Historic Masonry Walls Research Articles

Identification of Alternations in the Structure of Historical Masonry Walls Using the GPR Method Accompanied with Architectural Survey in the Former Piast Gymnasium in Brzeg

Widely used in civil engineering, GPR (ground penetrating radar) is increasingly being used to survey historic structures. However, there are still no conclusive directives on the use of GPR in the identification and diagnosis of masonry structures. The current state of the art allows only on the example of individual case studies, to draw conclusions about the effectiveness of the use of this tool. One such area, where the effective use of GPR has been experimentally confirmed, is the historic architectural survey of a heritage buildings. Due to diversity in the dielectric properties of individual construction materials, it is possible to observe on radargrams the change of electromagnetic wave patterns by materials from different phases. Traditional approach require extensive excavation efforts or core drilling, which may not always be acceptable for conservation reasons. Hence the GPR method could be interesting, non – destructive option for identification and diagnosis of historical masonry walls. The authors used the architectural survey and accompanying excavations at the former Piast Gymnasium in Brzeg to conduct a survey campaign using the GPR method. The brick walls of the building's nave have been scanned. The nave have undergone numerous alterations over hundreds of years. The GPR data has been subjected to adequate post-processing and then correlated with architectural surveys and validated on the basis of available excavations at the site. The authors highlight that GPR surveys, when combined with architectural investigations, offer a less invasive approach to examining historic structures, thereby mitigating the need for problematic excavation work.

Experimental investigation of the sonic velocity in historical masonry walls

AbstractThe structural assessment of historical buildings poses a significant challenge for engineers. However, when it comes to historical structures, more commonly used and reliable destructive testing may not always be viable. Instead, non-destructive testing has gained prominence, encompassing techniques like the Schmidt hammer test, georadar, and sonic-based tests.In this paper, the viability of employing sonic testing on historical masonry structures was investigated. This study involves using the measured sonic velocities to identify voids and solid parts within masonry walls. In addition, the purpose is to determine the compressive strength of both mortar and brick constituents and to analyze the effects of moisture and compressive stress on the propagation velocity of waves.

In-plane seismic performance of historical masonry walls with various brick bond patterns using micro-modeling approach

In-plane seismic performance of historical masonry walls with various brick bond patterns using micro-modeling approach

Selection of moisture reference year for freeze-thaw damage assessment of historic masonry walls under future climate: A simulation-based approach

Today, there is an increased research effort on improving energy efficiency in heritage buildings through retrofit measures. Hygrothermal simulations tools are often used to assess the long-term performance of building envelopes and determine whether they are suitable for interior insulation. To reduce the high computation time and cost incurred with these simulations, a moisture reference year (MRY) is typically selected based on long-term annual climatic conditions. Simulation results obtained under MRYs are assumed to represent the long-term performance. However, when assessing the risk to freeze-thaw (FT) damage of historic masonry walls, methods selecting climate-based MRYs have failed to represent the actual performance – determined based on results from simulations over the 31 consecutive years. This paper attempts to find an alternative method to select MRYs, based on the hygrothermal simulations of specific constructions. First, a parametric analysis was proposed to identify the parameters that have the greatest influence on FT damage. Then, simulations are performed for a continuous 31-year period and for each single year. A comparison of their results suggests that there is no accumulative effect on the annual freeze-thaw cycles; and therefore, MRYs can be selected as the single year with the 93rd percentile FT damage severity or the worst year commonly found between masonry walls pre and post retrofit. The application of MRYs was then verified for different insulation types and thicknesses. Results showed that simulation-based MRYs are construction and orientation dependent; however, they are reliable to use for retrofitting design decision making.

