Masonry Structures Research Articles

Case Study on Behavior of a Masonry Buildings Under Seismic Loading October 2023 Earthquake in Nepal

Abstract: This paper assesses the behavior of the corners of unreinforced masonry walls during a magnitude 5.3 earthquake that struck western Nepal on October 3 at 14:40 local time. A strong aftershock with a 6.3 Richter scale occurred immediately after the main shock at 15:06, followed by a second aftershock of 5.1 Richter scale. The epicenter of the quake was located in Bajhang district, with tremors felt in neighboring districts (Doti, Achham, Bajura, Dadeldhura, Baitadi, and Darchula), as well as in Kathmandu. According to the National Society of the Red Cross, 334 houses have been fully damaged, and 1,185 have been partially damaged. The assessment is still ongoing in the affected areas, with displaced people staying in schools or with neighbors. The response is slow due to access constraints, requiring one to two days of walking to reach the affected communities. The majority of the buildings in the affected region are constructed with masonry, most of which were formed with random or coursed stone and mud brick walls without any reinforcement. Many of these buildings were damaged or had collapsed. The cracking and failure patterns of the buildings are examined and interpreted according to current provisions for earthquake resistance of masonry structures. The damages are attributed to several factors, such as poor construction quality and workmanship. This study aims to contribute to the body of knowledge necessary for improving earthquake resilience in Nepal and similar regions around the world

Strengthening Effect Evaluation of Developed Stiff-Type Polyurea Sprayed on Masonry Beam Surface Under Static Loading in Experimental and Numerical Tests

Recently, deteriorated masonry structures aged over 30 years have shown serious structural problems. Simple and rapid maintenance plans are urgently needed for aging masonry structures. Polyurea (PU) is an effective retrofitting material for aging structures due to its easy spray application. This process saves time, reduces costs, and allows the structure to remain in use during retrofitting. However, a general PU is not suitable for retrofitting aged masonry and concrete structures due to its low stiffness. In this study, stiff-type polyurea (STPU) was selected as the reinforcement material for masonry structures. It was developed by modifying the chemical mix of general PU to improve stiffness. To evaluate the strengthening effect of STPU on masonry members under static loading, tests were conducted. The flexural load capacity of masonry beams with STPU-sprayed surfaces was assessed. Three different types of STPU applications were used to select the most efficient strengthening method. Reinforcing masonry structures with STPU allows brittle failure modes to achieve ductile behavior. This improves their structural performance under lateral stresses. The experimental data were used to calibrate FEM models for simulation. These models can be used for future parametric studies and masonry structural design.

Heritage clay brick characterization and assessment with compatible contemporary bricks for retrofitting of heritage monuments

Various mughal architecture clay brick masonry monuments were built in the Punjab state of northern India from the late 14th to late 19th centuries. Nanakshahi monuments (era of 1st Sikh Guru-Guru Nanak Dev Ji) are gigantic clay brick masonry structures constructed of lime and lime surkhi mortar (a powdered form of red burnt clay brick). Currently, this study is focused on identifying a suitable material for repairing and strengthening heritage clay brick monuments. Using the mineralogical composition of heritage Nanakshahi clay bricks (NSCB), the study compares them with contemporary clay bricks (CCB) from the same region, and then compares them to newly prepared clay bricks (NPCB), which have similar composition and dimensions to NSCB. The X-ray fluorescence confirms that the NSCB samples of southeast Punjab have an elemental composition consisting of filler SiO2 and binding elements like Al2O3, Fe2O3, CaO, K2O and MgO. The average density of ancient NSCB and CCB has been found to be similar; the ancient NSCB has a lower water absorption rate and porosity in contrast to the present-day clay bricks. The Initial rate of absorption of an ancient NSCB is quite higher. In comparison to the heritage NSCB, the CCB's compressive strength value is lower and uniaxial compression strength of newly prepared clay bricks (NPCB) of similar mineralogical composition and dimensions is comparable to that of the heritage NSCB from Punjab districts. The significance of the study is to suggest a compatible material for strengthening of heritage clay brick monuments of northern India.

