algorithms with constraints and evolutionary modeling has been developed. Topology of load-bearing rod system is synthesized on specified multitude of nodes at fixed number of rods. Established structures are considered redundant and are optimized by means of excluding individual members. Optimization is performed with the modified genetic algorithm pursuant to criterion of minimum weight of structure. An example of synthesis of rectangular rod structure showing performance of suggested approach in terms of shape synthesis of trusses has been given.

The article describes methods of optimal design of steel frame structures of buildings considering impacts not provided for standard operation conditions. In particular fast removal of support braces is analyzed. The frame optimization methodology based on evolutionary simulation is used for solving this task considering plastic deformation of the damaged structure in the genetic algorithm.