Temperature variations in masonry façades can induce expansion and contraction movements. When these movements are restrained, cracking and material degradation may occur, especially in older buildings lacking movement or expansion joints. Such temperature variations arise from factors as solar radiation, shading, material color, reflectivity, and environmental conditions. This study investigates the magnitude and spatial distribution of surface temperature variations (ΔT) on exterior masonry wall surfaces using outdoor infrared (IR) thermography. A better understanding of the magnitude and distribution of ΔT is essential for accurate damage assessment and for improving the attributability of observed damage to temperature effects rather than to other causes. Field data were collected in Delft, the Netherlands. Thermal images were captured with an IR camera to identify temperature differences across various points on exterior wall surfaces under direct solar radiation and varying shading conditions. The acquired imagery was analyzed using temperature histograms and profiles to quantify thermal gradients over the surface area of the façades. Results revealed significant spatial temperature variations, with measured ΔT values reaching up to 13 °C between the warmest and coolest zones on individual façades. Even where façades showed no pronounced surface gradients, temperature differences of up to 6 °C occurred between different, contiguous exterior walls of the same building. The study demonstrates that outdoor thermography, combined with targeted image processing, effectively identifies thermal gradients on masonry façades. These gradients reflect uneven thermal responses under real environmental conditions, which can accelerate moisture-related damage, cracking, and material fatigue. The findings emphasize the need to account for surface temperature heterogeneity in damage assessment of existing structures.

Historical buildings in the Netherlands are often founded on shallow, unreinforced foundations atop soft soils such as peat, clay, or loam, making them vulnerable to ground movements. These movements can result from autonomous settlements due to the building’s own weight, or from changes in the soil related to water table variations. Such sources typically induce differential vertical displacements, expressed as ground surface curvature. Movements from deeper sources, such as mining or tunnelling, also cause horizontal displacements or surface strains.

Masonry buildings are sensitive to strains from restrained shrinkage, temperature fluctuations, and soil movements. This study examines façade damage due to a combination of curvature and horizontal strain imposed through the foundations. Non-linear models of masonry façades were placed on a deformable soil block, whose boundaries were manipulated to create targeted combinations of curvature and strain at the surface.

The analysis of various combinations showed that while curvature and horizontal strain each cause damage—manifested as cracks in the masonry—their combination amplifies it. For instance, cracks 1 mm wide appear at a tensile strain of 5e−4 (0.5 mm/m), but when combined with an angular distortion of 1e−3 rad, only half that strain is needed to produce similar damage.

Understanding how curvature and strain interact to damage façades helps define safer deformation limits for vulnerable historical buildings, particularly in areas affected by water table regulation or mining. Additionally, the initial condition of structures must be considered when evaluating their vulnerability to external hazards, including seismic activity.

This paper presents a framework for developing fragility curves for masonry buildings on strip foundations exposed to subsidence using non-linear finite element (NLFE) analyses. A 2D plane-stress model of a masonry façade is used to evaluate the probability of cracking damage resulting from settlements. The model simulates the behaviour of typical Dutch two-storey historical buildings, using an established modelling approach to represent the non-linear behaviour of the façade, the transversal walls and the strip foundation, supported by a base interface for soil-foundation interaction. Settlements are imposed at the bottom of the interface, characterizing their intensity with the angular distortion. The damage severity is objectively quantified using the scalar parameter Ψ, computed considering the number, length, and width of the cracks. Cumulative probability functions are derived from 864 numerical analyses that account for realistic variations in building and soil features, including 3 masonry materials, 2 strip foundation systems, 2 interface soil materials and the 72 possible settlement patterns. The effect of each selected variation is evaluated individually. The proposed curves reveal a probability of over 25% for cracks up to 5 mm in width when the angular distortion equal to 0.2% (or 1/500), the threshold deemed acceptable by international codes, is applied to the models. Doubling the applied angular distortion results in an approximate doubling of the probability of damage. While the proposed curves are specific to the selected geometry, the framework can be adapted to accommodate different façade geometries, enabling the development of more comprehensive fragility functions.

