{"title":"How to reduce the risk in the proving process for quality construction products","authors":"Sonja Čerepnalkovska, Ljubica Vladiceska","doi":"10.5937/GRMK1701065C","DOIUrl":"https://doi.org/10.5937/GRMK1701065C","url":null,"abstract":"Quality infrastructure with its components ensures compliance of products and services with the mandatory requirements, interests of consumers and businesses, and contributes to the maintaining of the quality of products and services. Quality infrastructure promotes export, competitiveness and innovation. Conformity assessment helps ensure certainty that products and services deliver on their promises. In other words, conformity assessment builds trust. This paper, which is based on the questionnaire, presents the real situation or the number of accredited laboratories in the Republic of Macedonia for testing in the field of construction as well as the participation in PT schemes, with an emphasis on the cement as a crucial product in the construction industry.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"60 1","pages":"65-76"},"PeriodicalIF":0.4,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fiber element formulation for inelastic frame analysis","authors":"M. Kostic, B. Deretić-Stojanović","doi":"10.5937/grmk1602003k","DOIUrl":"https://doi.org/10.5937/grmk1602003k","url":null,"abstract":"The paper discusses two formulations for the fiber based distributed plasticity beam/column element. For force based and displacement based formulations, basic details and main differences are emphasized. The differences in results of analysis when elements with these two formulations are used are demonstrated on two numerical examples. The first example involves the nonlinear static pushover analysis of low-rise frame with distributed element loading. The second example is nonlinear time history analysis of two-story frame subjected to earthquake loading. The differences in global and local response depending on the used finite element discretization are shown. In conclusion, the advantages of force based formulation and directions for the use of the two elements are summarized.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"3-13"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Analysis and modelling composite timber-concrete systems: Design of bridge structure according to EN","authors":"D. Manojlovic, Tatjana Kočetov-Mišulić","doi":"10.5937/GRMK1604047M","DOIUrl":"https://doi.org/10.5937/GRMK1604047M","url":null,"abstract":"Timber-concrete composite structures are already applied more than 80 years in engineering practice, went trought the intuitive problem solution to the fully prefabricated hybride assemblies for dry building. The development path of timber-concrete composites was always followed by extensive theoretical and experimental research, whose results were successfully implemented in practice, i.e. on the market, but till presence didn't result in modern designer's code. In expectation of new European codes for timber-concrete composites, the objective of the paper is to provide a comprehensive review of available standards provisions and recent conclusions from literature. The key issues for practical design are highlighted and ilustrated on the example of glulam composite arch bridge structure with concrete deck, according the Eurocodes.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"47-74"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gordana Topličić-Ćurčić, Dušan Grdić, Nenad Ristić, Zoran Grdić
{"title":"Environmental importance, composition and properties of pervious concrete","authors":"Gordana Topličić-Ćurčić, Dušan Grdić, Nenad Ristić, Zoran Grdić","doi":"10.5937/GRMK1602015T","DOIUrl":"https://doi.org/10.5937/GRMK1602015T","url":null,"abstract":"Porous or pervious concrete was in use since the 60's of the previous century. It was first used in the USA and afterwards in Europe. The environmental importance of pervious concrete can be seen through fast collection of stormwater from the pavements, parking lots and other impervious surfaces. . Special purification systems remove the detrimental matter from the collected strormwater. As such, it can be used for other purposes. The pervious concrete has little or almost no fine aggregates. Its porosity is high, and ranges between 15 and 30 % in comparison to the concrete volume. Prior to massive usage of pervious concrete, it was necessary to prove, i.e. to examine its properties in service conditions. The paper elucidates the environmental character of pervious concrete, provides its usual composition and its properties.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"15-27"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Radeka, T. Milović, M. Malešev, V. Radonjanin, M. Laban
{"title":"Hydration process and compressive strength of cement pastes containing natural zeolite","authors":"M. Radeka, T. Milović, M. Malešev, V. Radonjanin, M. Laban","doi":"10.5937/GRMK1602029R","DOIUrl":"https://doi.org/10.5937/GRMK1602029R","url":null,"abstract":"This paper presents the results of the study examining the effect of natural zeolite from Igros, Serbia, on the hydration and compressive strength of Portland cement based pastes, in which a part of cement has been replaced by natural zeolite. The experimental part comprises three stages. In the first stage, the chemical composition of natural zeolite and the textural properties of both natural zeolite and Portland cement have been examined. In the second stage, Portland cement based pastes incorporating 0%, 10%, 20% and 30% per weight of natural zeolite have been prepared and cured for 28 and 60 days. Finally, mineralogical properties and compressive strength of pastes have been examined. The products of hydration and relative changes of portlandite consumption throughout hydration process (28 and 60 days) have been studied by the means of X-ray diffraction and Fourier transform infrared spectroscopy. Additionally, mercury intrusion porosimetry has been used to characterise pore structure.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"29-45"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Nonlinear stability analysis of the frame structures","authors":"Ćorić Stanko, Brčić Stanko","doi":"10.5937/GRMK1603027C","DOIUrl":"https://doi.org/10.5937/GRMK1603027C","url":null,"abstract":"In this paper the phenomenon of instability of frames in elasto-plastic domain was investigated. Numerical analysis was performed by the finite element method. Stiffness matrices were derived using the trigonometric shape functions related to exact solution of the differential equation of bending according to the second order theory. When the buckling of structure occurs in plastic domain, it is necessary to replace the constant modulus of elasticity E with the tangent modulus Et. Tangent modulus is stress dependent function and takes into account the changes of the member stiffness in the inelastic range. For the purposes of numerical investigation in this analysis, part of the computer program ALIN was created in a way that this program now can be used for elastic and elasto-plastic stability analysis of frame structures. This program is developed in the C++ programming language. Using this program, it is possible to calculate the critical load of frames in the elastic and inelastic domain. In this analysis, the algorithm for the calculation of buckling lengths of compressed columns of the frames was also established. The algorithm is based on the calculation of the global stability analysis of frame structures. Results obtained using this algorithm were compared with the approximate solutions from the European (EC3) and national (JUS) standards for the steel structures. By the given procedure in this paper it is possible to follow the behavior of the plane frames in plastic domain and to calculate the real critical load in that domain.