In Groningen, the Netherlands, induced earthquakes occur in a relatively densely populated area, the so-called Groningen gas field. Many houses and other buildings have been facing damage, from minor cracks to severe damage. The gas extraction company (NAM, a joint venture of Shell and Exxon Mobil) is held responsible for the earthquakes and has a legal liability to compensate for the damage. In addition to damage, several houses in the area are thought to be unsafe (not allowing occupants to leave their houses alive in case of a major earthquake). Both NAM and the Dutch government play a crucial role in the gas problems; where NAM is responsible for damage, the government has to guarantee citizens’ safety. Government has given orders to develop a strengthening operation for thousands houses.For many inhabitants, the practice of damage repair and strengthening has not been very effective and satisfying. First, the system of damage compensation, is neither simple nor expeditious; many citizens experience long waiting times, arbitrariness in causality and damage judgements and, as a result, unfair treatments. Second, after plans had been launched to inspect and eventually strengthen thousands of houses, the Minister decided to gradually reduce gas extraction. Immediately after that, he also decided to pause the intended strengthening operation, leaving many inhabitants in uncertainty about the current safety of their houses. In short, Groningen citizens don’t feel taken seriously by NAM, government and executing agencies, they are dissatisfied with damage settlements and their confidence in private (oil/gas companies) and public parties (government) has reached an all-time low. This situation has turned out to be very obstinate and difficult to turn. Our statement is that the architecture of the damage and strengthening operation is based on a systematic flaw. Although several minor changes have been made in the damage settlement and strengthening system, they have been limited to executing agencies and are not substantial. Therefore it is argued that, unless this structural flaw is being solved, the Netherlands will stay confronted with Groningen citizens whose trust in government is a far cry and will eventually lead to feelings of alienation.
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Purpose: The present study deals with the numerical modeling of the low-velocity impact damage of laminated composites which have increasingly important applications in aerospace primary structures. Such damage, generated by various sources during ground handling, substantially reduces the mechanical residual performance and the safe-service life. The purpose of this paper is to present and validate a computationally efficient approach in order to explore the effect of critical parameters on the impact damage characteristics.Design/methodology/approach: Numerical modeling is considered as one of the most efficient tool as compared to the expensive and time-consuming experimental testing. In this paper, a finite element model based on explicit dynamics formulations is adopted. Hashin criterion is applied to predict the intralaminar damage initiation and evolution. The numerical analysis is performed using the ABAQUS® programme. Findings: The employed modeling approach is validated using corresponding numerical data found in the literature and the presented results show a reasonable correlation to the available literature data. It is demonstrated that the current model can be used to capture the force-time response as well as damage parameter maps showing the intralaminar damage evolution for different impact cases with respect to the physical boundary conditions and a range of impact energies. Originality/value: Low-velocity impact damage of laminated composites is still not well understood due to the complexity and non-linearity of the damage zone. The presented model is used to predict the force-time response which is considered as one of the most important parameters influencing the structural integrity. Furthermore, it is used for capturing the damage shape evolution, exhibiting a high degree of capability as a damage assessment computational tool.
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This paper aims to quantify the evolution of damage in masonry walls under induced seismicity. A damage index equation, which is a function of the evolution of shear slippage and opening of the mortar joints, as well as of the drift ratio of masonry walls, was proposed herein. Initially, a dataset of experimental tests from in-plane quasi-static and cyclic tests on masonry walls was considered. The experimentally obtained crack patterns were investigated and their correlation with damage propagation was studied. Using a software based on the Distinct Element Method, a numerical model was developed and validated against full-scale experimental tests obtained from the literature. Wall panels representing common typologies of house façades of unreinforced masonry buildings in Northern Europe i.e. near the Groningen gas field in the Netherlands, were numerically investigated. The accumulated damage within the seismic response of the masonry walls was investigated by means of representative harmonic load excitations and an incremental dynamic analysis based on induced seismicity records from Groningen region. The ability of this index to capture different damage situations is demonstrated. The proposed methodology could also be applied to quantify damage and accumulation in masonry during strong earthquakes and aftershocks too.
