PROCJENA POTRESNOG RIZIKA OSJEČKOG NASELJA RETFALA NOVA

The Croatian territory, as part of the Mediterranean-trans-Asiatic belt, experiences pronounced earthquake activity. Seismic risk is the expected damage caused by earthquakes to buildings, measured both in social and economic losses, which can be described through seismic hazard, seismic vulnerability, and exposure. The city of Osijek is located in the eastern part of Croatia, and Retfala Nova is a residential settlement in the western part of the city. An important step in assessing earthquake loss is defining the exposure, so we created a form used to collect information on buildings and make a building database. In this paper, we estimated seismic vulnerability based on the capacity spectrum method, which involves constructing fragility curves and converting them to damage probability matrices, as well as constructing capacity curves.Područje Republike Hrvatske, kao dio mediteransko-transazijskog pojasa, odlikuje se izraženom potresnom aktivnošću. Potresni rizik predstavlja očekivani stupanj oštećenja građevina nakon potresa. Može se jednostavno opisati kroz četiri elementa: potresnu opasnost, potresnu oštetljivost, izloženost zgrada, te socijalne i ekonomske gubitke. Grad Osijek nalazi se u istočnom dijelu Republike Hrvatske. Retfala Nova je stambeno naselje smješteno u zapadnom dijelu grada. Budući da je bitni element u procjeni potresnog rizika izloženost, predložili smo obrazac koji će služiti kod stvaranja baze zgrada grada. U ovome radu potresna oštetljivost procijenjena je pomoću metode zasnovane na spektru sposobnosti nosivosti, koja podrazumijeva konstruiranje krivulja vjerojatnosti oštećenja i njihovu pretvorbu u matrice vjerojatnosti oštećenja, te konstruiranje krivulja sposobnosti nosivosti

STRENGTHENING OF HISTORICAL BUILDINGS WITH COMPOSITE POLYMERS

Većina građevina kulturne ili graditeljske baštine su zidane zgrade koje su izgrađene najčešće od kamenih ili opečnih zidnih elemenata povezanih mortom, a zidane su prije postojanja znanja i propisa o protupotresnom građenju. Kompleksnost sanacije povijesnih građevina uvjetuje nekompatibilnost tradicionalnih i novih gradiva te poštivanje njihovog izvornog postojanja, zbog čega se ne preporučuje ni uporaba armiranog betona. U radu je opisana inovacijska metoda ojačanja povijesnih građevina tehnikom postavljanja kompozitnih polimera te prednosti navedene tehnike u odnosu na tradicionalne metode ojačanja i njezina primjena na postojećim građevinama.Most buildings of cultural or architectural heritage are masonry buildings constructed mostly of stone or brick walls. Those kinds of buildings were built before the existence of seismic knowledge and regulations. The complex issue of rehabilitation of historic buildings is based on incompatibility of traditional and new materials as well as on the necessity to preserve the original appearance of these buildings. The use of reinforced concrete is not recommended in rehabilitation of historical buildings. This paper will describe the innovative method of reinforcement of historic buildings with composite polymer technology and the advantages of the aforementioned technique compared to some traditional reinforcement methods and its application to existing buildings

SPEKTRALNE FUNKCIJE OŠTETLJIVOSTI ARMIRANOBETONSKIH OKVIRNIH KONSTRUKCIJA UPORABOM NOVE FORMULE ZA KOEFICIJENT OŠTETLJIVOSTI

Structural damage under seismic force is quantified by the calculation of damage index (DI), a coefficient which represents the degree of damage of the structure, and typically ranges from 0 to 1, with the value of 1 representing collapse. Based on a few specified damage models, a new original deterministic declaration of the DI is presented. Damage Index spectral functions are performed by an extensive parametric study using different earthquakes and different structures modelled as SDOF systems. A detailed analysis of the dynamic properties of reinforced concrete (RC) frame structures, as well as post elastic parameters of vertical structural elements using a large number of available experiments is also carried out, thus relating the parameters of real buildings and seismic loads defined by peak ground acceleration to the DI coefficients of structures. The results are seismic damage spectrum functions of RC frame structures.Kvantifikacija konstrukcijskog oštećenja moguća je proračunom koeficijenta oštetljivosti (DI), koji predstavlja stupanj oštećenja konstrukcije i kreće se u granicama od 0 do 1, gdje vrijednost 1 predstavlja rušenje. Zasnovan na nekoliko specificiranih modela, dan je novi originalni deterministički izraz za koeficijent oštetljivosti (DI). Spektralne funkcije koeficijenta oštetljivosti izvedene su parametarskom studijom koristeći 20 različitih potresa i različite konstrukcije predstavljene SDOF modelima. Provedena je detaljna analiza dinamičkih karakteristika okvirnih konstruckija, kao i poslijeelastičnih parametara vertikalnih konstrukcijskih elemenata koristeći se velikim brojem eksperimenata skupljenim u bazu, povezujući na taj način parametre stvarnih zgrada i seizmičkog opterećenja, definiranog vršnom akceleracijom, s koeficijentom oštetljivosti konstrukcije. Rezultat navedenoga su spektralne funkcije okvirnih armiranobetonskih konstrukcija

