A new semi-analytical procedure is derived for the determination of buckling of the reinforced concrete column exposed to fire. The fire analysis is performed in three separate steps, of which the time development of temperatures in the fire compartment is performed first, followed by the coupled heat and moisture transfer analysis and, finally, by the mechanical analysis. A particular emphasis has been given to the critical buckling time and the remaining critical buckling load at a selected time. For this purpose, a parametric study has been performed by which the influence of different geometric parameters on the buckling load capacity of reinforced concrete columns has been assessed. The results of this study show that the load-carrying capacity of the column reduces significantly with the increasing time of fire exposure and the column slenderness. Moreover, the initial mechanical load has a small, although not negligible effect on the buckling load capacity.
COBISS.SI-ID: 6871137
A derivation of approximate, yet closed-form solutions of the following problem is presented: for a given curvature vector, determine both the rotation and the angular velocity. The quaternions are used for the parametrization of rotations, and the integrations are partly performed in the four-dimensional quaternion space. The resulting closed-form expressions for the rotational and angular velocity quaternions are ready to be used in the finite-element formulations of the dynamics of flexible spatial beams as interpolating functions. The present novel solution is assessed by comparisons of the numerical results with analytical solutions, as well as with the solutions of some existing numerical methods
COBISS.SI-ID: 7017313
This paper presents an efficient mathematical model for studying the global buckling behavior of concrete-filled steel tubular (CFST) columns with compliant interfaces. The present mathematical model is used to evaluate exact critical buckling loads and modes of CFST columns for the first time. The results prove that the presence of finite interface compliance may significantly reduce the critical buckling load of CFST columns. A good agreement between analytical and experimental buckling loads of circular CFST columns is obtained if at least one among longitudinal and radial interfacial stiffnesses is high. The design methods compared in the paper give conservative results in comparison with the experimental results and analytical results for almost perfectly bonded layers. The parametric study reveals that critical buckling loads of CFST columns are very much affected by the diameter-to-depth ratio and concrete elastic modulus. Moreover, a material nonlinearity has a pronounced effect for short CFST columns, and a negligible effect for slender ones.
COBISS.SI-ID: 7151457
The paper presents a simplified model for coupled heat and moisture transfer and charring behaviour of timber exposed to fire. A numerical method to calculate temperature, bound water, water vapour and pressure distribution over two dimensional domain in timber specimen exposed to fire was developed. In the model, a modified description of sorption for the temperatures above the boiling point is proposed. In addition, the model also accounts the char formation. Due to the non-linear system of governing equations describing coupled heat and moisture transport, together with the char formation, the solution is obtained numerically with the finite element method. Finally, the result from the numerical analysis are validated against experimental measurements.
COBISS.SI-ID: 7062369
This paper deals with the heat transfer analysis of the 63-year-old and 60-m-high Moste concrete arch-gravity dam, located in Northwest Slovenia. The analysis was performed after a new sophisticated monitoring system had been established, making it possible to perform continuous measurements of the temperatures of the concrete, water, and dam surroundings. An equation defining nonlinear and nonstationary heat conduction in the case of a two-dimensional space, for a homogeneous isotropic solid whose thermal conductivity is independent of temperature, was solved numerically. The results show that the measured and calculated temperatures of the concrete at different locations, and at different depths, were in very good agreement.
COBISS.SI-ID: 2114663