Temperature effects are frequently cited as the cause of light cracking in masonry façades, yet most modelling studies idealise thermal loading as uniform steps and represent restraint as fully fixed, assumptions that tend to exaggerate damage. This work evaluates whether realistic, non-uniform temperature gradients, like those produced by shading and insolation, together with soil–structure interaction as the dominant restraint mechanism, can generate cracking patterns consistent with field observations. A coupled thermo-mechanical FEM model with a homogenised masonry continuum and tensile softening is employed; the façade–foundation–soil system is modelled explicitly, and damage is quantified using a crack-based index Ψ. A parametric campaign (1200 simulations) spans two façade typologies (clay masonry on unreinforced masonry foundations; calcium-silicate on reinforced concrete strips), three layered soils, 33 geometries, and multiple vertical and two-dimensional gradient shapes. The results indicate that gradient shape is decisive: widely distributed vertical gradients trigger visible damage (Ψ≥1) at roughly half the temperature differential required by more localised gradients, with visible damage becoming likely around ΔT≈20 °C (warming) and ≈25 °C (cooling) for the most adverse shapes. Restraint stiffness governs severity: stiffer sandy profiles increase tensile stresses and cracking, whereas softer profiles accommodate thermal movement; relative to uniform, fully restrained models, crack initiation is delayed by ∼15–20 °C and cracking is less distributed. Geometric discontinuities also dominate sensitivity: larger/more openings and low vertical-masonry ratios promote earlier localisation, while overall length/height is secondary. Fragility-like curves provide thresholds useful for assessment and mitigation.

The seismic vulnerability of historical masonry structures has been extensively studied, with efforts primarily focused on assessing their earthquake resistance. However, such studies often consider these structures in isolation, disregarding their urban context. In densely built environments, the collapse of adjacent buildings during an earthquake can have a devastating impact on nearby heritage structures, even if they are inherently capable of withstanding seismic loads. On February 6, 2023, two major earthquakes, with magnitudes of Mw 7.7 and Mw 7.6, occurred nine hours apart, affecting the southeastern region of Türkiye. Post-earthquake site investigations revealed that the collapse of the historical Adıyaman Grand Mosque was likely triggered by the failure of a substandard reinforced concrete building in close proximity. This paper aims to investigate the failure mechanism of the Adıyaman Grand Mosque in a broader context. Preliminary study highlights the importance of conducting an extended analysis for heritage structures in urban environments, for reasons such as: (i) the complex interactions between buildings in densely populated areas during earthquakes, (ii) the detrimental effect of the failure of a nearby building on heritage structures, and (iii) the development of more effective mitigation strategies to protect and preserve heritage structures in such environments.

Historical masonry façades are susceptible to variations in temperature. This is because their movements—expansion caused by an increase in temperature or contraction by a decrease—are restrained by other structural elements. To analyse these effects, models typically assign a prescribed strain to the façade while enforcing a rigid boundary at the foundation (or the floors, if they are rigid). More advanced models include the foundation, with a stiffness different from that of the façade and no prescribed strain, as the restraining element. This leads to conservative estimations of damage since the restraining effect is large. Indeed, these models can be further improved. A temperature gradient across the façade, including the foundation, can produce more gradual strains in the material and thus less damage. For this study, the improvements consider the inclusion of the soil underneath the building. A realistic temperature gradient for a sunny summer day or a chilly winter night, including a gradient over the foundation and into the soil, is applied. The restraining effects are provided by the soil and the temperature gradients. In this manner, the consequences of temperature variations on clay-brick masonry façades are investigated. The models reveal that damage, observed as cracking in the non-linear masonry model, is significantly reduced when applying the more gradual temperature profiles. Moreover, the damage patterns observed are different from those obtained from a simpler model. This is an important observation since crack patterns are sometimes employed to determine the origin of the damage. Furthermore, the type of soil also plays a role in the intensity of damage observed for identical temperature profiles. Softer soils, such as clay, peat, or loam, provide less restraint than stiffer soils like sand. Hence, façades on softer soils are less likely to develop damage from temperature variations.

