Behavior Of Masonry Structures Research Articles

A contact-based constitutive model for the numerical analysis of masonry structures using the distinct element method

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.

Earthquake Performance Analysis of a Masonry School Building's Retrofitted State by the Equivalent Frame Method

Nonlinear analyses of masonry structures are frequently used in both engineering practice and academic studies. Due to the dominant nonlinear behaviour of masonry structures, complex and extensive finite element models are required to obtain accurate analysis results. While masonry walls are usually modelled using fine-meshed shells or solid elements in such structures, high computing power in modelling, analyzing, and post-processing results is necessary for the analyses of large structures. In recent years, the equivalent frame method, as a solution to this problem has been developed and presented in the literature. In this study, the equivalent frame method is used in a masonry structure modelling, and the axial force-bending relationship is represented by force-based fiber elements. The multi-linear load-deformation relationship reflects the shear behaviour of the walls. Within the scope of the study, an existing masonry school building is modelled using the equivalent frame elements with OpenSees software. Seismic performance analyses are done considering the existing and retrofitted states of the structure, and the results are discussed in a comparative manner.

A territorial scale analysis based on a map-oriented database for the out-of-plane seismic behaviour of masonry structures

A territorial scale analysis based on a map-oriented database for the out-of-plane seismic behaviour of masonry structures

Different Soil-Structure Interaction Modelling Strategies for Seismic Analysis of a Masonry Church

ABSTRACT Masonry structures can be damaged different external reasons such as war, flood, earthquake etc. For protecting and transfer to the next generations, these structures can be examined detailed. Finite element analysis has generally been used for the seismic evaluation of masonry structures. The fixed base assumption has been used in traditional finite element analysis of masonry structures. Interacting with the surrounding soil and structure was generally ignored. The seismic behavior of masonry structures is significantly influenced by the soil-structure interaction (SSI). There are various soil structure interaction modelling strategies in the recent studies. In this paper, the dimensions, mechanical properties and material model of the soil are considered constant. One of them had no soil-structure interaction. The others, roller support case, fixed support case, absorbing boundary case, free field columns and Winkler supports. Variations in the seismic response of a historical masonry church were investigated using 4 different SSI models and a fixed base (SSI ignored) model. Nonlinear time history analyses were employed for the finite element analysis. The soil borehole provided the material characteristics of the surrounding soil. According to the analysis results, higher response amplitudes were obtained when SSI was considered.

Thermal behavior of dry-cast concrete blocks masonry walls at elevated temperatures

This study aims to contribute to a better understanding of the behavior of masonry structures in the event of a fire, addressing a critical gap in both local and international standards and design guidance. Particularly in Brazil, the widespread adoption of structural masonry contrasts with the absence of national standards for evaluations at high temperatures, mainly due to the scarcity of research on the subject, potentially leading to severe consequences for life safety and property losses. This paper addresses a comprehensive study on the thermal behavior of dry-cast hollow concrete blocks masonry at high temperatures. The study combines both experimental and numerical analyses and involves underexplored topics, including characterization of thermal properties at elevated temperatures of commonly used blocks, post-fire condition of masonry's components, and determination of isotherms in the masonry cross-section in scenarios with one or both faces of the wall exposed to fire (separating and non-separating walls). Despite differences in the physical characteristics of the concrete used in block production, the temperature dependency of thermal properties obtained during experiments showed similar to that in Eurocode 2. Numerical and experimental results also indicate a low influence of block strength and mortar joints on the temperature evolution within the masonry. A key finding refers to a relatively fast temperature increase during heating due to the small thickness of the shells and webs of the blocks, thus impacting the performance of masonry structures in fire.

A New Macro-Element for Predicting the Behavior of Masonry Structures under In-Plane Cyclic Loading

A new macro model for the finite element modeling of unreinforced masonry (URM) exhibiting in-plane nonlinear cyclic behavior is proposed. The ultimate objective is to predict the seismic response of multi-story URM buildings. The macro model enables the modeling of URM shear walls with a limited number of degrees of freedom (DOF) at low computation times. The macro model consists of a deformable elastic frame supported by diagonal struts with nonlinear behavior aiming to capture all dissipative phenomena occurring during seismic events. The nonlinear constitutive behavior of diagonal struts is inspired by models documented in the literature, ensuring a robust foundation for the proposed approach. This paper first provides a comprehensive review of the principal models currently available for URM analysis. It then articulates the rationale behind the development of this new numerical model, aiming to address the limitations encountered in existing methodologies and to offer a simple and fast tool for predicting the seismic behavior of URM buildings. Afterward, the new model is presented and tested with the simulations of two experimental campaigns performed on different URM walls. The comparison between experimental and numerical results shows that with a limited number of DOF and parameters, it is possible to obtain a prediction of the experimental results with satisfying accuracy.

