Metalne konstrukcije u periodu 1948-1998

From year to year steel structures are more and frequently applied in civil engineering: for industrial halls, multi-storey buildings, sports and exhibition halls, aircraft hangars, public garages, bridges, reservoirs, bins, silos, chimneys, antenna supports, towers for high-tension lines, sluicegates and many other structures. There is almost no structure that could not be constructed in steel. Owing to its mechanical and functional properties, steel structures hold all the records in civil engineering concerning the spans of the bridges concerning the height in building industry, antenna towers and masts, and so on. Nowadays trends in architecture use bearing steel structures, visible in the interior and on the facades, with the details of the construction particularly elaborated and conceived in collaboration of designer and architect. The most important structures recently built in the world, are briefly described in the frame of this work, the range of our civil engineering, achievements within last 50years is also presented. Paper briefly presents Eurocode 3 as a modern standard for the steel constructions design, particularly the parts of this document which are introducing news in our usual building practice.Čelične konstrukcije se iz godine u godinu sve više primenjuju u izgradnji građevinskih objekata. Primenjuju se za industrijske hale, spratne zgrade, sportske i izložbene hale, hangare, javne garaže, mostove, rezervoare, bunkere, silose, dimnjake, antenske stubove, stubove dalekovoda, ustave i mnoge druge objekte. Skoro da i nema građevinskog objekta koji se ne može izgraditi od čelika. Blagodareći svojim izuzetnim mehaničkim i funkcionalnim osobinama čelične konstrukcije drže sve rekorde u građevinarstvu, kako po rasponu u mostogradnji, tako i po visini u zgradarstvu, antenskim stubovima i jarbolima i slično. Danas je trend u arhitekturi korišćenje nosećih čeličnih konstrukcija koje su vidljive u enterijeru i na fasadama, sa detaljima konstrukcije posebno obrađenim i konstruisanim u bliskoj saradnji konstruktera i arhitekte. U ovom radu biće ukratko opisani najznačajniji objekti koji su izgrađeni poslednjih godina u svetu. Takođe će se prikazati i dometi našeg građevinarstva ostvareni poslednjih 50 godina. U radu su najkraće izložene osnovne odredbe Evrokoda 3 kao savremenog standarda za projektovanje čeličnih konstrukcija, odnosno biće obrađeni oni delovi ovog dokumenta koji unose novine u našu uobičajenu građevinsku praksu

Contribution to calculation and construction of cold-formed open cross sections

Pod nazivom hladno oblikovani profili (HOP) podrazumevaju se konstruktivni element! proizvedeni hladnim oblikovanjem iz čeličnih limova i traka valjanjem ili presovanjem . Hladno oblikovani profili imaju veoma široko polje primene u g rad jevinarstvu i poslednjih godina su u nekim područjima primene potpuno istisli vru će valjane profile zbog svojih nesumljivih prednosti. Rožnjače, kao element noseće konstrukcije zgrada, za koje se najčešće i primenjuju hiadno oblikovani ^profili otvorenog poprečnog preseka, su bitan element u funkcional- nom, statičkom pa i u ekonomskom pogledu s obzirom da njihov udeo u ceni koštanja hala doseže i do 25%. Pristup analizi u projektovanju masovnih eleme- nata ko nstrukcije, kao što su rožnjače, je bitno različit od pristupa pri pro­ jektovanju unikatnih elemenata. Kod masovne, serijske, proizvodnje neophodno je sve parametre od uticaja uzeti u što preciznijem obliku, što je jedino mogu- će ostvariti eksperimentom. U okviru ove disertacije razmatrana su dva bitna parametra na nosivost rožnjača i to: 1) uticaj tehnologije proizvodnje na me- haničke karakteristike čeiika i 2) odredjivanje optimalnog statičkog sistema (kontinualne rožnjače sa podvezicama i kontinualne rožnjače sa preklapanjem) i konstrukcijskog oblikovanja. U okviru ovih oblasti u tezi su date originalne podloge u obliku pojednostavljenih i za svakodnevnu inženjersku praksu lako p rihvatljivih analitičkih izraza i dijagrama na osnovu kojih se mogu projektova- ti ovakvi savremeni sistemi rožnjača. Svi analitički izrazi su verifikovani sop- stvenim eksperimentima sprovedenim uz primenu najsavremenije opreme i mer- nog instrum entarija. Takodje je sprovedena i detaljna tehno-ekonomska analiza više tipova rožnjača diferenciranih prema sistemima, oblicima i postupku proiz­ vodnje koja je pokazala značajno preimućstvo u pogledu utroška čelika i košta- nja predloženih Z preseka sistema rožnjača sa podvezicama i sa preklapanjem u odnosu na sve druge tipove primenjivane u dosadašnjoj p raksi