Extracting cores with diameters of 100 to 150 mm from masonry structures has emerged as a novel, less destructive method for assessing the mechanical properties of masonry units, particularly their compressive strength. Unlike traditional methods, such as using larger wallets, this approach requires less material and causes minimal damage to the original structure, which is critical when dealing with historical buildings. However, to obtain consistent and reliable results, certain parameters, specifically the dimensions of the core cap, must be carefully defined, as they significantly influence the overall behaviour of the samples. The study employs a detailed block-based modelling approach, incorporating zero-thickness cohesive elements at the brick-mortar interfaces. Additionally, tangential and normal contact interactions were defined between the cap and core components. The concrete damage plasticity (CDP) model, implemented in ABAQUS, has been adopted as the constitutive model to account for the nonlinear behaviour of brick, mortar, and cap. The results indicate that the length of the cap has a more pronounced effect on the sample’s mechanical behaviour than its height. Additionally, the study investigates the mechanical properties of the interface between the cap and the core, identifying friction and normal stiffness as critical factors. These findings provide valuable insights for optimizing the core capping process and improving the reliability of masonry mechanical property assessments, particularly in the preservation of historical structures.

This study presents a semi-automated, data-informed framework for selecting parameter-consistent numerical models to approximate the in-plane behaviour of clay and calcium silicate masonry walls. A comprehensive experimental campaign has been executed on full-scale unreinforced calcium silicate and clay masonry walls at Delft University of Technology. The in-plane response of these walls was evaluated based on stiffness, strength, damage intensity at equivalent drift levels, and the overall impact of the damage. The findings indicate that unreinforced calcium silicate masonry walls are more prone to damage through the brick units, while cracks in unreinforced clay masonry walls predominantly align with mortar joints. Calcium silicate walls tend to develop larger and more prominent cracks, often requiring the replacement of individual bricks for a complete repair. In contrast, the damage in clay walls is typically easier to address through repointing of mortar joints. A parametric finite element analysis was performed to investigate these failure mechanisms, systematically varying input parameters to generate 3,456 numerical simulations. Each model permutation was evaluated to select models that closely approximate observed experimental responses. Unlike conventional calibration methods, this framework systematically explores possible combinations of input and output parameters to identify numerical models that replicate key structural behaviours. The preliminary results demonstrate that multiple parameter combinations can yield numerical responses closely matching experimental observations, providing a structured approach for improving masonry modelling practices.

Within the context of light damage to unreinforced masonry structures, recent tests have shown that the cracking behaviour of calcium-silicate brick masonry walls makes them more vulnerable to in-plane loads when compared against fired-clay brick walls. To further explore this observation, four nominallyidentical walls have been tested. Two of the specimens (3m wide and 2.7m tall) were built with calcium-silicate bricks and twowith fired-clay bricks. Additionally, two boundaries were compared: a top cantilever boundary, and a doubled-clamped configuration. The quasi-static, in-plane, two-way cyclic tests imposed small (0.03 to 0.1%), repeated drifts on the walls to investigate the initiation and propagation of small cracks. To monitor the cracking behaviour, high resolution Digital Image Correlation was applied. At the end of the tests, large drifts up to 2% were exerted to compare the near-collapse behaviour of the walls. The tests revealed that thewalls with the more restrictive boundary, deforming mostly in shear, behaved the stiffest and also developed cracks earlier than the cantilever walls. Additionally, this constraint also led to more vertical cracks that split bricks, while the cantilever walls saw more horizontal and diagonal cracks along mortar joints and at mortar-brick interfaces. While the calcium-silicate-proved to be more brittle than the fired-clay masonry for the cantilever test, the claymasonry exhibited similar brick-splitting cracks in the double-clamped configuration. In general, there were fewer but wider cracks in the calcium-silicate specimens, while the clay brick samples showed less localisation and more smeared-crack behaviour. In terms of stiffness, the calcium-silicate walls were initially stiffer and achieved a higher capacity. Moreover, these walls also presented a higher hysteresis associated with more frictional failures. In sum, while cracks on the calcium-silicate walls were confirmed to be more serious, their increased stiffness could lead to smaller drifts during dynamic loading, and the walls would develop less damage; this requires further study.

