Masonry Facades Research Articles

Reverse Engineering Workflows for the Structural Assessment of Historical Buildings

ABSTRACT Supported by advancements in 3D scanning and parametric modeling tools within the architecture, engineering, and construction sectors, reverse engineering processes for cultural heritage (CH) have recently gained popularity. While many studies have focused on simple 3D reconstructions to create virtual environments, a specialized subarea of this research field has targeted more specific digitization objectives, including, among many, structural analysis of building components. This emerging field has not yet been systematically developed due to the intrinsic challenges associated with CH. Within this context, this paper proposes and describes a reverse engineering-based method that utilizes terrestrial laser scanning and visual programming (VP) to analyze displacements and deformations that occurred over time in historical masonry buildings and applied it to the timber trusses, masonry facades, and columns of two selected Italian case study buildings. This method allows for comparing the surveyed condition of these components, considered the “deformed state”, with their ideal configuration, reconstructed using VP algorithms, considered the “original state”. The outcomes of this comparison facilitate the investigation of the components’ structural behavior and support joint considerations to assess the overall condition of the investigated building, providing helpful knowledge for guiding structural improvement interventions.

Glass panels supported by spider fittings: advantages, challenges, and applications in modern masonry facades

Glass panels supported by spider fittings: advantages, challenges, and applications in modern masonry facades

Internal Insulation – four systems in one historic residential building

Reducing the heat loss from European buildings must include thermal retrofitting of the historic buildings. In these cases, where buildings have facades worthy of preservation, internal insulation is the only solution although external insulation is better hygrothermal solution. Inspections in buildings with internal insulation have in multiple cases shown mold growth problems at the intersection between the original wall and the insulation. Thus, there is a need for real-life testing; i.e., raising the level of reality by using professional craftsmen to apply internal insulation to existing buildings inhabited by ordinary users. Building owners are more likely to accept these solutions when they have been tested in reality, and not only in the lab or with simulations, on efficiency, robustness, and moisture safety. In Denmark, the older, worthy-of-preservation, historic buildings are commonly built with solid masonry facades. Consequently, internal insulation might involve hygrothermal risks for the external walls. The present study describes a case study of a typical historic building built in 1837. In specific, the paper focuses on the top (5th) floor of the building, which is a residential area (a commune). On the 5th floor, four different types of insulation materials were installed in eight different rooms. The performance of the four insulation materials was determined by monitoring the temperature and relative humidity at the intersections between the insulation and the existing wall, as well as the indoor and outdoor climate. Results of the measurements of the available period showed that relative humidity is increasing for most of the sensors, with an exception of a few sensors that appear to have decreased values compared to the first month. Furthermore, the risk of mold growth was calculated with the VTT mold growth model based on performed measurements and indicated minimum to non-existent mold growth risk so far.

Full-Scale Assessment of Seismic and Wind Load Performance in the Design of a Flexible Solar-Shading Double-Skin Façade

Cable-supported façades represent a novel approach in the design and technology of double skin façades (DSFs). This type of system not only offers flexibility in terms of exterior finishes, but also regulates the access of solar radiation, thereby transforming the appearance of the building in response to varying daylight conditions. However, the structural performance of these façades under wind, impact, and seismic loads remains an active area of research. The study is a groundbreaking work that experimentally evaluates the wind and seismic behaviour of these type of façades. The methodology used for the evaluation of flexible masonry facades includes laboratory tests analysing the individual capacity of the connections and materials of the system under standardized and non-standardized procedures. A full-scale experimental sub-assembly specimen of a representative module of the façade is also subjected to uniformly distributed pressures of wind load tests, as well as hard body and soft body impact tests. The setup considered the border conditions, tension loads, and actual materials. Furthermore, the earthquake assessment includes tests of full-scale specimens subjected to these demands. The results show up to 30% enhanced performance relative to similar systems reported in the literature. Furthermore, research findings facilitated the refinement and redesign of the system components, thereby validating the DSF case study.

