Fleksiono izvijanje naknadno termički obrađenih i hladnooblikovanih stubova elipsastog poprečnog preseka: Numerička uporedna analiza

Even though structural elements of the elliptical hollow section (EHS) have been introduced to the construction market in the past years, the rules for their design were only partially introduced into the suitable codified procedures. The aim of this paper is to present a comparative numerical analysis of behaviour of cold-formed and hot-finished EHS columns exposed to flexural buckling under pure axial compression. Pin-ended columns of a various slenderness without lateral restrains and with incorporated geometrical imperfections are analysed. Material nonlinear behaviour is included through published experimental tensile test results, conducted in previous researches. In addition, numerical simulations of stub column behaviour are performed in order to obtain a cross-section compressive resistance. Results of the finite element analysis are compared to the design criteria defined in the draft version of Eurocode EN 1993-1-1:2015 and in North American specification for cold-formed member design AISI-S100. It is observed that North American standard provides more accurate predictions of both a cross-section resistance and a buckling column resistance. Equivalent diameter method described in Eurocode 3 led to more conservative results. According to the obtained numerical results, similar buckling behaviour is observed for both hot-finished and cold-formed columns of higher slenderness, while in the lower slenderness region, cold-formed compressed members tend to lower buckling curves. Underestimation of a column buckling resistance according to Eurocode regulations is noticed for cold-formed members of a higher slenderness.Iako se poslednjih godina šuplji profili elipsastog poprečnog preseka (EHS) mogu naći na tržištu, pravila za njihovo dimenzionisanje su tek delimično uvedena u odgovarajuće standarde za projektovanje. Cilj ovog rada jeste da prikaže komparativnu numeričku analizu ponašanja centrično pritisnutih hladnooblikovanih i naknadno termički obrađenih EHS stubova, usled fleksionog izvijanja. Analizirani su zglobno oslonjeni stubovi različitih vitkosti bez bočnog pridržanja duž elementa, uzimajući u obzir početne geometrijske imperfekcije. Nelinearno ponašanje materijala modelirano je na osnovu publikovanih eksperimentalnih rezultata testova pri zatezanju, sprovedenih u prethodnim ispitivanjima. Takođe, izvršene su numeričke simulacije ponašanja kratkih stubova kako bi se utvrdila nosivost poprečnog preseka na pritisak. Rezultati numeričke analize sprovedene metodom konačnih elemenata upoređeni su s računskim vrednostima graničnih nosivosti u skladu s revidiranom verzijom Evrokoda EN 1993-1-1:2015 i Severnoameričkom specifikacijom za projektovanje hladnooblikovanih čeličnih elemenata AISI-S100. Uočeno je da Severnoamerički standard daje preciznije predikcije – i za nosivosti poprečnog preseka i za nosivosti stuba na fleksiono izvijanje. Metoda ekvivalentnog prečnika, opisana u Evrokodu 3, daje konzervativnije rezultate. Prema dobijenim numeričkim rezultatima, slično ponašanje pri fleksionom izvijanju uočeno je kod naknadno termički obrađenih i hladnooblikovanih stubova veće vitkosti, dok u oblasti manje vitkosti, hladnooblikovani pritisnuti elementi teže nepovoljnijim krivama izvijanja. Primećeno je da Evrokod potcenjuje nosivosti na izvijanje hladnooblikovanih stubova veće vitkosti

Buckling of plates and plate girders subjected to patch load

The determination of the elastic critical load (buckling load) is an important element of the assessment of the ultimate load of plate girders. An analysis of the critical load of a plate corresponding to the web of an I-girder for different boundary conditions and the critical load of the I-girder itself is given in the paper. Conclusions regarding their correspondence are given. Also, experimentally determined ultimate loads of I-girders are compared with values according to Eurocode for the models used in this analysis

The influence of a roof mounted small-scale HAWT on headed studs fatigue resistance