The structural response of masonry walls during flood events is a critical concern for the flood resilience of (Dutch) buildings, as they typically constitute part of the load-bearing structure. This study investigates the out-of-plane behaviour of a full-scale single-wythe fired-clay-brick masonry wall under out-of-plane hydrostatic pressure and debris impact loads. Experimental tests were conducted on a 2.7 × 2.7 m masonry wall subjected to a vertical pre-compression and simultaneously varying water levels and debris impacts at the Flood Proof Holland facility in Delft, the Netherlands. Results demonstrated that the wall remained within the linear-elastic regime up to a water depth of approximately 90 cm when the interior side was dry. Beyond this threshold, crack initiation and stress redistribution occurred, leading to significant deformation. On the basis of calibrated models, failure was predicted at approximately 150 cm water depth for a fully restrained wall. Debris impact tests showed that soft debris, represented by a floating log, caused negligible additional damage, whereas repeated impacts with a steel cube (hard debris) resulted in progressive cracking and local failure, particularly at higher water levels. Numerical models, including analytical, linear-elastic finite element method (FEM), and non-linear FE approaches, were calibrated using the experimental data. While one-way bending models predicted conservative failure thresholds, two-way, non-linear models accurately captured the wall’s deformation and cracking behaviour, demonstrating the importance of lateral boundary constraints in determining wall capacity and stability. The findings emphasise that traditional masonry walls in Dutch buildings can safely withstand water depths up to 90 cm without significant damage. However, higher water levels or hard debris impacts pose substantial risks, highlighting the need for improved flood resilience strategies. Future work should focus on cavity wall systems, leakage effects, and the behaviour of walls with openings.

Damage assessment for masonry structures subjected to settlement is crucial for ensuring structural safety, guiding repairs, and preserving the built environment. Non-linear finite element modelling offers an effective approach for this purpose, though balancing model complexity, computational cost, and predictive reliability remains a key challenge. This study addresses the absence of a systematic comparison between macro- and simplified micro-modelling strategies for such analyses, clarifying their respective strengths, limitations, and sensitivity to key parameters. The performance and accuracy of semi-coupled NLFEM models are compared in simulating the response of a 1/10th scaled masonry façade under settlement, available from prior research. The two approaches considered are: simplified micro-modelling, where bricks are represented as expanded blocks with non-linear interfaces for mortar joints and their contact edges, and macro-modelling, where masonry is homogenised into an equivalent orthotropic composite material. The macro-models employ two well-established constitutive models, the Total Strain Rotating Crack Model (TSRCM) and the Engineering Masonry Model (EMM), to capture the non-linear cracking behaviour of masonry. Sensitivity analyses assess the influence of base interface models and the interface’s tangential stiffness. The results show how the selection of the modelling approach depends on the analysis objective: The macro-model with the Engineering Masonry Model best predicts damage severity, deviating by only 10% from the experiment, further improved by calibrating the minimum head-joint tensile strength. While all models yield similar predictions for vertical displacements of the façade, the TSRCM better captures overall and horizontal displacements, whereas the simplified micro-model more accurately represents the crack pattern. The EMM-based macro-models are the most computationally efficient, with TSRCM requiring 1.5 times the CPU time of EMM, and the micro-model requiring twice as much. The analysis also shows that the TSRCM-based macro-model is more sensitive to variations in the type of base interface models and base interface tangential stiffness, convergence criteria, incremental-iterative procedure, and analysis settings, whereas the EMM macro-model and the simplified micro-model are less affected. By identifying the strengths and limitations of each modelling approach, this study supports informed modelling choices for a more reliable assessment of settlement damage, contributing to the effective protection of existing masonry structures.

