P.A. Korswagen Eguren
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1
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.
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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.
Mechanism Matters
Lessons from Calibrating Continuum FE Models of Calcium-Silicate Masonry
This paper presents insights from numerical simulations of a quasi-static test on a full-scale calcium-silicate brick masonry building representative of Dutch terraced housing. A set of continuum finite-element models was evaluated using different combinations of material parameters, boundary conditions, and modelling strategies, while engaging multiple analysts. Several model configurations achieved good agreement with the experimental response, including stiffness, lateral strength, or damage evolution. However, despite this apparent agreement, the predicted global damage mechanisms could differ from those observed experimentally. The numerical models were dominated by diagonal in-plane cracking, whereas the experiment exhibited global rocking combined with in-plane and out-of-plane failure. By cross-comparing multiple parameter combinations, the study highlights the importance of explicitly verifying damage mechanisms and transparently documenting choices as integral components of mechanism-based calibrations.
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This paper presents insights from numerical simulations of a quasi-static test on a full-scale calcium-silicate brick masonry building representative of Dutch terraced housing. A set of continuum finite-element models was evaluated using different combinations of material parameters, boundary conditions, and modelling strategies, while engaging multiple analysts. Several model configurations achieved good agreement with the experimental response, including stiffness, lateral strength, or damage evolution. However, despite this apparent agreement, the predicted global damage mechanisms could differ from those observed experimentally. The numerical models were dominated by diagonal in-plane cracking, whereas the experiment exhibited global rocking combined with in-plane and out-of-plane failure. By cross-comparing multiple parameter combinations, the study highlights the importance of explicitly verifying damage mechanisms and transparently documenting choices as integral components of mechanism-based calibrations.
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. ...
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. ...
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.
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.
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.
...
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.
Seasonal changes, climate, and human activities can cause groundwater fluctuations, leading to differential settlements. Unreinforced masonry (URM) buildings are vulnerable to differential settlements due to low tensile strength and quasi-brittle behaviour. Damage prediction requires a better understanding of the interaction between structure, foundation, soil, and settlement causes. While previous studies focused on tunnelling or excavation, this study examines damage from progressive groundwater lowering using non-linear finite element (NLFE) modelling in DIANA FEA. The analysis employs a two-step approach. First, a 3D ground-only model is used to calculate the free-field (or “greenfield”) horizontal strain εh and angular distortion β, well-established metrics in previous tunnelling, excavation, and mining studies, under an imposed groundwater lowering scenario. This step establishes a baseline to assess how the presence of the building alters the greenfield εh and β through soil-structure interaction. Then, a 3D coupled model incorporating the URM building and its shallow foundation is used to evaluate the effects on displacements and damage.
...
Seasonal changes, climate, and human activities can cause groundwater fluctuations, leading to differential settlements. Unreinforced masonry (URM) buildings are vulnerable to differential settlements due to low tensile strength and quasi-brittle behaviour. Damage prediction requires a better understanding of the interaction between structure, foundation, soil, and settlement causes. While previous studies focused on tunnelling or excavation, this study examines damage from progressive groundwater lowering using non-linear finite element (NLFE) modelling in DIANA FEA. The analysis employs a two-step approach. First, a 3D ground-only model is used to calculate the free-field (or “greenfield”) horizontal strain εh and angular distortion β, well-established metrics in previous tunnelling, excavation, and mining studies, under an imposed groundwater lowering scenario. This step establishes a baseline to assess how the presence of the building alters the greenfield εh and β through soil-structure interaction. Then, a 3D coupled model incorporating the URM building and its shallow foundation is used to evaluate the effects on displacements and damage.
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.
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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.
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.
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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.
Predicting Capacity Loss in Settlement-Damaged Masonry Walls under Pushover Loads
An SLA-Based Framework
This study investigates how settlement-induced pre-damage modifies the in-plane pushover response of an unreinforced masonry (URM) wall with a window opening. An event-driven Total Sequentially Linear Analysis (Total-SLA) framework is used. Masonry units are linear elastic, while mortar joints and potential splitting planes are modelled by zero-thickness interface elements capturing tensile opening and frictional sliding through stepwise stiffness/strength reduction. Differential settlement is imposed through a spring-supported base referenced to a prescribed ground profile, and a tensionless condition allows local uplift and partial loss of contact. Settlement-induced damage differs for hogging, sagging, and asymmetric profiles. For the studied wall, sagging and asymmetric settlements reduce the subsequent pushover capacity with peak load reductions up to 25%. Moreover, three bond patterns (stretcher, English, and Flemish) are assessed for the asymmetric settlement case. Stretcher bond maintains a higher post-peak level and recovery, while Flemish bond is intermediate and English bond exhibits the lowest residual resistance after the secondary strength drop.
