The influence of the components of plaster mortars on their properties is considered in a lot of studies at a qualitative level without searching for optimal compositions of these multicomponent ...composite materials. The purpose of this study was to obtain the experimental-statistical models based on the results of the designed experiment, allowing the influence of light fillers and polymer admixtures on the properties of the mortars to be evaluated and analysed; the compositions complying with specified requirements and compromised optimally by a number of properties should be found. The quantities of fine limestone and perlite as well as of the hydroxyethyl methyl cellulose and dispersible polymer were varied in the experiment. The effective viscosity and thixotropy of the mix, compression, tensile, adhesive strength, frost resistance, and density of hardened mortars were determined for 18 compositions according to the experiment design. The obtained models have allowed the individual and synergetic effects of mix components to be evaluated. The fine perlite has turned out to have the greatest positive effect on the properties. This porous filler increases the strength while decreasing the density of the mortars. It is shown how the composition complying with specified requirements-and the best based on several properties-has been found.
The article shows the development of analytical method for the calculation of damaged reinforced concrete columns of circular cross-section. The theory and the basic settings for the calculation are ...based on European Eurocode standards. The paper describes the development of method, from basic assumptions (most important assumption arises in condition of the external and internal forces plain parallelism) to the final setting of five equations with five unknowns for further solving using Newton-Raphson method. The final results (via the input and resolved parameters) are given in the height of the compressed area x, the stresses in the reinforcement bars sigma.sub.si and finally, in the current bearing capacity of damaged rc section N.
The effects of particles orientation, as a result of filling technology, on horizontal pressure within the confined vertical walls is investigated in this experimental study. Experimental ...measurements of pressure were performed in a model of cell construction with confined rigid steel walls. Filling was performed in three different ways according to predominant angle of grain orientation to the horizontal line of 0°, 45° and 90°. Because of different particles orientation angle, certain anisotropy of shear failure parameters and significant difference in lateral pressure occur. Experiment results showed a significant difference in horizontal pressure at different angles of particle orientation. At angle 90° horizontal pressure was on average 200 % more than at 0°.
Feasibility of application of multifractal theory for evaluation of materials mechanical properties, cast iron in particular, has been considered. The proposed method enables evaluation of mechanical ...properties of materials based on determination of their sensitivity to dimensions of structure elements from the multifractal Renyi spectrum. Sensitivity of cast iron ultimate strength to informational dimension of carbides, ultimate bending strength to fractal dimension of carbides, impact strength to correlation dimension of carbides and hardness to fractal dimension of graphite have been determined. Fractal prediction models of quality characteristics of cast iron based on the analysis of the following its structure elements (carbides and graphite) have been received.
The article describes a developed technique of a numerical simulation of the stress-strain state of complex-reinforced elements, which allows you to create models of double-span continuous. The ...performed experimental and theoretical studies allowed us to carry out the testing of the developed design model and to justify the reliability of the proposed numerical simulation methodology. The results of the experimental studies were compared with those of the theoretical studies. The theoretical calculus algorithm was developed by using the finite element method. Theoretical calculations were performed by using the mathematical-graphical environment software system LIRA-SOFT and the mathematical and computer program MATLAB. On the basis of the experimental research, the iso-fields of displacements and stresses in the materials of an eccentrically compressed beam with a small bend of the slab were constructed, which collapse behind the inclined narrow strip of concrete and displacements and stresses in the materials of the eccentrically stretched beam, which is destroyed due to the yield of the upper mounting armature.
The work is devoted to researching the parameters of expanded clay lightweight concrete technology by using carbonation hardening that allows to maximally intensify the process of carbonization using ...methods such as decreasing the total water content in the system, applying optimal structure and formula concrete compositions, processing the products in carbon dioxide environment. The mechanism of structure formation of concrete compositions in conditions of artificial carbonation was studied. It was formulated using the basic techniques of rational intensification of the hardening process. Rational formulation and technological parameters of carbonization technology of lightweight aggregate concrete wall products were proposed: effective replacement of almost 30 per cent of concrete by powdered lime rock in process of carbonization without changing the physical and technical properties of material; the optimal size of porous aggregates; the optimal modes of composite carbonization that include preliminary placement in vacuum and step processing in carbon dioxide environment. The maximum demoulding strength of expanded clay lightweight concrete was received by using maximum concentration of carbon dioxide during carbonization in reaction area that is characterized by the maximum pressure value. In addition, the properties of concrete in an early stage after the carbonization were explored.
