Typical Masonry Research Articles

Experimental Evaluation of Shear Behavior of Stone Masonry Wall.

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

Creating the finite element mesh of non-periodic masonry from the measurement of its geometrical characteristics: a novel automated procedure

This paper presents an automated procedure that enables the creation of a finite element mesh directly from the image file representing the rasterized sketch of a generic masonry element. This procedure goes under the name “pixel strategy” if a 2D finite element mesh is needed, where the elements are planar and rectangular; conversely, its extension in the 3D case is named “voxel strategy”, and there the resulting finite elements are solid bricks. The finite element meshes so obtained are then used for extracting homogenized in-plane failure surfaces for historical masonry cells, which display a non-periodic arrangement of units. These surfaces are consistent with the expected results, and their shapes suggest that the behavior of such type of masonry may range between orthotropic (if bed mortar joints are clearly noticeable) and quasi-isotropic (if some units spread over two or more masonry layers).

Experimental Study on Basic Mechanical Properties of Core-Column Non-mortar Aerated Concrete Block Masonry

Autoclaved aerated concrete (AAC) block masonry has been widely used for bearing walls of multi-story buildings or non-bearing walls of high-rise buildings because of its unique advantages, such as lightweight, low pollution output, and excellent thermal insulation performance. However, traditional AAC block masonry has the disadvantages of high water absorption, poor adhesion to mortar, and low construction efficiency. In order to improve the performance of traditional AAC masonry, this paper proposed a new kind of mortar-free AAC block masonry with concrete core-columns. Fundamental mechanical properties of compression and shear were studied. We divided a total of 16 compression specimens into four groups according to different hollow ratios and strength grades of the block, and eight shear specimens into two groups based on different hollow ratios. Each specimen consists of three-layer blocks with two core columns at the point of quadri-section. The diameters of columns were, respectively, 100 mm and 80 mm. The specimens were loaded at a constant speed to evaluate their bearing capacity, displacement response, crack development, and damage state. The formula of the average values and design values of the compressive and shear strength of masonry were obtained statistically. The stress–strain constitutive relation of masonry expressed by a three-stage curve was presented. Furthermore, the result of numerical analysis using the ABAQUS finite element program aligned well with the experimental results. The compressive strength and shear strength of the new type of masonry are no less than traditional AAC masonry, and new masonry has higher construction efficiency and more stable strength.

Nonlinear static and dynamic analyses of Costa Rican reinforced concrete masonry structures

In Costa Rica, typical dwelling constructions are generally built with reinforced concrete masonry walls. This construction practice became one of the most common during the second half of the last century in Costa Rica. These kinds of structures exhibit high lateral stiffness and shear capacity, which makes them susceptible to semi-ductile failure or torsion if they are not correctly designed and constructed or the walls are not well distributed. However, recent research has shown that this type of masonry exhibits adequate capacity to dissipate plastic energy if the latter requirements are controlled. In this study, the seismic behavior of a recently designed and built reinforced concrete masonry structure is studied from a probabilistic perspective. Experimental results have been used to calibrate the probabilistic model. This structure was designed using the response spectrum method according to the Costa Rican Seismic Code. To verify its expected behavior considering more advanced analysis, it is analyzed through probabilistic incremental nonlinear static and dynamic computational-based methods. The aim is to obtain probabilistic damage curves in a series of permutations between the mechanical properties and the nonlinear behavior of the walls. Three different Damage Indices are estimated. Specifically, the Park & Ang damage index is used as a reference for two approximations that employ the capacity curve as input. Results indicate that the behavior of the analyzed structure is suitable for the seismic demand provided by the Costa Rican Seismic Code. Finally, correlations between input and output variables are calculated to analyze what are the variables governing the structural response. A strong relationship between masonry compression strength, Young’s module, and the post yielding slope (input variables) and all the output variables has been observed.