Cycles of settlement and uplift beneath existing masonry structures can lead to visible cracks, which not only affect the aesthetic appearance and functionality of the building but can also compromise its structural integrity and undermine the occupants' sense of safety. These cyclic ground movements can be triggered by seasonal actions, such as fluctuation in the groundwater table. In the Netherlands, many existing masonry structures on shallow foundations rest directly on the subsurface, making them vulnerable to cyclic ground movements. Settlement and uplift cycles cause “breathing” masonry cracks, which open and close over time without fully sealing. This study uses finite element analyses to investigate and assess the damage of structures subjected to cyclic quasi-static ground movements. A case study is presented for the analysis, featuring the geometry of an existing low-rise masonry structure with an age exceeding 50 years. A 3D non-linear shell-element model is used to evaluate the structural response, featuring an unreinforced strip foundation and including the non-linear tensile softening and cracking behaviour of masonry. Heaving and sinking displacements are applied to a non-linear interface simulating the soil-foundation interaction at the bottom of the strip foundation. The intensity of the ground displacements is quantified by their angular distortion. A damage parameter objectively assesses the severity of damage by considering the number, length, and width of cracks. Results indicate that repeated cycles of settlement (and uplift) have been observed to cause irreversible cracking damage in the model, with crack widths ranging from 1 to 5 mm, progressively increasing over time. Damage occurring during settlement is, on average, twice as severe as that during uplift. Overall, cycles of settlement and uplift may induce cracking damage up to twice as high as that caused by cycles of settlement alone, depending on the magnitude and shape of the ground movements.

Terraced buildings with cavity walls are among the most common types of construction in the northern part of the Netherlands. Since 1980, the inner walls of these buildings have been constructed using either calcium silicate bricks (214 × 102 × 75 mm) with thick mortar joints (10 mm) or, more recently, calcium silicate blocks (437 × 198 × 100 mm) with thin mortar joints (3 mm). The shear properties of these units play a crucial role in the seismic response of buildings, particularly in regions like Groningen, which is prone to seismic activity due to artificial extraction. This study investigates the shear interface behavior of these two types of masonry units by testing multiple triplet samples under varying levels of normal stress at the interface. The results provide detailed insights into the shear properties of both brick and block masonry, offering valuable data for enhancing the accuracy of numerical simulations and predicting the structural capacity of these types of masonry buildings.

The integration of bacteria-based self-healing mortars has emerged as a promising solution to address repair due to recurring cracks and preserving masonry durability. Building upon a recent pilot study demonstrating the efficacy of a self-healing agent in the repair of masonry made with cement-based mortar, this follow-up study explores the potential of integrating the added-in healing agent in a pre-bagged cement-lime mortar - more commonly used in masonry applications. Through bond wrench tests and a 30-day healing period involving wet-dry cycles, the study evaluates aesthetic and flexural bond strength recovery of couplets built with solid clay bricks. Results showed that the addition of the agent altered the initial flexural bond strength, with bacteria-based masonry couplets four times stronger than the plain reference ones - without containing the agent. The mortar’s colorwas also affected. Additionally, bacteria-based specimens demonstrated automatic repair, restoring up to 33% of the original flexural bond strength, while referencemasonry couplets showed no evidence of autonomous healing. However, instances of leaching, possibly attributed to the agent’s substrate, prompted a revision of the strategy employed for the healing environment. Further research will specifically target the observed leaching issue by exploring the effects of multiple healing environments.

