A severe earthquake hit Zagreb on the March 22, 2020 (magnitude ML = 5.5, with an epicenter 7 km north of the city center). During the COVID-19 lockdown, the event occurred and caused significant ...damage to the built environment and enormous disruption in everyday life. Brief facts about the Zagreb earthquake, the typology of buildings in the city, and the data collection after the quake itself are described. The paper focuses on post-earthquake assessment, damage classification, and failure patterns of residential buildings in Zagreb's old historical town, where masonry structures prevail. The earthquake critically damaged buildings that are important architectural achievements and ruptured Zagreb's historically recognizable city center. Furthermore, the data collected in the rapid post-earthquake assessment were analyzed and discussed. Graphical representations of damages are detailed and accompanied by photographs. This earthquake exposed Croatian building stock's vulnerability that should be mitigated as efficiently as possible in the coming years.
On 29 December 2020, a devastating Mw6.4 earthquake struck near the town of Petrinja, Croatia. The main earthquake was preceded by a Mw4.9 foreshock the day before. The earthquakes caused extensive ...damage to buildings, especially historic buildings made of unreinforced masonry but also to buildings of other typologies and to critical infrastructure. Today, recovery efforts in Croatia focus primarily on reconstruction and seismic retrofitting. Family homes and public, cultural, educational, and other facilities are top priorities. In this paper, a comprehensive study of existing building in the educational sector is presented as a case study. The seismic performance of the building is evaluated using numerical methods, first for the as-built condition and then for the retrofitted building. For each condition, the collapse mechanisms of the building were determined and critical structural elements were identified. The presented retrofit strategy of the dual structural system consisting of RC frame system and masonry walls aims to reduce the displacements of the RC frame system to a level sufficient to prevent the early brittle failure of the concrete. Additionally, the discrepancies when using different modelling approaches are discussed.
The city of Zagreb, the national capital and economic hub of Croatia, is situated in a seismically active region and hosts a significant array of historical buildings, from the medieval to ...Austro-Hungarian periods. These buildings possess varying but generally high degrees of vulnerability to seismic loading. This was highlighted in the Zagreb earthquake of 22 March 2020, emphasizing the need for seismic retrofitting in order to preserve this architectural heritage. In this paper, the seismic capacity of one such unreinforced masonry building is considered through a number of analysis methods, including response spectrum, pushover, and out-of-plane wall failure analyses. Given the advantages and disadvantages of the individual methods, their applicability and value in a seismic analysis is considered. Ambient vibration measurements before and after the Zagreb 2020 earthquake, used for model calibration, are also presented. Conclusions are drawn from each individual analysis and later compared. In conclusion, no single analysis method considers all relevant failure modes, and a combination of nonlinear static or dynamic analysis and out-of-plane analysis is recommended. Due to the large volume of the material, it is published in two parts, with ground motion record selection, dynamic analysis, and a comparison of the results published in part two.
On December 29, 2020, nine months after the March
Mw
5.4 Zagreb earthquake and amidst the COVID-19 lockdown, a devastating
Mw
6.4 earthquake struck near the town of Petrinja, about 50 km SE from the ...country’s capital Zagreb. It was preceded by the
Mw
4.9 foreshock from the day before. The main shock claimed 7 fatalities and caused widespread damage. Historical centers of nearby cities with invaluable heritage buildings were significantly affected as were the many residential buildings, built mainly of unreinforced masonry. Damage was observed as far as 60 km from the epicenter. This paper summarizes the seismological aspects of the
Mw
6.4 Petrinja earthquake, the emergency response and the main impacts to people and buildings. The description and findings are based on the field observations and a series of post-earthquake activities led by the team of the Faculty of Civil Engineering, University of Zagreb. Typical damage to buildings and usability data are presented with examples based on 50,000 inspection results. By far the most affected were the unreinforced masonry buildings, followed by confined masonry, whereas reinforced concrete buildings were the least affected. The total direct and indirect losses are estimated to 4.8 billion EUR. The provided information represents a useful basis and impetus for improving emergency action and long-term disaster reduction plans in other regions with similar building exposure and seismotectonic settings.
