Historical Masonry Constructions Research Articles

A variational-based non-smooth contact dynamics approach for the seismic analysis of historical masonry structures

A variational formulation of the non-smooth contact dynamics method is proposed to address the dynamic response of historical masonry structures modeled as systems of 3D rigid blocks and subjected to ground excitation. Upon assuming a unilateral-frictional contact law between the blocks, the equations of motions are formulated in a time-discrete impulse theorem format in the unknown block velocities and contact impulses. The variational structure of the problem to be solved at each time step is proven. On that basis, the numerical method requires at each time step to perform a collision detection that identifies antagonist contact points based on the given structural configuration, to solve a second-order conic programming problem that outputs block velocities and contact impulses, and to update the structural configuration for the solution to advance in time. As a merit of the formulation, large-scale problems can be robustly and efficiently addressed thanks to the convex setting of the time-step optimization problem. Numerical results are presented to test the computational performances of the proposed approach. Benchmark problems provide numerical evidence that the formulation is consistent with event-driven solutions based on the classical Housner impact model. The dynamic response, failure domains, and fragility functions of real-size masonry structures are then explored under ground impulse or earthquake excitation. The obtained results prove the reliability of the present computational method for the dynamic analysis and seismic assessment of historical masonry constructions of engineering interest.

An Analytical Safety Tree for Heritage Buildings: Application to the Archaeological Museum “Domenico Ridola”, Matera (Italy)

ABSTRACT Historical masonry construction is a significant architectural typology that represents the cultural identity of Western Europe. Exposure to seismic events seriously compromises the conservation of architectural heritage, as evidenced by recent earthquakes. In this context, the process of knowledge acquisition, vulnerability evaluation, and planning interventions becomes fundamentally important to identify and implement maintenance and conservation strategies. Safety trees, never used for seismic engineering purposes, are particularly effective in making safety-related decisions in potentially hazardous or complex situations. This paper proposes an analytical framework to evaluate the structural safety of cultural heritage buildings, using an analytical safety tree. This instrument is here applied to assist safety assessments, risk management, and process optimization. Specifically, the proposed tree encompasses a multi-step procedure characterized by three possible vulnerability assessments, with the advantage of providing an overview of the knowledge state, detected pathologies, and analysis of a heritage building, outlining a path to follow to ensure the safety of built heritage. The work first formalizes this new tool, starting from the classical theory of safety decision trees. Secondly, to demonstrate the potential of the approach, the decision tree is developed and applied to the safety assessment of the Archaeological Museum “Domenico Ridola” in Matera, Italy.

Effect of Textile Reinforced Mortar components on the mechanical behavior of historical masonry structures under cyclic loading

Masonry structures without reinforcement are generally considered unsuitable in seismically active areas due to their poor performance as a bracing system.Historical masonry is particularly affected by this issue. The need to find solutions to this problem has attracted the interest of the scientific community to preserve this cultural heritage.Textile reinforced mortar (TRM) has proven his efficiency to reinforce masonry structures and various researches have investigated this concept of reinforcement in the case of diagonal compression tests. Despite this, several parameters must be studied in order to optimize this reinforcement technique in boundary conditions close to seismic situation.The study presented here aimed at assessing the effect of varying the mesh size of the textile and the orientation of its threads in strengthening historical masonry constructions with testing conditions similar to those of an earthquake (cyclic tests). It also aimed to assess the influence of varying lime mortar on the reinforcement performance by using two different limes in the TRM reinforcement.The principal additional knowledge of the present work is to point out the effect of mesh orientation and mesh opening in terms of dissipated energy and in terms of delaying the debonding time of TRM (a longer time for the multidirectional EQ grid) which is the main issue in the case of TRM structural reinforcement.An increase in peak load (+110 % for RW-EQ-L2) and in the dissipated energy (+200 % for RW-EQ-L2) were hence observed during the tests. These results provide valuable information about masonry walls strengthening and repair for the scientific community.

