DJELOVANJE EKSPLOZIJA NA KONSTRUKCIJE

The paper describes the process of determining the blast load on structures and provides a numerical example of a fictive structure exposed to this load. The aim was to become familiar with the issue of blast load because of ever growing terrorist threat and the lack of guidelines from national and European regulations on the verification of structures exposed to explosions. The blast load was analytically determined as a pressure-time history and numerical model of the structure was created in SAP2000. The results confirm the initial assumption that it is possible with conventional software to simulate an explosion effects and give a preliminary assessment of the structure.Dana je analiza opterećenja eksplozijom na konstrukciju te numerički primjer djelovanja na fiktivnu građevinu. Cilj je bio upoznati se s fenomenom eksplozije kao opterećenja na konstrukcije uslijed sve veće terorističke prijetnje te nedostatka smjernica u nacionalnim i europskim propisima o provjeri konstrukcija izloženih djelovanju eksplozija. Analitički je određeno opterećenje eksplozijom kao vremenski zapis promjene tlaka zraka te numerički modeliranja konstrukcija i prethodno određeno opterećenje u programskom paketu SAP2000. Dobiveni rezultati potvrđuju početnu pretpostavku kako je moguće konvencionalnim softverom simulirati djelovanje eksplozije i dati preliminarnu ocjenu stanja konstrukcije

PRORAČUN ARMIRANO-BETONSKIH OKVIRA ISPUNJENIH ZIĐEM S OTVORIMA

Reinforced-concrete (R/C) frames infilled with masonry wall, especially with the presence of an opening, are insufficiently explored structural elements. We have experimentally investigated influence of the opening’s type and position to the lateral response of reinforced-concrete frames with masonry infill. Correction factors, that take into account influence of the opening’s type and position in the masonry infill in relation to frame without infill, are defined as an improvement of the equivalent diagonal compression strut model. This improvement enables use of R/C frames with masonry infill, with or without openings, as structural element. Its use would result in better seismic assessment of the masonry infilled R/C frames.Armirano-betonski okviri sa zidanim ispunom, naročito uz prisustvo otvora, nedovoljno su istraženi konstruktivni elementi. Eksperimentalno smo istražili utjecaj vrste i položaja otvora na seizmički odgovor armirano-betonskih okvira sa zidanim ispunom. Uvedeni su korekcijski faktori kojima se u obzir uzima utjecaj vrste i položaja otvora u zidanom ispunu u odnosu na okvir bez ispuna, u svrhu poboljšanja modela zamjenske tlačne dijagonale. Poboljšanje omogućava uporabu a-b okvira sa zidanim ispunom, s i bez otvora, kao konstruktivnog elementa. Primjena će omogućiti kvalitetniji seizmički proračun a-b okvira sa zidanim ispunom

ZYKLISCHE VERSUCHE AN EINFACHEN SCHWACHEN RAHMEN MIT MAUERWERKSAUSFACHUNG

U radu su prikazani rezultati eksperimentalnih istraživanja četrnaest uzoraka jednorasponskih, jednoetažnih, neseizmički projektiranih armiranobetonskih (slabih) okvira sa zidanom ispunom, izvedenih u mjerilu 1:2. Uzorci su ispitani pod približno konstantnim vertikalnim i ravninskim horizontalnim cikličnim opterećenjem. Promatrani su različiti parametri uzoraka u pogledu geometrijskih i mehaničkih karakteristika armiranobetonskih okvira i zidane ispune. Na temelju provedenih ispitivanja predložene su jednadžbe za procjenu relativnog međukatnog pomaka pri promatranim graničnim stanjima.Experimental test results for fourteen samples of single-span, single-storey, nonseismically designed reinforced-concrete (weak) masonry infill frames are presented in the paper. The samples, scaled 1 to 2, were subjected to the approximately constant vertical and in-plane horizontal cyclic load. Various geometrical and mechanical properties of reinforced-concrete frames and masonry infill were considered. Equations for estimating the interstorey drift ratio at the limit states under study are proposed based on testing conducted in the paper.In dieser Arbeit werden die Resultate experimenteller Versuche an 14 Proben im Massstab 1:2 ausgeführter, einfacher, einstöckiger, nicht für seismische Lasten ausgelegter (schwacher) Stahlbetonrahmen mit Mauerwerksaufachungen dargestellt. Die Proben wurden unter annähernd konstanten vertikalen und horizontalen zyklischen Lasten untersucht. Verschiedene Parameter in Bezug auf geometrische und mechanische Eigenschaften des Rahmens und der Mauerwerksausfachung wurden betrachtet. Aufgrund der durchgeführten Versuche wurden Gleichungen zur Abschätzung der relativen Stockwerksschiefstellung für die betrachteten Grenzzustände vorgeschlagen

