Papers by Ilija M MILIČIĆ
Journal of Faculty of Civil Engineering, 2024
In this study, a computer simulation was conducted in the MATLAB 2021a software environment to ve... more In this study, a computer simulation was conducted in the MATLAB 2021a software environment to verify the testing of the dynamic parameters of a wooden girder system. Accelerometer type TP54 with patent number 332/83 measured the oscillations. A digital oscilloscope, Hantek 6022BE, was used for visualizations of measurements. A low-pass Butterworth filter was used for signal filtering. We achieved good value of accuracy without applying a low-pass Butterworth filter. The signal filtering procedure applied during the software modelling of the response in the dynamic analysis only prolonged the processing and validation time of the treated girder. However, using a low-pass Butterworth filter is recommended as a "good practice". In conclusion, the original recorded individual responses of the girder's oscillations in the vertical plane under dynamic excitation exhibit high accuracy in the processed series of time-discrete signals with continuous amplitude.
Journal of Faculty of Civil Engineering, 2024
This study performed a theoretical-experimental procedure for monitoring and analysis of the inte... more This study performed a theoretical-experimental procedure for monitoring and analysis of the intersection allocation in the middle of the line girder in the vertical plane using a laser sensor VL6180X. The applied measuring system is a nondestructive method, a new, easy-to-apply case of monitoring static and dynamic parameters in the structures of constructive systems based on the treated physical model. Registering test results is a single format of an electrical continuous digital signal collected in the Arduino programming environment in the time domain with simultaneous exporting to the widely used MS Excel format. Measurement results prepared for the fast Fourier transform using a self-made software model in the Matlab2021a environment. Therefore, software modelling using DFT and iDFT verified the relevant data in the temporal and frequency domain. Finally, DFT analysis showed slight deviations in vertical displacement of the girder system treated in this study compared to the results of the FFT-treated analysis of the identical displacement signal in the vertical plane.
Zbornik radova Građevinskog fakulteta, 2015
У раду се рачунарским моделирањем и симулацијама динамичким моделом третирају принудне, пригушене... more У раду се рачунарским моделирањем и симулацијама динамичким моделом третирају принудне, пригушене осцилације система са једним степеном слободе кретања. Спољашње принудно дејство моделирано је као функција померања чија је учестаност односа 3-9-27 десетина од вредности природних учестаности осцилација модела. На основу теоријске анализе, рачунарским симулацијама одзива динамичког модела показано је да имамо мале величине померања при највишим учестаностима спољашње побуде.
Materijali i konstrukcije, 2003
Zbornik radova Građevinskog fakulteta, 2016
Zbornik radova Građevinskog fakulteta, 2019
In this paper, a 1D dynamical model with substrate resistance was imposed with three frequencies ... more In this paper, a 1D dynamical model with substrate resistance was imposed with three frequencies of displacement amplitudes with two amplitudes with frequencies in the resonant region. If the external excitation is treated as a continuous periodic real function with two variables (the basic oscillation period-the first and the ratio of the frequency of the external excitation and the response of the model-the second) then we can present the final solution of the motion of the 1D model in conjugated complex form. Applying FFT algorithms with MathCAD, the treated displacement amplitudes in the frequency and time domains respect the mapping suggested by the transfer function (I.M.Miličić, 2015) and with a smaller number of order members. Computer simulations confirmed that the harmonic response of a 1D dynamic model system can be successfully modeled based on the equivalent solution which shown here.
Zbornik radova Građevinskog fakulteta, 2019
In this paper, an excitation with two different frequencies of displacement amplitudes outside th... more In this paper, an excitation with two different frequencies of displacement amplitudes outside the resonant region is imposed on a 1D dynamic model with resistance of the substrate. Applying FFT algorithms with MathCAD applications, are treated displacement amplitudes in the frequency and time domains respect the mapping suggested by the transfer function (I.M.Miličić, 2015). Conducted computer simulations confirmed that the harmonic response of a 1D dynamic model system can be successfully modeled based on the demonstrated equivalent solution.
Materijali i konstrukcije, 2008
Zbornik radova Građevinskog fakulteta, 2014
Journal of Thermal Analysis and Calorimetry, Apr 5, 2020
The article presents the results of an extensive experimental study focused on the effect of supp... more The article presents the results of an extensive experimental study focused on the effect of supplementary cementitious materials (SCMs) on concrete thermal properties. In case of normal weight concrete (NWC) and three types of lightweight aggregate concretes (LWAC), made with 6 different types of cements, the heat transfer properties of the concrete were tested and compared with density-based recommendations. The measured heat conductivities showed a significant effect of SCM materials incorporated in cement mixes, especially in case of NWC. The results of volume heat capacities were less affected by the use of different cement types in LWAC, contrary to NWC. In one set of mixes, the natural quartz sand was replaced with dacite sand to evaluate the effect of SCM materials when the LWAC is made with low-heat conductivity sand. Further, the effect of cement replacement with fly ash and bottom ash, from waste disposal (FBW), was investigated, on LWACs heat transfer properties. First, the FBWs physical properties were optimized by mechanical activation in order to achieve LWAC with low-heat conductivity and fair compressive strength. The experimental investigation demonstrated the way to obtain a contemporary green LWAC by reducing more than 80% of the cement clinker amount with SCMs.
