The process of the abrasive water jet cutting of materials, supported by the theories of fluid mechanics, abrasive wear and damage mechanics, is a high-tech technologies that provides unique capabilities compared to conventional machining processes. This paper, along the theoretical derivations, provides original contributions in the form of mathematical models of the quantity of the cut surface damage, expressed by the values of cut surface roughness. The particular part of this paper deal with the results of the original experimental research. The research aim was connected with the demands of industry, i.e. the end user. Having in mind that the conventional machining processes are not only lagging behind in terms of quality of cut, or even some requests are not able to meet, but with the advent of composite materials were not able to machine them, because they occurred unacceptable damage (mechanical damage or delamination, fiber pull-out, burning, frayed edges).

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The paper points out to the differences of the First order theory and Second order theory and of the significance in practical calculations. The paper presents theoretical foundations and expressions of calculations of impacts on the stability of structure, that is, review of the Second order theory in a bridge with members semi-rigid connections in joints. In the real structures in general and the especially in the prefabricated structures the connection of members in the nodes can be partially rigid which can be very significant for the changes in tension and deformation. If the influence of the normal forces is significant and the structure is slender then it is necessary to carry out a calculation according to the Second order theory because the balance between internal and external forces really established on the deformed configuration and displacements in strict formation are also unreal. The importance and significance of the calculations and distribution of impact according to the Second order theory were presented in numerical examples as well as the calculation of critical load as well as the buckling length of members with semi-rigid connections in joint

Subject reviewThe paper presents an analysis of behaviour of plate girders (welded steel I girders) under patch loading. Concentrated or uniformly distributed loading on a short length of the flange, and in the plane of web is known as patch loading. Behaviour of the girder in non-linear area, as well as the ultimate load capacity, which is manifested by buckling in the loaded zone were analysed. Girder modelling was performed in ANSYS Workbench 15 software [1]. In accordance with the standing regulations EN 1993-1-5 [2] and BSK 07 [3], in the course of the numerical analysis, six different material models were employed. The obtained results were compared to the experimentally obtained results. Keywords: material nonlinearity; patch loading; steel girders; ultimate load capacity Analiza nelinearnosti materijala limenih nosača podvrgnutih lokalnom opterećenjuPregledni članak U radu se daje analiza ponašanja limenih nosača (nosači od zavarenog čelika I) pod lokalnim opterećenjem. Koncentrirano ili jednoliko raspoređeno opterećenje na maloj udaljenosti od prirubnice i u ravnini mreže, poznato je kao lokalno opterećenje (patch loading). Analiziralo se ponašanje nosača u nelinearnom području kao i učinak kritičnog opterećenja, koji se manifestira izvijanjem. Za modeliranje nosača primijenjen je softver ANSYS

Abstract-Monitoring of civil engineering structures and constructions requires techniques which can produce high precision and accuracy, reliable measurements and fast processing speed. The development of information and communication systems as well as of microprocessor controllers has enabled a creation of monitoring systems that can be used for tracking reliability of structures and constructions in civil engineering, with described key features. This paper describes in detail the architecture of the Civil Engineering Structures Reliability Monitoring (CERM) system. The system has been designed for the purposes of the Technical Mechanics and Theory of Constructions Department at the Faculty of Civil Engineering and Architecture, University of Nis. Unlike general commercial monitoring systems, the CERM system has been specially designed for the purpose of reliability monitoring, and its potential will be further exploited in this paper. It is based on usage of universal microprocessor controllers Integraf of series 10X, along with specially designed software package. This system provides real time acquisition of measurements for observed civil engineering structures and analysis of received values based on developed mathematical models.