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.
Masonry structures represent the highest proportion of building stock worldwide. Currently, the structural condition of such structures is predominantly manually inspected which is a laborious, costly and subjective process. With developments in computer vision, there is an opportunity to use digital images to automate the visual inspection process. The aim of this study is to examine deep learning techniques for crack detection on images from masonry walls. A dataset with photos from masonry structures is produced containing complex backgrounds and various crack types and sizes. Different deep learning networks are considered and by leveraging the effect of transfer learning crack detection on masonry surfaces is performed on patch level with 95.3% accuracy and on pixel level with 79.6% F1 score. This is the first implementation of deep learning for pixel-level crack segmentation on masonry surfaces. Codes, data and networks relevant to the herein study are available in: github.com/dimitrisdais/crack_detection_CNN_masonry.
Out-of-plane (OOP) wall collapse is one of the most common failure mechanismsin unreinforced masonry (URM) structures. Insufficient connections at wall-to-wall, wall-to-floor or wall-to-roof levels are one of the main reasons for OOP failures. The seismic assessment of URM buildings with insufficient connections became of high relevance. In particular, cavity walls are widely used in many regions, such as Central and Northern Europe, Australia, New Zealand, China, and Groningen in the Netherlands. Defining thus the behaviour of such connections is of prime importance to understand the overall response of URM buildings.This paper is about an experimental campaign conducted at the BuildinG laboratory of Hanze University of Applied Sciences on timber joist-masonry connections, reproducing cavity walls with timber joists in as-built condition. A total of six URM tests were performed, with varying configurations as: two different tie distributions, two precompression levels and two different as-built connections. The tests aim at providing a complete characterization of the behaviour of the timber-joist cavity-wall connections under axial cyclic loading with special attention on the developed failure mechanism and the definition of force-displacement curves for each group of tests performed. The experimental results show that cohesion and friction between joist and masonry are important parameters in terms of the governing failure mechanism, whether it is a joist-sliding or rocking failure.
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.
This top-up project is related to the on-going RAAK MKB-project SafeGo (Seismic Monitoring, Design And Strengthening For thE GrOningen Region) . SafeGo combines knowledge of SMEs in the earthquake region of Groningen with innovative solutions and demonstration of technologies, to improve the process of seismic strengthening of houses. Innovative methods and approaches for monitoring and strengthening of structures are tested and further developed in SafeGo In the monitoring part of the project, SafeGo combines soil data, structural data and the sensor data to reach conclusions for the reasons behind observed damages in buildings. Fraeylemaborg, a castle-museum in Slochteren dating back to the 14th century, is used as a testbed. Various sensors are used for monitoring accelerations, tilt and water pressure. In the strengthening part of the project, masonry walls were built and strengthened by the participating SMEs. These walls are placed on the shake table and tested with real earthquake vibrations. A shake table is an accurate laboratory equipment which simulates earthquakes. Majority of the tasks in SafeGo are related either to the site or to the laboratory, which are environments outside of the school. Although an intensive student participation was initially planned, this was not achieved due to COVID19 crisis and the series of mobility restrictions, neither in the monitoring nor in the shake table testing parts of the project. This top-up project aims to transfer the knowledge and create interaction with the students for the SafeGo project. Visitation to the monitored building and presentations to the students on the monitoring system, visitations to the shake table laboratory and interactive events are planned within this project.
In recent years there has been an increasing need for nature inclusive solutions in the construction sector. The practice asks for new solutions contributing to the development of sustainable, resilient and liveable cities. Under the guidance of the Dutch government, greening of the cities has become one of the aims of municipalities in the Netherlands and the focus of some emerging companies and design offices. In cities, quay masonry walls, thanks to their close contact with water, have the potential to be ecologically engineered to favour vegetation, thereby contributing to the renaturing of urban areas. By building a prototype of an innovative masonry building system, this project aims to investigate the potential for improving the integration between masonry quay walls and vegetation. The set-up consists of a dry-stacking system for brick masonry: strong polyamide elements interconnect the bricks, providing strength to the masonry without the need for mortar. The space in between bricks, traditionally filled with mortar, is to be filled with compost material, providing an ideal substrate for plant growth and a buffer for water storage (figure 1). In addition to improved integration between masonry walls and vegetation, the proposed dry-stacking system allows for easy reuse of bricks, thereby contributing to circularity and sustainability of the building industry. The project broadens and strengthens the national network in the field of urban ecology by bringing together expertise from the fields of architecture, ecology and the construction sector, from both academia and practice.