Classification of spherical tilings by congruent quadrangles over pseudo-double wheels (II)

We classify all edge-to-edge spherical isohedral 4-gonal tilings such that the skeletons are pseudo-double wheels. For this, we characterize these spherical tilings by a quadratic equation for the cosine of an edge-length. By the classification, we see: there are indeed two non-congruent, edge-to-edge spherical isohedral 4-gonal tilings such that the skeletons are the same pseudo-double wheel and the cyclic list of the four inner angles of the tiles are the same. This contrasts with that every edge-to-edge spherical tiling by congruent 3-gons is determined by the skeleton and the inner angles of the skeleton. We show that for a particular spherical isohedral tiling over the pseudo-double wheel of twelve faces, the quadratic equation has a double solution and the copies of the tile also organize a spherical non-isohedral tiling over the same skeleton.Comment: 28 pages, 14 figure

Mathematical interpretation of nonlinear relationship of stainless steel stress and strain

Basic distinctive characteristics of stainless steels are reflected in the nonlinear relationship of stress and strain, prominent ductility, strain hardening due to cold forming, asymmetry and anisotropy of material. These properties lead to a different behavior of structural elements of this material than the equivalent elements made of carbon steel. Implementation of a design concept based on an ideal elasto-plastic model of material such as carbon steel, often produces conservative results in case of stainless steel, which is already at a disadvantage due to its cost in construction engineering. Proper defining of recommendations for design and their implementation in technical codes requires a precise and accurate mathematical interpretation of nonlinearity of stainless steel. This paper presents the most important analytical models for description of the relationship of stress and strain of various alloys of stainless steel which have lately been developed worldwide. Most of these models are based on the original Ramberg-Osgood analytical expression

Design of class 4 cross section in axial compression according to EUROCODE 3

In this paper theoretic basis of design of class 4 cross section in axial compression according to EN1993-1-5 is given. Design procedure is given as an flow chart and ilustrated with an worked example. Plate buckling is treated localy and globaly through the concept of effective cross sections. Interaction between plate-like and column-like behaviour of panels is carried out thought buckling reduction factors and final effective area of cross section

Wind towers - design of flange ring connection

Today, wind power is second largest available renewable resource of energy, with 870 TW (terawatts). Large wind farms, with hundreds of wind towers are big opportunity for steel production industry. Designers and manufacturers of wind towers pay special attention on every single detail, always looking for some new solutions, trying to reduce price of wind towers. Some of the most interesting design and manufacturing details are connections used to assemble sections of tubular steel towers supporting wind turbins. There is traditional and actually more used flange ring connection and on the other side, as a new proposal which is used more and more, friction connection. In this paper theoretic basis of design of flange ring connection of wind towers is give

Comparative Analysis of Composite Beams in Large Span Floor Structures

U ovom radu su analizirane osnovne metode projektovanja spregnutih greda od čelika i betona u zgradarstvu, u skladu sa Evrokodom. Analizirana su tri različita tipa čeličnih greda spregnutih sa betonskom pločom na profilisanom limu: greda u vidu klasičnog vruće valjanog I – profila, ''STUB'' sistemi spregnute grede i spregnuta greda sa "saćastim" čeličnim nosačem. Data je komparativna analiza primene tri sistema spregnutih greda. Poređenje je izvršeno i na numeričkom primeru nosača međuspratne konstrukcije javne garaže, raspona 15.50 m.This paper deals with main design methods for steel and concrete composite beams in buildings design, according to Eurocode. There were analyzed three different types of steel beam in combination with concrete slab on profiled steel sheet: standard hot rolled I - profile, composite STUB girder, and castellated composite beam. Comparative analysis of application of three solutions for composite beam was given. Numerical example is shown for structural elements of public car park floor structure , with 15.50 m span