Journal of Structural Engineering-asce, Apr 1, 2013
In this study, free vibration analysis of a cross-ply laminated composite beam (LCB) on Pasternak... more In this study, free vibration analysis of a cross-ply laminated composite beam (LCB) on Pasternak foundation was investigated. Natural frequencies of beam on Pasternak foundation are computed using finite element method (FEM) on the basis of Timoshenko beam theory. Effect of both shear deformation and rotary inertia are implemented in the modeling of stiffness and mass matrices. The model was designed in such a way that it can be used for single-stepped cross-section, stepped foundation and multi-span beams. Results of few examples are compared with finding in literature and good agreements were achieved. Natural frequencies of LCBs with different layers arrangements (symmetric and non-symmetric) are compared. For multi-span beam, variation of frequency with respect to number of spans was also studied.
Tehnicki Vjesnik-technical Gazette, Nov 1, 2019
This paper considers the potential of designing and constructing floor slabs taking into account ... more This paper considers the potential of designing and constructing floor slabs taking into account three aspects of major importance: flexibility-adaptability, energy efficiency and seismic safety. Currently traditional reinforced concrete floor slabs at least 20 centimetres thick are still designed and built. Such practice has no justification, as thick concrete floor slabs hinder architectural creativity as well as all the other aforementioned aspects. In this paper, the authors analyse and demonstrate the simultaneous correlation between flexibility-adaptability, energy efficiency, seismic safety and the mass of the floor slabs in residential buildings. Massive floor slabs limit the distance between load-bearing walls and consequently the adaptability of residential space. A large mass directly intensifies the seismic forces it induces. Thick concrete slabs have high heat capacity, as they have high mass and volume. The solution to floor slabs which satisfy all three aspects is to design and build them as waffle slabs. These two-way spanning concrete slabs have low mass, are rigid and can span the distance of more than 10 metres between two load-bearing walls.The authors of this paper suggest that floor slabs conform to the limitation in mass provided in this paper under Eq. (5) and (6). By applying this principle, architects would be able to design more flexible, adaptable, energy efficient, and seismically safe living spaces.
Tehnika - Naše građevinarstvo, 2002
Zbornik Radova Građevinskog Fakulteta, 2019
In this paper, an excitation with two different frequencies of displacement amplitudes outside th... more In this paper, an excitation with two different frequencies of displacement amplitudes outside the resonant region is imposed on a 1D dynamic model with resistance of the substrate. Applying FFT algorithms with MathCAD applications, are treated displacement amplitudes in the frequency and time domains respect the mapping suggested by the transfer function (I.M. Miličić, 2015). Conducted computer simulations confirmed that the harmonic response of a 1D dynamic model system can be successfully modeled based on the demonstrated equivalent solution.
In this research, theoretical analysis, numerical modelling and simulations correlated with exper... more In this research, theoretical analysis, numerical modelling and simulations correlated with experimental procedures are used to analyze cross sectional static load distribution. This distribution is determined through general deformation measurements – deflections and changes of slope tangent on the deflection line according to usability criteria analysis for specially chosen bridge structures. In this research, special attention is systematically dedicated to classification of cross sectional load distribution as a crucial factor considering most, currently available, CAA software (in this case Tower and SAP 2000n). For this purpose numerical model evaluation is introduced that is based on the real behavior of bridge structure. Survey of domestic and foreign codes and regulations revealed that the criterion depicted in this research represents an innovation in bridge structure categorization form the urban planning point of view. Аn original proposal for classification of bridge structures is given in this work. It is compiled form a case studies of experimentally tested bridge structures that are compared regarding their numerical modeling and simulation methods. Considering deformation verification, geometric and mechanical analogy secured a simpler and more realistic numerical modeling of composite “steel – concrete” cross sections with geometrically identical modeling concept. It is shown, through geometric and mechanical analogy that stiffness varies along the girder. This variation is given with a width function of engaged concrete slab and a mechanical characteristics ratio of two materials. Cross sectional load distribution coefficient as model’s parameter is a function of measured deflections. It is stochastic in nature since it depends on a number of parameters that have different influences under different circumstances. However, for solving everyday problems it is usually defined as a constant. As a measure of special significance it is proposed that usability criteria, form general deformations stands, is adopted in a form of L/800 ratio – a regular behavior state of a structure, by which a necessary level is secured with regards to suitability in bridge structure maintenance. Key words: analysis, bridges, models and modelling, calculation model, CAD – CAA programme interaction, simulation, measurement, cross sectional static load distribution, usability of structures, stability of structures.
Uploads
Papers by Ilija M MILIČIĆ