The evaluation of the adhesion defects in FRCM reinforcements for masonry constructions by Sideband Peak Count based nonlinear acoustic technique

Fabric-reinforced cementitious matrix (FRCM) composites have emerged as reliable strengthening materials especially for historical masonry constructions. Their strengthening effectiveness strongly depends on the bond at the matrix-fibers interface and at the matrix-substrate interface; thus, the analysis of FRCM bond behavior is of crucial relevance. The strong diffusion of the FRCM composites for the reinforcement of masonry and concrete constructions requires suitable experimental techniques for assessing possible defects in the adhesion between FRCM and masonry, and between FRCM layers. To this aim, in this paper, an innovative nonlinear ultrasonic approach based on the sideband peak count technique is proposed. This approach is discussed and validated through acoustic (sonic and ultrasonic) tests performed on masonry tuff substrates reinforced with FRCM mortars embedding a basalt fibers grid and having known artificial defects at the adhesion between masonry and the reinforcement as well as in the fiber grid.

Investigating the historical building materials with spectroscopic and geophysical methods: A case study of Mardin Castle

Today, the building materials form the historical buildings are being exposed to various deteriorations increasingly due to different causes. Many historical masonry constructions in the world are on the edge of extinction due to the increasing frequency and changing models of material deterioration. The materials as close as possible to the original materials in terms of their chemical compositions and physical properties are required in the reconstruction and maintenance of the buildings that have historical importance. In addition, the properties of the materials used in the historical buildings are generally not known with a sufficient accuracy. This causes misapplications in case of emergencies, and also may lead to future potential greater damages on the building. The lack of data regarding the engineering properties of these buildings causes long-term damages on the buildings due to inappropriate conservation methods and materials. Therefore, it is necessary to investigate the properties of certain materials for application in the renewal of the historical buildings. Within this context, in this study the construction materials of Mardin Castle, which is located in Mardin Province, Turkey and existing for centuries as the symbol of the city, are investigated and its properties are reached. Experimental research methods were used in the study. Primarily, the castle structure was examined on-site by field study and sampling was carried out from the areas determined. The samples were analyzed via various spectroscopic and geophysical methods, and various findings were achieved. Relatively variable and high levels of salinization were determined in the findings regarding the average values in stone samples of Mardin Castle’s Fortification Walls. Results of the research document the conservation status regarding Mardin Castle and provide an experimental base and also a theoretical support for the conservation of historical buildings in Turkey; and present indicative suggestions to establish conservation schemes of the historical buildings.

Combined use of deformation and structural analysis for the structural damage assessment of heritage buildings: A case study in the Liguria region (Italy)

Cultural heritage buildings as they appear today are the result of continuous transformations occurred over the centuries. For this reason, their structural assessment should integrate structural analysis with a deep knowledge of the building history, actual geometry, damage, past alterations, and actions undergone over time. This paper presents the structural damage assessment of San Carlo Borromeo church, a historic masonry building located in the Liguria region (Italy) in a slow-moving landslide-affected area. To assess the effect of the landslide and identify the causes of the damage and deformations observed in the building, structural analysis was combined with historical research, on-site inspections, laser scanner survey and deformation analysis. A finite element model of the entire church in its geometric undeformed configuration was prepared by removing all the deformations identified through the deformation analysis from the actual deformed geometry obtained from the laser scanner survey. Nonlinear static analyses were then performed by applying at the base of the model a set of displacement fields obtained from the deformation analysis and representing the displacements experienced by the building due to the landslide and further phenomena that were found to have occurred. The damage and deformations predicted numerically were compared with those detected in the church. The good agreement proved that the deformation analysis is an effective tool to support structural analysis and assess the actual deformations and displacements experienced by historic masonry constructions.

Seismic Assessment of Historical Masonry Buildings at Different Scale Levels: A Review

The relevant losses determined by recent earthquakes stressed the vulnerability of historical masonry constructions towards horizontal seismic actions, therefore highlighting the need for reliable approaches for the structural assessment and following retrofit. During the last decades, the scientific community has widely investigated the tools to analyse the performance of such structural typologies, resulting in a multitude of different methodologies depending on the building’s features and the goal of the analysis. The task is particularly challenging because of the frequently limited knowledge concerning the state of the art and the high structural complexity due to overlapped construction phases. A general literature review of the methods adopted for the structural assessment of historical masonry buildings is proposed in the present paper. The methods are grouped according to the operational scale, providing an overview of the current state of the art.