Influence of openings, with and without confinement, on cyclic response of infilled R-C frames: an experimental study

This article presents the experimental results of a study on reinforced-concrete frames infilled with masonry with openings. The frames were designed according to current European codes. They were built in a scale 1:2.5 and infilled with masonry walls. Mid-size window and door openings were located centrically and eccentrically and were executed with and without tie-columns around them. Presence of masonry infill, although not accounted for in design, improved the system behavior (increase in stiffness, strength and energy dissipation capacity) at drift levels of up to 1%. During the test, openings did not influence the initial stiffness and strength at low drift levels. Their presence became noticeable at higher drift levels, when they lowered the energy dissipation capacity of the system. The infill wall had a multiple failure mechanism that depended on the opening height and position. Tie-columns controlled the failure type, independent of the opening type, prevented out-of-plane failure of the infill, and increased the system’s ductility. Negative effects of the infill on the frame were not observed. The infill’s contribution could be deemed positive as it enhanced the overall Structural Performance Level. Analytical expressions commonly used for infilled frames underestimate the infill’s contribution to strength and stiffness and overestimate the contribution of the bare frame

USPOREDBA NELINEARNIH MAKROMODELA ZIDANIH ISPUNA

Reinforced-concrete frames with masonry infill are composite systems, common in low and medium-high buildings, whose behavior under earthquake loads is difficult to predict. Because of that, most national codes ignore the contribution of infill to the structural response. In this paper, we determined the seismic behavior of infilled frames by using a numerical non-liner model (with various geometries and various masonry and r/c frame properties), using samples taken from the originally collected experimental data base on infilled frames “EDIF”. We then compared these experimental results to numerical models designed using recommendations from FEMA 356 (nonlinear model), Eurocode 8 (linear model), and other published methods (Stafford-Smith and Carter, Mainstone, Žarnić, Paulay and Priestley) in order to assess the most suitable, rational macro model for evaluating the behaviour of masonry infill in a reinforced-concrete frame during earthquake excitation.Armiranobetonski okviri sa zidanom ispunom predstavljaju kompozitne konstrukcije, dominante u području niskih i srednje visokih građevina, čije je ponašanje pri djelovanju potresa teško predvidjeti. Zbog toga se doprinos zidane ispune odgovoru konstrukcije općenito zanemaruje u većini nacionalnih propisa. Ponašanje uokvirenog ziđa pri djelovanju potresa primjenom numeričkog nelinearnog modela dokazano je uporabom eksperimentalnih uzoraka iz EDIF eksperimentalne baze i usporedbom prema metodama projektiranja uokvirenog ziđa u FEMA 356 (nelinearni model), Eurokodu 8 (linearni model), te drugim metodama (Stafford-Smith i Carter, Mainstone, Žarnić, Paulay and Priestley). Ova usporedna studija provedena je radi dobivanja najprikladnijeg i najracionalnijeg modela zidane ispune u armiranobetonskim okvirima pri djelovanju potresa

