PRIMJENE ALUMINIJSKIH LEGURA U GRAĐEVINARSTVU

Although aluminium is a long known structural material, its use is not in accordance with the benefits achieved by its implementation. There are several reasons for such an adverse state. Those that stand out are the late development of a regulative framework for the design of structures, and still the need for improvement, lack of knowledge on application examples and not stressed enough potential areas of use. However, positive trends are present and aluminium alloys are competitive, especially if their positive properties can be utilized and negative properties diminished through purpose oriented design approach. Given examples present good application utilization of aluminium alloys characteristics, and shown new application research can provide directions for further expansion of competitiveness. Structural uses are grouped in suitable areas of application and put into local and global context.Iako je aluminij već dugo prisutan konstrukcijski materijal, uporaba mu nije u skladu s dobrobitima koji se ostvaruju njegovom primjenom. Nekoliko je uzročnika takvog stanja. Ističu se relativno kasni razvoj normativnog okvira za dimenzioniranje konstrukcija, i još uvijek potreba za poboljšanjem, nedovoljna raširenost saznanja o primjenama te nedostatno naglašena potencijalna područja primjene. Međutim, pozitivni trendovi su prisutni, a legure aluminija su konkurentne, posebno ako se njegova pozitivna svojstva mogu iskoristiti, a negativna umanjiti kroz proračunski pristup orijentiran prema namjeni. Prikazani primjeri predstavljaju dobro iskorištavanje karakteristika aluminijskih legura kroz namjenu, a nova istraživanja primjena mogu pružiti oslonac za daljnje proširenje konkurentnosti. Konstrukcijske primjene su prikazane kroz moguća područja i stavljene u lokalni i globalni kontekst

Probabilistic assessment of calculation resistance models of composite section with partial shear interaction

Istraživani su spregnuti nosači u zgradarstvu s djelomičnom posmičnom vezom. Postupak određivanja točne otpornosti presjeka na savijanje takvih spregnutih nosača iterativan je i dugotrajan. Analizirana su četiri različita proračunska modela otpornosti, različitih autora, koji omogućuju neiterativno određivanje otpornosti ovakvih nosača. Laboratorijski utvrđena otpornost poprečnog presjeka na savijanje uspoređena je s otpornostima dobivenim korištenjem različitih modela, nakon čega su računski modeli probabilistički evaluirani. Rezultat ovakve analize je najpouzdaniji neiterativni proračunski model za određivanje otpornosti na savijanje poprečnih presjeka s djelomičnom posmičnom vezom Nadalje, predlaže se novi proračunski model otpornosti. Predloženi model se temelji na linearnom modelu koji se zatim prilagođava najpouzdanijem neiterativnom proračunskom modelu otpornosti. Koeficijent korekcije određuje se na determinističkoj razini, nakon koje se provodi probabilistička analiza novog modela. Rezultat istraživanja je vrlo jednostavan neiterativni model koji daje razinu pouzdanosti u skladu s ciljanom vrijednosti indeksa pouzdanosti.Composite beams in buildings with partial shear connection have been researched. The procedure of determining the exact resistance of such composite beams in bending with partial shear interaction is iterative and tedious. Four different calculation resistance models of various authors for non-iterative determination of such cross-section resistance have been analysed. Bending resistance of cross-section obtained from laboratory tests is compared with the resistance calculated from different models after which the calculation models are probabilistically evaluated. The result is the most certain non-iterative calculation resistance model of cross-section in bending for a beam with partial shear interaction. Furthermore, a new resistance model is proposed. The proposed model is based on a linear model which is then modified according to the most favourable non-iterative calculation resistance model. Correction coefficient is obtained on a deterministic level, after which probabilistic evaluation of the new model is conducted. The result is a very simple non-iterative model with the reliability levels close to the target value of the reliability index