The September 7, 2017 Tehuantepec, Mexico, earthquake: Damage assessment in masonry structures for housing

Mexico is located among five tectonic plates. Therefore, it is frequently disturbed by the action of several moderate and strong earthquakes, affecting both the population and its infrastructure. The origin, causes, and effects of the typical observed damage patterns during the September 7, 2017 Tehuantepec earthquake (Mw = 8.2), in masonry houses and apartment buildings, located in cities and towns of the Mexican states of Chiapas and Oaxaca in a radius of about 250 km from the epicenter are reported and discussed in this paper. The high structural vulnerability and the severity of the earthquake resulted in the death of 96 people and more than 110,000 houses damaged, where more than 41,000 were considered total losses (collapse, beyond repair or tagged for demolition). In order to analytically evaluate the seismic vulnerability of typical masonry structures ranging from one to five stories, displacement ductility demand spectra (DDDS) were computed for both earthquake ground motions records and artificial acceleration records for a wide range of base shear capacities. Special attention is given to relate the observed damage with conditions of structural irregularity. Effects of flexible diaphragms, structural pounding between adjacent structures and site effects are also addressed. From the information presented, it can be concluded that most of the observed typical damage it is mostly due to poor design, inadequate construction processes, poor quality of construction materials and low wall density ratios. Finally, it was clearly observed that DDDS is a useful tool for the simplified seismic vulnerability assessment of a large portfolio of existing structures under a given earthquake scenario.

Reflection on earthquake damage of buildings in 2015 Nepal earthquake and seismic measures for post-earthquake reconstruction

On April 25, 2015, a M8.1 earthquake happened near Pokhara, Nepal, and aftershocks occurred continuously which caused significant losses. In November 2015, the authors made an in-depth investigation on the earthquake damages of various engineering structures in Nepal. As the post-disaster reconstruction work has not been completed, up to this day, the current reconstruction work is still worthy of continuous attention. Firstly, the earthquake damage of typical frame and masonry buildings in Nepal was described and the causes of damage were analyzed. The reinforcement measures and suggestions were putted forward for post-earthquake reconstruction, which focused on the load transmission path of the structure, the enclosure structure, the beam-column joints, the integrity of the structure, house site selection and structural stiffness.With the help of the finite element software, the numerical modeling analysis of the wall reinforcement measures and a typical reconstruction house was carried out. The results show that the seismic performance of masonry wall can be greatly improved after being wrapped by reinforced concrete or seismic band, the use of seismic band in reconstruction of typical houses in Nepal can effectively improve the seismic performance of buildings. The surrounding areas of door and window openings are still the most vulnerable places to be damaged. Reinforcement should be strengthened in these locations.

Nested Buildings: An Innovative Strategy for the Integrated Seismic and Energy Retrofit of Existing Masonry Buildings with CLT Panels

The Italian building heritage is aged and inadequate to the high-performance levels required nowadays in terms of energy efficiency and seismic response. Innovative techniques are generating a strong interest, especially in terms of multi-level approaches and solution optimizations. Among these, Nested Buildings, an integrated intervention approach which preserves the external existing structure and provides a new structural system inside, aim at improving both energy and structural performances. The research presented hereinafter focuses on the strengthening of unreinforced masonry (URM) buildings with cross-laminated timber (CLT) panels, thanks to their lightweight, high stiffness, and good hygrothermal characteristics. The improvement of the hygrothermal performance was investigated through a 2D-model analyzed in the dynamic regime, which showed a general decreasing in the overall thermal transmittance for the retrofitted configurations. Then, to evaluate the seismic behavior of the coupled system, a parametric linear static analysis was implemented for both in-plane and out-of-plane directions, considering various masonry types and connector spacings. Results showed the efficiency of the intervention to improve the in-plane response of walls, thus validating possible applications to existing URM buildings, where local overturning mechanisms are prevented by either sufficient construction details or specific solutions.