DAUERHAFTIGKEIT VON FASERBEWEHRTEN POLYMEREN IN BETONKONSTRUKTIONEN

Polazi se od toga da je uporaba polimera armiranih vlaknima za armiranje betonskih elemenata moguće sredstvo za sprječavanje korozije. Primjena polimernih šipki za nove ili oštećene konstrukcije zahtijeva poznavanje mehaničkih karakteristika i trajnosti materijala pri dugotrajnom izlaganju uvjetima okoliša. Dan je pregled rezultata dosadašnjih istraživanja i spoznaja o ponašanju i karakteristikama polimernih materijala, kao i o interakcijskim mehanizmima utjecaja na trajnost.The paper starts with assertion that the use of fibre-reinforced polymers for reinforcement of concrete elements is a technique quite possible for corrosion prevention. The use of polymer bars for new or damaged structures requires knowledge of mechanical properties and durability of material subjected to long-term exposure to environmental conditions. An overview is given about current research results and knowledge gained on the behaviour and properties of polymer materials, and also about interaction mechanisms of consequence for durability.L'ouvrage commence par l'assertion que l'emploi des polymères renforcés de fibres pour le renforcement des éléments de béton est une technique tout-à-fait possible pour la prévention de corrosion. L'utilisation des barres de polymère pour les structures nouvelles où endommagées nécessite une connaissance des propriétés mécaniques et de la durabilité du matériau exposé à l'influence prolongée de l'environnement. Un aperçu est donné sur les résultats des recherches faites et sur les connaissances obtenues concernant le comportement et les propriétés des matériaux en polymère, et aussi sur les mécanismes d'interaction considérés importants pour la durabilité.Долговечность полимеров, армированных волокнами, в бетонных конструкциях Авторы исходят из того, что применение полимеров, армированных волокнами, для армирования бетонных элементов, является возможным средством предотвращения коррозии. Для использования полимерных стержней в новых или поврежденных конструкциях необходимо знание механических характеристик и сведений о долговечности материала при длительном воздействии условий окружающей среды. Приведен обзор результатов проведенных до настоящего времени исследований и полученных данных о поведении и характеристиках полимерных материалов, а также интеракционных механизмов, влияющих на долговечность.Man geht von der Tatsache aus dass die Anwendung von faserbewehrten Polymeren für die Bewehrung von Betonelementen ein mögliches Mittel fur Korrosionsverhinderung ist. Die Anwendung von Polymerstäben für neue oder beschädigte Konstruktionen verlangt Kenntnis der mechanischen Eigenschaften und der Dauerhaftigkeit des Materials bei lagdauernedem Aussetzen den Umweltbedingungen. Vorgelegt ist eine Übersicht der Ergebnisse bisheriger Untersuchungen und die Erkenntnis über Verhalten und Eigenschaften der Polymermateriale, sowie über die interaktiven Mechanismen des Einflusses auf Korrosion