...
This study investigates how settlement-induced pre-damage modifies the in-plane pushover response of an unreinforced masonry (URM) wall with a window opening. An event-driven Total Sequentially Linear Analysis (Total-SLA) framework is used. Masonry units are linear elastic, while mortar joints and potential splitting planes are modelled by zero-thickness interface elements capturing tensile opening and frictional sliding through stepwise stiffness/strength reduction. Differential settlement is imposed through a spring-supported base referenced to a prescribed ground profile, and a tensionless condition allows local uplift and partial loss of contact. Settlement-induced damage differs for hogging, sagging, and asymmetric profiles. For the studied wall, sagging and asymmetric settlements reduce the subsequent pushover capacity with peak load reductions up to 25%. Moreover, three bond patterns (stretcher, English, and Flemish) are assessed for the asymmetric settlement case. Stretcher bond maintains a higher post-peak level and recovery, while Flemish bond is intermediate and English bond exhibits the lowest residual resistance after the secondary strength drop.
Domino Collapse in Urban Settings
A 19th Century Mosque Collapsed During the 2023 Kahramanmaraş Earthquake Sequence
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.
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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.
...
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.
Non-proportional sequentially-linear analysis for masonry structures
Capturing combined foundation settlement and pushover loads
Unreinforced masonry (URM) walls are highly sensitive to non-proportional loading histories, particularly when foundation settlement precedes lateral loading. In such cases, pre-damage induced by settlement can significantly affect the subsequent structural response and cannot be adequately represented using proportional loading assumptions or equivalent reduction factors.
A Total Sequentially Linear Analysis (Total SLA) framework is developed to investigate the combined effects of boundary conditions, geometry, and settlement-induced pre-damage on the pushover response of URM walls. The numerical model represents masonry units as linear elastic continua and concentrates nonlinearity within zero-thickness interface elements governed by discrete damage modes. Settlement and pushover are applied sequentially within a unified event-driven formulation, allowing damage states to be inherited across loading stages.
The results show that the initial elastic response is largely insensitive to the top boundary conditions, whereas significant differences emerge during the softening phase. Fixed-top configurations exhibit a more gradual degradation of stiffness. Cantilever and free-top conditions, in contrast, show sliding-dominated behavior. Settlement causes irreversible damage, reducing both stiffness and peak capacity during subsequent pushover loading. The effects are amplified in walls with openings. These results demonstrate that neglecting load-path dependency may lead to inaccurate predictions of stiffness degradation and peak capacity in URM walls. ...
A Total Sequentially Linear Analysis (Total SLA) framework is developed to investigate the combined effects of boundary conditions, geometry, and settlement-induced pre-damage on the pushover response of URM walls. The numerical model represents masonry units as linear elastic continua and concentrates nonlinearity within zero-thickness interface elements governed by discrete damage modes. Settlement and pushover are applied sequentially within a unified event-driven formulation, allowing damage states to be inherited across loading stages.
The results show that the initial elastic response is largely insensitive to the top boundary conditions, whereas significant differences emerge during the softening phase. Fixed-top configurations exhibit a more gradual degradation of stiffness. Cantilever and free-top conditions, in contrast, show sliding-dominated behavior. Settlement causes irreversible damage, reducing both stiffness and peak capacity during subsequent pushover loading. The effects are amplified in walls with openings. These results demonstrate that neglecting load-path dependency may lead to inaccurate predictions of stiffness degradation and peak capacity in URM walls. ...
Unreinforced masonry (URM) walls are highly sensitive to non-proportional loading histories, particularly when foundation settlement precedes lateral loading. In such cases, pre-damage induced by settlement can significantly affect the subsequent structural response and cannot be adequately represented using proportional loading assumptions or equivalent reduction factors.
A Total Sequentially Linear Analysis (Total SLA) framework is developed to investigate the combined effects of boundary conditions, geometry, and settlement-induced pre-damage on the pushover response of URM walls. The numerical model represents masonry units as linear elastic continua and concentrates nonlinearity within zero-thickness interface elements governed by discrete damage modes. Settlement and pushover are applied sequentially within a unified event-driven formulation, allowing damage states to be inherited across loading stages.
