Development of a creep-free stress-strain law for fire analysis of steel structures

© 2015 John Wiley & Sons, Ltd.This paper presents a practical procedure for obtaining creep-free stress-strain laws for steel exposed to fire, on the basis of codified stress-strain laws that consider creep implicitly. The applicability of the proposed procedure has been tested on two commonly used stress-strain laws for steel at elevated temperature, the Eurocode 3 law and a Ramberg-Osgood model, both of which have implicit consideration of creep. The simulation of two published steel coupon experiments on steel of grades S275 and S355 shows that both the Eurocode and Ramberg-Osgood stress-strain laws produce inaccurate predictions of creep in fire at elevated temperatures. The proposed procedure was thereby used to extract the implicit creep according to the heating rates of the transient coupon tests and to derive the creep-free stress-strain laws. It has been shown that, by combining the creep-free stress strain law obtained by the proposed methodology with an explicit creep model, a more realistic prediction of steel behaviour in the selected coupon test studies can be achieved

Nők az abortusz előtt : Tények és adatok a terhességmegszakítást kérõ nõk szociális körülményeirõl, védekezési szokásairól = WOMEN BEFORE ABORTION Facts and Data about the Social Circumstances and Contraception Methods of Women Requesting Abortion

Az abortusz kérdése gyakran kerül előtérbe mind tudományos, mind társadalmi körökben. Mégis kevés az olyan statisztikai felmérés, amely kimondottan a terhességmegszakítást kérő nőkkel foglalkozik. Kutatócsoportunk egy részletes - szociális adatokra, szexuális magatartásra, védekezési szokásokra, az abortusz indokára és a szociális kapcsolatokra kiterjedő - kérdőívet szerkesztett. Budapest négy kerületéből 117 abortuszt kérő nő válaszait dolgoztuk fel. A feleletek megoszlását először a teljes felmért populációban, majd korosztályok és kerületek szerinti bontásban ismertetjük. Eredményeink között szignifikáns eltéréseket találtunk a védekezési szokások, az abortusz oka, az anyagi helyzet és az eddigi abortuszok száma tekintetében. Külön vizsgáltuk a fiatalabb korosztályok szokásait, amelyek több szempontból is eltérnek a többi korosztálytól. A védekezési szokások szintén különböznek az iskolai végzettség függvényében. Az abortusz okának legtöbben az „anyagi helyzetet” jelölték meg, amit más kérdések tükrében részletesebben megvizsgáltunk. Adatainkat országos felmérésekkel is összehasonlítottuk

A Bálint-mozgalom nemzetközi helyzete = International perspectives of the Balint method

E tanulmány a külföldi szakirodalom alapján áttekintést ad a Bálint-módszer jelenéről. Bemutatja a módszer elterjedtségét Európában és az Egyesült Államokban, majd a hatékonyságát vizsgálja, különös tekintettel a háziorvosi rezidensképzésre. A kutatók szerint a Bálint-módszer egyértelműen emeli a háziorvoslás pszichoszociális hatékonyságát. Főleg az intuíciót, az éntudatot és az attitűdöket fejleszti. Az irodalom fontos megállapítása, hogy a Bálint-módszer nem minden orvos számára megfelelő. A kutatók a pszichoanalízis hatékonyságát egyértelműen igazolják, ugyanakkor az amerikai családorvosi rezidensképzésben a módszer nyit a magatartástudományok irányában. A Bálint-módszer az egészségügyi hivatásokon túl is alkalmazható. | The present study reviews the current situation on the Balint method. The spread of the Balint group in Europe and the USA is presented, and their effectiveness is examined especially among GP residents. The Balint method develops mainly intuition, ego developments and attitudes. The literature points out that the Balint method is not compliant with all physicians. The studies prove the efficacy of psychoanalysis in family practice, but the training for GP residents in the US including the Balint method is open towards behavioral sciences. Apart form health professionals, the Balint group method can be adopted for other professionals

Fire analysis of steel frames with the use of artificial neural networks

The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress-strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature-displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies. (c) 2007 Elsevier Ltd. All rights reserved

Changes in the Legal System: A Comparative Essay Based on the Hungarian Experience

This article is an attempt to understand the development of law, more particularly the civil law, in a country under constant changes, addressing history, sociology, economics, political science, lan-guages, literature, arts, and, most importantly, civil law itself. The country’s history starts from the foundation of the Hungar-ian state in the 11th century, in the middle of Europe, trying to be independent between strong Western kingdoms and the Byzantine Empire, and creating legal rules based on Christian values. This aim was pursued under the domination of different empires: Tatar, Turk, Austrian, Russian, and German. Political history helps understand the slow economic and social development, the special importance of public (constitutional) law, the importance of cultural development. Over the centuries, the de-velopment of civil law was connected with legal development in other countries of Europe, yet without a formal “reception” of Ro-man law. Attempts were made to codify civil law on basis of the classical civil codes but for different (mainly political) reasons with-out success. Consequently, although special important laws were enacted, Hungary had no written Constitution until 1949 and no Civil Code until 1959. Hungarian civil law was to a great extent judge-made law, with published decisions of the Supreme Court (the Curia) since the early 19th century, having binding force under con-ditions specified by Acts of Parliament. After World War II a politically controlled and centrally di-rected planned economic system prevailed. Nevertheless, the Civil Code of 1959 reflected the previous Hungarian civil law. As a result of a slow political détente, the importance of comparative law kept growing and civil law could develop, to contribute to the profound changes in the political framework leading to a new political system in 1990. Since that time, the Hungarian civil law developed within the framework of European harmonization and Hungary became a member of the European Union in 2004. The Civil Code of 2013 was drafted in this context

