Post-earthquake structural damage shows that out-of-plane wall collapse is one of the most prevalent failure mechanisms in unreinforced masonry (URM) buildings. This issue is particularly critical in Groningen, a province located in the northern part of the Netherlands, where low-intensity ground shaking has occurred since 1991 due to gas extraction. The majority of buildings in this area are constructed using URM and were not designed to withstand earthquakes, as the area had never been affected by tectonic seismic activity before. Hence, the assessment of URM buildings in the Groningen province has become of high relevance.Out-of-plane failure mechanisms in brick masonry structures often stem from poor wall-to-wall, wall-to-floor or wall-to-roof connections that provide insufficient restraint and boundary conditions. Therefore, studying the mechanical behaviour of such connections is of prime importance for understanding and preventing damages and collapses in URM structures. Specifically, buildings with double-leaf cavity walls constitute a large portion of the building stock in the Groningen area. The connections of the leaves in cavity walls, which consist of metallic ties, are expected to play an important role. Regarding the wall-to-floor connections, the traditional way for URM structures in Dutch construction practice is either a simple masonry pocket connection or a hook anchor as-built connection, which are expected to be vulnerable to out-of-plane excitation. However, until now, little research has been carried out to characterise the seismic behaviour of connections between structural elements in traditional Dutch construction practice.This thesis investigates the seismic behaviour of two types of connections: wall-to-wall connections between cavity wall leaves and wall-to-floor connections between the masonry cavity wall and timber diaphragm, commonly found in traditional houses in the Groningen area. The research is divided into three phases: (1) inventory of existing buildings and connections in the Groningen area, (2) performance of experimental tests, and (3) proposal and validation of numerical and mechanical models. The thesis explores the three phases as follows:(i) An inventory of connections within URM buildings in the Groningen area is established. The inventory includes URM buildings of Groningen based on construction material, lateral load-resisting system, floor system, number of storeys, and connection details. Specific focus is given to the wall-to-wall and wall-to-floor connections in each URM building. The thickness of cavity wall leaves, the air gap between the leaves and the size and spacing of timber joists are key aspects of the inventory.(ii) Experimental tests are performed on the most common connection typologies identified in the inventory. This phase consists of two distinct experimental campaigns:o The first experimental campaign took place at the laboratory of the Delft University of Technology to provide a comprehensive characterisation of the axial behaviour of traditional metal tie connections in cavity walls. The campaign included a wide range of variations, such as two embedment lengths, four pre-compression levels, two different tie geometries, and five different testing protocols, including both monotonic and cyclic loading. The experimental results showed that the capacity of the wall tie connection is strongly influenced by the embedment length and the tie geometry, whereas the applied pre-compression and the loading rate do not have a significant influence.o The second experimental campaign has been carried out at the laboratory of the Hanze University of Applied Sciences to characterise the seismic behaviour of timber joist-masonry cavity wall connections, reproducing both as-built and strengthened conditions. Twenty-two unreinforced masonry wallets were tested, with different configurations, including two tie distributions, two pre-compression levels, two different as-built connections, and two different strengthening solutions. The experimental results highlighted the importance of cohesion and friction between joist and masonry since the type of failure mechanism (sliding of the joist or rocking failure of the masonry wallet) depends on the value of these two parameters. Additionally, the interaction between the joist and the wallet and the uplift of the latter activated due to rocking led to an arching effect that increased friction at the interface between the joist and the masonry. Consequently, the arching effect enhanced the force capacity of the connection.(iii) Mechanical and numerical models are proposed and validated against the performed experiments or other benchmarks. Mechanical and numerical models for the cavity wall tie and mechanical models for the timber joist-masonry connections were developed and verified by the experimental results to predict the failure mode and the strength capacity of the examined connections in URM buildings.o The mechanical model for the cavity wall tie connections considers six possible failures, namely tie failure, cone break-out failure, pull-out failure, buckling failure, piercing failure and punching failure. The mechanical model is able to capture the mean peak force and the failure mode obtained from the tests. After being calibrated against the available experiments, the proposed mechanical model is used to predict the performance of untested configurations by means of parametric analyses, including higher strength of mortar for calcium silicate brick masonry, different cavity depth, different tie embedment depth, and the use of solid bricks in place of perforated clay bricks.o The results of the experimental campaign on cavity wall ties were also utilised to calibrate a hysteretic numerical model representing the cyclic axial response of cavity wall tie connections. The proposed model uses zero-length elements implemented in OpenSees with the Pinching4 constitutive model to account for the compression-tension cyclic behaviour of the ties. The numerical model is able to capture important aspects of the tie response, such as strength degradation, unloading stiffness degradation, and pinching behaviour. The mechanical and numerical modelling approach can be easily adopted by practitioner engineers seeking to model the wall ties more accurately when assessing URM structures against earthquakes.o The mechanical model of timber-masonry connections examines two different failure modes: joist-sliding failure mode, including joist-to-wall interaction and rocking failure mode due to joist movement. Both mechanical models have been validated against the outcomes of the experimental campaigns conducted on the corresponding connections. The mechanical model is able to estimate each contribution of the studied mechanism. Structural engineers can use the mechanical model to predict the capacity of the connection for the studied failure modes.This research study can contribute to a better understanding of typical Groningen houses in terms of identifying the most common connections used at wall-to-wall and wall-to-floor connections in cavity walls, characterising the identified connections and proposing mechanical models for the studied connections.
