Although relevant information regarding the curtain walls structural damage state is available, hardly any data referring to the seismic loading effect on the overall façade performance is found in the literature. The present research attempts to assess the unitised curtain walls seismic performance by identifying the occurring damage mechanisms based on full-scale testing and finite element modelling.
The study initiates with a state-of-the-art discussing in detail the relevant research areas. Additionally, an introduction to the curtain wall numerical modelling field is provided. This literature review originates both from full-scale experimental testing and findings of academically developed finite element models. The case study of an experimental procedure is also described accompanied by the curtain wall response to the inter-storey drift implementation.
The modelling approach is introduced by presenting the mechanisms and the recreated curtain wall behaviour. Additionally, the process of identifying the properties of the curtain wall the boundary and loading conditions is displayed. The various modelling phases, the initial numerical development, its improvement through the calibration with the experimental results and the calibrated version, are also included.
The accomplishment of the first global curtain wall numerical model using DIANA FEA is a main research objective. The novelty consists in the exploration of the software possibilities and limitations which, although widely used for numerous applications, it hasn’t been utilised for façade numerical modelling. In general, the numerical representation of façade systems aims to provide a better insight of the curtain wall behaviour that will be eventually accurate to the extent that experimental tests won’t be needed for their validation.
Another interesting area is the correlation of the numerical behaviour to the experimental results measured on the curtain wall mock-ups while undergoing seismic loading. The model calibration intends for a realistic representation of the actual performance as recorded during the full-scale testing. Additionally, the contribution of structural silicone sealants in the system post-earthquake behaviour through the comparative performance of façade samples with dry gasket and systems with structural silicone is assessed. This evaluation aims to reinforce the knowledge regarding the strengths and weaknesses of wet and dry configurations and to indicate their appropriate application.
The research attempts to contribute to the seismic risk assessment of unitised curtain walls by identifying the governing failure mechanisms. This evaluation is performed with regards to the silicone sealant, simulating both dry and wet configurations. Thus, a sensitivity analysis varying over the structural silicone bite is developed with respect to the façade ultimate failure. The curtain wall overall response is addressed by evaluating several parameters (displacements, distortion, rotation and maximum stress per component). Moreover, the detection of the largest stress values occurring per element is used for the utilisation factors determination. This occurs by comparing the maximum stresses with the respective design values. The different outcomes provide the constructive context for further research of the façade response under seismic action. The study finalises with conclusions, considerations as well as suggestions for further research. Various challenges encountered are also introduced, aspiring to provide helpful information for future modellers. ... Read more

The light and frequent earthquakes in the north of the Netherlands, particularly in the province of Groningen, have recently exposed the unreinforced masonry structures to seismic activities. Since these structures do not adhere to seismic regulations, they are considered vulnerable to seismicity. The ultimate state capacity of the structures is important for an individual's safety, however, these earthquakes are of low intensity and cause aesthetic damage.

In order to investigate the light damage initiation and development, TNO has performed shaking table tests on an unreinforced masonry (URM) cavity wall specimen in out-of-plane (OOP) one-way bending with small increments in intensity. The test specimen consisted of calcium silicate brick inner leaf and perforated clay brick outer leaf. The damage development in the outer leaf was monitored during these tests using a high-speed digital image correlation (DIC) technique to study the initiation and development of damage in the outer leaf of the specimen. The experimental tests showed damage initiation at the mid-height of the outer leaf. The tests could not capture the development of cracks through the thickness of the cavity wall.

The scope of this research is a numerical assessment of the experimental study by using a Non-Linear Time History (NLTH) analysis of light damage initiation and development of a URM cavity wall under out-of-plane loading. The high-resolution experimental results are used as a basis for the development and calibration of models which can better predict the crack initiation and development in URM. The finite element software DIANA 10.5 FEA was used to set up the numerical model and conduct transient analysis.

The seismic signal as an input loading and the top boundary condition of the test specimen. The acceleration data measured from the shaking table tests at the base was used as an input seismic signal for the transient analysis of the models. The input signal needed to be processed before application as the presence of low-frequency content leaded to inaccurate results. Different approaches are discussed in this thesis regarding the processing of the input acceleration signal.

The experimental tests were modeled along the cross-section of the test specimen, thereby highlighting the thickness of the inner leaf and the outer leaf. This enabled tracking the light damage initiation and propagation through the thickness of the cavity wall. A total of thirteen shaking table tests were conducted on the experimental setup. In order to gain insight into the behavior of the specimen during each shaking table test, a model was created corresponding to each shaking table test. Preliminary analysis schemes were set in order to check the validity of all thirteen models. The two cases of top boundary conditions were checked, roller support and spring-mass support. The roller boundary condition proved to be stiff in comparison to the experimental results.

