Structural Masonry Walls Research Articles

Strength assessment of structural masonry walls: analysis based on machine learning approaches

ABSTRACT In conventional masonry buildings, masonry walls are key structural load-bearing elements. Likewise, masonry infill walls strengthen framed constructions against lateral stress. The material characteristics of brick units and mortar determine the compressive strength of structural masonry walls. In this study, advanced machine learning (ML) techniques were utilized to estimate the compressive strength of structural masonry walls based on the material properties of brick units and mortar. The Young’s modulus of brick units (Eu), compressive strength of brick units (Fcu), Young’s modulus of mortar (Em), and compressive strength of mortar (Fcm) were used as input parameters to model the compressive strength (Fc) of the structural masonry wall. Gradient Tree Boosting (GTB), Elman Neural Network (ENN), and Multivariate Adaptive Regression Splines (MARS) were developed using four diverse input and output (I/O) combinations to explore the effect of each input parameter on output estimation. The data used for modeling were obtained from prior studies published in the literature. The model’s performance was evaluated based on different statistical (error and efficiency) indices. For the third and fourth (I/O) combinations, the MARS model significantly outperformed other models. However, for the first I/O combination, the GTB model performed well. The study also revealed that the compressive strength of a structural masonry wall is more likely to depend on the strength and quality of the brick units than on the strength of the mortar.

Thermal performance of cavity masonry wall structures in the solar rich areas of Western China

Air cavities can effectively improve the thermal performance of building envelope. A cavity masonry wall (CMW) is a common and suitable envelope in the solar rich areas of Western China for integrating thermal insulation and heat storage. However, suitable structures for CMWs have not been obtained for different indoor and outdoor climates, which hinders the realization of near-zero energy buildings. In the present study, thermal performance was analyzed for different CMW structures to obtain the design method of the CMW structure. A mathematical model of CMWs was established and validated based on experiments. This model was used to analyze the effects of different structures for CMWs, and suitable structures were determined. Climate adaptability characteristics were analyzed for the suitable structures. Finally, the energy performance of buildings with CMWs was analyzed. A climate index for CMW structure design comprising the ratio of cooling relative to heating (RCH) was proposed to divide the outdoor climate, with winter heating when RCH ≤0.17, and winter heating and summer cooling when RCH >0.17. The suitable structures were obtained in different indoor and outdoor climates, where the closed air cavity was preferably placed on the low temperature side of the construction. The suitable structures exhibited better heat transfer attenuation delay characteristics to adapt to indoor and outdoor climates. It had a significant impact on the heating load compared with buildings with masonry walls, and a saving of above 10%. The design method of CMW structure proposed in this study can provide guidance for the application.

Improvement of the thermal performance of hollow clay bricks for structural masonry walls

Although structural masonry walls are widely used in construction, achieving lower U-value is crucial to minimize energy losses and greenhouse gas emissions. The effect on the U-value of hollow clay masonry walls is evaluated by modifying the clay and mortar thermal conductivities, as well as the brick grid and thickness. Heat transfer through bricks and walls was modeled using a 3D-finite element method while model validation was based on experimental tests. Smaller rectangular cavities reduce the U-value to 0.761 W/m2K; increasing the brick thickness reduces the U-value to 0.563 W/m2K. Moreover, reducing the clay thermal conductivity showed negligible reductions in the wall U-value.

The Seismic Performance of Infill and Retrofitted Structural Walls under Earthquakes

To account for the effects of infill walls, the Iranian Code reduces the period of the structure. As a result, filler walls in the plane of structural frames result in significant changes in the properties they possess; therefore, the resistance, stiffness, ductility, distribution of internal forces, and other characteristics of such a frame with an empty frame differ greatly. In this research using 7 far-field earthquakes, a nonlinear time history analysis was performed on reinforced concrete frames with and without masonry infill walls. The maximum relative displacements between the stories were determined. Also, to evaluate the seismic performance of structural masonry walls, the fragility curve of unreinforced masonry walls retrofitted with FRP sheet based on different scenario under the effect of earthquake loads has been investigated by the finite element method. According to the results, the presence of infill walls reduces the number of plastic hinges as well as the maximum relative displacement between the stories. Furthermore, by increasing the number of FRP sheet layers and the reinforced area of the FRP sheet to the entire wall of an unreinforced structural wall, the seismic behaviour of the wall is more effective than other reinforcement patterns and damages the wall less.