UNLINEARE ERWIEDERUNG VON KONSTRUKTIONEN BEMESSEN NACH KROATISCHEN UND EUROPÄISCHEN NORMEN

U radu se prikazuje usporedba nelinearnog seizmičkog odgovora konstrukcija dimenzioniranih prema hrvatskim normama (HRP) i prema Eurokodu (EC8) koja je napravljena na modelima regularnih armiranobetonskih konstrukcija sa tri sustava za preuzimanje horizontalnih sila. Odabrano je više modela konstrukcija, a njihovi odgovori na djelovanje potresa izračunani su za pretpostavljeno djelovanje niza potresa. Globalni i lokalni parametri odgovora su analizirani i predloženi su odgovarajući zaključci.The nonlinear seismic response of structures dimensioned according to Croatian standards is compared with that of structures designed according to Eurocode 8. This comparison is based on models of regular reinforced-concrete structures with three systems for assuming horizontal forces. Several structural models have been selected and their seismic responses were calculated for the assumed impact of a series of earthquakes. Global and local seismic response parameters are analyzed and appropriate conclusions are proposed.L’article présente une comparaison de la réponse sismique non linéaire des constructions dimensionnées selon les normes croates et selon l’Eurocode 8, faite sur les modèles des constructions régulières en béton armé à trois systèmes de prise en charge des forces horizontales. On a choisi plusieurs modèles de constructions, tandis que leurs réponses à l’action sismique ont été calculées pour l’action supposée d’une série de séismes. Les paramètres globaux et locaux des réponses ont été analysés et commentés par des conclusions correspondantes.В работе показываèтся сравнение нелинейного сейсмического ответа конструкций расчитанных по Хорватским нормам и по Еврокоду 8, выполненное на моделях репулярных железобетонных конструкций с тремя системами для переноса горизонтальных сил. Выбрано большее число моделей конструкций, а их ответы на действие землетрясений расчитаны для предполагаемого действия ряда землетрясений. Глобальные и локальные параметры ответов анализированы, и предложены соответствующие заключения.Dargestellt ist ein Vergleich der unlinearen seismischen Erwiederung von Konstruktionen,k bemessen nach kroatischen Normen und nach Eurokode 8, ausgeführt an Modellen regulärer Stahlbetonkonstruktionen mit drei Systemen für die Übernahme von horizontalen Kräften. Es wurden mehrere Konstruktionsmodelle auserwählt, und deren Erwiederungen auf die Erdbebenwirkung für vorausgesetzte Einwirkung einer Reihe von Erdbeben berechnet. Globale und lokale Erwiederungsparameter sind analysiert und entsprechende Schlüsse vorgeschlagen

KONTROLLIERTES SEISMISCHES VERHALTEN VON STAHLRAHMEN MIT MAUERWERKSAUSFACHUNGEN

Bilo da se radi o pregradnim ili nosivim zidovima, zidana ispuna značajno utječe na ponašanje primarne konstrukcije. U ovom se radu najprije razmatraju dvije različite vrste zidnih blokova (tzv. jaki i slabi) često korištenih u Hrvatskoj kao ispune čeličnih okvira. Na osnovu eksperimentalnih rezultata dobivenih ispitivanjem ponašanja tih dviju vrsta blokova predložena je treća vrsta ispune koja predstavlja specifičnu kombinaciju prethodnih dviju, kao mogućnost ostvarivanja kontroliranog ponašanja čeličnih okvira sa zidanom ispunom.Whether used as a curtain/partition wall or a bearing part of the structure, masonry infill significantly affects structural behaviour of the primary structure. Two different types of masonry units (‘strong’ and ‘weak’), often used in Croatia as infill of steel frames, are initially considered in the paper. Based on experimental results obtained by testing behaviour of these two types of masonry units, a third type of infill is proposed, which is a specific combination of the initial two types, and enables realisation of controlled behaviour of masonry-infilled steel frames.Unabhängig davon, ob es sich um Trennwände oder tragende Wände handelt, beeinflusst ausfachendes Mauerwerk das Verhalten des primären Tragwerks bedeutend. In dieser Arbeit werden zunächst zwei verschiedene Typen von Mauerwerksblöcken betrachtet (s. g. starke und schwache), die in Kroatien als Ausfachung verwendet werden. Basierend auf experimentellen Resultaten aus Versuchen an diesen Blöcken, wurde als ihre spezifische Kombination ein dritter Mauerwerkstyp vorgeschlagen, um ein kontrolliertes Verhalten von Stahlrahmen mit Mauerwerksausfachungen vorzuschlagen