Usporedba perioda vibracija AB okvirnih konstrukcija s empirijskim izrazima danim u Euronormi 8

For the earthquake design of RC structures, period of vibration is not known immediately, and because of that the simplified expressions are given in the construction rules, which usually link the base period with the height of the construction. The aim of this paper is to verify these empirical expressions, which are given by different authors and Eurocode 8 and to conclude whether the expressions are good enough as a starting assumption for the design of earthquake resistant buildings. Most attention will be devoted to the RC frame structures. When modeling, besides the general requirements on the structures, typical requirements for particular types of structural systems will be applied. Results of the models and empirical expressions will be compared and the conclusion about applicability of the expressions will be drawn.Za potresno projektiranje armiranobetonskih okvirnih konstrukcija period vibracija se ne zna odmah i zbog toga se koriste pojednostavnjene jednadžbe u građevinskim pravilnicima koje najčešće povezuju osnovni period s visinom konstrukcije. Cilj ovoga rada je provjeriti da li su empirijski izrazi dani različitim autorima i Euronormom 8 dovoljno dobri kao početna pretpostavka prilikom potresnoga projektiranja. Najveća pozornost će se posvetiti armiranobetonskim okvirnim konstrukcijama. Prilikom modeliranja osim općih zahtjeva na konstrukciju, primijeniti će se posebni zahtjevi za odgovarajući tip konstrukcijske. Rezultati modela i empirijskih izraza će se usporediti i izvući će se zaključak o primjeni izraza

USPOREDBA OSNOVNIH PERIODA MODELA ZGRADA S ARMIRANOBETONSKIM ZIDOVIMA S EMPIRIJSKIM IZRAZIMA

Empirical formulas for the estimation of the fundamental periods have been included in seismic codes, which mainly depend on building height, material (steel, reinforced concrete (RC)) and structural system type (frame, shear wall, etc.). These formulas have been usually derived from empirical data through regression analysis of the measured fundamental period of existing buildings subjected to seismic actions. A parametric study on 480 different RC building models with shear walls was performed with varied parameters: building height, number of bays and the ratio of shear walls area to floor area. The aim of this paper is to verify these empirical expressions, which are given by different authors and seismic codes and to conclude whether the expressions are good enough as a starting assumption for the design of earthquake resistant buildings.Empirijski izrazi za procjenu osnovnih perioda su sastavni dio propisa za proračun seizmičkih djelovanja te uglavnom ovise o visini, materijalu (čelik, armirani beton) i nosivom sustavu(okvir, posmični zidovi, itd.) građevine. Ovi izrazi su obično nastali iz empirijskih podataka kroz analizu mjerenih osnovnih perioda postojećih građevina pod djelovanjem potresa. Provedena je parametarska studija na 480 modela armiranobetonskih zgrada s posmičnim zidovima s različitim ulaznim podacima: visina zgrade, broj raspona i omjer površine posmičnih zidova i tlocrtne površine zgrade. Cilj ovog istraživanja je provjeriti empirijske izraze različitih autora i seizmičkih propisa u svrhu provjere točnosti izraza kao početnih pretpostavki kod projektiranja potresno otpornih građevina

SEISMIC RISK OF CROATIAN CITIES BASED ON BUILDING'S VULNERABILITY

Seismic risk is fundamental for the establishment of priorities in long-term prevention policy since urbanization and concentration of population in earthquake prone areas are increasing. To assess seismic risk, it is necessary to determine seismic hazard and vulnerability for which large amount of input data is required. Therefore, a rapid seismic risk assessment is proposed, based on seismic hazard maps and on statistical Census data for buildings. A case study is illustrated for Croatian cities in order to provide an overview of the overall relative risk in Croatia. As a result, the prediction model for threatened buildings in Croatia in function of peak ground acceleration is proposed. The prediction model gives an indicative outcome after possible earthquake event expressed in terms of percentage of threatened buildings. Most vulnerable cities according to prediction model are Dubrovnik, Zagreb, Split and Rijeka in accordance with their buildings distribution by age