The numerical results were calibrated on the basis of material properties. The results were compared to experimental results by checking the dynamic behavior at the mid-height, dynamic behavior over the height, and light damage initiation and development of the specimen. The results of the numerical models were stiff in comparison to the experimental results. According to the conclusions, it is recommended to research further regarding the boundary conditions, especially the bottom boundary condition due to the formation of a rocking crack. Another important aspect to focus on is the combination of all input signals, thereby, taking into consideration the damage accumulation. ... Read more

Over the past decades an increase in underground construction is observed. Deep excavations are among the structures used for underground construction. The construction of such structures often affects nearby existing structures and causes possibly even damages.
The prediction of these damages is usually done by following these steps:
1. Determining the free-field ground displacements
2. Imposing the displacements on the structure
3. Determining the deformations of the structure
4. Assess potential damages following these deformations
The ground and the structure are often modelled separately taking no (LTSM) or a factor (Relative Stiffness Method) into account for interaction between soil and structure. Taking no interaction into account is particularly conservative when looking at vertical displacements. The non-linear behaviour of structural elements is neglected by these methods. This could lead to errors when assessing deformations of a masonry building due to the extreme non-linear behaviour of masonry structures.
The objective of this thesis is to get a better understanding of the effect of deep excavations on adjacent (piled buildings) by using integrated 2D modelling. This is done by remodelling the construction of the building pit in PLAXIS.
Based on the analysis performed in Section 4 the load on the pile is the largest contributor to the vertical and horizontal displacements of the pile relative to the soil around the pile. The diameter and stiffness of the pile are also very important factor determining the vertical movement of the pile.
The difference in the soil between a free-field situation and a situation with foundation piles (and a building) the piles stiffen the soil around the piles. Especially, when these piles are in a group. This effect increases when the piles are coupled by a structure. Vertical displacements are more smeared out over the length of the pile. This is less the case for horizontal displacements. Foundation piles undergo negative skin friction as a result of the settlements of the upper soil layers leading to stress in the soil beneath the pile tip. The stress in the soil beneath piles increases with increasing load and skin friction on the pile. This increased stress results in more horizontal stress, which in close proximity to a retaining wall could lead to increased deformations in the retaining wall and therefore the soil.
The results of the numerical calculations and the analytic calculations are analysed and compared in Section 6. In the numerical models both linear elastic as non-linear material properties have been assigned to the masonry building façade in different models. The numerical model with linear elastic material properties for masonry showed stiff response of the building to the induced soil deformations, underestimating the potential damages. The numerical model with non-linear material properties assigned to masonry showed more realistic results. These results are in line with the established analytical models.
Integrated numerical modelling could be a viable solution for future projects where potential building damage is assessed next to deep excavation. it could help to identify weak points within a structure which need addressing during the construction of an adjacent deep excavation. This study has shown that it is possible to do damage assessment in a fully integrated model. The important factors in assessing such projects are the overall soil deformation. Secondly, the relation between the soil and foundation of the structure needs to be analysed. Thirdly, the interface between the foundation and the structure is important.
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Gas extractions are responsible for mostly all induced earthquakes in the Groningen area and this leads to damage of houses and buildings and issues regarding safety. Current strengthening measurements are mostly very visible. However, this can change by using the window frame as part of the structure, particularly interesting for Dutch houses characterized by large window openings. In this thesis, the focus is on the validation of the numerical model based on experimental testing. From this, the main research question was formulated as “How can the structural window frame be modelled to agree with the experimental results, in order to assess the seismic performance for unreinforced masonry structures?”. The structural window frame is made of a timber frame, an adhesive and a double-glazing unit. The timber frame is made of hardwood on the outside and plywood on the inside. The potential of the structural window frame is researched into several numerical, experimental and design studies using DIANA 10.4. It is concluded that a specific non-linear elastic interface model for the adhesive is the best suitable model. This numerical model is used as a loading protocol for the experiments. The structural window frames have been built and tested at the TU Delft. The experimental results showed that the structural window frame behaves plastically. Concluding, the glass panels and the hardwood are not damaged however, the plywood is pinched due to the glass panel. The numerical model is adjusted to include the pinching behaviour of the inner bar to suit the experiments. The next step is the masonry model. The masonry model including the structural window frame showed an increase of 15% for the in-plane shear force capacity and a decrease of 23% for the crack width for a displacement of 4 mm, compared to the unstrengthened masonry wall. The pushover calculation showed that both the unstrengthened and strengthened masonry wall can withstand the seismic loads in Appingedam. According to assumptions, the structural window frame results in an increase of the shear force capacity of 47% for larger displacements. The ductility of the structure can be increased by increasing the effective mass to 15000 kg. However, the calculation is only valid for the assumed values, these results should not be taken too strictly. The design of the window frame can be improved by using: a stiffer timber frame, a thinner adhesive and a more sustainable design. Using a frame that is twice as stiff and strong has resulted in: similar initial behaviour, higher maximum shear force and later stabilisation of the in-plane shear force. Using a thinner adhesive than 5 mm does not result in more beneficial results. Furthermore, making only screwed connections and maintaining the structural window frame frequently could increase the lifespan of the structural window frame. The structural window frame has potential however, more numerical and experimental research should be done. ... Read more

