Assoc. prof. Tomaž Hozajn visited University of Boråsu, Faculty of textiles, engineering and business from 4th of April till 7th of July 2017. Druring the visit he excecuted lectures in fire engineering and fire design in total of 20 hours in the class Structural Engineering III (bachelor level, 7.5 ECTS). He also participated in extensive experimental reserch of rheological behaviour of wood. Obtained results were successfully used to calibrate the material parameters of the new two-dimensional rheological model for wood, which was also recently presented in the international scientific article.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 8341345In 2017 programme group members Dejan Zupan and Tomaž Hozjan served as editors of the Proceedings of Congress of Slovenian Society of Mechanics. The goal of these annual proceedings is to present the achievements of Slovenian researchers working in the field of mechanics.
C.02 Editorial board of a national monograph
COBISS.SI-ID: 291722240This paper focuses on development of a new mathematical model and its analytical solution for the buckling analysis of elastic longitudinally cracked columns with finite axial adhesion between the cracked sections. Consequently, the analytical solution for buckling loads is derived for the first time. The critical buckling loads are calculated for different crack lengths and various degrees of the contact adhesion. It is shown, that the critical buckling loads can be greatly affected by the crack length and degree of the connection between the cracked sections. Finally, the presented results can be used as a benchmark solution.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 1537498819This work focuses on the modeling of constitutive bending behavior of cables. Inelastic effects are investigated in bending experiments using the well-known three point bending setup and a new pure bending device. The results will show that an elastoplastic constitutive model is not sufficient to model the bending behavior of cables undergoing large deformations, because damage effects are observed as well. These effects are modeled using a finite beam element, which uses incremental displacements and rotations as primary variables. It is based on the Cosserat rod theory where the constitutive law is formulated in the sectional quantities of the beam%s cross section. The constitutive model includes linear elastic behavior for small deformations, plasticity with isotropic hardening and a damage formulation, which account for the effects observed at large deformations. Computational experiments are executed and model parameters are identified with optimization routines in comparison to experimental results.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 8333409In the present PhD thesis, the thermal and mechanical phases of the fire analysis of spatial steel beamlike structures are addressed. An iterative procedure for the determination of air temperature in the void space between the fire-protective boards and the steel cross-section surfaces is proposed, accounting for the heat transfer with convection and radiation. A novel mathematical model for the planar heat transfer over the steel cross-section, protected with an intumescent coating is also presented. The model considers all main phenomena of intumescent coatings such as a progressive expansion, and time and temperature dependent thermal properties of the coating. These are determined from the rules of mixtures as the ratios of temperature dependent properties of material phases; virgin, intumesced and charred material phases are considered. The ratios of each material phase are based on the current progress of the chemical reaction of pyrolysis. The reaction is modelled by the Arrhenius equation. A fully new mathematical model is also presented for the determination of the mechanical response of spatial steel frames in fire. The recently developed model for the dynamical analysis of spatial beam-like structures is based on Reissner%s geometrically exact beam theory which properly considers multiplicative properties of spatial rotations. The first spatial derivatives of the velocities and the angular velocities are chosen as the basic unknowns of our new numerical model. The model has been expanded to account for temperature dependent mechanical properties of steel, and considers thermal deformations, Harmathy%s model of viscous creep, plastic hardening and softening of material and several non-linear stress-strain relations. The model has been validated against experimental and numerical results from literature. The effects of numerical, mechanical and thermal parameters have been assessed. The results show that the present thermal and mechanical models well enable us to determine the mechanical response of spatial steel frames in fire realistically and accurately.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 8202849