Stability of the ‘Tensyudai’ of a Japanese castle under a long-term load

‘Tensyudai’ is the term used for the truncated masonry base that supports the main tower (Tensyukaku) of a Japanese castle. In response to concerns regarding the structural integrity and conservation of Tensyudai masonry walls, this study seeks to investigate the mechanism of their collapse and load capacity. A reduced-scale model of Tensyudai, based on Osaka Castle, was constructed and subjected to a vertical load test to evaluate its three-dimensional mechanical properties. This paper postulates a collapse mechanism, and the equilibrium of forces for the Sumiishi and Hiraishi sections of the Tensyudai is analysed, considering the arch effect. Experimental results are compared, using a series of equations to calculate the collapse burden (q c). Additionally, the safety factor is determined, based on the active earth pressures at various masses. The findings indicate that the safety factor of a standard Tensyukaku weight is approximately 25, which rises with increased Tensyukaku weight. Moreover, this study contributes to future research and preservation efforts for historical structures, by shedding light on the structural stability and safety of Tensyudai masonry walls. It can also provide basic data for considering the protection of other masonry wall structures from earthquakes.

Investigation on the behavior factor of leaning masonry wall structures

In force-based seismic design, the behavior factor q (or response modification factor R) is devised to prevent overdesign by reducing the design force. Different values of the behavior factor q are available for various structure types. However, masonry fence walls are not categorized in the current seismic design codes. These walls are of poor quality due to the absence of proper quality assurance and maintenance, and most of those structures are inclined. In this study, the behavior factor q of leaning masonry fence walls is experimentally estimated. We fabricate three masonry wall structures that are inclined with three different wall angles of 1.5 $$^\circ$$ , 3.0 $$^\circ$$ , and 6.0 $$^\circ$$ , respectively. Monotonically increasing biaxial lateral loads are applied to the walls using a shaking table. The value q of each leaning wall is calculated by analyzing the dynamic load–displacement relationship. A relationship between the factor q and wall angle is discussed, and a new empirical formula representing q as a function of a wall angle is proposed. The proposed empirical formula would be useful in seismic design for severely leaning masonry walls.

DYNAMIC PROPERTIES OF THE MASONRY WALL STRUCTURES USING MORTAR WITH VARIOUS BRANDS OF RUBBER TIRE CRUMBS

This study investigates the application of rubber tire crumbs (RTC) as fillers in the mortar joint of the masonry wall to improve their damping capacity. The RTC used in this study is taken from used car rubber tires of various brands. The specimens are ½ brick walls with a dimension of 1x1m2. The specimen is subjected to cyclic lateral load until it breaks. The results show that the walls with normal mortar experienced a decrease in damping capacity of 7.9%, natural frequency of 31.24%, and stiffness of 98.33%, at the end of cyclic loading. While the application of RTC mortar for mortar joints in masonry walls can increase the damping ratio of masonry wall structures under cyclic loading up to 11.45%. The innovation of using RTC mortar as a mortar joint can be considered a solution for increasing the damping ability of masonry walls.

Seismic performance of crack-damaged masonry wall structures via shaking table tests

Masonry fence walls in run-down areas have cracks of various shapes, and these cracks can weaken the walls very seriously. However, research on this subject has been scarce, and the effect of different crack types on the seismic performance of unreinforced masonry walls needs to be investigated. In this study, two U-shaped wall structures were built: one without any cracks and the other with diagonal, horizontal, and vertical cracks on three sides. The effects of these cracks on the seismic performance characteristics (i.e., the drift ratio and base shear) are evaluated by comparing the dynamic responses of the two wall structures. Through shaking table tests exerting horizontal bi-direction ground motions, both the out-of-plane and in-plane responses of the walls are investigated. Diagonal cracks are found to be more likely to cause the early collapse of masonry walls than vertical and horizontal cracks. These results provide valuable knowledge that will facilitate the appropriate reinforcement for damaged masonry walls that might need urgent repair.

Failure analysis of a U-shaped concrete-block masonry wall structure via shaking table tests

Studies on the seismic behavior of masonry fence has been limited even though those structures have a high hazard potential during earthquakes. In this study, the seismic performance of a U-shaped concrete block masonry structure, which represents typical fence walls in South Korea, is assessed. We conduct dynamic shaking table tests using incremental horizontal bidirectional ground motion, and the experimental results are analyzed in terms of visual damage inspection, natural frequency trends, hysteretic responses, and damage limit identification. Thin cracks gradually initiated at the bottom mortar joints, and finally, a severe stair-step cracks developed abruptly, leading to complete structural collapse. Considering the rapid damage progression, we suggest a novel damage limit criterion for this specimen, which is unlike to that of other ordinary masonry structures. The findings of this study can improve the understanding of the collapse process of masonry fence walls and better estimate their damage conditions.

Sustainability Study of Concrete Blocks with Wood Chips Used in Structural Walls in Seismic Areas.

