The paper presents a finite element model of a reinforced concrete viaduct column retrofitted with a steel jacket. The model was developed in ANSYS software, accounting for material nonlinearity and contact interactions between the concrete column and the steel jacket. The selection of finite element types, material constitutive laws, and the friction coefficient is justified. Numerical simulations revealed three distinct stages in the composite behavior of the column–jacket system under loading. Particular attention was given to the analysis of the contact interface and the investigation of the steel–concrete friction coefficient, which significantly influences the system response at each loading stage and serves as the basis for distinguishing these stages. The study demonstrates that accounting for the composite action between the reinforced concrete column and the steel jacket yields an additional load-carrying capacity reserve of up to 16% compared to separate, non-composite design calculations. Furthermore, the paper includes an analysis of the influence of the spacing of transverse tie plates of the jacket on the load-carrying capacity of the retrofitted column and identifies optimal ranges for this spacing.
Keywords: material nonlinearity, stress–strain relationship или Constitutive law, steel jacket, Pipe rack column, coefficient of friction, strengthening, finite element model, reinforced concrete, composite action, nonlinear stress–strain model
The assumptions of mathematical models for calculating the crack resistance of reinforced concrete structures are considered. For each of them, an analysis was carried out to determine whether they correspond to reality throughout the entire life cycle of the structure: from the hardening of the concrete mix to destruction. Based on the results of the analysis, it was proposed to use only one single calculation at the level of standards to assess the crack resistance of structures - according to the crack opening width, acrc. So, for example, at a certain value of acrc, the structure will still remain airtight (the cracks will be non-through), and if this value is exceeded, it will not. At the same time, the calculations already available in the norms for limiting permeability and the safety of reinforcement will still remain in demand. At the junction of the theory of damage accumulation and nonlinear fracture mechanics, a compressed algorithm is proposed for possibly taking into account the influence of cracks at all scale levels of the concrete structure, the key for which is the normalization of the statistical parameters of the distribution of discontinuities by diameters, lengths, openings, depths, directions, distances between discontinuities, etc.
Keywords: reinforced concrete, crack resistance, cracking moment, crack width, plasticity coefficient, damageability, non-linear fracture mechanics
The assumptions of mathematical models for calculating the crack resistance of reinforced concrete structures are considered. For each of them, an analysis was carried out to determine whether they correspond to reality throughout the entire life cycle of the structure: from the hardening of the concrete mix to destruction. Based on the results of the analysis, it was proposed to use only one single calculation at the level of standards to assess the crack resistance of structures - according to the crack opening width, acrc. So, for example, at a certain value of acrc, the structure will still remain airtight (the cracks will be non-through), and if this value is exceeded, it will not. At the same time, the calculations already available in the norms for limiting permeability and the safety of reinforcement will still remain in demand. At the junction of the theory of damage accumulation and nonlinear fracture mechanics, a compressed algorithm is proposed for possibly taking into account the influence of cracks at all scale levels of the concrete structure, the key for which is the normalization of the statistical parameters of the distribution of discontinuities by diameters, lengths, openings, depths, directions, distances between discontinuities, etc.
Keywords: reinforced concrete, crack resistance, cracking moment, crack width, plasticity coefficient, damageability, non-linear fracture mechanics