Cement-Free Geopolymer Paste: An Eco-Friendly Adhesive Agent for Concrete and Masonry Repairs

This study aimed to investigate the feasibility of using geopolymer paste (GP) as an adhesive agent for (i) anchoring steel bars in concrete substrates, (ii) repairing concrete, and (iii) repairing limestone and granite masonry blocks commonly found in historic buildings. In this investigation, seven cement-free GP mixes were developed with different combinations of binder materials (slag, silica fume, and metakaolin). The mechanical properties, adhesive performance, and production cost of the developed GP mixes were compared to those of a commercially epoxy adhesive mortar (EAM). The results obtained from this study indicated that the use of GPs enhanced the bonding between steel bars and concrete substrates, achieving bonding strengths that were 19.7% to 49.2% higher than those of control specimens with steel bars directly installed during casting. In concrete repairs, the GPs were able to restore about 60.6% to 87.9% of the original capacity of the control beams. Furthermore, GPs exhibited a promising performance in repairing limestone and granite masonry blocks, highlighting their potential suitability for masonry structures. The best adhesive performance was observed when a ternary binder material system consisting of 70% slag, 20% metakaolin and 10% silica fume was used. This combination, compared to the investigated EAM, showed comparable adhesive properties at a significantly low cost, indicating the viability of GPs as a cost-effective, eco-friendly adhesive agent.

Development and Validation of a New Approach to Assess the Seismic Vulnerability of Masonry Structures Based on the CARTIS Form

ABSTRACT Rapid methodologies for seismic vulnerability assessment are crucial for implementing effective seismic risk mitigation strategies over large areas. This paper addresses data accuracy and specificity uncertainties in vulnerability indices by introducing a novel rapid methodology built upon the CARTIS form. To transition from typology identification to vulnerability analysis, the study proposes a new Informed Vulnerability Index for Structures (In.V.I.S.) calibrated upon a hybrid vulnerability index formulation based on the GNDT II level approach, and specifically tailored to fit the main CARTIS form fields. Collaboration with local experts, as required by the CARTIS form, aids in identifying representative building typologies within urban centres, informed by historical data and expert knowledge. The In.V.I.S. is computed based on the distinctive characteristics of these building typologies to accurately reflect vulnerability levels. The feasibility of this approach is proved by its application to six municipalities in the Garfagnana area (Lucca, Italy). Finally, vulnerability and fragility curves are proposed for the main building typologies, as a demonstration of the potential applications of the proposed index. Overall, this research underscores the importance of integrating local expertise, historical context and rapid vulnerability assessment methodologies to enhance the accuracy and effectiveness of seismic vulnerability assessments.

Fragility Analysis of Masonry Structures Subjected to Random Sequential Ground Motions

In this study, a fragility analysis of masonry structures is conducted using a random sequential ground motion model. Initially, the relationship between a mainshock and its aftershocks is clarified based on the physical mechanism of “source-path-local site”. Building on this, the random sequential ground motion model is developed by integrating a point-source model with a homogeneous isotropic medium model. A five-story masonry structure model is then constructed in ABAQUS (6.14), and its accuracy is validated through experimental testing. Following this, 21 sets of random sequential ground motions are generated. Using the Incremental Dynamic Analysis (IDA) method, 1260 nonlinear response samples of the structure under varying sequential ground motions are obtained, providing an insight into the fragility of the masonry structure subjected to these ground motions.

Strengthening of Masonry Structures by Sisal-Reinforced Geopolymers

The development of alternative environmentally friendly and sustainable materials in the construction industry has become a fundamental area of research. The current cementitious materials used in existing retrofitting techniques for masonry structures are unsustainable from an environmental point of view. The geopolymer, as a suitable alternative to ordinary Portland cement (OPC), has attracted interest in the last 20 years due to its environmental sustainability and improved properties compared to conventional concrete. To improve the ductile behavior of geopolymers, the adoption of fibers has been widely proposed in the scientific literature for a broad range of applications. The adoption of natural fibers can make geopolymers more advantageous based on their intrinsic environmental sustainability. The aim of this paper is to validate the performance of sisal fiber-reinforced geopolymer plaster as a strengthening material for masonry structures, which will be achieved by modeling the mechanical behavior of geopolymer samples in two different phases. The first phase accounts for the experimental results suitably obtained in the laboratory, while the second phase models the behavior of a masonry panel reinforced with geopolymer plaster using a suitable FEM model in Abaqus.