Analysis of castellated beams according to Eurocode 3

Razmatrani su saćasti nosači kao alternativa punostijenim nosačima na velikim rasponima. Opisana su novija istraživanja i mogući načini otkazivanja takvih konstrukcijskih elemenata. U radu je prikazan proračun takvih nosača prema normi Eurokod 3, a dobiveni rezultati uspoređuju se s normom DIN koja se rabila u nas. Na temelju provedenih parametarskih analiza upozoreno je na područje ekonomične primjene saćastih nosača s obzirom na njihove relativne vitkosti i veličine otvora.The use of castellated beams instead of solid web beams for large spans is considered. Some recent studies are presented, and conditions under which such structural elements can prove defective are proposed. The analysis of such beams according to Eurocode 3 is presented in the paper, and the results obtained are compared with the DIN standard, which is used in our country. Taking note of appropriate parametric analyses, the authors point to the area in which castellated beams can be economical, because of their relative slenderness and span sizes

A modern approach to proving fire resistance of structures

Prikazana je praksa i pristup zaštiti konstrukcija od požara u Hrvatskoj. Opisane su mjere zaštite od požara koje se predviđaju glavnim projektom. Iz toga se opisa vidi nesređenost stanja u pogledu primjene inozemnih i domaćih propisa i smjernica. Dane su temeljne postavke Eurokoda o pristupu problemu požara. Na primjeru je pokazana mogućnost dobivanja optimalnih rješenja adekvatnim proračunom. Autori preporučuju hitnu promjenu prakse vezane uz zaštitu konstrukcija od požara.Current practices and approaches to the protection of structures against fire hazard in Croatia are presented. Fire protection measures that are usually specified in detailed design documents are described. This description reveals that the current situation regarding application of foreign and national regulations and guidelines is quite disorderly. Principal Eurocode directives related to the fire protection issue are presented. An example is used to illustrate the way in which optimum analytical solutions can be found. The authors recommend urgent change of current practices regarding protection of structures against fire hazard

NEUESTER STAND ZUR STABILITÄT UND SCHWEISSUNG VON ELEMENTEN AUS ALUMINIUMLEGIERUNGEN

Iako je aluminij već dugo prisutan konstrukcijski materijal, uporaba mu nije u skladu s dobrobitima koje se ostvaruju njegovom primjenom. Sličan je čeliku, no između njih postoje značajne razlike kako u proizvodnji, tako i u fizikalnim i mehaničkim svojstvima. Upravo iz tih razlika proizlaze posebnosti u područjima stabilnosti dijelova poprečnih presjeka i konstrukcijskih elemenata te u područjima zavara. Ta polja još uvijek predstavljaju aktivna područja istraživanja zbog velikog broja legura, obrada i oblika poprečnih presjeka profila.Although aluminium is a structural material that has been present on the market for a long time, its use is not in accordance with the benefits that can be achieved by its application. While it is similar to steel, there are significant differences between these materials, both in manufacturing and in physical and mechanical properties. Due to such differences, these materials exhibit distinct features in the areas of cross sectional and elements stability and welds. These areas are still an active field of research due to a large number of alloys, processing methods, and cross-sectional shapes.Obwohl Aluminium schon lange als Konstruktionsmaterial bekannt ist, wird es nicht den Vorteilen seiner Anwendung entsprechend eingesetzt. Auch wenn das Material mit Stahl verglichen werden kann, bestehen bedeutende Unterschiede, sowohl in der Herstellung, als auch in den physikalischen und mechanischen Eigenschaften. Folglich umfassen die Stabilität der Querschnitte oder Elemente und die Schweißflächen eine Reihe von Besonderheiten, die weiterhin einen aktiven Forschungsbereich darstellen, insbesondere aufgrund der großen Anzahl von Legierungen, Verarbeitungsmethoden und Querschnittsformen

Analysis of castellated beams according to Eurocode 3

Razmatrani su saćasti nosači kao alternativa punostijenim nosačima na velikim rasponima. Opisana su novija istraživanja i mogući načini otkazivanja takvih konstrukcijskih elemenata. U radu je prikazan proračun takvih nosača prema normi Eurokod 3, a dobiveni rezultati uspoređuju se s normom DIN koja se rabila u nas. Na temelju provedenih parametarskih analiza upozoreno je na područje ekonomične primjene saćastih nosača s obzirom na njihove relativne vitkosti i veličine otvora.The use of castellated beams instead of solid web beams for large spans is considered. Some recent studies are presented, and conditions under which such structural elements can prove defective are proposed. The analysis of such beams according to Eurocode 3 is presented in the paper, and the results obtained are compared with the DIN standard, which is used in our country. Taking note of appropriate parametric analyses, the authors point to the area in which castellated beams can be economical, because of their relative slenderness and span sizes