Flanges' Impact on Persian Historical Masonry Walls: Modeling Safety Factors

Flanges' Impact on Persian Historical Masonry Walls: Modeling Safety Factors

Experimental and numerical insights on the in-plane behaviour of unreinforced and TRM/SRG retrofitted brick masonry walls by diagonal compression and shear-compression testing

The experimental determination of the parameters that characterise the in-plane shear behaviour of masonry structures is still a challenging task. Different authors have identified the key role of tensile strength in the definition of the in-plane shear behaviour of masonry, but unfortunately its direct experimental characterisation is not always feasible, and masonry’s tensile strength needs to be obtained from complex testing methodologies. As a result, tensile strength needs to be assessed from testing setups such as diagonal compression testing and shear compression testing when the failure mode of masonry is featured by tensile diagonal cracking. However, different formulations are available in the scientific literature regarding the interpretation of the experimental results derived from such tests. This work provides new insights on the interpretation of in-plane shear experimental behaviour of double-leaf historical clay brick masonry walls with low strength mortar joints, both unreinforced and retrofitted with textile reinforced mortar and steel reinforced grout. The research evaluates results derived from both testing methodologies, and investigates the potential correlation between them to fully characterise the in-plane shear behaviour of masonry walls. Finally, a numerical model is used to simulate each testing configuration and study the stress state at the centre of the walls to determine the tensile strength and its correlation with the shear strength and the maximum load attained.

An automated sonic tomography system for the inspection of historical masonry walls

An automated sonic tomography system for the inspection of historical masonry walls

An automated sonic tomography system for the inspection of historical masonry walls.

Background: The conservation of the built masonry heritage requires a comprehensive understanding of its geometrical, structural, and material characteristics. Non-destructive techniques are a preferred approach to survey historical buildings, given the cultural value of their fabric. However, currently available techniques are typically operated manually, consuming much time at operational and processing level and thus hindering their use for the on-site inspection of heritage structures. Methods: A novel automated sonic tomography system was designed and built to inspect and obtain information about the inner structure and damage of historic masonry walls. The system consists of a hitting device mounted on a frame that can be placed adjacent to the wall under analysis. The hitting device can move along the surface within the frame area in X, Y and Z directions, generating the sonic wave. The receiving system is a scanning laser vibrometer, able to measure from the distance the displacement of a focused point over time, recording the wave when it reaches the opposite surface. Results: Six stone masonry walls with different interior geometries were constructed at the laboratory by a professional stonemason. The construction of the walls was carefully documented, including the generation of detailed photogrammetric models of each single stone. The system was applied to survey the six masonry walls. Since the inner morphology of the walls is known, the resulting tomographic images could be compared with the ground truth. Conclusions: Automating the inspection allowed to collect thousands of data in a few hours. New software was also developed to automate the processing of the data. Results are expected to highlight the potential of tomography to obtain quantitative information about the interior of heritage structures, while providing new tools that make the implementation of the technique more practical for professionals. Data, software and models have been made publicly available.

Assessment of frost damage risk in a historic masonry wall due to climate change

Abstract. Historic masonry buildings are an integral part of human cultural heritage, and they need to be preserved for future generations. Brick is susceptible to frost damage which is common in regions with cold and humid climates. The frost damage on the masonry walls is accumulated over the years becoming more and more critical for the integrity of the historic buildings and it is also affected by climate change (CC). In the current research, the focus was placed on a coastal region in southern Norway with a significant number of historic masonry buildings. The frost damage risk of the masonry walls was assessed by using data from a climate reanalysis for the present conditions and from a climate model under past, present, and future conditions. Two climate-based (CB) indices accounting for the air temperature and one material response-based (MRB) index considering the temperature and moisture content inside a simulated masonry wall were used for the frost damage risk assessment. The inputs for the MRB index were calculated by heat, air, and moisture (HAM) transfer simulations. Within the HAM simulations, the indoor climate was in one case representative of an unconditioned building with air leakages and many openings, while in the second case it was representative of a small, conditioned room. The overall impact of CC was a decrease in the frost damage risk of the masonry walls. However, an increased frost damage risk was observed from the present to the future conditions according to the MRB index for the walls of small, conditioned rooms with higher driving rain load and lower solar radiation gains. The (i) number of freeze-thaw events, (ii) periods during which freeze-thaw events occur, and (iii) CC-related trends varied based on the considered index with the most explicit risk assessment being the MRB one. Moreover, the freeze-thaw events experienced by the masonry walls of unconditioned, leaky buildings were 20 times more than the ones for the small, conditioned rooms. Significant differences were observed between the results from the climate model and the climate reanalysis which were mainly linked to the underestimation of the air temperature and the overestimation of the precipitation by the climate model. The outputs of the MRB index were translated into certain damage categories while suggestions on improving the limitations of the current research were made.