Post-disaster investigations of damage feature of buildings and structures due to several local strong winds in China during 2021–2024

Local strong winds such as tornadoes and downbursts are rare in terms of measured wind speed data due to their rapid formation and strong destructive power. Post-disaster investigations have become an important approach for rating the strength of these two kind of winds and analyzing structural failure mechanism. From 2021 to 2024, several tornadoes and downbursts occurred in China. This study delineated changes in the intensity levels of wind disasters along their paths based on on-site disaster investigations and established standards for the level of structural damage based on the extent of functional loss and repair. This study focused on the damage feature to light steel structures, masonry structures, steel-concrete structures, and pole structures, and discussed the causes of the damage from the perspectives of construction and force transmission mechanisms. In addition, this study estimated the equivalent wind speeds based on the damage feature of pole structures and metal roof claddings. To reproduce the damage process for a group of high-rise buildings, the computational fluid dynamic (CFD) technology is used to simulate the airflow distribution inside buildings under two conditions of open and closed interior doors. The investigation results can provide useful information for the wind intensity classification and rating standards in China. Meanwhile, compared with the interior doors being open or closed, closing indoor doors during strong winds can significantly reduce indoor wind speeds, which is beneficial for ensuring safety.

Study on the Settlement and Deformation Characteristics of Surrounding Rock of Loess Tunnel

There is a water culvert with masonry structure in the mountain of Hanguguan Tunnel. Soil deformation caused by tunnel excavation leads to channel cracking. On the one hand, channel water infiltration leads to loess tunnel collapse, which can easily cause engineering accidents and delay the construction period. On the other hand, it will affect the channel water supply and cause social problems. In this paper, the spatial deformation of the tunnel excavation process in the loess layer is revealed through the settlement of the vault in the tunnel, the monitoring of the convergence of the perimeter, and the force monitoring of the lining support structure of the Hanguguan tunnel, and the influence of the tunnel excavation deformation on the culvert is revealed through numerical calculation. The results show that the arch at the tunnel exit has the largest settlement deformation, the larger cumulative settlement, and the faster settlement rate, and the deformation of the culvert is small, only a millimeter. Compared with the monitoring data, the numerical simulation of tunnel excavation and the vertical settlement are basically consistent with the actual situation.

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

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

Modelado de paredes de mampostería confinada: revisión de métodos y aplicación utilizando macroelemento discreto

One of the main challenges assessing masonry structures is numerical simulation. An overview and classification of the current developments and available techniques for nonlinear analysis of confined masonry structures is presented. As an exploratory study, an application of a numerical model using a Discrete Macro Element Method was carried out. It consisted on the calibration of mechanical parameters for representing the capacity curve and damage progression of a confined masonry wall tested under quasi static cyclic load. Then a sensitivity analysis was carried out. It has been found that global behavior is well captured by the model regarding strength and deformation. However, failure mode at confining elements was not consistent with the observed damage. Calibration has been made only for one experimental test; thus, conclusions are only valid for this set of experimental results. It is considered that the Discrete Macro Element Method is suitable not only to reproduce the global behavior of complete buildings, which is its original purpose, but also it may be used to study element behavior with appropriate modifications. ILIA: Investigaciones Latinoamericanas en Ingeniería y Arquitectura, No. 01, 2024: 108-114.

Damage Analysis of 3D Masonry Structures under Explosion Shock Waves Based on the CDEM

Damage Analysis of 3D Masonry Structures under Explosion Shock Waves Based on the CDEM

Comparative analysis between continuous and discontinuous methods for the assessment of a cultural heritage structure

AbstractIn an era marked by the urgent need to ensure the safety of existing buildings according to current standards, evaluating the stability of masonry structures against hazard events has become a significant challenge. Despite the versatility and durability of masonry, structural assessments are hampered by factors such as limited information on material properties, irregular geometries, and ageing. To address this issue, numerous modelling techniques have been developed, supported by extensive scientific literature. However, significant factors related to the case study replication, such as the geometric complexity, the mechanical behaviour of masonry, the loading applications, contribute to the challenges associated with modelling procedures, including computational time, discretization procedures, and step incrementation. This paper critically discusses the most innovative modelling approaches. Specifically, it aims to compare the efficiency of the Distinct Element (discontinuous) Methods and the Finite Element (continuous) Method, both applied to the numerical simulation of a case study structure severely damaged by the 2016 Central Italy earthquake under lateral loading conditions. The continuous method is analysed using Midas FEA NX©, while the discontinuous methods are studied using 3DEC© and LMGC90© software, each with different contact conditions. Finally, the investigation highlights the main advantages and disadvantages of each method. In particular, the discontinuous method demonstrates reliability in accurately replicating failure patterns, whereas the continuous method allows for a faster model setup, making it suitable for preliminary studies on structural dynamics.

