Jovan Tepić

Mathematical identification of influential parameters on the elastic buckling of variable geometry plate

The problem of elastic stability of plates with square, rectangular, and circular holes as well as slotted holes was discussed. The existence of the hole reduces the deformation energy of the plate and it affects the redistribution of stress flow in comparison to a uniform plate which causes a change of the external operation of compressive forces. The distribution of compressive force is defined as the approximate model of plane state of stress. The significant parameters of elastic stability compared to the uniform plate, including the dominant role of the shape, size, and orientation of the hole were identified. Comparative analysis of the shape of the hole was carried out on the data from the literature, which are based on different approaches and methods. Qualitative and quantitative accordance of the results has been found out and it verifies exposed methodology as applicable in the study of the phenomenon of elastic stability. Sensitivity factor is defined that is proportional to the reciprocal value of the buckling coefficient and it is a measure of sensitivity of plate to the existence of the hole. Mechanism of loss of stability is interpreted through the absorption of the external operation, induced by the shape of the hole.

Modeling Elastic Stability of a Pressed Box Girder Flange

The paper examines the elastic stability of pressed sheet metal flange of a box girder. Mathematical interpretation of elastic stability is performed on the model plate with two freely supported and two elastically restrained edges subjected to combined loads. The research is based on the energy analysis approach, using the principle of minimum deformation energy and the method of cross-sectional girder element decomposition. The plate elastic stability mechanism is investigated in an interactive environment that simulates local loads and compressive longitudinal forces produced by global stress. The significant geometric parameters, as well as support and load conditions affecting the loss of stability, are identified. The research results can be applied as a constraint on the local flange stability in the optimization of box girders.

Markovian ants in a queuing system

The synthesis of memoryless Markovian systems and Ant based concept with memory characteristics of deposit pheromone is the basis for the presented artificial intelligence hybrid Only the initial elements of the system are specified in this paper by illustrating the routes of two ants The pheromone capacity was first modelled as an exponential-type random variable The Ant Queueing System was formed The pheromone capacity was then used to form two independent exponential random variables The convolution of these variables induces significant quality and quantity changes, mainly the decrease in entropy The study also provides a possible method for dealing with stationary queueing systems when we are familiar with the state probability and the arrival rate and service rate are unknown.

Unconventional Bearing Capacity Analysis and Optimization of Multicell Box Girders

This study deals with unconventional bearing capacity analysis and the procedure of optimizing a two-cell box girder. The generalized model which enables the local stress-strain analysis of multicell girders was developed based on the principle of cross-sectional decomposition. The applied methodology is verified using the experimental data (Djelosevic et al., 2012) for traditionally formed box girders. The qualitative and quantitative evaluation of results obtained for the two-cell box girder is realized based on comparative analysis using the finite element method (FEM) and the ANSYS v12 software. The deflection function obtained by analytical and numerical methods was found consistent provided that the maximum deviation does not exceed 4%. Multicell box girders are rationally designed support structures characterized by much lower susceptibility of their cross-sectional elements to buckling and higher specific capacity than traditionally formed box girders. The developed local stress model is applied for optimizing the cross section of a two-cell box carrier. The author points to the advantages of implementing the model of local stresses in the optimization process and concludes that the technological reserve of bearing capacity amounts to 20% at the same girder weight and constant load conditions.

A virtual mass model in train aerodynamics

This paper describes a new method of research in to the aerodynamics of vehicles, and how to interpret them. The virtual mass is related to the absorption of kinetic energy and the unit coefficient of restitution of a central collision. Train systems are used to exemplify the approach, and the virtual mass effect is air. Successive collisions of these two factors and systems offer a model of air resistance. Thereby, a relationship between the most important aerodynamic characteristic (the coefficient of aerodynamic profile) and the virtual mass is established.