Installation of small-scale wind turbines in urban regions can gain higher energy efficiency, considering that energy production takes place at the place of its consumption. The aim of this work is to investigate effects of installation of a small-scale horizontal axis wind turbine (HAWT) on a roof structure of an existing building. This paper is focused on fatigue resistance of headed studs that are preinstalled in the building roof composite steel-concrete deck to ensure shear connection and that are indirectly dynamically loaded during wind turbine operation. Turbulent wind profiles with mean wind speeds from 3 m/s up to 15 m/s are generated and applied on the model of HAWT with 5 m rotor diameter using Ashes software package. Time-dependent forces and bending moments induced by wind turbine operation are applied on the composite roof deck model. Based on the time-history of transverse force in the composite steel-concrete beam and wind speed records during a year, fatigue cumulative damage of headed studs is calculated according to Eurocode. It is obtained that installation of HAWT do not significantly affect residual life of headed studs with reference to fatigue

The influence of a roof mounted small-scale HAWT on headed studs fatigue resistance

Installation of small-scale wind turbines in urban regions can gain higher energy efficiency, considering that energy production takes place at the place of its consumption. The aim of this work is to investigate effects of installation of a small-scale horizontal axis wind turbine (HAWT) on a roof structure of an existing building. This paper is focused on fatigue resistance of headed studs that are preinstalled in the building roof composite steel-concrete deck to ensure shear connection and that are indirectly dynamically loaded during wind turbine operation. Turbulent wind profiles with mean wind speeds from 3 m/s up to 15 m/s are generated and applied on the model of HAWT with 5 m rotor diameter using Ashes software package. Time-dependent forces and bending moments induced by wind turbine operation are applied on the composite roof deck model. Based on the time-history of transverse force in the composite steel-concrete beam and wind speed records during a year, fatigue cumulative damage of headed studs is calculated according to Eurocode. It is obtained that installation of HAWT do not significantly affect residual life of headed studs with reference to fatigue

Demontažni smičući spoj sa zavrtnjevima i moždanicima sa glavom [Novo tehničko rešenje (nije komercijalizovano)]

M85 - Novo tehničko rešenje (nije komercijalizovano

Numerical evaluation of flexural buckling of hot-finished and cold-formed EHS columns

Elliptical hollow sections (EHS) have been recently introduced to the construction market. However, in the current Eurocode standard for steel structures EN 1993-1-1, there are no design criteria defined for EHS. The aim of this paper is to present a comparative numerical analysis of behaviour of cold-formed and hot-finished EHS columns exposed to flexural buckling under pure axial compression. Pin-ended columns of various slendernesses without lateral restrains and with incorporated geometrical imperfections are analysed. Material nonlinear behaviour is included through experimental tensile test results adopted from previous researches. According to obtained numerical results, similar buckling behaviour is observed for both hot-finished and cold-formed columns of higher slenderness, while in the lower slenderness region, cold-formed compressed members tend to lower buckling curves

Numerical study on bending behaviour of hot-finished and cold-formed elliptical hollow sections

Elliptical hollow sections (EHS) are new products on the construction market. Their growing implementation in steel structures led to complementing design rules in the draft version of Eurocode EN 1993-1-1:2015. In this paper bending strength of elliptical hollow sections is being discussed, analysing cold-formed and hot-finished EHS profiles under pure bending. Numerical models include short members of diverse section slenderness with applied concentrated moments at the ends about either the major or the minor axis of inertia. Material nonlinear behaviour is included through experimental tensile test results adopted from previous researches. Influence of geometrical imperfections is incorporated in the analysis, however, imperfection amplitude variation has shown an insignificant effect on bending strength. For all analysed members, it is shown that numerically obtained ultimate moments are higher than bending strengths prescribed in EN 1993-1-1:2015. Differences in responses of hot-finished and cold-formed EHS are discussed. Comments on elliptical cross-section classification according to the design standard are made, as well as comments on the defined effective cross-sectional geometrical properties. Review of the set limiting slenderness for class 3 is suggested

Elastična kritična sila ploča i limenih nosača pod dejstvom lokalizovanog opterećenja