Stochastic simulation of earthquake ground motions for the seismic assessment of monumental masonry structures: Source‐based vs site‐based approaches

AbstractEarthquakes are among the most destructive natural disasters and have resulted in a massive number of fatalities and economic losses all over the world. Simulated ground motion records are valuable, particularly for regions lacking seismic stations or with a limited history of large‐magnitude earthquakes. Notably, a significant percentage of monumental masonry buildings are located in regions with limited access to real records; hence, simulated records play a paramount role in their seismic protection. However, few studies have investigated the structural response of heritage buildings via response history analyses to assess the performance of simulated earthquakes against real ones. To accomplish this, this study simulates the recorded time‐series of the 9th of July 1998 Faial earthquake in the Azores (Mw = 6.2) at four available stations, using two different simulation approaches, that is, a source‐based stochastic finite‐fault method and a site‐based broadband stochastic method. First, two masonry facades with sidewalls characterized by different slenderness levels are adopted to conduct this research. Moreover, the proposed approach is also applied to an existing monumental structure, that is, São Francisco Church, located at Horta, which was affected by damage during the Faial earthquake. Results demonstrate that both simulation approaches provide similar results in terms of structural response prediction. The proposed framework also demonstrates that a small mismatch in terms of predicted damage patterns can result in a significant relative error in terms of displacement predictions.

Out-of-plane flexure of external Thermal-insulation attached to Non-load-bearing masonry walls

The out-of-plane flexure of thermo-insulation attached on the external facades of full-scale clay masonry walls is studied. This is of importance because a considerable number of multistory buildings are in need of thermal insulation considering at the same time the seismic performance of such attachments together with the unreinforced masonry walls. Full-scale clay masonry wall specimens with or without thermal insulation were subjected in the laboratory to out-of-plane flexure. Such thermo-insulating attachments resulted in noticeable increase of the total out-of-plane flexural capacity and deformability when the thermo-insulating panels are subjected to flexural-tension. This increase is quite substantial when these panels are of either expanded polystyrene (EPS) or extruded polystyrene (XPS) and insignificant for mineral wool (MW). The observed response was used to validate a numerical methodology aimed at predicting this out-of-plane flexural performance of masonry walls with thermal insulation attachments. The beneficial effect of the thermo-insulating attachments on the out-of-plane flexural response of masonry facades depends on the adopted construction technique. This is also true for the safe performance of the thermo-insulating attachments themselves after their debonding. Despite that both the masonry facades and their attachments are considered as non-structural elements appropriate construction techniques should safeguard their acceptable out-of-plane performance when subjected to seismic type loads.

Siamese Convolutional Neural Networks to Quantify Crack Pattern Similarity in Masonry Facades

ABSTRACT This paper proposes an automated approach to predict crack pattern similarities that correlate well with assessment by structural engineers. We use Siamese convolutional neural networks (SCNN) that take two crack pattern images as inputs and output scalar similarity measures. We focus on 2D masonry facades with and without openings. The image pairs are generated using a statistics-based approach and labelled by 28 structural engineering experts. When the data is randomly split into fit and test data, the SCNNs can achieve good performance on the test data (). When the SCNNs are tested on ”unseen” archetypes, their test values are on average 1% lower than the case where all archetypes are ”seen” during the training. These very good results indicate that SCNNs can generalise to unseen cases without compromising their performance. Although the analyses are restricted to the considered synthetic images, the results are promising and the approach is general.

Fabrication and energy efficiency of translucent concrete panel for building envelope

A translucent concrete panel (TCP) is a novel construction material for building envelopes. It combines light conduits, such as optical fibers (OFs), and lightweight, high-strength concrete, enabling it to transmit light and carry the external load. A set of TCPs was cast using OFs with a large diameter (17.8 mm). The compressive strength was 39.6 N/mm2, which is qualified to carry the external load as the structural components. The thermal conductivity of the TCP was 0.2114 W/(m·K), indicating excellent thermal insulation performance compared to traditional building envelopes, such as glass curtain walls (GCW) and masonry facades. To investigate the energy consumption of a TCP, a one-roomed office building was modeled numerically. Three cities were selected to analyze the monetary cost and energy consumption of various building envelopes. These building envelopes were made of a masonry wall, GCW, and TCP. The simulation results revealed that the model with a TCP envelope had the lowest electricity consumption, monetary cost, and payback period. Moreover, it was more energy efficient in Stockholm and Nanjing than in Singapore. The novel TCP is applicable in building envelopes and other areas where light transmission and load-bearing are required.