The Tuscany Masonry Database Website

The Tuscany Masonry Database (TMDB) is an online database containing the results and the complete experimental data of in situ experimental tests carried out on masonry panels of masonry buildings located in the Tuscany Region (Italy), starting from 1990. The results can be freely downloaded by users after registration on the site. To date, the TMDB includes 142 georeferenced tests, comprising 50 diagonal tests, 5 compression tests, and 87 flat-jack tests. In addition, there are tests on the components, such as compression tests on blocks, penetrometric testing on mortar, macroscopic or microscopic analysis of mortar, and coring. The results are supported by a qualitative description of the masonry texture and are compared with the reference values of the mechanical characteristics proposed by the Italian Building Code. The data come from scientific literature and are the result of collaborations between the Seismic Sector of the Tuscany Region and some Tuscan University Laboratories, or they are shared by private test laboratories mainly acting in Tuscany. The TMDB was developed and is constantly updated by the authors to provide support to researchers and freelance engineers in the knowledge process phase of masonry buildings, as well as for that of particular structures, such as heritage buildings. Furthermore, it allows for the filling of the lack of particularity of masonry classification and for the consideration of particular masonry types existing in local areas, for which there are no literature data or specific experimentation. Further tests are currently being processed to be included in the database, and divulgation activity on the project is foreseen. Furthermore, national and international collaborations are underway for the expansion of the database, with the aim of unifying test procedures and updating the codes.

Seismic protection of unreinforced masonry buildings by means of low cost elastomeric isolation systems

Thousands of rural houses in developing countries with high seismicity were built without adequate seismic protection due to economical reason. This paper discusses a possibility to improve the seismic protection of typical unreinforced masonry in developing regions using low cost base isolation devices. The proposed isolation system involves fibre reinforced elastomeric isolators (FREIs) having small dimensions and few layers of rubber pads to reduce the fabrication cost. A series of 3D FE simulations are carried out to investigate the performances of the proposed FREIs utilised in the isolation of a one story masonry house prototype. The model is assumed subjected to several accelerograms to have an insight into the sensitivity of the isolation system against different earthquakes. The results reveal that the proposed low cost FREI system provides significant damage mitigation to the masonry house with good applicability of the FREI devices.

Response surface-based model updating to detect damage on reduced-scale masonry arch bridge

Response surface (RS) methods, a combination of mathematical and statistical techniques, have been widely used in design optimization, response prediction, and model validation in structural engineering systems. However, its usage in structural damage identification, especially for historic structures has not been quite common. For this purpose, this study attempts to investigate damage detection in a masonry arch bridge. Within the scope of this, a reduced-scale model of a one span historical masonry arch bridge was built in a laboratory environment. To determine the modal parameters of the reduced-scaled bridge model, operational modal analysis (OMA) was performed under ambient vibrations. Signals originated by sensitive accelerometers were collected to quantify the vibratory response of the reduced-scaled model bridge. The experimental natural frequencies, mode shapes, and damping ratios resulting from these measurements were figured out by using the Enhanced Frequency Domain Decomposition (EFDD) technique. The three-dimensional model of the reduced-scale bridge was created in the ANSYS finite element (FE) software program to expose the analytical dynamic characteristics of the bridge model. The results obtained in the experimental application were compared with those of the finite-element analysis of the bridge model. The calibration of the numeric model was utilized depending on the experimental modal analysis results of the reduced-scale bridge by using the RS method. Design of experiments was constructed by using central composite design, and the RS models were generated by performing the genetic aggregation approach. The optimum results between the experimental and numerical analyses were found by using the RS optimization. Then, regional damages created on the scaled model and the changes of dynamic properties of the damaged case were evaluated. The damage location was approximately identified by using the RS method in the calibrated finite-element model. The results demonstrated that the RS-based FE updating approach is an effective way for damage detection and localization in masonry type structures.

