Assessment of RC Frames for SD Limit State Using Nonlinear Methods of Analysis According to EN 1998-3

Design of structures in seismically active areas according to EN 1998-1 includes a choice between two ductility classes, medium or high, without conditioning by other parameters or favouring any of them. The behaviour factor q is applied as a global reduction factor of internal forces that would develop in the structure in the event of elastic response. According to EN 1998-3 a seismic assessment is determined by comparing the demands with the corresponding capacities. For ductile element, seismic demand and capacity are expressed in terms of chord rotation. The research in this paper was focused on the study of influence of the design ductility classes, as well as of the design seismic actions and the number of frames storeys, on seismic response of reinforced concrete frames designed according to European codes. Seismic performance evaluation of newly designed code-conforming structures is of interest, in order to identify any potential weaknesses and deficiencies in new structures that are designed with appropriate acceptable level of structural damage in the event of a design earthquake. The considered frames were evaluated for the significant damage limit state, for which the return period corresponds to the designed seismic actions. Nonlinear methods of analysis were used, which are the reference methods for assessing seismic performance. The frames designed for high class ductility manifested more favourable seismic performance and the frames designed for lower seismic action had lower values of demand/capacity ratio

Ocjenjivanje drva prema čvrstoći kao nužna osnova za projektiranje konstrukcija na području bivše Jugoslavije: dio 1.

Classification of timber for various commercial purposes is essential for its proper application in order to ensure the reliability and economic use. Visual grading of structural timber is commonly used in a number of EU countries, with different grading national standards optimized for locally available wood. Countries in the ex-YU region are traditional partners in wood trade and had the same standards for visual grading, but in most of the regions these standards are not completely compliant with EN requirements. Consequently, that leads to the fact that the most of regionally available structural timber is not assigned into strength classes, which is the starting point for the limit-state concept in design of timber structures. The aim of this paper is to emphasize the lack of strength classification of structural timber in the ex-YU region, which is a prerequisite for the design of timber structures made by civil engineers. Based on an overview of visual classification types with regional experience in grading, relevant EN standards, and differences in design concepts with possible consequences of grading approach, it can be concluded that “quality” grades and “strength” classes are not easily comparable.Klasifikacija drvne građe za različite komercijalne namjene ključna je za njezinu pravilnu upotrebu kako bi se zajamčila sigurna i ekonomična uporaba. Vizualno ocjenjivanje konstrukcijskog drva obično se provodi u mnogim zemljama EU-a uz pomoć različitih nacionalnih standarda ocjenjivanja optimiziranih za lokalno dostupno drvo. Zemlje bivše Jugoslavije tradicionalni su partneri u međusobnoj trgovini drvom i imale su zajedničke standarde za vizualno ocjenjivanje drvne građe, ali u većini njih ti standardi nisu u potpunosti usklađeni s EN zahtjevima. To posljedično rezultira činjenicom da većina regionalno dostupnoga konstrukcijskog drva nije razvrstana u klase čvrstoće, što je polazište za koncept graničnog stanja u projektiranju drvnih konstrukcija. Cilj rada jest upozoriti na nepostojanje klasifikacije čvrstoće konstrukcijskog drva na području bivše Jugoslavije, a to je preduvjet za projektiranje drvnih konstrukcija, što je posao građevinskih inženjera. Na temelju tipova vizualne klasifikacije i regionalnih iskustava u ocjenjivanju, relevantnih EN normi te razlika u konceptima projektiranja s mogućim posljedicama pristupa ocjenjivanju, zaključeno je da ocjene razreda kvalitete i klase čvrstoće u promatranim zemljama jednostavno nisu međusobno usporedive

The estimation of seismic performances of reinforced concrete girder bridges using nonlinear dynamic analysis

varijantama konstrukcija grede mosta jeste kontinuirni nosač sa četiri polja (35 m + 50 m + 50 m + 35 m) i zglobno je oslonjena na vrhove stubova i krajnje oporce. Stubovi su potpuno uklješteni u tlo sa dužinama 7 m, 14 m i 21 m, tj. analizirano je 18 različitih kombinacija dužina stubova. Geometrijska nelinearnost se obuhvaća preko P–Δ efekta, a materijalna nelinearnost se uključuje u analize kroz vlaknaste modele plastičnih zglobova. Procjena seizmičkih performansi je izračunata na osnovu zahtijevane lokalne duktilnosti i kapaciteta lokalne duktilnosti koje posjeduju kritični poprečni presjeci u stubovima analiziranih varijanti mostova. Za nelinearne dinamičke analize upotrebljeni su umjetno (sintetički) generirani i realni zapisi zemljotresa.The paper applies nonlinear dynamic analysis to estimate seismic performances of reinforced concrete girder bridges. In all analysed variations, the structure of the beam implies the continual girder with four fields (35 m + 50 m + 50 m + 35 m) hinged to the pier tops and the abutments. The piers are completely fixed to the ground with the lengths of 7 m, 14 m and 21 m; hence, 18 diverse combinations of pier lengths have been analysed. Geometric nonlinearity is included via the P–Δ effect, while the material nonlinearity is included into the analyses using the fibre models of plastic hinges. The estimation of seismic performances has been calculated on the basis of the demanded local ductility and the local ductile capacity of the critical cross-sections in the piers of all bridge analysed variations. Artificially (synthetically) generated and recorded earthquake accelerograms have been utilized for nonlinear dynamic analyses

Analysis of parameters for seismic response assessment of multy-storey reinforced concrete frames

U radu su analizirani uticaji parametara: klase dukktilnosti, projektnog seizmičkog dejstva i spratnosti na seizmički odgovor AB okvira projektovanih prema evropskim normama EN 1992 - 1 i EN 1998 - 1.Odgovor konstrukcije, dobijen primenom nelinearnih statičkih i dinamičkim metoda, je razmatran na globalnom, spratnom i lokalnom nivou. Procena stanja je sprovedena pre svega direktnim poređenjem zahteva rotacije tetiva stubova i greda okvira sa kapacitetom za dva granična stanja prema EN 1998 - 3. Pored toga, upoređeni su zahtevi sa kapacitetom u pogledu duktilnosti krivina kritičnih poprečnih preseka i zahtevi odnosa međuspratnog pomeranja i spratne visine sa tipičnim vrednostima za očekivani nivo oštećenja konstrukcije.The paper analyzed influence of parameters: ductility class, design seismic actions and the number of story on seismic response of RC frames designed according to EN 1992-1 and EN 1998-1. Seismic response, obtained using nonlinear static and dinamic methods, at global, storey and local levels was discussed. Assessment was carried out primarly by direct comparison chord rotation RC frames columns and beams demands with a capacity of two limit states according to EN 1998-3. In addition, curvature ductility critical regions demands and capacitiy and inter storey drift demands and tipical values for expected level of structural damage, were compared

Confined concrete models according to EC 2 and EC 8 and their influence on the RC frame seismic response

Seismic design according to European norms implies the design of ductile rc structures. By confining the concrete, the ratio of stress-strain is changing and increases ductility. In Eurocode 2, a model of confined concrete was proposed, and in the Eurocode 8 an improved model was shown. The paper also analyzes the compared values of obtained strengths and ultimate strains for both models of confined concrete, as well as their impact on the global and local seismic response in the case of a six-storey rc frame