Facade Damage Assessment of the Buildings in Bam, Iran 2003 and Kermanshah, Iran 2017 Earthquakes

One of the essential factors in buildings frontage is the continuity of the structural and building envelope parts. In this investigation, a comparison was made between Bam and Kermanshah earthquakes. A strong earthquake (magnitude 6.6) struck the city of Bam in southeast Iran on 26 December 2003, and similarly, another strong earthquake struck the city of Kermanshah (magnitude 7.3) in Iran on 12 November 2017. Damage in the facades of the buildings was a clear contributor to the overall building damage. This paper presents the damage assessment of the different facade systems from multi-story buildings in Bam and Kermanshah, Iran. The survey covers the buildings greater than three stories in height, excluding most unreinforced masonry facades. As far as a building can have more than one facade system, any facade systems are evaluated individually. Observation of facade damage is discussed and is presented in terms of its performance level.

Thermographic Analysis of Joints of Supporting Structures

The external partitions of a building (walls, roof, etc.) in addition to their supporting functions must also ensure an internal microclimate suitable for comfortable human work, recreation and other activities. This article analyzes the thermal characteristics of the external walls of a residential house and thermographically examines the joints of the different structures of the building. Thermographical examination may be performed either passively or actively. In the former case, the object of the examination ir heated up to a given temperature, after which thermographical images of the object are taken and analyzed. In the latter case, thermographical analysis is made of the object in its naturally established thermal conditions. This article examines the thermal characteristics of the partition structures of a residential building. The values of the thermal properties of the materials are taken from the documentation provided by their manufacturers, and in their absence, the data of the technical building regulations is used. Calculated analytically: the wall of the western annex only meets the C energy class requirements, the insulation of the old part of the building raised the heat transfer coefficient of the partition to class A, the thermal characteristic of the eastern annex wall corresponds to the A + energy class. This thermographic examination showed that the facade covered by the fibrous cement siding absorbed less heat compared to the masonry facades. Based on theoretical calculations and the thermographic analysis, it is recommended to additionally insulate the western annex from the inside. If possible, it is also recommended to additionally insulate both facade joints with polyurethane foam and to seal them with waterproofing mastic to prevent the sunrays from reaching the foam.

Facades of Manhattan Apartment Buildings from the 1902–1915 Period. II: Life Cycle Prediction

The 3,500 apartment buildings erected in New York City between 1902 and 1915 form a typology characterized by similarities in structural and architectural solutions. About 87% of these buildings are still standing and are home to about half a million people. To predict the remaining life of facades of this typology, the author rated the condition of 171 masonry facades. For each surveyed building, a timeline of repairs since 2006 was constructed. The data collected—condition ratings, type of material, and area of ornamentation allowed analysis of the deterioration of various materials as they have been interacting in the same facade. The sample included 74 facades subject to mandated periodic inspections. The results of these inspections performed by others provided additional points of control. The condition ratings and the 13-year timeline of activities were used to predict the remaining life of the facades in terms of rate of repairs. Deterioration developing in stone and terra-cotta ornamentation is the main concern. Corrosion of steel anchoring the ornaments was found to be the main factor determining the deteriorations’ critical path.

Impact of surface waterproofing on the performance of brick masonry through the moisture exposure life-cycle