The determination of the elastic critical load (buckling load) is an important element of the assessment of the ultimate load of plate girders according to Eurocode 3 for design of steel structures. An analysis of the critical load of a plate corresponding to the web of an I-girder for different boundary conditions and the critical load of the I-girder itself subjected to patch load is given in the paper. Conclusions regarding their correspondence are given. Also, experimentally determined ultimate loads of I-girders are compared with predictive values according to Eurocode 3 for the models used in this analysis. A modified procedure for the ultimate load determination is proposed by following the Eurocode 3 algorithm and changing only buckling coefficient. In order to improve the ultimate load prediction, it is suggested to calculate the buckling coefficient also as a function of patch load length.Određivanje elastične kritične sile (sile izbočavanja) predstavlja važan element u određivanju granične nosivosti limenih nosača prema Evrokodu 3 za proračun čeličnih konstrukcija. U radu se daje analiza kritične sile izbočavanja izolovane ploče koja odgovara rebru Inosača s variranim uslovima oslanjanja i kritične sile koja odgovara samom I-nosaču, usled dejstva lokalizovanog opterećenja. Dati su zaključci o njihovoj vezi. Takođe, upoređena su eksperimentalno određena granična opterećenja I-nosača s vrednostima prema Evrokodu 3, za modele korišćene u ovoj analizi. Predložena je izmenjena procedura za određivanje granične nosivosti, koja sledi algoritam dat u Evrokodu 3, a prema kojoj se modifikuje izraz za određivanje koeficijenta izbočavanja. Kako bi se poboljšalo određivanje granične nosivosti, predloženo je računanje koeficijenata izbočavanja i u funkciji dužine lokalizovanog opterećenja

Numerical study on the composite shear connection with bolts and welded headed studs

In the past decades, many novel shear connectors for implementation in steel-concrete composite beams have been investigated. In this paper, a demountable shear connection between a structural steel beam and a solid concrete deck, consisting of bolts and welded headed studs, is analysed. This system features the indirect shear force transfer through the additional element, a steel plate that is placed between a concrete deck and a top flange. Following the experimental results of previously conducted push-out tests, a numerical model has been developed. The model is used for a detailed analysis of the system behaviour as well as for the parametric study. Influence of a bolt diameter and a bolt hole diameter on shear behaviour of the connection has been discussed.Prethodnih decenija intenzivno su ispitivana nova rešenja spojnih sredstava u smičućim spojevima spregnutih greda od čelika i betona. U ovom radu analiziran je montažno-demontažni podužni smičući spoj konstrukcionog čelika i pune armiranobetonske ploče, ostvaren pomoću zavrtnjeva i elastičnih moždanika s glavom. Ovakav spoj odlikuje se indirektnim prenosom sile smicanja kroz dodatni element, čelični lim, između betonske ploče i gornje nožice grede. Formiran je numerički model testa smicanja prema dostupnim prethodnim eksperimentalnim ispitivanjima. Model je iskorišćen za detaljnu analizu ponašanja podužnog smičućeg spoja, kao i za parametarsku analizu. Ispitivan je uticaj prečnika zavrtnja i prečnika rupe na ponašanje spoja pri smičućem opterećenju

Demountable composite steel-concrete floors: A state-of-the-art review

U skladu sa zahtjevima za održivi razvoj u svim segmentima industrije, brojna su istraživanja u području spregnutih čelično-betonskih konstrukcija usmjerena na razvoj demontažnih sredstava za sprezanje. Proteklih godina predlagana su različita demontažna sredstva za sprezanje koja su različitim mehanizmima prenosila posmičnu silu između čeličnog profila i betonske ili spregnute ploče. U ovom radu prikazana su najnovija dostignuća na tu temu dajući sažetke eksperimentalnih i numeričkih rezultata istraživanja vezano uz potisna (push-out) ispitivanja i ispitivanja na nosačima.In keeping with current demands for sustainable development in all segments of the industry, numerous research in the field of steel-concrete composite structures has been focused on developing demountable shear connectors. In the past years, various demountable shear connectors have been suggested, with various mechanisms for transferring shear force between a steel profile and a concrete or composite slab. In this paper, a state of the art on the topic is given, and experimental and numerical research results of push-out and beam tests are summarized