This report consists of two parts and describes the highlights of the investigations carried out in the Province of Groningen as part of the Right Project to understand the Regional Innovation Ecosystem in the region. The first part is focusses on the socio-economic and R&D profile (Part 1A) and a SWOT analysis on salient aspects related to Regional Innovation Ecosystems (Part 1B). The second part (Part 2) focuses on the SME innovation capacity and needs, and presents the highlights of 6 interviews with SMEs in the region. The RIGHT project, an Interreg North Sea Program, will contribute to territorial growth in the North Sea Region by connecting smart specialisation strategies to human capital and the skills of the workforce by defining existing and potential regional growth sectors and sub-sectors.
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Few studies have investigated staying intentions and house attachment of residents who are confronted with physical damage to their dwelling in a risk area. This paper examines whether and how homeowners who are confronted with human-induced risks and the consequences of gas extraction in the Dutch Groningen rural earthquake region are attached to their damaged dwellings and why they stay. A content analysis was performed on 92 published interviews with homeowners of damaged dwellings. Additionally, three semi-structured interviews were held with key journalists and a homeowner. The results show that the homeowners’ staying intentions are interrelated with their house attachment; moreover, their awareness of their house attachment arises precisely because of the damage. We identify five subdimensions of physical and social house attachment, related to family history, heritage, (agricultural) business, personal refurbishment, and cohabiting family members, which make homeowners want to stay. The family history is especially mentioned by mid-to-later life homeowners, while some younger homeowners emphasize social house attachment to their children.We conclude that a homeowner's decision to stay in a damaged dwelling is a continuous cycle of reconsideration and renegotiation, punctuated by potential new risks and damages influencing the house attachment and staying intentions. Based on the found dimensions of house attachment, policymakers in risk areas could apply different approaches to homeowners in case of damage repair, rebuilding, or relocation plans, as homeowners - even those with damaged dwellings - may prefer to stay.
The pipelines are buried structures. They move together with the soil during a seismic event. They are affected from ground motions. The project aims to find out the possible effects of Groningen earthquakes on pipelines of Loppersum and Slochteren.This project is devised for conducting an initial probe on the available data to see the possible actions that can be taken, initially on these two pilot villages, Loppersum and Slochteren, for detecting the potential relationship between the past damages and the seismic activity.Lifeline infrastructure, such as water mains and sewerage systems, covering our urbanised areas like a network, are most of the times, sensitive to seismic actions. This sensitivity can be in the form of extended damage during seismic events, or other collateral damages, such as what happened in Christchurch Earthquakes in 2011 in New Zealand when the sewerage system of the city was filled in with tonnes of sand due to liquefaction.Regular damage detection is one of key solutions for operational purposes. The earthquake mitigation, however, needs large scale risk studies with expected spatial distribution of damages for varying seismic hazard levels.
Within the framework of resource efficiency it is important to recycle and reusematerials, replace fossil fuel based products with bio-based alternatives and avoidthe use of toxic substances. New applications are being sought for locally grownbiomass. In the area of Groningen buildings need reinforcement to guarantee safetyfor its users, due to man-induced earthquakes. Plans are to combine the workneeded for reinforcement with the improvement of energy performance of thesebuildings. The idea is to use bio-based building materials, preferably grown andprocessed in the region.In this study it is investigated whether it is feasible to use Typha (a swap plant) as abasis for a bio-based insulation product. In order to start the activities necessary tofurther develop this idea into a commercial product and start a dedicated company,a number of important questions have to be answered in terms of feasibility. Thisstudy therefore aims at mapping economic, organisational and technical issues andassociated risks and possibilities. On the basis of these results a developmenttrajectory can be started to set up a dedicated supply chain with the appropriatepartners, research projects can be designed to develop the missing knowledge andthe required funding can be acquired.
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.