An integrated approach for the investigation of the seismic behaviour of churches: the case study of St. Maria Maggiore in Tuscania

The behaviour of historic masonry constructions under earthquake is strictly dependent on structure geometry and masonry morphology, whose precise representation influences the robustness of the seismic assessment. In this process, a crucial role is played by the structural survey. Within this framework, the paper proposes an integrated methodology for assessing the seismic safety of churches, from photogrammetric survey to collapse mechanisms analysis. As a first step, a photogrammetric survey, both aero-photogrammetric and on the ground, is carried out and a 3D model is obtained through structure from motion software. This model allows to derive geometrical details and blocks shape and arrangement, the latter obtained through a semi-automatic edge detection technique based on orthophotos processing. The resulting geometry of the building is therefore imported in the Distinct Element code UDEC. Finally, the local collapse mechanisms are analysed, both in terms of failure development and capacity curve, by applying an automatic push over algorithm. The proposed integrated procedure is performed to the Romanesque Church of St. Maria Maggiore in Tuscania - Italy.

Seismic Vulnerability Evaluation of a Historical Masonry Tower: Comparison between Different Approaches

Throughout the last few decades, the scientific community has paid great attention to the structural safety of historical masonry constructions, which have high vulnerability with respect to seismic activities. Masonry towers are very widespread in Italy and represent an important part of the built heritage to be preserved. Different numerical methods with different levels of refinement were developed in the literature to evaluate their seismic performance. The present study shows a practical application of the seismic vulnerability evaluation of a masonry tower using different approaches. The aim is to provide practical suggestions to engineers for the successful evaluation of the performance of masonry towers under seismic loads. An in situ survey was performed to characterize the geometry of the structure and its constitutive material. All the collected information was introduced in a building information model, later used to generate different finite element models for the structural analyses. The global capacity of the structure was evaluated using three different models with different levels of complexity: the first simplified model is made of beam elements with cross-sections discretized in fibers; the second model is made of shell elements and uses a concrete damage plasticity model to describe the nonlinear masonry behavior; the third model adopts solid elements with a concrete smeared crack constitutive law. A preliminary eigen-frequency analysis is performed on the shell model to obtain some basic information about the structural behavior. Nonlinear static analyses were carried out for each model to understand the response of the tower under seismic loads, highlighting the main differences between the approaches. The behavior factor was evaluated on the basis of the analyses results and compared with the ones suggested by the Italian building code. The results showed that the towers do not satisfy the seismic demand required by the standards for all the considered models. Furthermore, the behavior factor calculated according to the Italian design code is overestimated, while the one evaluated by the simplified model is underestimated due to the neglection of the shear behavior. From all the analyzed configurations, the shell model resulted as a good compromise between reliable results and computation efficiency.

Experimental study on the bonding behavior of post-embedded steel bar and brick masonry

Post-embedding of steel bars into mortar joints of unreinforced masonry walls is a widely used strengthening technique in historic masonry construction. Despite its widespread use, limited research is available on the effectiveness of this technique for improving the bonding performance of post-embedded steel bars. In this study, the bond-slip relationship for bars embedded in mortar joints was investigated. The masonry specimens were built using mortar with a strength of 5 MPa, and then reinforced with 5, 10, 15, and 20 MPa mortar and plain steel bars 6 and 8 mm in diameter, and a series of pull-out tests were performed on these specimens. By analyzing the bond strength between the post-embedded steel bars and brick masonry, the bond failure modes, and the bond-slip curves, a typical bond-slip curve and bonding parameters were obtained. The effects of the mortar strength, steel bar diameter, and bond length on the bond strength were discussed, and a mathematical expression for the bond strength between the post-embedded steel bars and brick masonry was presented. In addition, the relationship between the bond strength and the slip distance of the steel bars was obtained, and the interfacial bond fracture energy was analyzed.