The floods of 1953, 1993, 1995, 2021 and the almost flood in Rivierenland show that floods have major consequences. Before a flood people can evacuate preventively or vertical and during a flood people can flee, being rescued or permanently stay behind. This research focuses on fleeing and being rescued to a safe region. The research question is: ‘How much time does it take to flee to a safe region during a flood, and what are the core factors that determine the success of a rescue operation by a lifeboat in the Netherlands?’. To indicate how much time it takes for people to flee to a safe region, an experiment took place at test facility Flood Proof Holland in Delft. During this experiment 25 persons walked or bicycled over a parcourse divided into five rounds with different water depths, namely 0.2, 0.4 and 0.6 meter. Additionally, there were other variations, such as walking with a floating object, bringing luggage, bringing a domestic animal, fleeing during darkness and the addition of debris in the water. Time measurements took place during the experiment. If people cannot flee, rescue is needed. To gain more insight into rescuing of people during floods, a questionnaire is spread among experts. Relations between time measurements are found with the use of the Pearson moment correlation coefficient, paired t-test and determining the line by using intersept free linear regression. The relations are combined into a flow chart. Further, the time needed during a rescue attempt is combined into a formula. The navigation speed deviates for different water depths and types of lifeboats. Further, it is estimated by the experts that it takes 7½, 30 and 1 minutes from the contact with a person located at respectively a higher floor or attic, collapsed building and out of the water until having this person into a lifeboat. There is no direct singular answer to the research question, because it depends on the area where the flood takes place and the extent of the flood. Larger water depths increase the fleeing time. If a person decides to flee, it is recommended to walk with a bicycle or bring an air mattress. A stick is useful to check where the road is located. Avoid areas with a lot of debris and do not flee during darkness, except if this is inevitable to survive. People can also wait for rescue at a higher (dry) floor. For the rescue crew, number one priority is safety. Try to avoid to navigate through areas with a lot of debris as this may damage the lifeboat. Search the area systematically and make notes of where people are located. ... Read more

Because of the fortunate absence of great flood events in The Netherlands during the second half of the twentieth century, no physical data was added to the structural understanding of flood fragility on walls. Considering that during the same period the cavity wall became standard in the construction of houses, a certain inconsistency can be recognized between the expected and observed (structural) behaviour of a modern wall during flood events. Nevertheless, failure, or collapse, of residential buildings is included in the Dutch flood protection standards as an important cause of damage and one of the main reasons for loss of life. It is generally believed that the developments in terms of building materials translate to a safer residence i.e. less prone to flood actions. This consensus is also found in the trade-off for certain mitigation measures, especially in areas where horizontal evacuation is difficult. An improved understanding of the flood fragility of a modern cavity wall is thus needed to prove the general consensus or to adjust the current mitigation measures to comply with the allowed fatality risks.

A window-featured cavity wall section was constructed at the Flood Proof Holland facility, using calcium silicate bricks, fired clay bricks, and a weaker mortar to partly account for the virgin effect of any newly-built wall. Both inner and outer walls were connected with adequate wall ties. The wall section was subjected to several hydrostatic pressures at both sides. These experiments were performed to physically grasp the deformations corresponding to certain flood scenarios affecting cavity wall sections from ordinary terraced houses. Additionally, the effect of the window was investigated; both on the stability and its contribution to the water height inside a residence.