Experimental Study on the In-Plane Seismic Performance of a New Type of Masonry Wall System

The authors developed two types of block systems consisting only of main block and key block without joint mortar to improve the seismic performances and to enhance the workability. Two types of block systems have different key block shapes: one is the peanut shape, and the other is the dumbbell shape. The proposed block systems have a half-height difference between the main block and the key block to significantly improve seismic performance compared to typical masonry walls with joint mortar. In this study, in order to evaluate the in-plane seismic performance of the proposed block systems, two types of block walls are experimentally investigated, including the typical block wall. In the tests, three full-scale, single-story specimens are tested under in-plane cyclic loading, and failure patterns and cracks are carefully observed. In this paper, the in-plane loading bearing capacity, energy dissipate capacity and reuse ratios of block walls are discussed in detail. As a result, the deformability, energy absorption capacity and reuse ratio of the proposed block systems were considerably higher than those of a typical block system.

Inherent Adaptive Structures Using Nature-Inspired Compound Elements

Biomimicry studies have attracted significant attention in research and practice, leading to effective engineering solutions to develop new types of structures inspired by natural systems. The objective of this study is to employ natural structures' inherent adaptivity under changing loading conditions. Three new types of compound elements are proposed that are able to improve the structure load-bearing capacity through passive inherent adaptivity. A self-centering system, inspired by the human spine, which comprises a column pre-stressed through cables, is employed as a kinematic isolator. A similar self-centering system is applied to increase the load-bearing capacity of unreinforced masonry columns. An axially loaded element, inspired by the bamboo stem, which comprises a steel core reinforced by a series of cylindrical plates that are encased in a steel tube, is employed to control the onset of instability in long-span truss structures. Application to typical frame, masonry, and truss structures is investigated through finite element analysis. Results show that the proposed compound elements are effective to increase the structure load-bearing capacity and to reduce the response under seismic excitation owning to their inherent adaptive features.

CAPACITY ASSESSMENT OF ANCIENT MASONRY ARCH BRIDGE: A CASE STUDY

Most masonry arch railway bridges in the world are servicing the communities well beyond their intended design lives. However, these bridges would have undergone numerous deteriorations over the period of several decades of service life. The asset owners of these bridges are confronted with the decision over whether to continue servicing or decommissioning these bridges. Such decisions are critical from safety and economic points of views, and it can be addressed only by conducting a proper investigation of such structures. This paper presents the capacity assessment of typical in-service masonry arch bridges based on properties of masonry obtained through core testing. The bridges were modeled and analyzed for the ultimate capacity through limit state analysis method. Important parameters such as influence of backfill properties, strength of masonry, and span-to-rise ratio are discussed. The results indicate that the investigated bridges can sustain the current operating loads with a reasonable margin of safety index.

The Failure of Masonry Walls by Disaggregation and the Masonry Quality Index

The visual method for assessment of the structural behaviour of historic masonry walls, known by the acronym MQI (Masonry Quality Index) was introduced in 2002 by a team of researchers from the University of Perugia, Italy. This is based on a visual survey of the faces and the cross section of a wall panel, and it aims at verifying if a wall complies with the “rules of the art”. Based on this analysis, it is possible to calculate a numerical index: numerous tests, carried out on site by the authors to validate the method, have demonstrated that the index is able to provide useful information about the mechanical characteristics and structural response, in general, of the analysed wall panel. The failure mode of a wall panel under the action of an earthquake is a critical aspect. In general, the failure modes can be categorized in two classes: masonry disaggregation and the development of a local or global mechanism of wall elements (macroelements). Several theoretical models and numerical simulations only consider the latter. In this paper, application of the MQI method is further investigated, with particular emphasis to those masonry typologies which are more prone to collapse by disaggregation during a seismic event. Under the action of an earthquake, some types of masonry are typically unable to deform and to split in macroelements, and another type of failure occurs: this is the so-called “masonry disaggregation” or “masonry crumbling”. This type of failure anticipates the ones resulting from macroelement methods or stress analysis. As a conclusion, these latter methods become completely inappropriate and potentially hazardous, as they overestimate the seismic capacity of the building under investigation. The MQI method has been adapted to assess the structural response of different types of masonry under the action of an earthquake. In detail, the aim was to verify when the phenomenon of masonry disaggregation is likely to occur.