Thermography Investigation and Seismic Vulnerability Assessment of a Historical Vaulted Masonry Building

Typically, historical masonry constructions were only designed due to gravity loads. The structural detailing, aimed at improving the seismic performance, was introduced thanks to the advancement in performance-based seismic design approaches in recent decades. In this context, the vaults play a key role. Depending on the construction technology, material, shape and constraints, the vault can modify the load patterns both in static and/or dynamic conditions. Furthermore, in heritage buildings, the possible presence of frescos or decorations increase the difficulties in assessing the technological nature of the vault. Non-destructive in situ investigation techniques, such as thermography, can be a powerful tool to improve the level of knowledge with respect to structural detailing and increase the prediction capability of the numerical model. The present paper discusses the results of a large thermography campaign performed in a cultural masonry building located in the south of Italy. The extensive investigation was aimed at identifying the typologies of vaults covered by worth frescos. This peculiarity was considered in the structural analysis in order to investigate the influence of the vault typology, in terms of plan stiffness versus the global seismic vulnerability. The outcomes demonstrated that thermography was decisive in improving the level of knowledge and obtaining a more reliable prediction of the seismic response.

Investigating the Relation between Thrust Networks and Thrust Surfaces for Masonry Domes subjected to Vertical Loads: A Case Study

ABSTRACT Thrust Network Analysis and Thrust Surface Analysis are two well-established methods for studying the stability of vaulted masonry structures. Working within the framework of limit analysis and adopting the well-known Heyman hypotheses, both methods search for generalized statically admissible stress fields in historical masonry constructions. Although these two methods are sometimes considered to be linked, it is still unclear how this link can effectively be exploited from a practical standpoint. In this paper, we focus our attention on the conditions that enable establishing a proper connection between the two methods, which are based on different structural models, and we apply them to a case study, the dome of Pisa Cathedral. The analogies and differences in the results obtained are highlighted, and the feasibility in practice of a possible method combining thrust network and thrust surface is checked.

Simulation of humidity fields in aerial lime mortar

• Pioneering simulation of humidity diffusion in aerial lime mortars. • Modeling the humidity diffusion in aerial lime mortar using a model proposed to concrete. • Modeling strategy able to appropriate simulate the experimental results. • Best pair of D 1 and f boundary presenting values higher than in concrete. The structural safety of historic buildings frequently demands an advanced structural analysis. These constructions often have cultural and architectonic values and were constructed with porous materials bond with mortar. Mortar usually presents a complex composition and structural behavior. This fact supports the requirement for a meticulous analysis of the role of mortar within the scope of the structural behavior of historic masonry construction. In different parts of the world, there is a significant quantity of historic constructions comprehending binders based on aerial lime mortars. Aerial lime is one of the oldest binders discovered and used. Moisture content in aerial lime structures has an important influence on their behavior and performance. An experimental program was developed to study the humidity flux in aerial lime mortar including the self-desiccation phenomenon. In order to simulate this drying process, a software based on a Finite Difference Method Algorithm (1D and axisymmetric cases) is used. The pioneer software used to identify the main material parameters that better fit the experimental data, considering the approach presented by Model Code 2010. The modeling strategy was firstly applied to experimental results of cylinders specimens and in sequence to experimental results of a prismatic mold. In general, the model was able to satisfactory fit the experimental results. When compared to concrete material, higher values for diffusivity and for boundary coefficient were found. For the studied specimens, the experimental and numerical results indicated reduced humidity gradient. These results are probably associated with the high porosity of the mortar.

Seismic behavior and damage assessment of two historical fortified masonry palaces with corner towers

