The construction sector has proven to be one of the slowest sectors to embrace technology—a problem that must be addressed. This problem can be quickly and efficiently addressed in certain aspects of ...seismic engineering: from seismic risk assessment to damage detection, as well as condition assessments existing structures before or after an earthquake. In this paper, the literature review of assessment methods and damage detection technologies for existing (mainly) masonry structures is presented. Traditional methods are briefly explained, and modern are critically discussed. Special focus is given to unmanned aerial vehicles, as well as, photogrammetry and close-range remote sensing as a technology that can complement traditional ways of assessment and give us data about a structure that is often different to obtain. Graphical interpretation of one post-earthquake case study is provided. Open challenges and opportunities of emerging technologies for faster and easier assessment of seismic safety and vulnerability are presented.
In the wake of recent strong earthquakes in Croatia, there is a need for a detailed and more comprehensive post-earthquake damage assessment. Given that masonry structures are highly vulnerable to ...horizontal actions caused by earthquakes and a majority of the Croatian building stock is made of masonry, this field is particularly important for Croatia. In this paper, a complete assessment of an educational building in Zagreb Lower Town is reported. An extensive program of visual inspection and geometrical surveys has been planned and performed. Additionally, an in situ shear strength test is presented. After extensive fieldwork, collected data and results were input in 3Muri software for structural modeling. Moreover, a non-linear static (pushover) analysis was performed to individuate the possible failure mechanisms and to compare real-life damage to software results.
More than two years have passed since the devastating earthquakes struck Croatia in 2020, in which many educational buildings were damaged. In addition, several damaged educational buildings are ...under heritage protection, representing a special challenge for civil engineers during structural renovation. Strengthening methods that achieve adequate level of seismic capacity are limited in order to preserve the identity of these buildings. In the manuscript, a short overview of the damage to the educational sector is given with a special focus on a renovation of one case study. The case study is an educational building with a masonry structure located in the Lower Town of Zagreb and from the 19th century. An assessment of the structural condition was performed and a model was developed in the 3Muri software. Three variants of strengthening methods were applied to the model – FRCM, shotcrete and a combination of FRCM and shotcrete. Finally, each variant model was analyzed using the pushover method. The results are compared in terms of achieved earthquake capacity, expected cost and environmental impact.
Use of timber as a construction material has entered a period of renaissance since the development of high-performance engineered wood products, enabling larger and taller buildings to be built. In ...addition, due to substantial contribution of the building sector to global energy use, greenhouse gas emissions and waste production, sustainable solutions are needed, for which timber has shown a great potential as a sustainable, resilient and renewable building alternative, not only for single family homes but also for mid-rise and high-rise buildings. Both recent technological developments in timber engineering and exponentially increased use of engineered wood products and wood composites reflect in deficiency of current timber codes and standards. This paper presents an overview of some of the current challenges and emerging trends in the field of seismic design of timber buildings. Currently existing building codes and the development of new generation of European building codes are presented. Ongoing studies on a variety topics within seismic timber engineering are presented, including tall timber and hybrid buildings, composites with timber and seismic retrofitting with timber. Crucial challenges, key research needs and opportunities are addressed and critically discussed.
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.
Serviceability limit states are very important in the design of reinforced concrete elements but they are complex to calculate. Simplified serviceability calculations are provided in EN 1992-1-1 ...(2013) for steel reinforced elements. The crack widths are assumed to be acceptable if the bar diameters or bar spacings are not too large, while deflections are acceptable if the slenderness is not too large. In recent decades, FRP bars have become an adequate replacement for steel bars, especially in aggressive environments. The calculation procedures for FRP-reinforced concrete elements (FRPRC) were developed from calculation methods for steel reinforced elements. The first part of this paper demonstrates the procedures and parametric investigation for calculating the maximum bar diameter and bar spacing for the purpose of controlling the crack width, focusing on calculations for the maximum bar diameter for which cracks widths are acceptable. The second part of the paper demonstrates the procedures and parametric calculations for the slenderness limits for concrete elements reinforced with FRP bars in order to satisfy the usual deflection limits. Due to the different modulus of elasticity values of FRP and steel, the tables used for steel cannot be used for concrete beams reinforced with FRP bars. Therefore, new tables and diagrams are proposed in the paper. The new tables and diagrams for the maximum allowable bar diameters for the different modulus of elasticity values of FRP can be useful for the rapid control of the crack width in FRPRC elements. They are conservative compared to the exact calculations because some assumptions taken in the calculations are different to those taken in the exact calculation procedure for the crack width. The results of parametric calculations for the slenderness limits for FRPRC elements are provided in the form of a diagram for different concrete classes. Satisfying the slenderness from these curves will result in a smaller deflection than that allowed for each parameter related to that class of concrete.