SPECTRAL FUNCTIONS OF DAMAGE INDEX (DI) FOR MASONRY BUILDINGS WITH FLEXIBLE FLOORS

Most of the buildings in old city cores of Croatia, built between 1860 and 1920 with wooden floors, are mainly designed to bear vertical loads. In this paper we propose a methodology for seismic vulnerability assessment of unreinforced masonry buildings with flexible floors. The methodology is based on the calculation of Damage Index (DI), a numerical value indicating the level of structural damage. In this methodology, the structure is represented using an SDOF model determined by damping, weight, elastic base shear capacity, elastic stiffness and post-elastic stiffness. Using accelerograms of earthquakes, step by step time-history numerical integrations are provided along with the results: top displacement, yield excursions, cumulative energy and base shear–displacement. These results serve as parameters which are then input in the formula for Damage Index (DI). The results of the paper are presented in the form of diagrams with DI values on the y axis and fundamental period of the structure on the x axis. These spectral functions of DI, along with knowledge of fundamental period and chosen accelerogram, can be used to quickly determine the level of damage for unreinforced masonry buildings with flexible floors

The Vulnerability of Buildings From the Osijek Database

Estimating of buildings vulnerability is based on a well-organized and detailed database of buildings and their characteristics. Creation of the buildings database of the city Osijek is in progress. This database contains, for each building, information regarding its location, geometric and structural characteristics, materials which were used for structural elements, and other relevant data. This paper presents numerical and statistic values of some characteristics of the buildings from the database. Different methods can be applied for the prediction of damage probability in the field of earthquake risk assessment. With the empirical Macroseismic method and the analytical Capacity Spectrum Method, the vulnerability of the few blocks of buildings, typical for the city Osijek, is estimated. For unreinforced masonry structures with flexible floors, the probability of reaching a certain degree of damage is estimated by the two selected methods, and the obtained results are compared

Spectral functions of RC frames using a new formula for Damage Index

Kvantifikacija konstrukcijskog oštećenja moguća je proračunom koeficijenta oštetljivosti (DI), koji predstavlja stupanj oštećenja konstrukcije i kreće se u granicama od 0 do 1, gdje vrijednost 1 predstavlja rušenje. Zasnovan na nekoliko specificiranih modela, dan je novi originalni deterministički izraz za koeficijent oštetljivosti (DI). Spektralne funkcije koeficijenta oštetljivosti izvedene su parametarskom studijom koristeći 20 različitih potresa i različite konstrukcije predstavljene SDOF modelima. Provedena je detaljna analiza dinamičkih karakteristika okvirnih konstruckija, kao i poslijeelastičnih parametara vertikalnih konstrukcijskih elemenata koristeći se velikim brojem eksperimenata skupljenim u bazu, povezujući na taj način parametre stvarnih zgrada i seizmičkog opterećenja, definiranog vršnom akceleracijom, s koeficijentom oštetljivosti konstrukcije. Rezultat navedenoga su spektralne funkcije okvirnih armiranobetonskih konstrukcija.Structural damage under seismic force is quantified by the calculation of damage index (DI), a coefficient which represents the degree of damage of the structure, and typically ranges from 0 to 1, with the value of 1 representing collapse. Based on a few specified damage models, a new original deterministic declaration of the DI is presented. Damage Index spectral functions are performed by an extensive parametric study using different earthquakes and different structures modelled as SDOF systems. A detailed analysis of the dynamic properties of reinforced concrete (RC) frame structures, as well as post elastic parameters of vertical structural elements using a large number of available experiments is also carried out, thus relating the parameters of real buildings and seismic loads defined by peak ground acceleration to the DI coefficients of structures. The results are seismic damage spectrum functions of RC frame structures

OJAČANJE POVIJESNIH GRAĐEVINA KOMPOZITNIM POLIMERIMA

Većina građevina kulturne ili graditeljske baštine su zidane zgrade koje su izgrađene najčešće od kamenih ili opečnih zidnih elemenata povezanih mortom, a zidane su prije postojanja znanja i propisa o protupotresnom građenju. Kompleksnost sanacije povijesnih građevina uvjetuje nekompatibilnost tradicionalnih i novih gradiva te poštivanje njihovog izvornog postojanja, zbog čega se ne preporučuje ni uporaba armiranog betona. U radu je opisana inovacijska metoda ojačanja povijesnih građevina tehnikom postavljanja kompozitnih polimera te prednosti navedene tehnike u odnosu na tradicionalne metode ojačanja i njezina primjena na postojećim građevinama