Recent earthquakes have highlighted that historical fortified masonry constructions may suffer extensive damage, even under low-to-moderate seismic actions, and corner towers may be one of the most vulnerable structural elements. An accurate assessment of the structural seismic performance is one of the most effective tools to deeply understand and identify the main structural weaknesses of such a building typology. To this aim, the need to properly simulate the dynamic behavior of large complex masonry buildings can strongly limit the application of simplified analysis methods widely used in common practice and largely presented in the literature. The objective of this study is to provide a comprehensive numerical insight into the earthquake response and seismic vulnerability of historical fortified masonry palaces with corner towers using non-linear dynamic analyses and a macro-modelling FE-based approach, which is able to take into account the complex interactions between different macro-elements and the characteristics of the seismic action. After a knowledge phase of the geometrical and constructive features of the two palaces under study, detailed three-dimensional FE models have been developed and predictive non-linear dynamic analyses have been performed to assess damage patterns and identify the most critical macro-elements. The numerical analyses highlight that the seismic response and damage distributions are significantly influenced by the geometrical features and main dynamic properties of the two palaces. A fundamental role is also played by the interactions of the different macro-elements with the adjacent structural parts. The results of the non-linear dynamic analyses point out that the two palaces are highly vulnerable to seismic actions, highlighting the onset of possible local collapse mechanisms and recurrent damage concentrations. For both the palaces, the most critical elements are the corner towers that present remarkable cracks patterns along the height, in the connection regions with the adjacent walls, in the upper part and in the vaults. Widespread damage is also observed in the macro-elements that are characterized by high slenderness, large openings and small walls thickness, and in the large vaults of the two palaces. A clear correlation between large displacements and high values of energy density dissipated by tensile damage is generally observed for the main critical macro-elements of both the palaces. The main outcomes presented in this study may also represent a useful insight to improve the knowledge and better understand the earthquake response and seismic vulnerability of similar historical fortified masonry palaces located in the same region, providing valuable information for practical applications in seismic risk assessment and mitigation at territorial scale.

Sensitivity analysis of the hygrothermal behaviour of homogeneous masonry constructions: Interior insulation, rainwater infiltration and hydrophobic treatment

Historical masonry constructions are difficult to mimic in hygrothermal models. The material properties of the walls are often highly uncertain due to the natural origin of the aggregates and the various, manual production processes used through time. Therefore, sensitivity analyses based on probabilistic simulations are powerful tools to indicate the risks on damage in masonry constructions. Damage criteria for relevant pathologies such as frost damage, potential decay of wooden beam heads and mould growth at the interior surface are used. The assessment methods (Scatter plots, Classification trees and Sobol indices) are based on 1D Heat, Air and Moisture simulations, including realistic variations on climate parameters and wall properties. These methodologies are applied to probabilistic simulations in which a potential damage risk is expected in historic masonries. The application of interior insulation, the use of hydrophobic treatments, and the impact of potential water infiltrations through cracks are discussed. In most of these situations a high dependency of each of the damage criteria on the rain intensity, the trend of the moisture retention/liquid conductivity curve and the absorption coefficient is evident, but also additional insights are found. For example, the thermal impact of interior insulation is negligible compared to its reduction of the first phase drying potential towards the interior. For hydrophobic treatments, the risk for damage typically decreases, but in combination with a rain water infiltration rate above approximately 5% of the wind driven rain the risk on mould growth at the interior surface significantly increases.

Dynamic Identification of Tensile Force in Tie-Rods by Interferometric Radar Measurements

An experimental investigation on the accuracy of dynamically determined tensile force in tie-rods by applying the interferometric radar technique was performed. Tie-rods were used in historical masonry constructions for absorbing thrusts of arches and vaults, and the radar interferometry may represent a fast and easy non-destructive approach for the tensile force identification in the occasion of structural assessments. Laboratory dynamic tests on a cable under a known tensile force show that, provided that a suitable dynamic identification model is used, tensile force evaluations made stating from interferometric radar measurements were characterized by a very good accuracy (mean error in the tensile force estimation less than 2%), comparable with evaluations made starting from accelerometric measurements. In particular, the dynamic identification model considered is a modified version of a model proposed in the literature. The influence on the accuracy in the determination of the tensile force of some features of the experimental setup, like, e.g., the employ of corner reflectors, is discussed.

Shear behavior of single- and triple-thickness masonry panels strengthened by bed-joint structural repointing

Bed-joint structural repointing is a widely used strengthening technique in historic masonry constructions, particularly in applications where the material appearance needs to be preserved. Despite its wide use, limited research is available on the effectiveness of this technique in masonry elements of greater thickness subjected to in-plane shear loading. In the reported study, the shear behavior of single- and triple-thickness masonry panels strengthened with Near Surface Mounted (NSM) steel bars was investigated. Masonry panels were built following the material characteristics and bonding types of a reference case and tested in diagonal compression. Two lime-based mortar mixes with different compressive strength were employed to assess the effect of existing mortar quality on the strengthening technique performance. The investigated parameters were the number of courses with reinforcement in single-thickness panels, and the depth of the reinforcement and number of the faces reinforced in those of triple-thickness.The technique proved effective in improving the shear deformation capacity regardless of specimen thickness and, in panels of triple-thickness, both the eccentricity (result of reinforcing one or two faces) and depth of reinforcement were observed to significantly affect shear behavior.

