NUMERICAL ANALYSIS OF BFRP REINFORCED CONCRETE SLAB EXPOSED TO IMPACT LOADS

Článok popisuje numerickú analýzu s využitím MKP jednoducho uloženej betónovej dosky zaťaženej rázovouvlnou od blízkeho výbuchu TNT nálože. Prúty výstuže dosky obsahujú bazaltové vlákna. Je vytvorený 3Dnumerický konečnoprvkový model a na analýzu je použitý software s explicitným riešičom. Na účely modelovaniaúčinkov rázového zaťaženia od tlakovej vlny je použitá zjednodušená metóda. Sú porovnané viaceré prípadys rôznymi veľkosťami siete, formuláciou konečných prvkov. Výsledky sú porovnávané s experimentálnymidátami.This paper describes advanced numerical analysis of a simply supported reinforced concrete slab exposed to close range explosion of a TNT charge. Finite element method (FEM) has been utilized in order to conduct the analysis. Non-linear material model for concrete slab is adopted. Reinforcing bars made of basalt fibre reinforced plastic (BFRP) are considered by elastic-plastic material model. 3D numerical model has been created, and a software with explicit solver (LS-Dyna) has been used in order to conduct analyses. A simplified modelling method of the blast loading has been utilized, which is based on the consideration of the load effects as a time dependent pressure. Several cases with different mesh size or different finite element formulation are investigated. The results are compared with experimental data based on study of fellow researchers. Match between the numerical analyses and measurements is discussed and considered as satisfying

Responses of structures to mining induced seismic event in the area near Karviná town

Response analyses of a selected group of typical structures to mining induced rockburst-type seismic event have been carried out. Sophisticated FEM models of analyzed structures have been developed. The measured three-directional seismogram selected to characterize the “typical mining induced seismic event” for the important mining area near Karviná town has been used to derive typical base acceleration time histories and corresponding response spectra as well. Seismic responses of structures with alternative parameters have been computed. Conclusions have been drawn for advanced seismic analyses

Investigation of eigenvalue problem of water tower construction interacting with fluid

The paper concerns problems, in which both the structural and fluid responses of a complex construction to mechanical actions are strongly coupled. Particularly, there are treated problems, in which the structural dynamic response to actions is significantly affected by the presence of the fluid in the structure. The work presents the evolution of the way of solving that problem of the complex solution of the generalized problem of the structure using multiphysical ANSYS program package. The formulation of fluid finite elements is discussed, considering both pressure (Euler) with/without sloshing and displacement (Lagrange) approaches. The solution is demonstrated on thin-walled steel water tower structure

Study of the Efficiency and Accuracy of Optimisation Algorithms within Inverse Identification of the Parameter Values of a Nonlinear Concrete Material Model

The inverse identification of the parameter values of nonlinear material models, which have been developed for, inter alia, concrete modelling, is currently a process that is widely used and investigated in the field of research and development. Today there are several approaches that can be employed for the inverse identification process. One of the most significant of these approaches involves the use of optimisation algorithms which, however, often demonstrate varying levels of precision and efficiency within specific tasks. These aspects are the subject of the research presented in this contribution

Inverse Identification of the Material Parameters of a Nonlinear Concrete Constitutive Model Based on the Triaxial Compression Strength Testing

The aim of this paper is to perform the inverse identification of the material parameters of a nonlinear constitutive model intended for the modeling of concrete which is known as the Karagozian & Case Concrete model. At present, inverse analysis is frequently used because it allows us to find the optimum parameter values of nonlinear material models. When applying such parameters, the resulting response of the structure obtained from a computer simulation is very similar to the real response of the structure based on the related experimental measurement. This condition then undoubtedly constitutes one of the progressive steps to refine the current numerical approaches. For the purposes of the inverse analysis performed in this paper the experimental data was obtained from the triaxial compression strength tests carried out on the concrete cylinders

Finite Element Modelling of Reinforced Concrete Slab Exposed to Extreme Fire Loads

Numerical approach using the finite element method has been used to determine the mechanical resistance (criterion R) of a reinforced concrete structure exposed to fire. Geometry of the structure is considered as a simply supported slab in one dimension. Fire load has been defined by a nominal standard ISO 834 fire curve. Both, thermal and structural response are obtained using a finite element method software ANSYS. Temperaturedependent nonlinear thermal and mechanical properties of concrete and reinforcement are adopted in accordance with Eurocode standards. Nonlinear material model Menetrey-Willam with exponential functions for compression hardening (and softening) and tension softening has been used to describe the behaviour of concrete elements. Discrete option of modelling reinforcement has been considered. Mechanical resistance of the slab is determined by reaching the limit mid-span deformation. Results have been compared with simplified method of isotherm 500 °C described in Eurocode

Mesh Size Influence of the Concrete Slab FE Model Exposed to Impact Load for Various Material Models

Numerical approach using the FEM has been used to model the behaviour of the reinforced concrete specimen subjected to the pressure blast wave. The concrete structure is a slab freely supported around the perimeter by a steel plate and a concrete base. A simplified 3D blast model has been used, which involves the pure Lagrangian approach of FEM. The analyses have been conducted using explicit solver. 3 different non-linear material models of concrete have been used to capture the concrete behaviour: CSCM (Continuous surface cap model), Schwer Murray continuous surface cap model, and JHC (Johnson-Holmquist-Cook) material model. Influences of various mesh sizes on the final results (crack patterns, vertical deflection, strain-time dependence) are being monitored, compared with physical experiment data and discussed.Ostrav

Requirements of technical standards for the dynamic analysis of the load-bearing structures of footbridges

The load-bearing structures of footbridges are designed to be slender and feature spans of considerable length. It can be expected that the natural frequencies of such load-bearing structures range from 0.5 Hz to 5.0 Hz. These low natural frequencies are problematic as regards the effects caused by the dynamic component of wind or the movement of persons. Increased acceleration values can lead to the serviceability limit state of structures being exceeded or the heightening of stress which can result in damage to the structure mainly in the area of details prone to fatigue. The contribution deals with the requirements concerning the execution of dynamic analyses which are listed in the relevant technical standards. It will present procedures for the determination of dynamic loading, methods of solving dynamic tasks as well as design criteria enabling delicate bridge structures to be designed correctly