Seismic Analysis of Historical Urban Walls: Application to the Volterra Case Study

Several Italian cities are characterized by the presence of centuries-old historic walls, which have a cultural heritage value and, due to their structural role as a retaining wall, often influence the safety of adjacent buildings and infrastructure. Ancient urban walls are increasingly subject to instability and collapse phenomena, because the greater frequency of extreme meteoric events aggravates the static condition of the walls and of the wall–soil system. Since the seismic risk in the contexts in which the historical urban walls are located is often medium-high, it is advisable to evaluate the influence of soil moisture on the seismic response of the soil–structure system. In this paper, the seismic vulnerability of historical urban walls was examined through considering scenarios of both dry and wet soil, in order to evaluate the seismic response of the structure as a function of soil imbibition. Seismic vulnerability analyses were carried out on the case study of the historical urban masonry walls of Volterra (Italy), which have been affected by two major collapses in the last ten years. Seismic vulnerability was assessed by means of the limit equilibrium method and the finite element method, and through adopting proper soil imbibition models. The results highlight which sections of the walls are at greater seismic risk due to the presence of soil moisture, as well as the influence of soil imbibition on the structural safety and failure mechanism.

Intertidal biodiversity and physical habitat complexity on historic masonry walls: A comparison with modern concrete infrastructure and natural rocky cliffs

Maritime built heritage (e.g., historic seawalls) represents an important component of coastal infrastructure around the world. Despite this, the ecological communities supported by these structures are poorly understood. At seven locations across the UK, we compared the biodiversity and physical habitat characteristics of (1) historic (pre-1900s) masonry walls, (2) concrete walls, and (3) natural rocky cliffs.Historic masonry walls were found to support significantly more species than concrete walls, and in some locations, more diverse communities than nearby rocky cliffs. Nevertheless, community composition remained distinct between the three habitat types at each location. We also found that historic masonry walls provided substantially more cryptic space (i.e., crevices) than both concrete walls and rocky cliffs, and this is positively associated with the ecological value of these structures. Overall, our results suggest that the unique physical properties of historic masonry walls make them an important component of habitat diversity along developed coastlines.

In-plane shear strengthening of traditional unreinforced masonry walls with near surface mounted GFRP bars

In this study, the effectiveness of Near Surface Mounted (NSM) method, for in-plane shear strengthening of traditional and historical Unreinforced Masonry (URM) walls, is investigated through a comprehensive experimental study. For this purpose, square solid clay brick masonry wallettes (42 samples) with three different types of traditional mortars including gypsum mortar, lime-cement-sand mortar and lime-sand mortar are prepared and retrofitted with NSM Glass Fiber Reinforced Polymer (GFRP) bars. Then, diagonal shear tests are conducted to evaluate the in-plane shear behavior of the masonry wallettes. The effects of some key variables such as wall thickness, the retrofitted face of the wall, reinforcement ratio, and the type of paste for mounting the reinforcing bars, on the effectiveness of the retrofitting method are investigated. The results of the tests are presented in terms of the failure modes and the lateral shear stress-drift curves of the test specimens. Accordingly, the retrofitting method can enhance the in-plane shear strength, and the ultimate lateral drift capacity of the URM wallettes. According to the test results, the type of filler paste and reinforcement ratio influence the strength enhancement of the test specimens. Furthermore, in specimens retrofitted with the one-side retrofitting scheme, due to the asymmetry of walls under in-plane loads, an unexpected out-of-plane deformation is induced in the walls under in-plane load which adversely affects its global behavior.