The results show that the initial elastic response is largely insensitive to the top boundary conditions, whereas significant differences emerge during the softening phase. Fixed-top configurations exhibit a more gradual degradation of stiffness. Cantilever and free-top conditions, in contrast, show sliding-dominated behavior. Settlement causes irreversible damage, reducing both stiffness and peak capacity during subsequent pushover loading. The effects are amplified in walls with openings. These results demonstrate that neglecting load-path dependency may lead to inaccurate predictions of stiffness degradation and peak capacity in URM walls.
A Total Sequentially Linear Analysis (Total SLA) framework is developed to investigate the combined effects of boundary conditions, geometry, and settlement-induced pre-damage on the pushover response of URM walls. The numerical model represents masonry units as linear elastic continua and concentrates nonlinearity within zero-thickness interface elements governed by discrete damage modes. Settlement and pushover are applied sequentially within a unified event-driven formulation, allowing damage states to be inherited across loading stages.
The results show that the initial elastic response is largely insensitive to the top boundary conditions, whereas significant differences emerge during the softening phase. Fixed-top configurations exhibit a more gradual degradation of stiffness. Cantilever and free-top conditions, in contrast, show sliding-dominated behavior. Settlement causes irreversible damage, reducing both stiffness and peak capacity during subsequent pushover loading. The effects are amplified in walls with openings. These results demonstrate that neglecting load-path dependency may lead to inaccurate predictions of stiffness degradation and peak capacity in URM walls.
Bacteria-based self-healing agent for masonry crack repair
Assessing watertightness restoration
The preservation and long-term durability of masonry structures, particularly in the context of built heritage, are strongly affected by water ingress. Cracking in mortar joints or at the brick–mortar interface compromises watertightness, accelerates decay mechanisms such as salt crystallisation and freeze–thaw damage, and increases maintenance demands. Traditional repair strategies, such as repointing, are effective but require repeated interventions and monitoring.
In this context, autonomous self-healing mortars are currently gaining increasing attention as a complementary approach to conventional repair. Inspired by developments in self-healing concrete, bacteria-based healing agents have recently been explored for masonry applications. Previous pilot studies demonstrated that a polylactic acid (PLA)-based bacterial agent can promote crack filling in masonry couplets, contributing to aesthetic recovery and partial restoration of bond strength. However, the ability of such systems to restore watertightness, a performance aspect directly linked to durability, has not yet been systematically investigated.
Assessing watertightness recovery in masonry presents methodological challenges. Existing standards typically focus on large-scale wall assemblies or surface water penetration tests, which are not well suited for early-stage material evaluation. Consequently, there is a need for adapted, small-scale methods capable of quantifying changes in permeability associated with cracking and healing. This study addresses this gap by introducing an adapted permeability test derived from research on self-healing concrete and applying it to evaluate watertightness recovery in masonry containing the above-mentioned agent. ...
In this context, autonomous self-healing mortars are currently gaining increasing attention as a complementary approach to conventional repair. Inspired by developments in self-healing concrete, bacteria-based healing agents have recently been explored for masonry applications. Previous pilot studies demonstrated that a polylactic acid (PLA)-based bacterial agent can promote crack filling in masonry couplets, contributing to aesthetic recovery and partial restoration of bond strength. However, the ability of such systems to restore watertightness, a performance aspect directly linked to durability, has not yet been systematically investigated.
Assessing watertightness recovery in masonry presents methodological challenges. Existing standards typically focus on large-scale wall assemblies or surface water penetration tests, which are not well suited for early-stage material evaluation. Consequently, there is a need for adapted, small-scale methods capable of quantifying changes in permeability associated with cracking and healing. This study addresses this gap by introducing an adapted permeability test derived from research on self-healing concrete and applying it to evaluate watertightness recovery in masonry containing the above-mentioned agent. ...
The preservation and long-term durability of masonry structures, particularly in the context of built heritage, are strongly affected by water ingress. Cracking in mortar joints or at the brick–mortar interface compromises watertightness, accelerates decay mechanisms such as salt crystallisation and freeze–thaw damage, and increases maintenance demands. Traditional repair strategies, such as repointing, are effective but require repeated interventions and monitoring.
In this context, autonomous self-healing mortars are currently gaining increasing attention as a complementary approach to conventional repair. Inspired by developments in self-healing concrete, bacteria-based healing agents have recently been explored for masonry applications. Previous pilot studies demonstrated that a polylactic acid (PLA)-based bacterial agent can promote crack filling in masonry couplets, contributing to aesthetic recovery and partial restoration of bond strength. However, the ability of such systems to restore watertightness, a performance aspect directly linked to durability, has not yet been systematically investigated.