Soil heterogeneity, due to variations in the subsurface stratigraphy or properties within a layer, can trigger or amplify differential settlements that affect buildings and infrastructure and can thus lead to (increase in) damage. The state-of-the-art mainly focuses on the effect of heterogeneous properties within a layer on engineering problems. From this, it is known that the variation in properties can increase the vulnerability of a structure. However, nearly always variations in the soil lithological conditions are disregarded, while they can influence subsidence potentially even more. Lithological variations are relevant both at the scale of individual buildings as well as different scales (city, regional, country), for which often detailed soil information is not available. Thus, for a better prediction of potential building damage related to subsidence, knowledge about the scale and influence of lithological variations is needed. This paper describes an approach to quantify and investigate the influence of lithological heterogeneity at the scale of a single building. Moreover, this exploratory study evaluates the influence of lithological heterogeneity on the spatial variability of settlements, intending to upscale the approach to regional application. Two independent datasets at high resolution (site-specific) and low resolution (national level) are used to retrieve the stratigraphic conditions for the area selected for the analyses. One-, Two- and Three-dimensional numerical models, based on the collected information are used to simulate the consolidation process and settlement due to a uniform load imposed on the surface level of the study area. Additional analyses investigate the influence of loading conditions and groundwater table. The parameter “correlation length” is used to quantify the spatial variability of the soil layer thickness and then of the computed settlements. The analyses reveal that the spatial variability of the soil strata thickness matches that of the computed settlements, ranging from 2 to 10 meters. In other words, the lithological variability of the soil leads to differential settlements occurring at the scale of man-made structures such as houses, roads, and embankments. Thus, the results encourage including the contribution of lithological heterogeneity in models and predictions of differential settlement at the scale of individual structures. Moreover, the statistical properties, in terms of mean, spread and distribution shape, of the settlement computed through in-situ specific models, match with those derived at the national scale. These results are expected to support the identification of areas potentially influenced by lithological soil heterogeneity, thus showing potential for upscaling to regional or national levels.

Masonry buildings in the Netherlands are especially prone to damage in the form of small cracks. This is because the masonry is unreinforced, the foundations are shallow and often also unreinforced, the bedding is composed of soft soils like peat or clay, dilation joints are missing in older or historical structures, and current loading conditions, such as earthquake vibrations, were never considered in the design of the buildings. The latter includes mining operations for salt and gas that have led to subsidence and induced seismicity. Moreover, farming policy and water management, in combination with regional subsidence, have led to varying groundwater table levels which, in turn, cause wetting and drying of sensitive soils. This process is exacerbated by more extreme seasons of precipitation and drought because of climate change, leading to swelling and compaction of the ground underneath buildings. To understand building damage in this context, it is necessary to evaluate the combined effects of these various hazards. Their actions can be decomposed into vibrations caused by earthquakes and ground deformations. The former can be characterized by the PGV or PGA of the vibrations, and the latter by the induced curvature of the soil surface and/or by the horizontal strains at the surface because of deformations deep in the underground. Moreover, repeated earthquake events and seasonal soil subsidence or heave lead to cyclic actions. The contribution and interaction of these loads causing progressive damage to masonry buildings have been the focus of an extensive modelling study with detailed non-linear models of the buildings and the soil. The slow soil deformations were analyzed first and served as the starting point for subsequent, repeated vibrations. For example, a horizontal strain of 0.1 mm/m caused by mining, in combination with an angular distortion of 1/2000 due to local soil compaction, can produce cracks of about 1 to 2 mm wide in a particular masonry façade. The damage is then aggravated by an earthquake vibration in the order of 5 mm/s, which is further increased by about 10% with a repeated event. The expected final damage may include multiple cracks of up to 3 mm. In this manner, the combination of all actions can lead to the establishment of conservative thresholds to prevent or limit damage to existing structures.

Subsidence caused by natural or human-induced factors can occur unevenly, resulting in differential settlements. Existing unreinforced masonry (URM) buildings are susceptible to damage from differential settlements. However, the extent of the damage varies between structures, depending on factors such as the magnitude and pattern of the settlements, along with the features of the building and the properties of the underlying soil. Non-linear finite element analyses (NLFEA) are often used for studying the damage response, accounting for variability in soil and structural features. This study uses 6912 NLFEA, including 8 variations in façade geometry, 3 masonry materials, 2 soils, 2 shallow foundation systems, and 72 settlement patterns, to develop fragility curves for URM buildings undergoing subsidence. Old Dutch URM buildings with strip foundations are modelled using 2D plane-stress façade models, accounting for non-linear smeared shearing, cracking and crushing of masonry and 3D effects of transverse walls. Settlement troughs are applied at a non-linear soil-foundation interface, with angular distortion (β) progressively increasing to quantify settlement intensity and building deformation. As β increases, the NLFE models exhibit progressive cracking damage, with severity objectively assessed through the parameter Ψ considering crack width, length, and number. Then, the distortion β is used as the demand parameter to develop the fragility curves. The analysis shows that long façades are twice as likely to experience 5 mm cracks from settlement damage compared to short façades under an applied β of 2 ‰ (1/500). For this applied β, proposed as an acceptable limit for many structures in the Eurocode, half of the models exhibit cracks up to 5 mm wide. Therefore, while 1/500 may be considered safe for structural integrity, it can still lead to noticeable damage. Light damage occurs even at angular distortion values below 0.5 ‰ (1/2000), with 10 % of models showing cracks up to 1 mm wide.