Rubble Stone Masonry Buildings With Cement Mortar: Design Specifications in Seismic and Masonry Codes Worldwide

Nearly 325 seismic and masonry codes from all over the world have been analyzed, of countries where stone masonry was, or still is, abundantly practiced. This paper compares and summarizes design specifications and construction requirements, with a specific focus on “nominally reinforced rubble stone masonry (NRM) with cement mortar and wooden diaphragms in seismic areas”. Currently, the technique is only allowed and described in some detail in the codes of Nepal, India, China, Tajikistan, Georgia, Iran and Croatia. It is concluded that the design specifications vary greatly without any consensus on the main sizes, dimensions or details. This raises questions about the completeness and correctness, as well as the reliability and actual value of the knowledge in this field. It is further observed that types of stone masonry and stone properties are seldom clearly described in the codes. It is also noted that several countries where stone masonry is still broadly practiced, are currently not allowing the technique (or have no codes in place), such as Afghanistan, Pakistan, Bhutan, Azerbaijan, Kyrgyzstan, Morocco, Tunisia, Turkey, Yemen and Albania. This, however, does not serve the current engineering practices and construction needs in these countries. To address all shortcomings, the paper recommends clear descriptions and terminology; the international adaption of NRM as a fourth masonry category; and the development of a stand-alone code specifically for this technique. Therefore, the authors propose a full assessment, validation, optimization and complementation of the existing knowledge, by means of the current state-of-the-art for calculating, testing and modeling. This envisions a structured research approach with focus on vernacular and traditional construction techniques, called “Non-Engineered 2.0”, for which a research initiative is started under the name “SMARTnet”, meaning “Seismic Methodologies for Applied Research and Testing of non-engineered techniques”. The findings of this paper will serve as the starting point for the upcoming follow-up paper, which will complement the seismic demand with hand-made base shear calculations for countries that still allow the technique. The paper ends with an appeal to experts, academics and final-year students worldwide, to exchange their knowledge and to support the project with their time and expertise.

Analysis of uniaxial compression behavior of hollow concrete block masonry: experimental and analytical approaches

This article focuses on the uniaxial compression behavior of concrete hollow brick masonry assembly. This study was performed both by experimental and analytical approaches. In the first experimental part, the compression tests were done according to the European standard EN1052-1. It is highlighted from the tests that this concrete hollow brick masonry is a very high dispersive material and that the compression behavior of this masonry is similar and depends principally on that of bricks. In addition, the vertical splitting failure modes reflect the effect of "expanding/restraining" for this type of masonry and the elastic properties determined from these tests are comparable with the values found in the literature. Then, in the analytical approach, the simple calculations were done by different existed models to predict the compressive strength of masonry prism. A comparison of the results obtained by using these models with those of experimentation shows that only the model which takes into account the effect of vertical joints is mostly adapted for the safe design of this masonry prism under uniaxial compression load.

Analysis of uniaxial compression behavior of hollow concrete block masonry: experimental and analytical approaches

This article focuses on the uniaxial compression behavior of concrete hollow brick masonry assembly. This study was performed both by experimental and analytical approaches. In the first experimental part, the compression tests were done according to the European standard EN1052-1. It is highlighted from the tests that this concrete hollow brick masonry is a very high dispersive material and that the compression behavior of this masonry is similar and depends principally on that of bricks. In addition, the vertical splitting failure modes reflect the effect of "expanding/restraining" for this type of masonry and the elastic properties determined from these tests are comparable with the values found in the literature. Then, in the analytical approach, the simple calculations were done by different existed models to predict the compressive strength of masonry prism. A comparison of the results obtained by using these models with those of experimentation shows that only the model which takes into account the effect of vertical joints is mostly adapted for the safe design of this masonry prism under uniaxial compression load.