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Risk assessments on trees in urban areas and roadside plantings have become common practice and a large body of information exists on qualitative aspects on the risks of tree failure. Quantitative analysis of financial damage due to tree failure is generally lacking. The objective of this paper is to determine the amount of tree failure related property damage and to derive possible trends in the number of cases and monetary claims and compensations. This paper presents the analysis of 1610 observations on urban tree failure in the Netherlands. The data originate from two different sources, i.e. jurisprudence (4% of the data) and 21 municipalities (96%). The data covers property damage in urban areas between the early sixties and 2010. Within municipalities, paid compensations due to tree failure are found to range from €0 to € 49,296 with an average of €2,244 per paid compensation. Results demonstrate a significant annual increase in tree failure as well as in paid compensations.
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The majority of houses in the Groningen gas field region, the largest in Europe, consist of unreinforced masonry material. Because of their particular characteristics (cavity walls of different material, large openings, limited bearing walls in one direction, etc.) these houses are exceptionally vulnerable to shallow induced earthquakes, frequently occurring in the region during the last decade. Raised by the damage incurred in the Groningen buildings due to induced earthquakes, the question whether the small and sometimes invisible plastic deformations prior to a major earthquake affect the overall final response becomes of high importance as its answer is associated with legal liability and consequences due to the damage-claim procedures employed in the region. This paper presents, for the first time, evidence of cumulative damage from available experimental and numerical data reported in the literature. Furthermore, the available modelling tools are scrutinized in terms of their pros and cons in modelling cumulative damage in masonry. Results of full-scale shake-table tests, cyclic wall tests, complex 3D nonlinear time-history analyses, single degree of freedom (SDOF) analyses and finally wall element analyses under periodic dynamic loading have been used for better explaining the phenomenon. It was concluded that a user intervention is needed for most of the SDOF modelling tools if cumulative damage is to be modelled. Furthermore, the results of the cumulative damage in SDOF models are sensitive to the degradation parameters, which require calibration against experimental data. The overall results of numerical models, such as SDOF residual displacement or floor lateral displacements, may be misleading in understanding the damage accumulation. On the other hand, detailed discrete-element modelling is found to be computationally expensive but more consistent in terms of providing insights in real damage accumulation.
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This paper aims to quantify the cumulative damage of unreinforced masonry (URM) subjected to induced seismicity. A numerical model based on discrete element method (DEM) has been develop and was able to represented masonry wall panels with and without openings; which are common typologies of domestic houses in the Groningen gas field in the Netherlands. Within DEM, masonry units were represented as a series of discrete blocks bonded together with zero-thickness interfaces, representing mortar, which can open and close according to the stresses applied on them. Initially, the numerical model has been validated against the experimental data reported in the literature. It was assumed that the bricks would exhibit linear stress-strain behaviour and that opening and slip along the mortar joints would be the predominant failure mechanism. Then, accumulated damage within the seismic response of the masonry walls investigated by means of harmonic load excitations representative of the acceleration time histories recorded during induced seismicity events that occurred in Groningen, the Netherlands.
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Kahramanmaraş Earthquake Sequence of 6th of February is the deadliest earthquake that happened in Turkey in the era of instrumental seismology, claiming more than 55 thousand lives and leaving torn down cities and towns behind. More than 450 km long lateral strike-slip fault ruptured during these catastrophic earthquakes. As a result, more than 38 thousand buildings collapsed causing life losses. Considering that the large share of the Turkish building stock consists of RC buildings, the vulnerable RC building stock is the main responsible for this picture. Deficiencies of the Turkish RC building stock are well known since they manifested themselves several times in the past earthquakes. However, considering the improvements in the seismic codes and the seismic hazard maps achieved in the last two decades, the widespread collapse of buildings constructed after year 2000 was rather unexpected. Some of the observed structural damage patterns are similar to those observed also in the pre-2000 buildings in recent earthquakes, however, some other types of damages, such as out-of-plane bending and shear failures or shear-friction capacity failure of RC walls, brittle fracture and bond-slip failure of reinforcement, tension failure of beams and slabs are usually not witnessed. This paper presents a carefully selected set of examples comparing the pre-2000 and post-2000 building damages and collapses, also referring to a detailed summary and comparison of the code developments in Turkey.