Structural behavior of historical Obruk Inn under different earthquakes

Masonry structures is one of the most preferred structure types throughout history. The advantageous of these structures can be categorized as longevity, affordability and easy access to materials. Due to a lack of information and constructive errors, masonry structures suffer major damage under effect of earthquakes. While the vertical load carrying capacity of a masonry structure is excellent, its performance under horizontal loads is very poor. The brittle behavior of masonry structures, in particular, causes the structure to suffer significant damage or collapse completely during an earthquake. Türkiye is situated over a major earthquake zone. Throughout history, there has been numerous major earthquakes. These earthquakes have demolished the masonry structures resulted in significant life and economic losses. Therefore, in recent days, the examination of the seismic resilience performance of masonry structures as well as the required strengthening have become a pivotal issue. Thus, the aim of this study is to analyze the seismic performance of historical Obruk Inn subjected to different earthquake effects via finite elements method (FEM). To do this, the plans obtained from on-site inspections for historical Obruk Inn to create structural FEM model and its performance was evaluated under the influence of various earthquake excitations. As a result of the analyses, it was determined that the historical Obruk Inn structure should have immediate be strengthened against a possible earthquake.

Numerical Modeling of Two Adjacent Interacting URM Structures

Masonry structures in addition to their long heritage are still widely used in civil engineering practice. It should be emphasized that a lot of research has already been done on the seismic behavior of masonry structures. However, due to the nature of such a problem, its complexity and seriousness, the development of numerical models and their connection with experimental tests are always important. This is particularly significant considering their vulnerability to the action of horizontal forces generated during seismic excitations. In recent decades, many researchers have tried to capture the behavior of unreinforced masonry (URM) structures or reinforced concrete (RC) frames with masonry infills exposed to earthquakes, using different approaches. This paper tackles numerical modeling based on the finite element method (FEM) for the estimation of the dynamic response of two adjacent interacting URM units, subjected to shaking table motions. Geometrical and material properties of the specimen are provided by the Horizon 2020 project SERA-AIMS (The Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe – Seismic Testing of Adjacent Interacting Masonry Structures). The analyses of dynamic performance were executed in SAP2000 software. Obtained results on the numerical model provide useful guidelines for modeling the nonlinear seismic behavior of masonry buildings.

Diaphragm effect of unreinforced historical masonry vaults

In historical masonry structures, and particularly in churches, vaults have a fundamental role in bearing the vertical loads of floors and roofs. However, in past earthquakes they have proved vulnerable, representing a source of fragility under horizontal loading. In addition, the global seismic behavior of masonry structures is strongly affected by the stiffness of flooring elements (diaphragm effect), which, when sufficient, allows for transfer of horizontal actions to stiffer wall working in-plane.In this paper, the diaphragm effect of historical masonry vaults under horizontal loads is investigated numerically. A parametric nonlinear Finite Element model of a cross vault is subjected to in-plane shear actions on two supports to evaluate the response and damage during an earthquake. This work is preparatory for future physical testing activities on scaled prototypes to be performed within a broader research project, aimed at the enhancement and exploitation of artistic and cultural heritage.

Complete stress-strain analysis of masonry prisms under compressive loading-unloading cycles through digital image correlation

