P.A. Korswagen Eguren
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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.
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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.
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.
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.
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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.
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.
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.
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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.
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.
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.
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.
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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.
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.
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.
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.
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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.
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.
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.
Regional subsidence due to mining and gas extraction in the northern Netherlands exposes masonry façades to combinations of greenfield horizontal strain (εGF) and angular distortion (βGF) that differ from classical settlement-only scenarios. Existing approaches, epitomised by the empirical Boscardin–Cording diagram, provide deterministic damage envelopes in the (ε,β) space but do not distinguish between greenfield and façade-level measures, are not probabilistic, and do not explicitly account for Dutch typologies or soil-structure interaction (SSI). This paper presents a numerical, computational-based, façade-specific counterpart and reinterpretation of the Boscardin–Cording diagram: crack-based (damage measure Ψ) fragility surfaces in the (εGF,βGF) space for Dutch masonry façades. A two-tier SSI framework is adopted in which Tier 1 generates target ε,β through boundary-driven non-linear soil blocks with a small-strain hardening law, and Tier 2 couples identical soil blocks to non-linear masonry façades with embedded strip foundations. Three stratigraphic profiles, two typologies (clay brickwork on URM footings, CLBR; calcium-silicate brickwork on RC strips, CSBR), 33 façade geometries and multiple material sets yield over 6 500 simulations and roughly one million (ε,β,Ψ) triplets. The results show that greenfield ε and β are strongly and non-linearly filtered before reaching the façades, with elastic modification factors typically below 0.25 but increasing markedly as cracking and Ψ grow. Fragility surfaces quantify the influence of typology, soil profile and aspect ratio and reveal where Boscardin–Cording bands correspond to median Ψ-based damage and where they are conservative. The proposed framework enables probabilistic, typology-aware use of εGF–βGF from geomechanical models and geodetic monitoring for assessing light, crack-dominated damage in masonry façades.
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Regional subsidence due to mining and gas extraction in the northern Netherlands exposes masonry façades to combinations of greenfield horizontal strain (εGF) and angular distortion (βGF) that differ from classical settlement-only scenarios. Existing approaches, epitomised by the empirical Boscardin–Cording diagram, provide deterministic damage envelopes in the (ε,β) space but do not distinguish between greenfield and façade-level measures, are not probabilistic, and do not explicitly account for Dutch typologies or soil-structure interaction (SSI). This paper presents a numerical, computational-based, façade-specific counterpart and reinterpretation of the Boscardin–Cording diagram: crack-based (damage measure Ψ) fragility surfaces in the (εGF,βGF) space for Dutch masonry façades. A two-tier SSI framework is adopted in which Tier 1 generates target ε,β through boundary-driven non-linear soil blocks with a small-strain hardening law, and Tier 2 couples identical soil blocks to non-linear masonry façades with embedded strip foundations. Three stratigraphic profiles, two typologies (clay brickwork on URM footings, CLBR; calcium-silicate brickwork on RC strips, CSBR), 33 façade geometries and multiple material sets yield over 6 500 simulations and roughly one million (ε,β,Ψ) triplets. The results show that greenfield ε and β are strongly and non-linearly filtered before reaching the façades, with elastic modification factors typically below 0.25 but increasing markedly as cracking and Ψ grow. Fragility surfaces quantify the influence of typology, soil profile and aspect ratio and reveal where Boscardin–Cording bands correspond to median Ψ-based damage and where they are conservative. The proposed framework enables probabilistic, typology-aware use of εGF–βGF from geomechanical models and geodetic monitoring for assessing light, crack-dominated damage in masonry façades.
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.
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.
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.
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.
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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 preservation of historic masonry structures requires durable repair techniques that minimize intervention while maintaining the original appearance. In this context, bio-based self-healing mortars present a promising solution, yet their application in masonry remains underexplored. Previous research demonstrated the potential of a poly-lactic acid (PLA)-based agent to heal cracks in masonry with cement-based mortars, restoring both bond strength and aesthetics. However, when extended to more porous cement–lime mortars and clay bricks, new challenges emerged. Leaching, likely resulting from interactions between the mortar’s porosity and the healing environment, underscored the need for further investigation. To this purpose, the study investigates clay brick couplets built with two mortar compositions of increasing lime content, exposed to two different healing environments. Specifically, a PLA-based healing agent was incorporated into cement–lime mortars with lime/cement ratios of 1.0 and 3.33 by volume. Each mortar was used both plain and with 10% of the healing agent (by binder volume) to build the specimens. After pre-cracking through bond wrench testing, the couplets were left to heal for 60 days under either high humidity or wet–dry cycle conditions. The results highlight the critical influence of the healing environment on overall performance. While wet–dry cycles proved ineffective in this case, humid conditions enabled partial recovery of flexural bond strength, with values reaching up to 15% in samples containing the healing agent and higher lime content. Visual inspection confirmed complete crack closure, supporting the aesthetic—and potentially watertightness—restoration. Additionally, reference samples with higher lime content also exhibited minor strength recovery, likely due to the migration of free lime and its reaction within the crack. These advancements underscore the potential of bio-based self-healing mortars for masonry repair and establish a foundation for further research.
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The preservation of historic masonry structures requires durable repair techniques that minimize intervention while maintaining the original appearance. In this context, bio-based self-healing mortars present a promising solution, yet their application in masonry remains underexplored. Previous research demonstrated the potential of a poly-lactic acid (PLA)-based agent to heal cracks in masonry with cement-based mortars, restoring both bond strength and aesthetics. However, when extended to more porous cement–lime mortars and clay bricks, new challenges emerged. Leaching, likely resulting from interactions between the mortar’s porosity and the healing environment, underscored the need for further investigation. To this purpose, the study investigates clay brick couplets built with two mortar compositions of increasing lime content, exposed to two different healing environments. Specifically, a PLA-based healing agent was incorporated into cement–lime mortars with lime/cement ratios of 1.0 and 3.33 by volume. Each mortar was used both plain and with 10% of the healing agent (by binder volume) to build the specimens. After pre-cracking through bond wrench testing, the couplets were left to heal for 60 days under either high humidity or wet–dry cycle conditions. The results highlight the critical influence of the healing environment on overall performance. While wet–dry cycles proved ineffective in this case, humid conditions enabled partial recovery of flexural bond strength, with values reaching up to 15% in samples containing the healing agent and higher lime content. Visual inspection confirmed complete crack closure, supporting the aesthetic—and potentially watertightness—restoration. Additionally, reference samples with higher lime content also exhibited minor strength recovery, likely due to the migration of free lime and its reaction within the crack. These advancements underscore the potential of bio-based self-healing mortars for masonry repair and establish a foundation for further research.
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.
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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.