Improving thermal resistance of lightweight concrete hollow bricks: A numerical optimisation research for a typical masonry unit

Heat loss/gain through the walls accounts for about 30% of the total building energy losses. Bricks are indispensable parts of buildings as a very common masonry wall unit; hence the present work aims at optimising thermal resistance of lightweight concrete hollow bricks through a CFD based numerical research. The optimisation is conducted over a certain number of independent variables such as hollow geometry and design, number of hollow rows across the heat transfer path and hollow depth for natural convection aspects within the hollow enclosure. A reliable CFD software ANSYS FLUENT 18.1 is utilised in the research. The accuracy of the CFD results is justified first through the reference model brick (RMB). Overall heat transfer coefficient (U-value) of RMB is determined to be 0.916 W/m2. K, which is in good accordance with the manufacturer’s data report (0.9 W/m2.K). Following this, parametric research is carried out for various scenarios to optimise the U-value as a function of brick mass. Based on the findings, the maximum improvement is found to be about 53% (U-value 0.43 W/m2. K) through the case of B48 which has an h-ratio of 1 (continuous hollow from top to bottom). Moreover, depending on the increase in h-ratio, it is achieved that the thermal performance of the bricks proportionally increases. The minimum weight of the brick design (B45) is found to be 7.645 kg and the corresponding U-value is obtained as 0.44 W/m2. K.

Masonry structures subjected to tsunami loads: Modeling issues and application to a case study

Tsunamis are among the most dangerous natural disasters for coastal areas experiencing tsunami hazard. One of the major concerns in the assessment of strategies for the risk mitigation is to estimate vulnerability of structures and infrastructures. However, reliable approaches for the evaluation of the structural capacity under tsunami loads are nowadays not always available for all the types of structures, especially masonry. On this aim, the paper deals with the modeling issues of 3D masonry structures subjected to tsunami loads and the effect on the structural behavior of different modeling approaches. First, a brief state of the art on the available studies is presented regarding the evaluation of tsunami forces on buildings and the studies carried out on the determination of structural capacity.Then, an advanced structural analysis software based on the Finite Element Method (FEM) is used to analyze the influence of parameters such as load type, masonry type and interaction properties type. Finally, an application on a typical two-storey masonry structure subjected to tsunami load according to the actual codes is presented and discussed, providing recommendations on the assumptions to be made for the definition of a reliable numerical model.The findings of the numerical simulations revealed that the structural response is strongly influenced by the modeling approach defined for the masonry walls in terms of interaction properties and the type of connection between orthogonal walls. Moreover, it was observed that, as for the case of seismic analysis, when local behavior governs the failure, lower structural capacity is obtained, while in the case of global behavior governing the failure, higher structural performances are provided.

Experimental pull-out tests and design indications for strength anchors installed in masonry walls

This study deals with the identification of the mechanical behavior of chemical anchors embedded in masonry walls. 108 pull-out tests are carried out in five types of masonry walls built with clay brick or vertically perforated units with cement mortar. Different parameters are taken into account: embedment depths, masonry type, anchor position (injection either in brick units or in mortar joints). The axial load capacity and the failure mode are observed for each test. The results are examined by means of elastic and plastic models assessing the efficiency of anchors installed in headers, stretchers or mortar joints. The anchors injected in mortar joints are shown to have much greater pull-out capacity than that found for anchors in bricks. Passing from 90 to 160 mm of embedment depth, a minimum increase by 40% of pull-out strength is observed. The most common failure modes are the sliding failure, which occurs for short anchors or weak masonry, and mixed sliding/cone failure, for long anchors or strong masonry. An analytical model is proposed to design anchors in order to avoid or at least to limit brittle masonry failures and to identify the field of application of uniform stress models.