Assessing watertightness recovery in masonry presents methodological challenges. Existing standards typically focus on large-scale wall assemblies or surface water penetration tests, which are not well suited for early-stage material evaluation. Consequently, there is a need for adapted, small-scale methods capable of quantifying changes in permeability associated with cracking and healing. This study addresses this gap by introducing an adapted permeability test derived from research on self-healing concrete and applying it to evaluate watertightness recovery in masonry containing the above-mentioned agent.
In this context, autonomous self-healing mortars are currently gaining increasing attention as a complementary approach to conventional repair. Inspired by developments in self-healing concrete, bacteria-based healing agents have recently been explored for masonry applications. Previous pilot studies demonstrated that a polylactic acid (PLA)-based bacterial agent can promote crack filling in masonry couplets, contributing to aesthetic recovery and partial restoration of bond strength. However, the ability of such systems to restore watertightness, a performance aspect directly linked to durability, has not yet been systematically investigated.
Assessing watertightness recovery in masonry presents methodological challenges. Existing standards typically focus on large-scale wall assemblies or surface water penetration tests, which are not well suited for early-stage material evaluation. Consequently, there is a need for adapted, small-scale methods capable of quantifying changes in permeability associated with cracking and healing. This study addresses this gap by introducing an adapted permeability test derived from research on self-healing concrete and applying it to evaluate watertightness recovery in masonry containing the above-mentioned agent.
Full-field identification of elastic and shear moduli of perforated masonry walls using DIC and stiffness-based shear partition (Euler-Bernoulli vs Timoshenko)
Comparison across clay brick, calcium silicate brick, and calcium silicate block masonry
Digital Image Correlation (DIC) is increasingly used in masonry testing for full-field crack mapping, yet its potential for quantitative identification of elastic properties at structural scale is still not fully exploited for perforated walls where load paths split into multiple piers. This contribution presents a DIC-driven procedure to estimate the Young’s modulus E and the shear modulus G of windowed masonry walls made of three materials: clay brick masonry, calcium silicate brick masonry, and calcium silicate block masonry. Axial strains are extracted at the wall extreme fibres and converted to E using section-dependent bending stresses that account for the reduced cross-section within the window height. For G, pier-average shear strains are obtained from DIC strain fields within defined regions of interest, while pier shear forces are computed by stiffness-based partition of the applied top shear between the left and right piers. Two bounds are considered: Euler–Bernoulli theory (shear-rigid) and Timoshenko theory (shear-flexible) with a shear correction factor. The comparison clarifies how the inferred G depends on pier aspect ratio and the assumed shear deformability. Finally, a parametric study is conducted to quantify how the assumed Poisson’s ratio affects the back-calculation of E from the measured G. The results further indicate that elastic parameters obtained from standard small-scale tests (e.g., prisms or wallets) tend to overestimate the effective E and G inferred at wall scale, which can significantly bias the calibration of continuum and macro-element numerical models.
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Digital Image Correlation (DIC) is increasingly used in masonry testing for full-field crack mapping, yet its potential for quantitative identification of elastic properties at structural scale is still not fully exploited for perforated walls where load paths split into multiple piers. This contribution presents a DIC-driven procedure to estimate the Young’s modulus E and the shear modulus G of windowed masonry walls made of three materials: clay brick masonry, calcium silicate brick masonry, and calcium silicate block masonry. Axial strains are extracted at the wall extreme fibres and converted to E using section-dependent bending stresses that account for the reduced cross-section within the window height. For G, pier-average shear strains are obtained from DIC strain fields within defined regions of interest, while pier shear forces are computed by stiffness-based partition of the applied top shear between the left and right piers. Two bounds are considered: Euler–Bernoulli theory (shear-rigid) and Timoshenko theory (shear-flexible) with a shear correction factor. The comparison clarifies how the inferred G depends on pier aspect ratio and the assumed shear deformability. Finally, a parametric study is conducted to quantify how the assumed Poisson’s ratio affects the back-calculation of E from the measured G. The results further indicate that elastic parameters obtained from standard small-scale tests (e.g., prisms or wallets) tend to overestimate the effective E and G inferred at wall scale, which can significantly bias the calibration of continuum and macro-element numerical models.
