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.
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.
Post-earthquake structural damage shows that wall collapse is one of the most common failure mechanisms in unreinforced masonry buildings. It is expected to be a critical issue also in Groningen, located in the northern part of the Netherlands, where human-induced seismicity has become an uprising problem in recent years. The majority of the existing buildings in that area are composed of unreinforced masonry; they were not designed to withstand earthquakes since the area has never been affected by tectonic earthquakes. They are characterised by vulnerable structural elements such as slender walls, large openings and cavity walls. Hence, the assessment of unreinforced masonry buildings in the Groningen province has become of high relevance. The abovementioned issue motivates engineering companies in the region to research seismic assessments of the existing structures. One of the biggest challenges is to be able to monitor structures during events in order to provide a quick post-earthquake assessment hence to obtain progressive damage on structures. The research published in the literature shows that crack detection can be a very powerful tool as an assessment technique. In order to ensure an adequate measurement, state-of-art technologies can be used for crack detection, such as special sensors or deep learning techniques for pixel-level crack segmentation on masonry surfaces. In this project, a new experiment will be run on an in-plane test setup to systematically propagate cracks to be able to detect cracks by new crack detection tools, namely digital crack sensor and vision-based crack detection. The validated product of the experiment will be tested on the monument of Fraeylemaborg.
Induced seismicity problems in the Groningen area caused by gas extraction have been one of the major challenges for the engineering and construction companies in the region and the Netherlands, not only because earthquake phenomena are new to the Dutch engineering community but also because the problem is very much complicated due to its social extents. The companies working in the structural engineering field in the region in different disciplines were forced to adapt very quickly to the earthquake related problems. It was a real size and investment problem for the SMEs, several of which benefited from this rush, however, only under certain conditions can this new skill set be sustainable. The SafeGo project aims mostly to help to facilitate sustainable development and build confidence for the SMEs in the field of earthquake engineering, rather than producing new scientific knowledge for them. SMEs are positioned in the seismic strengthening process either for collection of data or for providing and applying strengthening solutions. The proposed project aims to answer the question on how the “data-collection SMEs” can translate their data into more valuable assets to be used in the earthquake problem because the collection and the use of field data are vital. Furthermore, the question is also how the “strengthening SMEs” can verify and demonstrate their systems on a seismic shake table, because strengthening requires proven methodologies. The project goal is to combine these two central questions into findings on how the experimental and field data can efficiently be translated into suitable procedures, products and computer simulations for seismic assessment and strengthening of buildings, allowing SMEs to provide novel, integrated and accurate solutions not only in the region but also in international markets.
Induced seismicity problems in the Groningen area caused by gas extraction have been one of the major challenges for the engineering and construction companies in the region and the Netherlands, not only because earthquake phenomena are new to the Dutch engineering community but also because the problem is very much complicated due to its social extents.The companies working in the structural engineering field in the region in different disciplines were forced to adapt very quickly to the earthquake related problems. It was a real size and investment problem for the SMEs, several of which benefited from this rush, however, only under certain conditions can this new skill set be sustainable. The SafeGo project aims mostly to help to facilitate sustainable development and build confidence for the SMEs in the field of earthquake engineering, rather than producing new scientific knowledge for them.SMEs are positioned in the seismic strengthening process either for collection of data or for providing and applying strengthening solutions. The proposed project aims to answer the question on how the “data-collection SMEs” can translate their data into more valuable assets to be used in the earthquake problem because the collection and the use of field data are vital. Furthermore, the question is also how the “strengthening SMEs” can verify and demonstrate their systems on a seismic shake table, because strengthening requires proven methodologies. The project goal is to combine these two central questions into findings on how the experimental and field data can efficiently be translated into suitable procedures, products and computer simulations for seismic assessment and strengthening of buildings, allowing SMEs to provide novel, integrated and accurate solutions not only in the region but also in international markets.