Experimental investigation of the effects of different reinforcement configurations on the shear strength of reinforced concrete block masonry

Reinforced concrete block masonry walls exhibit complex behaviour under lateral loading due to their composite nature and the interaction between their constituents, including units, mortar, grout, and reinforcement. The shear strength of reinforced masonry walls depends on various factors, including the properties of each constituent material, wall geometry, boundary conditions, and the presence of reinforcement with different configurations. International masonry design standards vary significantly in how they address the parameters influencing the shear capacity of reinforced masonry shear walls. Consequently, the predicted capacities show varying levels of conservatism when compared to experimental values. Given that masonry materials and construction practices are similar in the countries being compared, these discrepancies suggest differing interpretations of the significance of each parameter and possibly different philosophies regarding the balance between conservatism and accuracy in shear design. Therefore, this study investigated the influence of different reinforcement schemes on the shear strength of reinforced concrete block masonry (RM) assemblages with running bond. Forty-one concrete block masonry assemblages were tested under diagonal tension following the ASTM E519 to examine the effect of various parameters, namely, the presence of vertical or horizontal reinforcement, the vertical and horizontal reinforcement ratios, and the spacing and combination of vertical and horizontal reinforcement within the masonry assemblages. The behaviour of the masonry assemblages was evaluated based on the maximum shear stress and the corresponding shear strain, shear modulus, toughness, and pseudo-ductility. Furthermore, the effect of the studied parameters on the stress-strain curves, failure mechanisms, and crack propagation was assessed. The obtained maximum shear stresses of the tested concrete block masonry assemblages were compared with the nominal shear capacity calculated using codified equations of different design standards. The RM assemblages showed an enhancement in the shear behaviour, ductility, and distribution of cracks, especially when combining horizontal and vertical reinforcement. The results showed that adding vertical reinforcement improved the shear capacity of reinforced masonry assemblages by 21%, with an increase in the peak shear strain by 52%. Moreover, combining the vertical and horizontal reinforcement in the reinforced concrete block masonry assemblages increases the shear capacity by 15% with an enhancement in the maximum shear strain by 23%. The CSA S304–14, TMS 402/602–22, and NZS 4230 showed an underestimation of the actual shear capacity of masonry assemblages constructed in running bond and with vertical reinforcement by 177%, 138%, and 79%, respectively. Additionally, the results revealed the need for a re-evaluation of the above mentioned code equations that estimate the shear capacity for different configurations of concrete block masonry assemblages. The analyses aimed to provide insights into the effectiveness of different reinforcement configurations in enhancing the shear resistance of RM walls. The findings of this research contribute to the development of optimized design guidelines for reinforced masonry structures, thereby enhancing their overall seismic performance and safety.

Distinct Element macro-crack networks for expedited discontinuum seismic analysis of large-scale URM structures

Discontinuum analysis is a powerful tool for the detailed seismic assessment of unreinforced masonry (URM) structures, whose widespread use is however still mostly limited to small-scale assemblies or isolated components. Despite their unique capabilities, including the explicit simulation of separation phenomena, collapses and out-of-plane (OOP) failures that are hardly replicable using traditional continuum solutions, the high computational cost entailed by micro-to-meso-scale discontinuum modelling strategies, which are the standard approaches in applied research, presently prevent their employment for building-scale problems. The few available macro-scale discontinuum models specifically conceived for URM, on the other hand, rely on complex geometrical discretization processes that require costly manual work, as well as on less efficient deformable block formulations. In this paper, a new simplified discontinuum macro-model is presented and validated against full-scale laboratory test outcomes on walls, pier-spandrel systems and building specimens, in addition to various meso-scale numerical results, under either in-plane (IP) or OOP actions, and considering quasi-static (monotonic, cyclic) or dynamic loadings. The proposed simulation technique, implemented in a robust Distinct Element Method (DEM) framework, leverages a semi-automated Equivalent Frame discretization algorithm that idealizes masonry piers, spandrels and nodes as an assembly of interlocked rigid macro-blocks connected by a network of zero-thickness interface springs. The latter are herein demonstrated to effectively replicate URM damage at the component-level through fracture energy contact laws, providing macro-scale yet representative failure patterns, as well as adequate predictions of overall strength and deformation capacities. Results obtained show a good agreement between macro- and more sophisticated meso-scale predictions, as well as with experimental outcomes, albeit dissimilarities among measured and computed force-displacement responses – similarly to other simplified strategies – were detected as vertical overburden increases. Notably, for analogous levels of accuracy, the analysis time required by our new macro-models is up to 150 times lower than its meso-counterparts. The use of the proposed simplified strategy also enabled the satisfactory simulation of the quasi-static cyclic and seismic responses of full-scale building-scale specimens, prohibitive tasks using traditional detailed DEM models, while also being up to 10 times faster than previous deformable macro-models.