Quasi-Static Nonlinear Seismic Assessment of a Fourth Century A.D. Roman Aqueduct in Istanbul, Turkey

The majority of architectural heritage consists of load-bearing masonry components made up of stone units and relatively weak mortar joints, yielding potential weak planes for masonry structures where tension and shear failures are expected to occur. Advanced nonlinear analyses are required to simulate these phenomena and predict the corresponding nonlinear structural behavior of historic masonry constructions. In this context, this paper presents a model of a stone masonry Roman aqueduct (the Valens Aqueduct), constructed in the fourth century A.D. in Istanbul, Turkey, to explore the seismic capacity and behavior using the discrete element method (DEM). The employed modeling approach comprises distinct rigid blocks interacting along their boundaries based on the point-contact hypothesis. Thus, the discontinuous stone skeleton of the masonry aqueduct is represented explicitly in the computational model. First, a validation study was conducted on the laboratory experiment to demonstrate the capabilities of the adopted modeling approach. Then, a discontinuum model representing the Valens Aqueduct was used to assess the seismic capacity of the structure under gradually increasing lateral forces. The numerical simulations gave insight into the structural response of the aqueduct from the elastic range to total collapse. Additionally, parametric research was performed considering joint properties, namely the joint tensile strength, contact stiffness, joint friction angle, and compressive strength of the masonry, to quantify the effects of contact parameters on the displacement response of the DEM model. Further inferences were made regarding the modeling parameters, and practical conclusions were derived.

Possibility of Using Microwave Radiation for Rehabilitation of Historical Masonry Constructions

In the last years, there has been a growing demand for renovations and redevelopment of older buildings that do not meet today's building standards. A very common problem is the insufficient, damaged or completely missing waterproofing of buildings, which leads to water (or moisture) penetration into the structure of the building, but there are several possibilities to disseminate moisture into structures. Many rehabilitation methods require mechanical intervention into the structure of the building, but we mustn’t forget the structures where these procedures cannot be used, specifically objects with a rich historical value, that are protected by the National Heritage Institute.This article is focused on suitability, functionality and possibilities of using a non-destructive method of drying historic masonry with microwave radiation. First the method of microwave drying is described in general, then its use in construction practice is explained. Following is a description of the experimental work carried out at the Faculty of Civil Engineering. Outcome of this work is comparison of effects of microwave drying on samples of masonry containing three different types of building materials. One of these samples is made of brick construction, which has reached the age of 350 years. At the end, the results of the experiment and the consequent suggested recommendations are summarized.

Analysis of Equivalent Diaphragm Vault Structures in Masonry Construction under Horizontal Forces

In seismic areas, masonry construction is prone to brittle failures due to the mechanical behavior of the constituent materials and to the low capacity of force redistributions. The redistribution capacity is mainly due to the presence of horizontal connections upon the walls and to the stiffness of the roof, which is typically a vaulted structure. The modeling of the global behavior of a masonry building, taking into account the accurate stiffness of the vaults, is a major issue in seismic design and assessment. The complex geometry of the vaults can be considered as an equivalent plate, able to replicate the stiffness behavior and the force redistribution capacity of the real vault. In this study, the efforts of the authors are addressed to the definition of a plate, able to replace the vaulted surfaces in a global numerical model. The ideal diaphragm is considered as a generally orthotropic plate with the same footprint and the same thickness of the original vault. An extended parametric study was conducted in which the mechanical and geometrical parameters were varied, such as the vault thickness, its dimensions, the constraint conditions, and the possible presence of side walls. The results are presented and discussed herein, with the aim of providing useful information to the researchers and practitioners involved in seismic analyses of historical masonry construction.