Današnji složeni komunikacijski prostor predstavlja preplet najrazličitijih formi izričaja i tehnika stvaranih i mijenjanih kroz mnoga tisućljeća. U suvremenoj komunikologiji prevladava mišljenje da ...je sluh nositelj glavnog komunikacijskog kanala! Ako je to točno onda tome treba dodati i drugu stranu medalje, tj. da je sluh izričito fragilna komunikacijska kategorija, pa se stoga u vremenskom protoku vrlo nepouzdano oslanjati na sluh. Pojava pisma prije više od 5000 godina (Sumer) kompenzirala je glavni nedostatak sluha (nepostojanost), no i mnogo prije toga spontano je začeta komunikacijska kategorija koja je s „malo riječi“ puno toga mogla „reći“. Bilo je to GRADITELJSTVO. „Jedini“ je problem u tome što za „čitanje” graditeljskih „zapisa“ postoji imperativ prethodnog dešifriranja „ugrađenih kodova“. U ovom se članku težište stavlja upravo na dekodiranje nekih od kodova koji su prevladavali kroz ljudsku povijest.
Today's complex communication space is interwoven with many different forms and techniques that have been created and altered through milleniums. Contemporary communication observes the sense of ...hearing as the front runner of the main communication canal! If this is true, we should also look at the other side of the coin. Hearing is a very fragile communication category especially in a longer time span when it becomes an unreliable source. The emergence of the script more than 5000 years ago (Sumer) substituted the main flaw of hearing (inconstancy) but there is another communication category that had sponetaneously emerged way before the script. This communication category which could always „say a lot with few words“ is known as construction. But in order to be able „to read“ the „building/construction signs“, there is an imperative of prior deciphering the „built-in codes“. This articles puts an emphasise on deciphering some of the prevailing codes in human construction history.
Today's complex communication space is interwoven with many different forms and techniques that have been created and altered through milleniums. Contemporary communication observes the sense of ...hearing as the front runner of the main communication canal! If this is true, we should also look at the other side of the coin. Hearing is a very fragile communication category especially in a longer time span when it becomes an unreliable source. The emergence of the script more than 5000 years ago (Sumer) substituted the main flaw of hearing (inconstancy) but there is another communication category that had sponetaneously emerged way before the script. This communication category which could always „say a lot with few words“ is known as construction. But in order to be able „to read“ the „building/construction signs“, there is an imperative of prior deciphering the „built-in codes“. This articles puts an emphasise on deciphering some of the prevailing codes in human construction history.
Na objektima izgrađenim u prošlom stoljeću jasno su vidljivi određeni tipovi oštećenja kod kojih je razvidno da su nastali zbog kombinacije određenih faktora: dugotrajne eksploatacije konstrukcije, ...dugotrajnog kontinuiranog opterećenja, dinamičkih i na kraju kemijskih utjecaja. Analizirajući sve moguće uzroke oštećenja, u članku je detaljno razrađena klasifikacija oštećenja ab konstrukcija. Analiziran je armiranobetonski stup kao tipičan, strukturni element mnogo puta korišten u konstrukciji. Pregledom literature i raznih eksperimentalnih istraživanja u posljednjih 80-ak godina izdvojen je jedinstven tip oštećenja eksperimentalnih modela koji se nedvosmisleno poklapa s oštećenjima nastalih tijekom eksploatacije stupa. Dan je prijedlog modela ispitivanja oštećenih ab stupova te su analizirani osnovni parametri koji će dovesti do sloma elementa tijekom ispitivanja.
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