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This paper presents an experimental–numerical analysis of damage localization of concrete plate‐like elements on the basis of hybrid approach. The proposed hybrid approach uses the fast discrete wavelet transform, energy approach, and time of flight criterion for the purpose of localization of single and multidamage problems inside or on the periphery of concrete elements. Verification of the proposed damage localization approach has been performed under laboratory conditions using a laser scanning‐based system with piezoelectric excitation of the wave propagation. Numerical simulation of the wave propagation is performed using the explicit finite element method using 3D models with linear‐elastic material model of concrete with Rayleigh damping. The Rayleigh damping coefficients are determined on the basis of experimental data and implemented in numerical models. Validation of the numerical model is conducted, based on the comparison with sensor output signals obtained through experimental measuring and a very good agreement of results is obtained. The proposed hybrid approach to damage localization is verified using 15 different models/specimens, varying the number, shape (circular or notched), and position of damage, as well as the number and placement of actuators/sensors. For all the analyzed scenarios, the hybrid approach successfully localized the damage even for the least number of used sensor positions. In the models with the circular damage, the damage image created on the basis of the hybrid approach is almost identical to the actual shape of the damage, indicating a good potential of the method for damage localization.

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Monitoring of structures implies integration of sensors and actuators, smart materials, data transfer as well as computer analyses and simulations with the purpose of damage detection, localization, assessment and prediction of the state of damage at the certain moment and in time. This paper presents the application of the explicit finite element method for modeling of the wave propagation. The examples of concrete plates and thin steel plates in which the propagation of the Lamb waves occur were analyzed. Explicit finite element method was shown to be very efficient even for the waves in ultrasound range. Efficiency, ease of the use and reliability of the wave propagation modeling by the explicit finite element method can contribute to the development of a new and the improvement of the existing methods for the monitoring of structures. The main purpose of this paper is to demonstrate a waveform propagation model using an explicit FEM in ABAQUS software.

The construction of energy efficient buildings using innovative building materials such as phase change materials, in addition to improving indoor comfort, energy savings and costs, can be achieved by increasing their market value. Because of its ability to absorb and release energy at predictable temperatures, phase change materials are effective in controlling and maintaining the thermal environment in the building. The use of phase changing materials, materials stored latent energy storage is an effective form of heat. [Projekat Ministarstva nauke Republike Srbije, br. TR36016: Experimental and theoretical investigation of frames and plates with semi-rigid connections from the view of the second order theory and stability analysis

Original scientific paper Concrete is one of the most widely used materials in civil engineering structures. Extremely high temperatures can seriously damage the concrete structure, leading to degradation of its mechanical properties. Considering high temperatures in civil engineering applications is strongly connected with the fire scenarios in which temperatures in concrete can reach 1000 °C. For using computer software for analysis of the reinforced concrete structures, it is essential to formulate constitutive stress-strain models of steel and concrete, which can be done using fundamental approach or by fitting curves to experimental data. In this paper, new stress-strain model was proposed using the two-parameter equation for fitting curves to experimental data. Verification of the model is done using experimental results available in the literature for temperatures up to 800 °C. Comparison with the models available in the literature was provided. The new model showed better agreement with experimental results, especially for the temperatures higher than 500 °C. Keywords: concrete; high temperature; stress-strain curve Novi model za opisivanje krivulje naprezanje-deformacija betona pri povišenim temperaturamaIzvorni znanstveni članak Beton je jedan od najrasprostranjenijih materijala koji se koriste za izradu građevinskih objekata. Djelovanje visokih temperatura može ozbiljno oštetiti strukturu betona, što dovodi do degradacije njegovih mehaničkih karakteristika. Razmatranje glavnih karakteristika ponašanja građevinskih konstrukcija pri visokim temperaturama je povezano s djelovanjem požara, pri kojima se javljaju temperature u betonu i do 1000 °C. Za uporabu računarskih softvera za analizu armirano betonskih elemenata izloženih požarima neophodno je formulirati konstitutivne σ-ε modele kako čelika tako i betona, što se može postići fundamentalnim pristupom, ali i prilagodba krivulja prema eksperimentalno dobivenim podacima. U ovom radu predložen je novi dvoparametarski model za opisivanje krivulje naprezanje-deformacija. Novi model je potvrđen na eksperimentalnim podacima dostupnim u literaturi za temperature do 800 °C. Dana je njegova usporedba s drugim modelima dostupnim u literaturi. Rezultati pokazuju bolje poklapanje s eksperimentalnim podacima, posebice pri temperaturama većim od 500 °C.

The University campuses represent a dominant type of organization of the living activities of students. Buildings and common features, were usually built, in a classical manner. This means that majority of the student living complexes was built in the massive and skeletal structural systems of concrete and steel. This paper deals with the possibilities, advantages and examples of an innovative structural system, named CLT or XLAM system. The XLAM system was developed in Germany around 12 years ago and it has been rapidly spreading in most European countries such as Austria, Switzerland, Italy and Nordic Countries. It is a European innovative timber based material in which timber boards, made of domestic timber species are assembled in layers and glued together crosswise in order to form massive timber wall and floor panels characterized by significant mechanical properties. Such type of structural system can serve as a models for construction of residential, commercial and student facilities in Serbia. [Projekat Ministarstva nauke Republike Srbije, br. TR 36037: Construction of Student hostels in Serbia at the beginning of 21st century]

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