This paper presents the findings of an experimental study focused on the behaviour of masonry structures subjected to uniaxial loading-unloading compression. The study's primary objective is to examine the impact of joint mortar on the failure mode and the development of permanent strains using the digital image correlation technique (DIC). Masonry prisms were constructed using two types of fired bricks and five different mortars, each with varying cement and lime contents. The prisms were instrumented with a linear variable differential transformer (LVDT) for displacement measurements and prepared for image processing using DIC. The prisms were then subjected to compression testing until failure to capture their complete behaviour. The experimental results obtained through DIC and LVDT measurements showed good agreement. The DIC technique proved its effectiveness in providing comprehensive strain evaluations of the brick prisms, enabling a detailed stress-strain analysis at a full-scale level. Furthermore, the study revealed that prisms with lower cement content exhibited a more ductile behaviour in the post-peak region, with strain localisation observed at the joint mortar interface.To validate DIC's reliability in characterising masonry's cyclic behaviour, the results obtained from analytical modelling were compared with those derived from DIC. This comparison aimed to confirm the accuracy and consistency of DIC measurements. Overall, this study contributes to our understanding of masonry behaviour under compression and highlights the capabilities of DIC in capturing strain patterns and providing valuable insights into the influence of joint mortar on the structural response of masonry elements.

Influence of Lime on Strength of Structural Unreinforced Masonry: Toward Improved Sustainability in Masonry Mortars

The choice of a sustainable construction material needs to take into account not just the environmental impact of the material, but according to the 2030 Agenda for Sustainable Development by the UN, one also needs to consider ease of access, the utilization of locally available materials, and the durability and reliability of the construction itself. Mortared masonry has been used around the world for several hundred years as an accessible type of construction. In masonry mortars, lime and cement are often integrated together for combined advantages: enhanced workability, breathability, and better environmental performance due to the former, and higher strength and shorter setting duration due to the latter. However, despite being extensively studied for their effects on the mechanical properties of mortar, not much is known about the impact of varying lime and cement ratios in the binder on the mechanical performance of masonry as a whole. Variations in the properties of mortars do not always have a significant impact on the mechanical behavior of masonry structures. Therefore, this article details an experimental campaign to measure the compressive strength, E-modulus, flexural strength, and shear bond strength of masonry samples containing two distinct lime–cement mortars (1:2:9 and 1:1:6 cement:lime:sand) and one cement mortar (1:0:5). The results show that more than the presence of lime in the mortar, the strength of the mortar influenced the flexural strength of the masonry ranging from 0.1 to 1.2 MPa. No discernable correlation was observed between the presence of lime in the mortar and the cohesion in the masonry (0.29 to 0.41 MPa). The values of the compressive strength (6.0 to 7.2 MPa) and E-modulus (3.8 to 4.5 GPa) of the masonry decreased and pre-peak ductility increased with an increase in the quantity of lime in the mortar. The recommendations of Eurocode 6 for the flexural strength of the initial shear bond strength were found to be conservative for different mortar strength classes, and significantly unconservative for compressive strength (by 50% to 70%).

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.

Performance criteria expressed by means of relative displacements for a retrofitted masonry school building

In order to study how retrofitting techniques applied to URM structures influence the failure modes and the displacement capacity of the buildings, a school building from Bucharest was modelled using 3DMacro software. The mixed structural system required a particular approach for the calculation model, in a software able to capture the interaction between the reinforced concrete elements (columns and tie beams) and the URM masonry panels.Damage pattern evolution was analyzed for the three models capturing the gradual seismic improvements done in the past century, transforming the unreinforced masonry structure into a confined masonry one, with few RC elements, and eventually into a fully jacketed structure with densely spaced RC columns. The results obtained from the nonlinear static analyses were validated by means of global and local displacement limits associated with specific damage criteria.The damage suffered after 1977 Vrancea earthquake and the current performance requirements in terms of seismic safety led to structural changes aimed at improving the behavior of masonry structures by means of interventions that marked the transition from an unreinforced masonry structural system to a retrofitted masonry structural system. The comparative analyses carried out between the behavior of the initial and the strengthened structure of the school intend to highlight the benefits of the retrofitting interventions performed, but also the situations in which the applied strengthening measures might prove to be excessive. Considering the case study is representative for the existing building stock in the education sector in Romania which needed subsequent seismic retrofitting in order to reach the required seismic safety, the results highlight the improved behavior after these interventions. The present works represent a topic of interest at national level, since it targets a large part of the existing building stock subjected to losses in case of an earthquake. Moreover, the past retrofitting interventions assessed in this paper represent a typical intervention done for similar structures, and therefore, the results obtained are representative for the Romanian building stock.