In the pursuit of introducing bacteria-based self-healing mortar for masonry repair, this study examined the potential of incorporating a poly-lactic acid (PLA) agent—already established in concrete repair—into cement-lime mortars, typical of historical constructions. Testing prisms constructed with varying lime/cement ratios revealed decreased flexural and compressive strength in high-cement-concentration mortars upon the addition of the agent; for mortars with high lime concentration, however, the agent led to an increase in both strengths. Furthermore, the agent's potential to self-repair was confirmed by allowing the remaining portions of tested samples to heal under humid conditions. Irrespective of mortar composition, cracks were resealed thus confirming the aesthetic, and potentially watertightness, restoration.

In the Netherlands, subsidence due to different causes is linked to damage to the ubiquitous masonry structures. Finite element (FE) analyses can be used to assess the response of the structures subjected to settlements. This paper presents the comparison between three-dimensional FE modelling strategies to investigate the response of an unreinforced masonry building on a strip foundation. The aim is to investigate whether different modelling approaches demonstrate consistent results. The soil-structure system is modelled employing two strategies: a coupled model, in which the structure is tied to the soil volume, and an uncoupled approach that divides the soil and structure into two sub-systems. Two displacement fields, imposed at the bottom of the soil volume, idealize various shapes of the subsidence troughs, with increasing intensity measured by their distortion. Non-linear interfaces are used to simulate the soil-foundation interaction, and their stiffness values vary based on the type of model. The displacements, interface stresses and crack patterns of the selected modelling strategies are consistent. The interface types do not influence the response of the façade, whereas the shape of the settlement does play a key role. The uncoupled models exhibit, on average, slightly higher values of damage than coupled models for a given imposed distortion. The two modelling strategies require almost the same computational time and show similar convergence. Because of the limited contribution of small soil volumes in uncoupled models, the superstructure sub-system can be directly utilized to assess the response of structures undergoing vertical displacements, thereby reducing the modelling burden.

Drift limits are useful thresholds; during design or retrofitting analyses, engineers can compare the expected behaviour of a structure to drift limits that predict when the structure will reach a certain condition. This helps ensure that structures satisfy specified performance goals when exposed to certain hazards. Masonry walls are susceptible to damage from lateral in-plane actions such as wind or earthquake loading; ensuring that in-plane drift remains sufficiently small will help limit this damage. Drift limits based on crack-based damage are scarce, however, with DS1 limits being extrapolated from higher damage grades based on structural strength capacity or ductility. In this work, crack-based damage is evaluated on a multitude of full-scale experimental walls surveyed with digital image correlation. This method observes the initiation and propagation of cracking. Cyclically incremental in-plane tests provide a range of drift-damage relationships. These are explored with machine learning to determine influential predictors and ultimately establish drift limits for light damage. Two types of brick masonry are explored: fired-clay and calcium-silicate. For the latter, light damage begins at an in-plane drift of 0.5 mm/m and can extend to 4.8 mm/m (or 0.48%) for the former before the masonry surpasses light damage and reaches structural damage grades. In comparison to drift limits set by other authors and (international) guidelines to characterise light damage, significant damage, or the ultimate capacity of masonry walls, the resulting drift limits for light damage from this work are set directly on the basis of experiments and are in good agreement with other authors. Most importantly, all the consulted values for ultimate capacity are much larger than the upper threshold for light damage determined herein, with limits for significant damage in the same order of magnitude. This result verifies the accuracy of the experimental crack-based characterisation used to establish the drift thresholds.