Masonry structures are notoriously vulnerable to horizontal actions caused by earthquakes. Given the high seismicity of the European region, and that the European building stock comprises a lot of ...masonry buildings, knowledge about their structural response to seismic excitation is particularly important, but at the same time difficult to determine, due to the heterogenous nature of materials and/or constructional techniques in use. An additional issue is represented by the current methods for mechanical properties assessment, that do not provide a reliable framework for accurate structural estimations of existing buildings characterized by different typological properties. Every structure, in other words, should be separately inspected in regard to its mechanical behaviour, based on dedicated approaches able to capture potential critical issues. In this review paper, an insight on the Croatian ARES project is presented (Assessment and Rehabilitation of Existing Structures), including a state-of-the-art of the actual building stock and giving evidence of major difficulties concerning the assessment of existing structures. The most commonly used techniques and tools are compared, with a focus on their basic features and field of application. A brief overview of prevailing structural behaviours and Finite Element numerical modelling issues are also mentioned. As shown, the general tendency is to ensure “sustainable” and energy-efficient building systems. The latter, however, seem in disagreement with basic principles of structural maintenance and renovation. The aim of the ongoing ARES project, in this context, is to improve the current knowledge regarding the assessment and strengthening of structures, with a focus on a more reliable design and maintenance process for existing masonry buildings.
After the Zagreb earthquakes in March 2020, around 25,000 buildings were estimated damaged, most of them being in the historic city center. This fact is not that surprising since most of the city ...center buildings are unreinforced masonry structures that have not been assessed in quite some time and usually no retrofitting methods were ever applied. The rapid post-disaster assessment began the same day after the first earthquake occurred. Through mostly visual assessment methods, the basic idea is to identify the safety and usability of buildings in general. This type of assessment was also conducted in one of the oldest Croatian cultural institutions, Matica Hrvatska. It is a building of great historical significance and cultural value, as is most of the city center. Accordingly, this building was constructed with no consideration given to seismic events and with the use of traditional materials and building techniques. In the scope of this paper, urgent actions that were taken are shown with problems and challenges that occurred. Furthermore, the decision-making process after an earthquake is elaborated. In addition, a numerical model is developed in 3Muri software for structural modeling. A non-linear static pushover analysis is performed, and possible failure mechanisms are examined. Furthermore, real-life damage is compared to the software results, and a conclusion process of the building’s usability is explained. In the end, the results obtained are analyzed and conclusions regarding the efficiency of the used software are drawn.
Following the Zagreb earthquake in March of 2020, a destructive 6.2 magnitude earthquake struck Croatia again in December of 2020. The Sisak-Moslavina county suffered the most severe consequences; ...many historical and cultural buildings were badly damaged. In the education sector, 109 buildings were damaged. One such building is the case study of this research. The heritage-protected building of the First Primary School in Petrinja is an unreinforced masonry structure, constructed using traditional materials and building techniques. The historical background of the building and the results of the post-earthquake assessment are presented. A numerical calculation of three strengthening methods was performed in 3Muri software: FRCM, FRP, and shotcrete. Non-linear pushover analysis was performed for each model. Finally, the strengthening methods are compared based on the achieved earthquake capacity, cost, and environmental impact.
Historic buildings represent our cultural heritage and identity. Due to their age and building tradition, they are extremely vulnerable to seismic excitations, as confirmed by the recent earthquake ...in the city of Zagreb. In addition, historic buildings are among the buildings with the worst energy performance and very low indoor comfort. In the scope of this paper, the seismic and energy integrated approach is applied to a typical multi-residential building in Zagreb historical downtown. The main focus of the paper is on building envelope energy efficiency measures. Different variants of thermal insulation (external and internal), secondary windows (maintaining existing ones vs. new efficient ones) and ventilation (natural vs. mechanical with heat recovery) are analysed in terms of building energy performance (3D level). Furthermore, replacement of existing technical systems and installation of RES are also considered. Moreover, the acceptability of the proposed retrofitting solutions for opaque elements is evaluated in terms of thermal bridges (2D level) and long-term hygrothermal performance (1D level). Finally, the results show that it is possible even for a 100-year-old building to meet the current national primary energy requirements for new buildings and provide good indoor environmental quality for occupants while respecting the cultural heritage.
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