Effects of aspect ratios and strengthening methods on seismic behavior of masonry piers strengthened by using hybrid-fibers modified reactive powder concrete

Piers are the main load-bearing elements of masonry structures. Damage to piers in earthquakes will lead to the collapse of the whole structure, so piers need to be strengthened. In order to study the effectiveness of hybrid-fibers modified reactive powder concrete (HFMRPC) coating strengthening on masonry piers and the influence of different strengthening methods and aspect ratios on the seismic behavior of masonry structures, six masonry walls with different aspect ratios (0.8, 1.0, and 1.4) and strengthened by different methods (unreinforced, single-sided coverage in piers, double-sided coverage in piers, and double-sided cross-bracing) were tested under in-plane quasi-static loading. The test and analysis results showed that the seismic behavior of masonry walls in terms of bearing capacity, displacement ductility, stiffness, and energy dissipation was effectively enhanced by HFMRPC coating. The improvement range of ductility coefficient, initial stiffness, and cumulative energy dissipation were 86.3% ∼ 229.3%, 18.2% ∼ 104.0%, and 57.0% ∼ 139.7%, respectively. The most suitable strengthening method for strengthening piers was double-sided cross-bracing compared with other methods. The strengthening effect of the double-sided coverage in piers was improved with the increased aspect ratio. Additionally, masonry wall shear strength and flexural capacity calculation methods were proposed based on GB 50003-2011, N-M interaction diagrams, and equivalent rectangular stress block.

Evaluation of the load-bearing wall design of Edirne Old Harbiye Barracks according to the Turkish Building Earthquake Code (TBEC-2018)

The masonry construction system consists of stone, brick, and mortar, in which the wall element acts as the vertical load load-bearing and generally allows low-rise buildings. The buildings built with this system are mostly seen in rural areas today, but also in traditional and historical textures in city centers. Stone, brick, mortar, etc. used in the masonry construction system. The materials are materials with a low stretching rate but are resistant to pressure. In this case, against the driving force of a possible horizontal load source, the bearing walls will inevitably be damaged because they do not allow sufficient oscillation. In Türkiye, earthquake-resistant building design principles and calculation methods related to the behavior of masonry structures against earthquakes are guiding at this point. Inspecting the masonry structures planned and built in the past in terms of compliance with today's conditions and regulations is important for the sustainability of the structure. Making a building that has a negative profile in terms of compliance with the masonry construction rules is important for both the structure and the health of the user. In this study, the compliance of the load-bearing walls in the architectural design of the old Harbiye Barracks building, which is currently used by the Faculty of Architecture of Trakya University, to the rules regarding the wall design in the current regulation, Türkiye Building Earthquake Code 2018, is investigated. As a result of the study, it was seen that the building showed different suitability in different blocks. While the occupancy-to-space ratio of the b block on the bearing wall is better, it has been determined that the block does not fully comply with the rules.

Proposal for improving the solid clay brick contact surface to increase the initial shear strength of masonry

Under normal service conditions, masonry is mainly subjected to the action of gravity loads, however, under the action of seismic loads, masonry is subjected to the combined action of vertical and lateral forces which develops a biaxial stress state and generates considerable shear stresses at the brick/mortar joint interfaces. The work of masonry under the action of shear forces parallel to bed joints is widely studied and leading researchers in the field of masonry structures have studied the behaviour, constitutive models, failure criteria and numerical models of masonry, however there are almost not studies on the influence of the horizontal contact surface of bricks on the initial shear strength of masonry. This work proposes a slight modification of the horizontal contact surface of solid brick to increase the initial shear strength of the masonry. The experimental proposal consists of drilling superficial blind holes with a depth of 6–8 mm with an overall drilled area of 10–13% of the horizontal surface of the brick. The arrangement of the holes is such that main difference with similar proposals is that the central part of the brick remains unaltered. Experimental results show that this proposed modification of the brick increases the initial shear strength by about 45% and allows the development of the plastic deformation phase, which is an important improvement for the structural behaviour of masonry structures under the action of considerable lateral forces.

