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.
DOCUMENT
Existing unreinforced masonry buildings in seismically active regions are in urgent need of consolidation and preservation against seismic action to prevent damage and loss of financial resources. In this research, an experimental study of externally confined brick masonry piers, which are frequently preferred as load-bearing elements in historical buildings, was conducted. The confinement system included a combination of open-grid basalt textile and mortar. Eighteen masonry pier specimens were produced using solid bricks collected from a historical building constructed in approximately the 1930s and a local mortar with substandard mechanical characteristics to simulate mortar properties in existing heritage buildings. All the square/rectangular pier specimens were tested under concentric compressive loads. In general, confinement of the tested textile-reinforced mortar (TRM) improved the energy dissipation of the masonry piers significantly. A comparison was made between the experimental results and theoretical predictions using the available analytical models. The compressive strengths predicted by the models are satisfactory.
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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.
DOCUMENT
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.
In recent years, human-induced seismicity in the northern part of the Netherlands increased rendering the seismic response of unreinforced masonry (URM) structures critical. Majority of the existing buildings in the Netherlands are URM, which are not designed to withstand earthquakes. This issue motivates engineering and construction companies in the region to research on the seismic assessment of the existing structures.The companies working in the structural engineering field in the region were forced to adapt very quickly to the earthquake related problems, such as strengthening of existing buildings after earthquake. Such solutions are of prime importance for the Groningen region due to the extent of the earthquake problems and need for strengthening the houses. The research published in the literature show that the connections play an important role in seismic resistant of the houses. Fixing or improving the poor wall-to-wall or floor-to-wall connections may have a large positive impact on the overall seismic behaviour. Some strengthening solutions are already provided by SMEs, and an extensive experimental campaign was carried out at TU Delft on retrofitted connections. In this project, a new experiment will be run on a large shake-table, unique in the Netherlands, that can simulate earthquake vibrations. These tests, together with the previous experience, will complement the overall knowledge on the strengthening solutions and their performance under real-time actual earthquake vibrations.
In recent years, human-induced seismicity in the northern part of the Netherlands increased rendering the seismic response of unreinforced masonry (URM) structures critical. Majority of the existing buildings in the Netherlands are URM, which are not designed to withstand earthquakes. This issue motivates engineering and construction companies in the region to research on the seismic assessment of the existing structures. The companies working in the structural engineering field in the region were forced to adapt very quickly to the earthquake related problems, such as strengthening of existing buildings after earthquake. Such solutions are of prime importance for the Groningen region due to the extent of the earthquake problems and need for strengthening the houses. The research published in the literature show that the connections play an important role in seismic resistant of the houses. Fixing or improving the poor wall-to-wall or floor-to-wall connections may have a large positive impact on the overall seismic behaviour. Some strengthening solutions are already provided by SMEs, and an extensive experimental campaign was carried out at TU Delft on retrofitted connections. In this project, a new experiment will be run on a large shake-table, unique in the Netherlands, that can simulate earthquake vibrations. These tests, together with the previous experience, will complement the overall knowledge on the strengthening solutions and their performance under real-time actual earthquake vibrations.