A novel deep learning-based method for generating floor response spectra of building structures

Accurately and efficiently generating floor response spectra is crucial for the seismic design and analysis of nonstructural components, and seismic analysis of equipment placed on floors. In this article, a direct spectra-to-spectra method for generating floor response spectra is designed based on deep learning algorithms. The dataset was developed using the records of 102 building observation arrays in the Center for Engineering Strong Motion Data, which included 48 concrete structures, 44 steel structures and 10 masonry structures. The procedure involves training a deep learning model (FRSNet) with the ground response spectra and easily obtained structural parameters as inputs and the floor response spectra as outputs. Analysis results show that the prediction performance of the model is good on concrete structures, steel structures and masonry structures. The proposed model has sufficient accuracy, and the prediction performance is better than that of other models compared in this article. Finally, the proposed model is validated through two numerical models, a shaking table model structure and an actual structure. Convincing results confirm the accurate prediction capabilities of the proposed method.

Computer vision-based cascade detection of peeling and cracking in masonry house walls

Self-built masonry structures are commonly used as houses in rural areas of the central plains of China. These structures pose significant safety risks due to the low level of self-building and non-standard designs. The primary type of damage to the walls of masonry houses is cracks, while the decorative layers of the walls may also experience peeling or cracking. The shapes, sizes, and surface characteristics of these damages are complex and unique to each type. To achieve fast identification of surface damage on masonry house walls, this paper proposes a cascade detection model that combines a multilevel cascade classifier with a parallel sub-segmentation network. The VGG16 neural network is used as the backbone for a multi-level series classifier. The model is trained by using a damage image set of the wall decorative layers in rural masonry houses. The classification of background and damage, as well as the classification of cracks and peels, are sequentially completed. Then, the parallel sub-segmentation model uses EfficientNet-B7 as the encoder and combines it with the U-Net framework skeleton to perform pixel-level segmentation of peeling and cracks. Finally, the output of parallel sub-segmentation networks is superimposed and fused to generate a complete image containing segmentation information of peeling and cracks. The cascade form network structure adopted in this model significantly reduces the training difficulty and enhances the model accuracy. Compared with Segformer and Deeplabv3+ network, the average IoU of the proposed method for on-site masonry wall images can be increased by 0.29 and 0.08, respectively.

Safety of reinforced AAC structures

In recent years, several failures of reinforced aerated concrete [AAC] roof panels have occurred in public buildings in the UK. In September 2023, 104 schools were closed due to this. This has sparked a pan-European discussion on the safety of reinforced AAC masonry structures. This article concerns the safety of Polish reinforced aerated concrete and foam concrete structures. The work describes the reinforced structures used in Poland in the past and present. It describes the results of tests on reinforced AAC lintels conducted at the Silesian University of Technology. Based on the test results, an analysis of the safety of reinforced structures was performed.

Improving the thermal and mechanical performance of cement-based mortars for reinforcing masonry structures: computational and experimental methods

Improving the thermal and mechanical performance of cement-based mortars for reinforcing masonry structures: computational and experimental methods

Effects on upper masonry structures caused by double-line parallel shield cutting group pile construction

The effects on the upper masonry structure and the construction parameters of shield cutting piles were studied during shield construction, focusing on a shield interval of Zhengzhou Metro Line 5. The study utilized the actual engineering case of left and right double-lane shields superimposed on cutting cement soil group pile composite foundations beneath masonry structures. Findings revealed that masonry structures within approximately 30 m (5.0 times the tunnel diameter) were impacted before and after shield cut pile construction, resulting in deflection and twisting deformations of houses along the central axes of the left and right tunnel lines. Implementation of “clay shock” grouting outside the shield shell, radial grouting through small conduits, shield tail synchronous grouting, and secondary reinforcement grouting effectively mitigated the disturbance caused by shield construction to the ground. When shield cut piles passed beneath masonry structures, pressure on the soil chamber, total thrust, and cutterhead speed were consistently controlled. Furthermore, the cutterhead torque was appropriately reduced, and slurry injection volume increased, contributing to better control of house settlement.