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The objective of this study is to evaluate the energetic, exergetic, sustainability, economic and environmental performances of a 4-cylinder turbodiesel aviation engine (TdAE) used on unmanned aerial vehicles for the take-off operation mode to assess the system with large aspects. Energy efficiency of the system is found as 43.158%, while exergy efficiency 40.655%. Thermoeconomic analysis gives information about the costs of the inlet and outlet energy and exergy flows of the engine. Hourly levelized total cost flow of the TdAE is found as 21.036 $/h, when the hourly fuel cost flow of the engine is found as 30.328 $/h. The waste exergy cost parameter is determined as 0.0144 MJ/h/$ from exergy cost-energy-mass (EXCEM) analysis, while it is estimated as 14.043 MJ/$ from modified-EXCEM analysis. Environmental damage cost analysis evaluates the cost formation of the exhaust emissions. The total environmental damage cost of the TdAE is computed as 12.895 $/h whilst specific environmental damage cost is determined as 0.054 $/MJ for 494.145 MJ/h TdAE power production. It is assessed that the main contributors to the environmental impact rate of the TdAE are the fuel consumption and the formation pollutants of combustion reaction.
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Laminated composites have important applications in modern aeronautical structures due to their extraordinary mechanical and environmental behaviour. Nevertheless, aircraft composite structures are highly vulnerable to impact damage, either by low-velocity sources during maintenance or high-velocity sources during in-flight events. Even barely visible impact damage induced by low-velocity loading, substantially reduces the residual mechanical performance and the safe-service life of the composites structures. Despite the extensive research already carried out, impact damage of laminated composite structures is still not well understood and it is an area of on-going research. Numerical modelling is considered as the most efficient tool as compared to the expensive and time-consuming experimental testing. In this paper, a finite element model based on explicit dynamics formulations is adopted. Hashin criterion is applied to predict the intra-laminar damage initiation and evolution. The numerical analysis is performed using the ABAQUS ® programme. The employed modelling approach is validated using numerical results found in the literature and the presented results show an acceptable correlation to the available literature data. It is demonstrated that the presented model is able to capture force-time response as well as damage evolution map for a range of impact energies.
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Groningen gas field is the largest on-land gas resource in the world and is beingexploited since 1963. There are damaging earthquakes, the largest of which was 3.6 magnitude. The recursive induced earthquakes are often blamed for triggering the structural damages in thousands of houses in the area. A damage claim procedure takes place after each significantly felt earthquake. The liability of the exploiting company is related to the damages and the engineering firms and experts are asked to correlate the claimed damages with a past earthquake. Structures in the region present high vulnerabilities to the lateral forces, soilproperties are quite unfavourable for seismic resistance, and structural damages are present even without earthquakes. This situation creates a dispute area where one can claim that most structures in the region were already damaged because of the fact that the soil is soft, the ground water table oscillates, and structures are vulnerable to external conditions anyhow and deteriorate in time, which can be the main cause of such structural damages. This ambiguity of damage vs earthquake correlation is one of the main sources of the public unrest in the area up until today. This study presents the perspective of people in the region in terms of liveability and the social acceptance of earthquakes in their lives. An attempt has been made to translate these social effects and expectations into structural performance metrics for ordinary houses in the region. A new seismic design and assessment approach, called Comfort Level Earthquake (CLE) has been proposed.
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