Simplified methods for the evaluation of mechanical properties of tuff masonry walls in Campania (Italy)

Conservation of heritage buildings still poses many challenges. Throughout the history, monuments have been exposed to catastrophic earthquakes. Assessment and retrofitting of this architectural heritage are effective measures to prevent heavy damage by future earthquakes. These operations require good knowledge of the material mechanical properties, it being one of the most important steps for a suitable seismic assessment. Mechanical characteristics may be determined through destructive, semi-destructive and non-destructive tests. As the application of destructive and semi-destructive testing on heritage buildings is often impossible, many attempts have been made to propose fully non-destructive methods for determining mechanical properties. One of the methods is called the Masonry Quality Index (MQI), only based on visual inspection. This method aims to develop a simple and systematic approach to the analysis of masonry constructions based on idealised typologies, different parameters and the mechanical properties of the constitutive materials (stone, brick, mortar, etc.). The aim of the present research is to propose a simplified approach to obtain mechanical properties of the historical masonry walls with lime mortar in Campania, by correlating the MQI, double flat jack and further non-destructive test results.

Thermal renders for traditional and historic masonry walls: Comparative study and recommendations for hygric compatibility

To reach European climate neutrality by 2050, the strategic importance of retrofitting the existing building stock is clear. For this scope, thermal rendering systems have emerged as a very feasible solution for historic and traditionally constructed walls. Nonetheless, a definitive guideline for the selection of suitable solutions for the application in this context is not yet available. This research aims at providing recommendations for the choice of hygric-compatible solutions in an early-stage design, for the context of temperate climates with mild winters. In this study, the massive masonry walls of three historic buildings located in Portugal and Italy are considered. Mono-dimensional hygrothermal simulations are validated against the data measured on-site. Simulations are then used to evaluate the impact of thermal renders on the walls, in comparison to more common insulation materials. Two moisture-related risks are considered: moisture accumulation and reduction of drying. This investigation shows that, for traditional porous walls, retrofitted configurations should be simulated not only under typical operational conditions but also considering a very high initial water content in the wall substrate, when the insulation is applied. Otherwise, moisture-related risks may be overlooked. Recommendations on the choice of thermal rendering systems are provided.

A new sensorized ceramic plug for the remote monitoring of moisture in historic masonry walls: First results from laboratory and onsite testing

A new sensorized ceramic plug for the remote monitoring of moisture in historic masonry walls: First results from laboratory and onsite testing

Nonlinear numerical assessments for the in-plane response of historic masonry walls

This study examines the in-plane cyclic response of historic masonry elements using a micro modelling approach that incorporates damage-plasticity and surface-based cohesive-contact interface approaches. The nonlinear procedures adopted are validated against tests on dry and wet panels in diagonal compression and large walls under reverse shear-compression loading. Considering the inherent material variability, the numerical results are shown to correlate well with the test results in terms of stiffness, strength, ductility, overall hysteretic response, and cyclic degradation. Based on the validated models, followed by exploratory sensitivity studies, detailed parametric assessments are carried out. The parameter ranges are selected to cover historical masonry materials, consisting of bricks and mortar, and address both dry and wet conditions. Four typical failure modes, namely, flexural strut crushing, diagonal cracking, flexural toe crushing, and mixed sliding, in an order of increasing ductility, are quantified and discussed. It is shown that wet masonry walls have an average reduction of 16% in terms of stiffness and capacity compared with the dry counterparts. Although the failure modes in dry and wet wall pairs are similar, some cases are identified in which the weaker moisture-affected joint strength results in a shift to a more brittle mode. It is also shown that the ductility of the flexural strut crushing mode, which often governs the failure of historical masonry due to its low strength, is considerably overestimated in existing guidelines. Based on the results of the parametric investigations, analytical models for predicting the inelastic response are evaluated, and suggestions for modifications are proposed.

