KNAW – minisymposium ‘Aardbevingsbestendige woningen’ 24 maart 2020Ondanks absentie van het symposium door de Corona crisis is dit boekje samengesteld voor digitale verzending en het drukken van een papieren versie.
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.
Using technology to improve the adolescents' journey to school by bike in province of Drenthe and Groningen.All unsafe area that children spotted on the map, are because the lack of traffic safety ( lack of visibility, high speed, etc). In general children do not have a positive perception of cycling to school, and their favourite mode of traveling to school is car. What technology based intervention can make adolescents’ cycling to and from school safer and more attractive for them? Also does it help to encourage those who live far from the school (>10 km) to cycle to and from school more often?
Automated driving nowadays has become reality with the help of in-vehicle (ADAS) systems. More and more of such systems are being developed by OEMs and service providers. These (partly) automated systems are intended to enhance road and traffic safety (among other benefits) by addressing human limitations such as fatigue, low vigilance/distraction, reaction time, low behavioral adaptation, etc. In other words, (partly) automated driving should relieve the driver from his/her one or more preliminary driving tasks, making the ride enjoyable, safer and more relaxing. The present in-vehicle systems, on the contrary, requires continuous vigilance/alertness and behavioral adaptation from human drivers, and may also subject them to frequent in-and-out-of-the-loop situations and warnings. The tip of the iceberg is the robotic behavior of these in-vehicle systems, contrary to human driving behavior, viz. adaptive according to road, traffic, users, laws, weather, etc. Furthermore, no two human drivers are the same, and thus, do not possess the same driving styles and preferences. So how can one design of robotic behavior of an in-vehicle system be suitable for all human drivers? To emphasize the need for HUBRIS, this project proposes quantifying the behavioral difference between human driver and two in-vehicle systems through naturalistic driving in highway conditions, and subsequently, formulating preliminary design guidelines using the quantified behavioral difference matrix. Partners are V-tron, a service provider and potential developer of in-vehicle systems, Smits Opleidingen, a driving school keen on providing state-of-the-art education and training, Dutch Autonomous Mobility (DAM) B.V., a company active in operations, testing and assessment of self-driving vehicles in the Groningen province, Goudappel Coffeng, consultants in mobility and experts in traffic psychology, and Siemens Industry Software and Services B.V. (Siemens), developers of traffic simulation environments for testing in-vehicle systems.
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.