Degradations analysis and prediction methods of the mechanical behavior of masonry structures in the archaeological site Volubilis (Morocco)

The archaeological site of Volubilis is located in Morocco, 60 km from the city of Fez. It is one of the most preserved sites of a large Roman city registered in the UNESCO world heritage list. This site is composed of several historical monuments, most of which are built in masonry. These structures are composed of blocks of stones bound or not with mortar. These components have different physical and mechanical characteristics, which makes understanding the mechanical behavior, mainly the mode of failure and damage and the bearing capacity of these structures, a complex task due to their anisotropic, heterogeneous, and composite nature. The constructions built on the site Volubilis have experienced deterioration and intense degradation over time, affecting their structures due to several factors. This makes the protection and conservation of these structures paramount. The present study aims firstly to classify the types of degradations observed at the level of the existing masonry structures in the Volubilis site by giving explanations, interpretations as well as the causes of these degradations; secondly, to explain the various analytical, empirical and numerical approaches usually adopted to predict the mechanical behavior of these masonry structures affected by degradations and more precisely their modes of failure, their zones of weakness as well as their bearing capacities. The analytical and empirical approaches presented in the literature only allow us to estimate the compressive strength of these masonry structures, which have a specific geometry. In contrast, the numerical approaches will enable us to highlight the causes of degradation and predict the modes of failure and damage of these masonry structures. Three modeling techniques are used in the numerical approach: detailed micromodeling (DMM), simplified micromodeling (SMM), and Macromodeling (MM), based on the finite element method (FEM). These techniques differ from each other in their degree of accuracy.

Effects of temperature variations on the modal properties of masonry structures: An experimental-based numerical modelling approach

Long–term ambient vibration monitoring campaigns show that environmental parameters (such as temperature, humidity, wind speed and direction) can influence the structures' static and dynamic behaviour. In particular, thermal variations can affect the modal characteristics of ancient masonry constructions. This work presents a procedure combining experimental and numerical steps to monitor, assess and model the dynamic behaviour of masonry structures subjected to thermal loads. The procedure is tested and validated through two numerical examples and the simulation of a full-scale masonry structure, the Mogadouro clock tower in Portugal, monitored with accelerometers and temperature and humidity sensors.

Explicit approach for the in-plane cyclic behaviors of unreinforced masonry structures using finite particle method

Masonry structures, especially historical ones, are vulnerable to earthquakes. Their structural performance subjected to cyclic loadings such as earthquakes should be fully understood before retrofitting. This study proposes an explicit approach for analysis of the in-plane cyclic behavior of masonry structures, combining the finite particle method and an elaborated mesoscale model. The proposed approach is intrinsically dynamic, and it can deal with both quasi-static and dynamic problems in the same framework. Specifically, kinetic damping and static convergence criteria are incorporated to accelerate quasi-static analysis. In the modeling, the rigid element is proposed for bricks based on rigid-body motion assumption. The zero-thickness interface element for mortar joints is derived, and the plastic behaviors in the tension regime, shear regime, and composite regime are developed. Specifically, the strength softening, residual plastic displacement, and stiffness degradation during cyclic loadings are fully considered. A single-story masonry wall subjected to quasi-static loads is analyzed, and the crack lines and horizontal force – rotation curve agree well with those in the experiment. The behavior of a two-story masonry wall subjected to seismic loads is then investigated, and the crack pattern and the first-order frequencies before and after cracking agree well with those in the shaking table test. The results indicate a decrease of the natural frequencies as well as story stiffnesses due to fracture in the mortar joints.

Shake table tests on 1:2 reduced scale masonry house with the application of horizontal seismic bands

The safety of people's lives is crucial in structures that provide shelter. Earthquakes are a major natural disaster that have claimed thousands of lives over the years, but other factors can also cause damage to these structures. Building collapses are often due to their inability to endure the seismic loading, not the earthquake itself. Most residential buildings are masonry structures. There are many strategies for enhancing structural behavior, but very little research has been done on masonry structures, which house about 1/3rd of the world's population. This study focuses on characterization of seismic response using shake table tests to assess the dynamic behavior of masonry structures when horizontal seismic bands are applied. Horizontal seismic band is one of the traditional techniques used in masonry structure. Three reduced scale models were constructed with one using a reinforced concrete band, one with a timber band, and one without a band. All models were constructed using extruded earth block and mud mortar, common building materials in developing nations. The models were tested on a shake table using the same loading signal to compare their response behavior. A high-speed camera was also used to capture images; accelerometers and displacement sensors were installed to record the response. Digital Image Correlation (DIC), which provides non-contact optical measurement, has been essential in obtaining full-field measurement. The results showed significant improvement in the seismic response of structures with horizontal seismic bands. The behaviors are compared in terms of natural frequency, damping, energy dissipation, and crack propagation patterns using two types of materials as seismic bands.