Moisture is one of the major causes of damage to building systems, affecting the hygrothermal performance and durability of building systems. Surface treatment products are available in the market that can influence the hygric performance of masonry facades under water exposure. These are of a wide range of chemical compositions, and they claim to waterproof the masonry surfaces while not diminishing vapour transmissibility. This paper presents and discusses the findings from a series of benchtests carried out to measure hydrophobicity, water absorption and water vapour transmission following the relevant codes for an appraisal of the hygric behaviour change in brick masonry induced by waterproofing through three distinct phases of the life-cycle of moisture exposure, i.e. first contact with water, wetting and drying. To this end, 4 waterproofing products including silane/siloxane blend liquid and cream, and acrylic and stearate-based liquids were selected for testing, along with 3 brick types common in the 50s and 60s to be representative of the majority of the UK building stock. The findings show that the treatment products indeed enhance the surface hydrophobicity and reduce water absorption while allowing water vapour transmission to differing degrees: silane/siloxane blend cream overall was found the most effective throughout the moisture-exposure life-cycle, with an average of ~96% reduction in water absorption and 18% of increase in water vapour resistance in comparison to the untreated case, followed by the stearate-based liquid with 57% reduction in water absorption and 12% increase in water vapour resistance. The acrylic-based product demonstrated good performance in hydrophobicity and water vapour transmission tests, however led to a comparatively higher water absorption capacity than the other treatment products with only ~40% reduction in comparison to the base-case. Finally, silane/siloxane blend liquid was found to lead to the lowest contact angle, demonstrating a lower-than-others capacity to developing surface hydrophobicity, and led to 35% reduction in water absorption and 28% increase in water vapour resistance, making it the poorest product in the dataset to lead to watertight and vapour open systems under water exposure. Based on the test results it was also deemed beneficial to use masonry specimens to account for its composite nature, rather than using results obtained from brick and mortar separately to infer the wall response under exposure.

Masonry panels with external thermal insulation subjected to in-plane diagonal compression

Partial collapse of masonry facades during past strong earthquakes is well documented together with the increased vulnerability due to the presence of thermo-insulation within double wythe masonry. The combined seismic and energy retrofit of existing aged buildings represents a topic of importance for the building stock. The current study investigates the in-plane performance of a specific thermo-insulation scheme with panels attached on the external facades of multistory buildings. Diagonal compression tests of prototype specimens are done to study the influence of thermal insulation on the in-plane behaviour of clay brick masonry panels with or without thermal insulation. It was found that the thermo insulating attachment of the tested type performs in a satisfactory way when subjected to the stress field that arises to these masonry panels when subjected to diagonal compression. The thermo insolating panels, although finally debonded from the masonry substrate, do not collapse, even when the masonry panel develops large diagonal cracks, due to the presence of the used plastic anchors. The presence of such thermo insulating attachments leads to an increase of the in-plane load capacity and to a less brittle behaviour than the one without this thermo-insulation. This may also lead to a less vulnerable seismic performance than that of the same masonry panel without this thermo insulating attachment, although further validation is needed considering also the out-of-plane performance. The employed numerical modeling was successful in simulating the most important aspects of the in-plane response of the tested masonry wallets with or without thermo-insulating attachments. The good agreement with observed performance as well as the general nature of this numerical simulation confirms its validity.

Factorial Study on the Impact of Climate Change on Freeze-Thaw Damage, Mould Growth and Wood Decay in Solid Masonry Walls in Brussels

Previous studies show that climate change has an impact on the damage risks in solid masonry facades. To conserve these valuable buildings, it is important to determine the projected change in damages for the original and internally insulated cases. Since historical masonry covers a wide range of properties, it is unknown how sensitive the climate change impact is to variations in different parameters, such as wall thickness, brick type, etc. A factorial study is performed to determine the climate change impact on freeze-thaw risk, mould growth and wood decay in solid masonry in Brussels, Belgium. It is found that the critical orientation equals the critical wind-driven rain orientation and does not change over time. Further, the freeze-thaw risk is generally decreasing, whereas the change in mould growth and wood decay depends on the climate scenario. Knowing the brick type and rain exposure coefficient is most important when assessing the climate change impact. For freeze-thaw risk and wood decay, it is found that simulating one wall thickness for the uninsulated and one insulated case is sufficient to represent the climate change impact. Finally, the effects of climate change generally do not compensate for the increase in damage after the application of internal insulation.