Verification of Mechanical Properties of Historical Brick Masonry Walls with Masonry Quality Index Method in Iran

ABSTRACT Identification of mechanical characteristics of the materials used in heritage constructions is one of the most important steps in their seismic assessment, which may be determined through destructive, semi-destructive (or minor destructive) and non-destructive tests. Due to the fact that destructive and semi-destructive testing on heritage buildings is often impossible, Italian researchers have proposed a qualitative method called the masonry quality index to estimate the mechanical properties of heritage building materials. In this article, the MQI method has been validated in seven different historical buildings in Qajar dynasty period dating back to 1785–1925 A.D. The results were compared to those of double flat jack tests performed with permission from the Ministry of Cultural Heritage, Tourism and Handicrafts in Iran. The compressive strength and elastic modulus for brick masonry were in the range of 0.4–2.5 MPa and 650–4150 MPa, respectively. In addition, two equations were presented to estimate the compressive strength and elastic modulus of historical masonry walls without the need for performing minor destructive in-situ tests.

Experimental out-of-plane damage limits of historical stone masonry walls

In stone masonry buildings, failure under strong ground motions usually occurs in the form of out-of-plane overturning of the walls before reaching their in-plane strength, as the walls have long unsupported spans perpendicular to their plane and the lack of slabs ensuring a diaphragm effect. Post-earthquake damage observations reveal this specific weakness of the historic masonry walls. Experimental determination of the out-of-plane damage limits of these walls, emerges as a need for use, especially during numerical evaluations. This article presents the results of static and dynamic testing of double- and three-leaf large-scale U-shaped masonry wall specimens. For this purpose, nondestructive material characterization was conducted on a reference historical masonry structure. Large-scale wall specimens were designed considering these findings and material tests performed on mortar samples. Quasi-static cyclic tests and ambient vibration tests for both initial and damaged conditions were performed on these specimens to capture the damage evolution and the corresponding drift limits. Damage limits are suggested to be used in performance-based evaluations of other territorial structures.

Hygrothermal modelling of historic rubble masonry walls: Accounting for geometric and compositional variability

An established issue when assessing the hygrothermal performance of heritage buildings is the correlation between measured data and model outputs. This can be attributed to many factors including climate data and hygrothermal material property data. Two overlooked factors are the variation in geometry and level of decay in the structure. This can be true for several historic wall assemblies with irregular geometries and elevated levels of decay. There is a lack of guidance on how and when to incorporate this into a hygrothermal model. The goal of this paper is to examine how this variability in geometry and composition may affect model outcomes using a simulation approach with stochastic methods for a sample rubble core masonry wall.Geometrically stochastic models were generated from a script accounting for varying levels of air voids in the wall and irregular stone patterns. The presence of voids alters heat, capillary and vapour transport. This was combined with hygrothermally dissimilar mortar and stone units. Simulations were performed under four boundary conditions: heat, drying, wetting and actual weather data. The results showed that geometric stochasticity can lead to a large variation of results. The presence of voids in the wall also led to a reduction in heat and moisture transport in the assemblies. The results of the stochastic simulations were then compared to a set of simplified one and two-dimensional models to judge their appropriateness. It was found that 2-D parallel like models that account for the mortar joint in some fashion are most appropriate.

Hygrothermal assessment of internally insulated historic solid masonry walls with focus on the thermal bridge due to internal partition walls

This study investigated the hygrothermal performance of five insulation systems for internal retrofitting purposes. Focus was on the hygrothermal performance near partition brick walls compared to the middle of the wall. The setup comprised two insulated reefer containers with controlled indoor climate, reconfigured with several holes containing solid masonry walls with interior embedded wooden elements, an internal brick partition wall and different internal insulation systems, with and without exterior hydrophobisation. Relative humidity and temperature were measured over five years in the masonry/insulation interface and near the interior surface, in the centre of the test field and near the partition wall. In addition, calibrated numerical simulations were performed for further investigation of the thermal bridge effect. Findings for the masonry/insulation interface showed higher temperatures and lower relative humidity near the partition wall in comparison with the central part of the wall. Near the interior surface, measurements showed only minor differences between the two locations. The relative effect of the thermal bridge was smaller in the case of a high driving rain load on the exterior surfaces. The numerical simulations showed that the hygrothermal conditions were affected further away from the partition wall than what could be measured in the experimental setup.