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"27-44"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The properties of the cement screeds with the addition of polypropylene fibres and the shrinkage-reducing admixture","authors":"Radan Radulovic, D. Jevtić, V. Radonjanin","doi":"10.5937/grmk1601017R","DOIUrl":"https://doi.org/10.5937/grmk1601017R","url":null,"abstract":"The paper points out the problems of damage that can occur during the preparation and exploitation of a cement screed. There were described the types and properties and presented test results obtained on the samples of cement composites prepared with the addition of fibre reinforcement and shrinkage-reducing admixture. Testing procedure included the following properties: density, compressive strength, ultrasound, coefficient of construction advantages and shrinking, and above all the impact of compaction procedure on the quality of cement screed. The testing results of experimental research show that the use of polypropylene fibres and shrinkage-reducing admixture contributes to the improvement of mechanical and deformation properties of cement screeds and that installation which includes some method of vibration is crucial for screed quality. The above statements are also recommendations in the execution of cement screed in practice.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"17-35"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71224952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fracture toughness of ultra high performance concrete by flexural performance","authors":"E. Manolova","doi":"10.5937/grmk1601003M","DOIUrl":"https://doi.org/10.5937/grmk1601003M","url":null,"abstract":"This paper describes the fracture toughness of the innovative structural material - Ultra High Performance Concrete (UHPC), evaluated by flexural performance. For determination the material behaviour by static loading are used adapted standard test methods for flexural performance of fiber-reinforced concrete (ASTM C 1609 and ASTM C 1018). Fracture toughness is estimated by various deformation parameters derived from the load-deflection curve, obtained by testing simple supported beam under third-point loading, using servo-controlled testing system. This method is used to be estimated the contribution of the embedded fiber-reinforcement into improvement of the fractural behaviour of UHPC by changing the crack-resistant capacity, fracture toughness and energy absorption capacity with various mechanisms. The position of the first crack has been formulated based on P-δ (load- deflection) response and P-e (load - longitudinal deformation in the tensile zone) response, which are used for calculation of the two toughness indices I5 and I10. The combination of steel fibres with different dimensions leads to a composite, having at the same time increased crack resistance, first crack formation, ductility and post-peak residual strength.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"59 1","pages":"3-9"},"PeriodicalIF":0.4,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71224900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Estimation of concrete compressive strength using artificial neural network","authors":"Srdjan Kostic, D. Vasović","doi":"10.5937/GRMK1501003K","DOIUrl":"https://doi.org/10.5937/GRMK1501003K","url":null,"abstract":"In present paper, concrete compressive strength is evaluated using back propagation feed-forward artificial neural network. Training of neural network is performed using Levenberg-Marquardt learning algorithm for four architectures of artificial neural networks, one, three, eight and twelve nodes in a hidden layer in order to avoid the occurrence of overfitting. Training, validation and testing of neural network is conducted for 75 concrete samples with distinct w/c ratio and amount of superplasticizer of melamine type. These specimens were exposed to different number of freeze/thaw cycles and their compressive strength was determined after 7, 20 and 32 days. The obtained results indicate that neural network with one hidden layer and twelve hidden nodes gives reasonable prediction accuracy in comparison to experimental results (R=0.965, MSE=0.005). These results of the performed analysis are further confirmed by calculating the standard statistical errors: the chosen architecture of neural network shows the smallest value of mean absolute percentage error (MAPE=, variance absolute relative error (VARE) and median absolute error (MEDAE), and the highest value of variance accounted for (VAF).","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"58 1","pages":"3-16"},"PeriodicalIF":0.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"EVALUATION OF STRUCTURAL RELIABILITY USING SIMULATION METHODS","authors":"M. Baballëku, B. Isufi","doi":"10.5937/GRMK1501017B","DOIUrl":"https://doi.org/10.5937/GRMK1501017B","url":null,"abstract":"Eurocode describes the 'index of reliability' as a measure of structural reliability, related to the 'probability of failure'. This paper is focused on the assessment of this index for a reinforced concrete bridge pier. It is rare to explicitly use reliability concepts for design of structures, but the problems of structural engineering are better known through them. Some of the main methods for the estimation of the probability of failure are the exact analytical integration, numerical integration, approximate analytical methods and simulation methods. Monte Carlo Simulation is used in this paper, because it offers a very good tool for the estimation of probability in multivariate functions. Complicated probability and statistics problems are solved through computer aided simulations of a large number of tests. The procedures of structural reliability assessment for the bridge pier and the comparison with the partial factor method of the Eurocodes have been demonstrated in this paper.","PeriodicalId":40707,"journal":{"name":"Gradevnski Materijiali I Konstrukcije-Building Materials and Structures","volume":"58 1","pages":"17-23"},"PeriodicalIF":0.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71225215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}