Out-of-plane mechanism in the seismic risk of masonry façades

A framework for evaluating the risk of the out-of-plane mechanism of masonry facades subjected to earthquake excitations is presented. The effect of seismic events on masonry facades is investigated and results are presented in terms of fragility curves and seismic risk for several masonry supporting restrictions. The restrictions considered are (1) masonry facade unrestricted to rock on a firm base, (2) masonry facade restricted to rock in one direction, and (3) restrained rocking masonry facade in one-sided motion. Because the available empirical information is insufficient to obtain fragility functions for masonry facades, the study is based on numerical analysis and recent studies on seismic risk. The conceptual framework is illustrated with information from masonry facades characteristic of Mexican religious structures and within the seismic hazard areas of Mexico. Since the frequency characteristics of ground motions strongly depend on the distance from the epicenter to the site, which is of cardinal importance to the vulnerability of these structures, the impact of this distance for hard-soil sites is thoroughly investigated. The probability of failure for the three types of masonry facades was calculated. It was found that the probability of failure decreases with an increased width-to-height relation; conversely, the probability of failure (reported in terms of the reliability index) increases with increased block size dimensions. Results in this study show that restraining conditions of the facades inconsequentially affect the probability of failure. Although the reliability of freestanding masonry facades are marginally greater, this finding holds true regardless of whether or not one considers far-field ground motions. The results in this study can be useful for evaluation and reinforcement tasks of masonry facades located in areas of high seismic hazard.

MASONRY IN PARALLEL. A KNOWLEDGE BASED STRATEGY POST CENTRAL ITALY EARTHQUAKE 2016

Abstract. This research aims to propose a classification of masonry typologies in Central Italy after the earthquakes that in 2016 involved about 120 municipalities. This territory, since several decades, presents high fragility features due to the depopulation process that increase the vulnerability and risk degree. This condition affects even the maintenance practices of traditional buildings by the inhabitants and the extraordinary post-traumatic situation acts as an accelerating factor of the abandonment. In this article we will explain deeply the first part of the research, focusing in particular on methods and tools that were defined and used to carry out this study. The research highlights the need of a specific comparative tool for masonry facades classification. This was elaborated through the comparison of existed bibliography as the EMS-98, the Aedes schedules and the local classification by Umbria Region and the De Meo book. The result then is the production of another synoptic map that would simplifies the correlation between different approaches to classification and the censed facades. Moreover, it was elaborated a second synoptic map moving from the analyses of many survey forms already discuss in literature. The result of this comparison is a new survey form to carry out the field research on vernacular masonry buildings. This new form focuses on the characteristics of the buildings that the research aims to study in Central Italy. The two tools that are illustrate in the following paper were applied on one hundred survey of masonry buildings carried out during August 2018. The last part of this paper proposes a statistical analysis of the results of the field research.

Experimental evaluation of permeable cable-supported façades subjected to wind and earthquake loads

In building engineering, non-structural components represent a significant cost of the overall budget of a construction project. However, in many cases their design is essentially based on architectural criteria rather than on structural performance mainly because the structure stability does not necessary rely on them. Among nonstructural elements, façades are one of the most visible and expensive components where innovation is very popular. Permeable cable-supported façades are a recent frontage proposal designed to allow not only flexible exterior finishes, but also the flow of natural light and the apparent building transformation according to the daytime and light; however, their structural performance for wind and earthquake loads is still a subject of research. This paper, for the first time, experimentally evaluates the wind and seismic behavior of these type of façades. A five-step comprehensive approach is proposed for the evaluation of cable-supported masonry facades including field and laboratory tests. In the first step, the individual capacity of the connections and materials of the system is evaluated under standardized and non-standardized procedures. The next step consisted in quantifying the fundamental vibration periods and the modal shapes of the façade system including the effect of the border and hanging conditions. The following phase is to estimate the wind load using computational fluid dynamics (CFD). In order to understand the effect of the wind at the different scales of the structure, simulations are performed starting with few bricks and progressively increasing the size of the computational model until assessing the entire building. These analyses allow understanding how the micro and macro components distribution and geometry can affect the wind in-and-out-flow and the possibility of vortexes. Then, a full-scale experimental sub-assembly specimen of a representative module of the façade is subjected to uniformly distributed pressures; the setup considered the border conditions, tension loads, and actual materials. Finally, the seismic assessment phase includes a simplified non-linear procedure to calculate critical accelerations at the building roof, and shaking-table tests of full-scale specimens subjected to these demands. The proposed methodology is apply to a case study consisting on a 40-m height permeable façade of the 12-story Santafe Foundation Hospital located in Bogota (Colombia). The main conclusions of this study are: (1) the dynamic properties of the system mainly rely on the cable tensioning and mass of the system; (2) fundamental vibration frequencies of the façade are much higher than wind demands, so no wind-related amplifications are expected; (3) the façade porosity avoids that high wind pressures may be developed; and (4) for design level earthquakes no major damage is expected. Overall, results show an appropriate performance of this type of façades.