A unified rheological model for modelling steel behaviour in fire conditions

This paper presents a newly developed rheological model capable of modelling the behaviour of carbon steel at high temperature under stress- and strain-rate controlled tests. By combining two serial Kelvin elements with the appropriate spring-and-damper constitutive behaviour models it is possible to model creep strain development under stationary and transient heating conditions. Furthermore, the model is able to take into account the inherent increase of the yield strength if the strain rate is raised to moderately high levels usually expected in a fire-induced collapse of the structure. Constitutive behaviour models for each of the rheological elements are based on the test data from which the Eurocode 3 stress-strain law originated. The model was verified by using the test results of constant stress- and strain-rate tests from various sources. Overall comparison of results indicates the applicability of the proposed rheological model to structural fire engineering analysis for steel grades S275 and S355

Structural Performance of Reinforced Concrete Flat Plate Buildings Subjected to Fire

El siguiente artículo se propone estudiar la poesía de Luis Hernández a partir de los problemas que surgen al intentar estudiar su obra reunida. Antes que ser valorada como una poesía “inacabada”, la deliberada asistematicidad de su poética debe ser entendida como el resultado de un calculado y consciente ejercicio artístico, cuyas fuentes filosóficas tradicionalmente han pugnado por una ontología del movimiento frente a una metafísica de la permanencia. Bajo esta perspectiva, la obra de Hernández se revela como un “plano de inmanencia”, desde el cual acontece el sentido de su poesía en el quehacer de la escritura.The article aims to study Luis Hernández’ poetry from the point of view of the problems that emerge when trying to analyze his Complete Works. Rather than being assessed as “unfinished”, the deliberate and unsystematic appearance of his poetic, should rather be understood as the result of a calculated and conscious artistic practice that stems from philosophical trends which traditionally have fostered an ontology of movement against a metaphysics of permanence. Under this view, Hernández work shows up as “plane of immanence” from where sense becomes an event for the creative writing process.El següent article es proposa estudiar la poesia de Luis Hernández a partir dels problemes que sorgeixen al tractar d’estudiar la seva obra reunida. Abans de ser valorada com una poesia “incabada”, la deliberada asistematicitat de la seva poètica deu ser entesa com el resultat d’un calculat i conscient exercici artístic, fonts filosòfiques de les quals han pugnat tradicionalment per una ontologia del moviment davant una metafísica de la permanència. Sota aquesta perspectiva, l’obra d’Hernàndez es revela com un “pla d’inmanència”, des del qual esdevé el sentit de la seva poesia en el afer de l’escriptura

Building Design and the Fire Hazard

Building codes cover only the minimum requirements for fire safety and leave ample room for the expertise and conscience of the building designer. Providing life safety starts with securing conditions under which sufficient time is left for the occupants to escape from an incipient fire. It also involves measures that reduce the probability of exposure of the occupants to smoke and ensure their evacuation from the fire-stricken area. The safety of both life and property is served by ensuring the structural integrity of all key elements of the building even in spreading fires, but at the same time employing all available techniques to confine the fire to its place of origin

A thermoanalytical, X-ray diffraction and petrographic approach to the forensic assessment of fire affected concrete in the United Arab Emirates

For most fires, Forensic investigation takes place well after building materials have cooled and knowledge of the structural damage due to heat exposure can reveal the temperature reached during an incident. Recently, there have been significant changes in the characteristics of cementitious materials used in the United Arab Emirates. Few studies focus on the application of thermo-gravimetric and petrographic techniques on newly developed structures and this work aims to address this deficiency by utilising a series of parametric laboratory-based tests to assess the effects of heat on hardened concrete. Specimens were made with a design mix used for low-rise residential homes and storage facilities. The key constituents were: Portland cement (PC), crushed gabbro stone and dune sand with water/cement ratios of 0.4-0.5. Cement substitutes included slag (GGBS), and silica fume (SF) at replacement percentages of up to 50% and 4%, respectively. The concrete cubes were exposed to heat inside an electric furnace with pre-determined temperature regimes of 150°C, 300°C, 600°C and 900°C. Petrographic examination was utilised to compare the discolouration of the cooled concrete. Data derived from thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are reported in order to assess the usefulness of these techniques in fire scene investigation to differentiate between these temperature regimes.. The results from the TGA indicate that the majority of the percentage weight loss for all the mixtures occurred in the range 650-700°C, which corresponds to the decarbonation of calcium carbonate, mainly from the aggregates. The endothermic DSC peak at 70-120°C relates to the loss of evaporable water. Since both of these reactions are irreversible, this information can help fire investigators estimate the temperature history of concrete after exposure to fire. On the other hand, the portlandite in the cement matrix dehydroxylates at 450-550°C but then reforms as the concrete cools. The onset temperature for the dehydroxylation of the reformed mineral is always lower than in virgin samples and its enthalpy furthermore depends strongly on the thermal history of the portlandite. Thus, this feature can be used to establish the temperature to which the material was exposed to during a fire incident