Line geometry and 3D graphic statics Iva Kodrnja; Maja Baniček; Krešimir Fresl
Građevinar (Zagreb),
01/2019, Letnik:
71, Številka:
10
Journal Article
Odprti dostop
The mathematical basis for the line geometry, with the line as its basic element, is presented in the paper because the forces that act on a body in space - whether we are interested in conditions of ...movement or immobility (balance) of that body - are vectorial values related to specific lines of action, so that the system of forces can be linked to the set of lines in space. The application of line geometry has proven the known claim that the system of forces in space, provided the forces are in a general position, can be reduced to two forces on reciprocal lines. The visualisation of this claim via the 3D graphic statics is also presented.
Earthquakes are natural phenomena that can strongly affect the human population, infrastructure, and the environment. Croatia is part of a tectonically and seismically active area so its habitants ...and relevant institutions should be aware of possible hazardous events, which can be devastating. Therefore, crisis communication is extremely important, and in the event of natural disasters such as earthquakes, it must be clear, timely and concise. Scientific institutions dealing with earthquakes should also be involved in crisis communication. The information on two strong earthquakes in 2020 that shocked the area of Zagreb and Petrinja and the wide surrounding area, have shown how relevant institutions can deal with information on earthquakes and their consequences and share them publicly. This paper adopts a mixedmethods research design, combining both qualitative, and quantitative data on the Zagreb and Petrinja earthquakes from various sources of scientific and professional institutions in the field of geology, geophysics, seismology and civil engineering in Croatia. Empirical data suggest that interactive communication that strives to address local contextual concerns, explain actions, and provide honest, timely, accurate and reliable information is most effective. In the future, institutions have to find a way to react or share their information to help in the crisis.
The method for reducing total computational time during iterative application of the force density method, intended to attain prescribed force values in cables or prescribed lengths of cable ...segments, is described in the paper. In each step of the iterative procedure, linear systems are solved with the accuracy that takes into account differences between the calculated and required values. The rule that prevents excessively fast increase in accuracy, while maintaining it high enough not to compromise the convergence of the iterative process, is proposed.
This paper analyzes critical forces and stability of steel thin-walled C-cross-section beams without lateral restraints. Mechanical properties of the rods material are determined by testing standard ...specimens in a laboratory. Based on the obtained data, the stability analysis of rods is carried out and critical forces are determined: analytically by using the theory of thin-walled rods, numerically by using the finite element method (FEM), and experimentally by testing the C-cross-section beams. The analysis of critical forces and stability shows that the calculation according to the theory of thin-walled rods does not take the effect of local buckling into account, and that the resulting critical global forces do not correspond to the actual behaviour of the rod. The FEM analysis and experimental test show that the simplifications, which have been introduced into the theory of thin-walled rods with open cross-sections, significantly affect final results of the level of the critical force.
Jedan od problema sustava za pričvršćenje tračnica na podlogu (sustav pričvršćenja) koji se javlja s razvojem željeznica jest oštećenje elastičnih pritiskalica, čime se gubi konstrukcijski integritet ...između tračnice i podloge. Stoga postoji potreba za razvojem novih ili poboljšanjem postojećih pritiskalica. U radu je kroz dosadašnja istraživanja opisan doprinos i uloga pojedinih komponenata sustava pričvršćenja pri djelovanju raznih slučajeva opterećenja, a kao alatu čijom se promjenom parametara može utjecati na učinkovitost sustava pričvršćenja, posebno je usmjereno na pritiskalice. Detaljno je opisan postupak izrade numeričkih modela kojima je moguće provođenje parametarskih analiza za razvoj novih ili modifikaciju postojećih pritiskalica za pričvršćenje tračnica.
Assessments of building damage and usability were of primary importance after the Zagreb earthquake of 22 March 2020. Due to deficiencies of preparatory phase, where education of experts was not ...carried out before the earthquake, but later on, the assessments contained certain subjectivity and interpretations, based on knowledge and experience, but also on intuition of individuals. Detailed methodology, which should improve rapid assessments and detailed engineering inspections to be performed before reconstruction, is highlighted in the paper. This methodology may be utilized if another devastating earthquake occurs, which could happen already tomorrow.
PDF