Gypsum efflorescence on clay brick masonry: Analysis of potential efflorescence origins

Gypsum efflorescence on clay brick masonry is a growing problem, leading to a persistent grey-white staining of masonry facades. Gypsum efflorescence has been reported in the United Kingdom, the Netherlands and Belgium, with a specific occurrence on masonry facades erected over the last few decades. This article investigates the origin of this recent occurrence of gypsum efflorescence, with accelerated testing of the gypsum efflorescence sensitivity of separate and combined masonry components. It is demonstrated that both brick and mortar may provide a gypsum source, respectively, via the dissolution of anhydrite and the carbonation of ettringite. Neither does however directly result in gypsum efflorescence, as the released gypsum commonly subfloresces below the brick surface. The efflorescence is instead triggered by mortar admixtures, the application of which has indeed risen strongly in recent decades. Avoiding gypsum efflorescence on clay brick masonry hence requires an inert alternative for the mortar admixtures.

Liquid moisture transport in combined ceramic brick and natural hydraulic lime mortar samples: Does the hygric interface resistance dominate the moisture transport?

To reduce the energy use of the European building stock, a large potential can be found in the renovation of cultural heritage buildings. However, insulating these valuable masonry facades often increases the risk of moisture-related damage phenomena such as mold growth and frost damage. Therefore, detailed heat, air and moisture simulations are required to quantify and assess these risks. One of the unknown parameters in the simulations for historic masonries is the hygric interface resistance between the bricks and the lime mortars. Consequently, microfocus X-ray scans are performed during a capillary water absorption test on brick–lime mortar–brick samples to increase the insight into the moisture transport over the interface, dependent on the capillary pressure at the interface and the curing conditions of the mortar. The hygric interface resistance is found to be highly dependent on both capillary pressure and the curing conditions of the mortar. For the exact quantification of the interface resistance, highly detailed moisture transport and moisture storage properties of the brick and mortar are a prerequisite.

The effects of wind-driven rain on the hygrothermal conditions behind wooden beam ends and at the interfaces between internal insulation and existing solid masonry

An inevitable measure when energy retrofitting historic buildings in Europe, is the reduction of building envelope heat loss. On preservation-worthy facades where external insulation is not an option, installation of internal insulation is gaining pace. The historic buildings in Denmark are often constructed with solid masonry facades and wooden decks. The internal insulation may, however, entail potential hygrothermal risks in walls and embedded wood. Measures such as vapour barriers and capillary active insulation materials are continuously evolving and the subject of much current research. The hygrothermal conditions are of great importance for the durability of the building constructions, and for the health and wellbeing of occupants. Wind-driven rain (WDR) is a central factor contributing to water penetration and moisture loads of the exterior walls. Numerous studies have shown that WDR loads influence the moisture conditions in masonry walls and embedded wooden beams, and can even affect interior relative humidity. In the present paper WDR loads on existing façades in a cold temperate climate were determined by measurements and compared to a semi-empirical model. Simultaneously, the hygrothermal conditions within internally insulated walls with exposed brick and embedded wooden beams were monitored. Furthermore, numerical simulations were implemented for clarification of WDR impact. Hygrothermal simulations and previous studies, inevitably show that high WDR loads result in higher moisture content behind the interior insulation. Results from the field measurements of WDR however, cannot directly be referred to the moisture content measured in walls behind interior insulation or beam ends. However, fluctuations in external air humidity proved to be influential on condiditons in the construction. Implementation of a semi-empirical model for calculations of WDR agreed with previous studies in predictions being too conservative when compared to measured WDR.