MODELLIERUNG VON STAHLRAHMEN MIT AUSFACHUNGSMAUERWERK

Prikazana je problematika numeričkog modeliranja čeličnih okvira sa zidanim ispunom pri djelovanju potresa. U novim europskim normama (EN 1998-1) predviđeno je proračunavanje interaktivnog djelovanja kod takvog sastavljenog sustava, ali se ne daju pravila proračuna. Na primjeru su prikazane najčešće primjenjivane mogućnosti modeliranja ponašanja takvih konstrukcija, primjenom metode konačnih elemenata te je upozoreno na potrebu praktičnog pristupa rješavanju ovoga problema.Problems encountered in numerical modelling of masonry-filled steel frames subjected to earthquake action are presented. According to new European standards (EN 1998-1) an interactive action should be calculated for such composite systems, but calculation rules are not provided. A practical example is used to show most frequent possibilities for modelling behaviour of such structures based on the finiteelement method, and the need to use a practical approach to find solution to this problem is emphasized.Des problèmes rencontrés au cours de modelage numérique des cadres d'acier à remplissage en maçonnerie soumis à l'action sismique sont présentés. Selon les normes européennes nouvelles (EN 1998-1) l'action interactive devrait être calculée pour de tels systèmes composites, mais les règles de calcul ne sont pas fournies. Un exemple pratique est utilisé pour montrer les possibilités les plus fréquentes dans le modelage du comportement de telles constructions selon la méthode des éléments finis, et l'accent est mis sur la nécessité d'utiliser l'approche pratique pour trouver solution à de tels problèmes.Dargestellt ist die Problematik des numerischen Modellierens von Stahlrahmen mit Ausfachungsmauerwerk bei Erdbebenwirkung. In den neuen europäischen Normen (EN 1998-1) ist die Berechnung des interaktiven Wirkens bei solchem zusammengesetzten System vorgesehen, aber sind Berechnungsgrundsätze nicht angegeben. Am Beispiel zeigt man die häufigst angewendeten Modellierungsmöglichkeiten für das Verhalten solcher Konstruktionen durch Anwendung der Methode der endlichen Elemente. Es wird auf die Notwendigkeit des praktischen Zutritts zum Lösen dieses Problems hingewiesen

PONAŠANJE A-B OKVIRA S JAKIM ZIDNIM ISPUNOM NA HORIZONTALNO CIKLIČKO OPTEREĆENJE

This paper gives an overview of the experimental results obtained by testing three reinforced concrete (RC) frame models with strong infill walls and one bare RC frame model for comparison. The experimental results of the RC frame models with and without a strong masonry infill are presented in terms of the collapse mechanism, lateral resistance, lateral stiffness and hysteretic energy. Based on those results, we obtained the ductility coefficients, behaviour factors, and equivalent damping coefficients of the RC frames with strong infill walls ("frame-wall") and the bare RC frame, all of these variables depending on storey drifts. The experimental and analytical results of frame-wall and RC frames, regarding their lateral capacity and lateral stiffness, were compared. Experiments showed that the masonry infill contributed to the lateral capacity, lateral stiffness, hysteretic energy, changed behaviour, as well as the equivalent damping coefficient of RC frames. It is shown that "frame-wall" composite behaved as full-fledged building type having lower vulnerability than RC frames and enough displacement capacity to sustain displacement cycles in the nonlinear range of response.U radu je dan prikaz eksperimentalnih rezultata tri ispitivana modela armirano-betonskih okvira (a-b) s jakim zidnim ispunama ("uokvireno ziđe") i jednog modela praznog a-b okvira. Prikazani su eksperimentalni rezultati u pogledu mehanizma sloma ispuna, poprečne nosivosti, poprečne krutosti kao i histereznih energija. Na osnovu eksperimentalnih rezultata dobiveni su koeficijenti duktilnosti, faktori ponašanja i koeficijenti ekvivalentnog prigušenja uokvirenog ziđa i praznog a-b okvira u ovisnosti o nivou relativnog katnog pomaka. Utvrđene su razine oštećenja zidnog ispuna koje su povezane s nivoima relativnih katnih pomaka. Eksperimentalni rezultati, dobiveni na uokvirenom ziđu, uspoređeni su s analitičkim rezultatatima iz literature, glede poprečne nosivosti i poprečne krutosti. Iz eksperimentalnih rezultata vidljiv je doprinos zidnog ispuna na poprečnu nosivost, poprečnu krutost, histerezne energije, koeficijent duktilnosti, faktor ponašanja, i na koeficijent ekvivalentnog prigušenja u odnosu na prazan a-b okvir. Uokvireno ziđe može se korisiti kao ravnopravan nosivi element za preuzimanje horizontalnih opterećenja, unutar ograničenja promatranih parametara