A modern approach to proving fire resistance of structures

Prikazana je praksa i pristup zaštiti konstrukcija od požara u Hrvatskoj. Opisane su mjere zaštite od požara koje se predviđaju glavnim projektom. Iz toga se opisa vidi nesređenost stanja u pogledu primjene inozemnih i domaćih propisa i smjernica. Dane su temeljne postavke Eurokoda o pristupu problemu požara. Na primjeru je pokazana mogućnost dobivanja optimalnih rješenja adekvatnim proračunom. Autori preporučuju hitnu promjenu prakse vezane uz zaštitu konstrukcija od požara.Current practices and approaches to the protection of structures against fire hazard in Croatia are presented. Fire protection measures that are usually specified in detailed design documents are described. This description reveals that the current situation regarding application of foreign and national regulations and guidelines is quite disorderly. Principal Eurocode directives related to the fire protection issue are presented. An example is used to illustrate the way in which optimum analytical solutions can be found. The authors recommend urgent change of current practices regarding protection of structures against fire hazard

Reliability of castellated beams subjected to lateral-torsional buckling

Linija izvijanja za određivanje otpornosti saćastih nosača na bočno-torzijsko izvijanje u Eurokodu 3 nije jednoznačno određena. Prikazani su rezultati vlastitih laboratorijskih ispitivanja na temelju kojih je na probabilističkoj razini istražena veličina indeksa pouzdanosti ß u odnosu na ciljanu vrijednost za klasu konstrukcija RC2 primjenom sve četiri linije izvijanja. Utvrđene su linije izvijanja (b i c) prikladne za određivanje bočno-torzijske otpornosti saćastih nosača.The buckling curve that defines resistance of castellated beams to lateral-torsional buckling has not been unambiguously defined in Eurocode 3. The authors present laboratory results on the basis of which the reliability index ß was defined on the probabilistic level in relation to target value for structural category RC2, using all four of buckling curves. The buckling curves (b and c) have been determined as appropriate for defining lateral-torsional resistance of castellated beams

Influence of Alcohol Abuse of the Father on the Intensity of Clinical Picture of Posttraumatic Stress Disorder

The subject of the study is the influence of alcohol abusing father on the clinical picture of PTSD patient. The father plays an important identification role in the psychological development of his son. Therefore it is to be expected that an alcohol abusing father will become a (negative) role model for his son and that he will also later on in stressful situations try to reduce the anxiety and depression by consuming larger quantities of alcoholic drinks. The aim of the study is to find out whether there are differences in PTSD clinical picture in patients whose fathers abused alcohol and in those whose fathers did not have such problem. The participating patients were from the Psychiatric hospital »Sveti Ivan«. Mississippi and Watson scales were applied, as well as a questionnaire named »Early traumas« from which the variable »alcohol abuse of the father« was selected. The analysis shows that the participants who in their family histories had fathers who abused alcohol developed a milder clinical picture of PTSD, i.e. they reactions to the stress later on were less sensitive compared to the control group of participants whose fathers did not abuse alcohol and whose clinical pictures of the disorder were more severe

Thermal effects on buildings - meteorological input data for Croatian standards

Uvodno je prikazano termičko djelovanje na građevine prema prednormi ENV 1991-2-5:1997, što ovisi o klimatskim parametrima. Slijedi opis istraživanja režima ekstremnih temperatura zraka za Hrvatsku na bazi podataka iz razdoblja 1961-1990. Temperaturno zoniranje Hrvatske provedeno je prema vertikalnim gradijentima parametara Tmax50 i Tmin50 i njihove ovisnosti o nadmorskoj visini. Definirano je pet zona za maksimalne temperature zraka i šest zona za minimalne temperature zraka.Thermal effects on buildings, defined in the draft standard ENV 1991-2-5:1997, and dependant on climatic parameters, are presented in the introductory part of the paper. The paper continues with the description of the study of extreme air temperature regimens in Croatia, based on data from the 1961-1990 period. The temperature-based zoning of Croatia was conducted according to vertical gradients of parameters Tmax50 and Tmin50, and based on their dependence on altitude. Five zones were defined for maximum air temperatures while six zones were defined for minimum air temperatures