Computations showed that the cavity wall in a one-way bending configuration starts to show significant cracks between 1.3 and 1.6 meters of outside water level. Because of the brittleness of the masonry, this would imply failure. It was further found that the non-linear deformations would reach 4 millimeters. Considering that for these water levels the internal moments were still far from their maximum capacity, the results suggest that failure occurred due to cracks that were forced to form because of the deformations. This indicates that modern cavity walls are still quite vulnerable for floods and their flood actions. The influence of the hydrostatic pressure, however, can be decreased considerably by a water level inside the residence that acts as a counter force. Contrary to what was expected, the window does not contribute to this inside water level, since its leakages turn out to be negligible. To keep the damages to a minimum and preserve the overall stability, it is advised to seal the residence to a height of 1.0 meter; floods that exceed this sealing should not be countered anymore and rather be allowed to enter the residence.
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In recent years, unstable quay walls are a problem in The Netherlands. 100-year-old quay walls in cities like Amsterdam are collapsing and endanger people and property. The government needs to renovate unstable quay walls quickly. With 600 kilometre of quay wall in Amsterdam alone, this is a great challenge. Currently, unstable walls are found by deformation monitoring using tacheometry, which takes too much time for large scale monitoring. To increase both speed and coverage, a photogrammetric deformation analysis is proposed. In multiple epochs, at months interval, a series of images of the quay wall is made from a boat. In these images, feature points are identified and matched, where part of the feature points are matched across multiple epochs. All feature point observations are put in a multi-epoch least squares adjustment. This adjustment integrates both feature point observations of individual epochs and point deformations between multiple epochs. Using photogrammetry in combination with such a deformation adjustment has not been done previously, but has great advantages. The least squares adjustment allows to take the stochastic nature of the observations into account. This enables proper error propagation, such that not only quay wall stability can be assessed, but also the corresponding error budget. Results show that using two epochs 300 multi-epoch feature points can be found per square meter quay wall. With these points, sub-centimetre deformation can be estimated. ... Read more

In recent decades, gas production has caused numerous human-induced shallow earthquakes in the province of Groningen, The Netherlands. The buildings in this area were not designed for these unexpected earthquake loads and have shown to be vulnerable. However, current strengthening measures are considered to be time-consuming, expensive, and a great hindrance to the residents. Consequently, the question rises whether unconventional strengthening measures can offer relatively simple and quick-to-implement alternatives. This thesis researches if replacing existing windows by structural windows could provide an effective strengthening alternative. The structural window design aims to increase the in-plane seismic force capacity of an existing masonry structure by utilising the glass pane as a structural element. The structural window is designed to be composed of a timber frame, a semi-rigid adhesive, and a double glazing unit. The structural layer of the double glazing unit has a thickness of 20mm and is composed of two laminated annealed glass panes with equal thickness.

The potential of the structural window is investigated in various numerical studies, using DIANA FEA 10.2. The numerical studies are split into validation studies and seismic strengthening predictions. In the validation studies, results from numerical models are compared to and validated against experimental results reported in literature. Subsequently, the potential of the structural window is assessed by seismic strengthening predictions that combine and extrapolate the validation studies. A mass proportional one-directional monotonic pushover loading scheme is adopted. The seismic strengthening predictions address masonry walls and one type of terraced house (Dutch: “Rijtjeshuis") with two rigid floors, masonry spandrels, and two large windows in the front façade wall.

The numerical strengthening predictions of the masonry walls and the terraced house indicate that a structural window improves the in-plane seismic performance significantly. It is found that strengthening not only greatly increases the seismic force capacity, but also reduces the expected damage. For example, the strengthened terraced house with openable window sections reaches 205% of the seismic force capacity of the unstrengthened terraced house. Furthermore, it is found that the stress levels in the glass pane are expected to remain well below the stress levels at the onset of glass cracking. The numerical strengthening predictions are promising. Therefore, it is recommended to validate these numerical predictions with an experimental testing campaign. ... Read more

The growing need to understand the behaviour of un-reinforced masonry URM), subjected to
repeated light man-made earthquakes caused by the extraction of gas in the north-eastern part
of The Netherlands has resulted in intense research to determine the exact process of crack
initiation and propagation. The historical masonry buildings and Dutch terraced houses in
Groningen are prone to light damages which become severe upon repeated lateral earthquake
loading. Although there are material models that describe the behavior of modern brick
masonry, they do not accurately represent the mechanical properties of 19th century clay brick
masonry. This led to a large-scale research into the mechanical behavior of un-reinforced
masonry and an orthotropic continuum macro-model called the Engineering Masonry Model
(EMM) was proposed. The existing tension constitutive model in EMM assumes a secant
unloading-reloading branch which does not consider the strength degradation of URM under
repeated loading. Since tension mode-I fracture results in cracking of URM, it is important
to study the effects of repeated loading on the propagation of the crack and its effects on the
capacity of the structure.
This thesis presents a degradation model to represent the strength deterioration of URM
observed during repeated loading. The constitutive model formulated in this thesis is based on
hyperbolic functions along with a secant slope for the unloading-reloading branch. To justify
the model assumptions, a single linear 4-node element is analysed with the new model and the
effect of varying different components of the constitutive equations is established. The window
bank spandrel sample modeled as a 4-point bending test is analysed using the new model for 10,
30 and 100 repetitions. It is shown that the hyperbolic model can predict accurately the stress
reduction within each repetition displacement set and also represent the crack width widening
and crack propagation accurately when compared to the experimental results. The new model
is tested on a wall with a window opening sample and the results closely matched that of the
experiment. Finally, recommendations are provided for further development of the hyperbolic
model and calibration of the material properties. ... Read more