Decades of induced seismicity in Groningen have exposed unreinforced clay masonry to frequent, shallow, small-to-moderate earthquakes. Conventional, event-centric vulnerability assessments largely ignore the cumulative effects of repeated shaking and therefore under-predict visible (light, crack-based) damage. We propose a sequence-aware Damage Accumulation Function (DAF) that advances a measured crack-based state Ψ across arbitrary PGV histories by separating similar-intensity repetitions (small increments) from events that set a new maximum (disproportionate jumps). The method integrates (i) earlier full-scale wall and spandrel experiments with high-resolution digital image correlation to quantify crack initiation, widening and extension; (ii) earlier calibrated nonlinear time-history analyses of Groningen-type motions using the Engineering Masonry Model; and (iii) a semi-empirical surrogate linking ∆Ψ to PGV and typological parameters with heteroskedastic, PGV-dependent uncertainty whose incremental contribution decays with sequence position. Applied to historical records and hypothetical futures, DAF results indicate that repeated low-intensity events meaningfully affect accumulation (≈10–20% additional ∆Ψ for same-intensity repeats), while a record-high PGV produces a marked jump. Regional analyses yield exceedance maps that differ from single-event fragility, especially at the edges with low but repeated PGV values and enable decision-facing metrics such as “damage hastening.” The formulation is intended for DS1/early DS2 crack damage of in-plane URM walls and uses PGV as the intensity measure. The DAF provides an interpretable, probabilistic complement to standard fragility where history and repetition govern light-damage progression.
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Decades of induced seismicity in Groningen have exposed unreinforced clay masonry to frequent, shallow, small-to-moderate earthquakes. Conventional, event-centric vulnerability assessments largely ignore the cumulative effects of repeated shaking and therefore under-predict visible (light, crack-based) damage. We propose a sequence-aware Damage Accumulation Function (DAF) that advances a measured crack-based state Ψ across arbitrary PGV histories by separating similar-intensity repetitions (small increments) from events that set a new maximum (disproportionate jumps). The method integrates (i) earlier full-scale wall and spandrel experiments with high-resolution digital image correlation to quantify crack initiation, widening and extension; (ii) earlier calibrated nonlinear time-history analyses of Groningen-type motions using the Engineering Masonry Model; and (iii) a semi-empirical surrogate linking ∆Ψ to PGV and typological parameters with heteroskedastic, PGV-dependent uncertainty whose incremental contribution decays with sequence position. Applied to historical records and hypothetical futures, DAF results indicate that repeated low-intensity events meaningfully affect accumulation (≈10–20% additional ∆Ψ for same-intensity repeats), while a record-high PGV produces a marked jump. Regional analyses yield exceedance maps that differ from single-event fragility, especially at the edges with low but repeated PGV values and enable decision-facing metrics such as “damage hastening.” The formulation is intended for DS1/early DS2 crack damage of in-plane URM walls and uses PGV as the intensity measure. The DAF provides an interpretable, probabilistic complement to standard fragility where history and repetition govern light-damage progression.
Aspects To Consider When Modelling the Response of Masonry Façades to Ground Movements
Lessons From A Few Studies
In the Netherlands, quasi-static soil movements from subsidence/consolidation are a major cause of differential settlements and crack damage in masonry façades and buildings. Recent studies have clarified where modelling gives reliable insight and where it misleads. The paper presents these insights as a checklist. Key aspects include façade geometry and its effect on crack patterns and deformation transfer, the distinction between greenfield and building deformations, explicit representation of soil–foundation–façade interaction, small-strain soil stiffness and progressive nonlinearity, masonry cracking and stiffness loss, and the role of initial damage and foundation behaviour. Systematic variations are needed to quantify uncertainty.
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In the Netherlands, quasi-static soil movements from subsidence/consolidation are a major cause of differential settlements and crack damage in masonry façades and buildings. Recent studies have clarified where modelling gives reliable insight and where it misleads. The paper presents these insights as a checklist. Key aspects include façade geometry and its effect on crack patterns and deformation transfer, the distinction between greenfield and building deformations, explicit representation of soil–foundation–façade interaction, small-strain soil stiffness and progressive nonlinearity, masonry cracking and stiffness loss, and the role of initial damage and foundation behaviour. Systematic variations are needed to quantify uncertainty.
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.
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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.
Damage From Ups and Downs
Investigating Cracking in Unreinforced Masonry Structures Exposed to Settlement and Uplift Cycles Using Finite Element Analyses
Conference paper
(2025)
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Alfonso Prosperi, Michele Longo, Paul A. Korswagen, Mandy Korff, Jan G. Rots
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.
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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.
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.
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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.
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.
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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.
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.
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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.