The concept of sustainability has become a priority in the construction field, in a context where there is an increasing discussion about reducing carbon dioxide emissions, as the construction industry is one of the most polluting industries with a focus on the production of building materials. At present, the classic solution used for structural masonry walls worldwide is the ceramic block. Given that the production of ceramic blocks represents an environmentally polluting process, the alternative solution of using concrete blocks with wood chips is proposed. The proposed solution is more environmentally friendly, both in terms of production technology and materials used, as it is made of wood chips, wood being a sustainable material. These types of blocks are currently used in non-seismic areas due to their poor structural performance. This paper deals with a study on the use of recyclable materials, such as wood chips, from waste materials and aims to propose viable solutions for the use of this type of blocks for structural walls in seismic areas. Two solutions, including concrete blocks with wood chips, have been proposed and numerical analyses have been carried out. Numerical analyses were also carried out for the classical solutions, so that, finally, a comparison could be made between them from a structural point of view. Following the numerical analysis of four types of walls, the two proposed solutions of concrete blocks with wood chips had the best results in terms of force–displacement relationship. Moreover, the quantitative results are presented in a force–displacement graph for the four wall types. This stage represents the first phase of the research, while phase II will continue with experimental tests of the proposed solutions.

Aspects on the masonry structural walls computation

Aspects on the masonry structural walls computation

Shake Table Test of Scaled Masonry Structure Using Rubber Tire Crumbs Mortar

The existence of masonry walls in structures is very useful in increasing the structure's resistance to lateral loads. The role of the walls is more important in providing adequate stiffness and damping than in resisting axial forces. The use of rubber tire crumbs (RTC) mortar on masonry walls is to increase the ductility and damping capacity of the wall. This study examines the application of RTC mortar on masonry walls, in particular for increasing the damping ratio of the wall. This study aims to determine the optimum RTC content in mortar by observing its dynamic properties using the shake table test. The specimens were 4 scaled models with mortar containing 10%, 20%, 30%, and 40% RTC. The prototype is a 3D half-brick wall 2.5 m high and a 2.5 x 2.5 m² plane, with a scale of 2 to provide a miniature model. There are 2 types of loads, namely sinusoidal loads and Yogya earthquake loads. The sinusoidal load has an amplitude of 0.1g with a frequency range between 4 Hz and 20 Hz, while the Yogya earthquake load has an amplitude between 0.1 g and 0.9 g. The results showed that the use of RTC mortar on the masonry wall structures can increase the damping capacity of the walls and reduce the drift ratio. This study recommends that the optimum RTC content is 30% of the sand volume.

Innovative impact testing machine for enhancing impact related research in Australia

This paper summarises the development of a state-of-art impact testing machine for simulating impacts such as vehicular crashes or debris impacts onto structures. The machine has a 200 kg pneumatically powered projectile which can travel horizontally within the barrel of the machine with a maximum velocity of 50 m/s to impact the target structure. The maximum kinetic energy that can be generated by the projectile is 125 kJ by using different combinations of mass and velocity. The diameter of the projectile is 214 mm, and its impacting face can be changed to different shapes, such as flat circle, flat square or an elliptical nose to suit different impact scenarios. An innovative braking mechanism incorporating a crush tube is attached within the barrel to ensure safety when the projectile fails to be restrained by the impact. The crush tube can absorb the maximum imparted by the moving projectile. An advanced data acquisition system is installed to collect quantitative and qualitative test data during a period of 50 ms to 1 s. Two high-speed digital image correlation (DIC) cameras are attached and synchronised with the operation of the impact testing machine to record the images at the rate of 50,000 frames per second. Outputs in terms of strains, deformations, accelerations of the target structure with a record of damage history can be analysed using this 3D DIC technique. The paper also briefly presents the first application of this machine for impact testing masonry wall structures.

Unbonded Post-Tensioned Structural Masonry Wall with Rubber Interface for Limited-Damage Systems

Unbonded post-tensioned (UPT) tendons have been used in structural masonry walls to enhance the self-centering capability of the walls. However, the lateral displacement capacity of masonry walls with UPT tendons can be compromised by early crushing of the compression toes. To prevent toe crushing, this research study employed rubber pads underneath the bottom corners of a full-scale one-story wall. This concept was investigated by subjecting the wall sequentially to free vibration and quasistatic tests, which minimized damage to the masonry and reduced the strength degradation of the wall with increasing lateral drift. Two major damping components were identified: one is due to the instantaneous impact of the wall on the foundation base, and the other is due to the inelastic action occurring within the rubber pads during the continuous phase of rocking motion. Using the test results, a procedure is presented for designing masonry walls with rubber pads and UPT tendons.

Numerical analysis of eco-friendly ductile cementitious composite influence on structural masonry reinforcement

The behaviour of structural masonry walls reinforced with a ductile sustainable cementitious coating, called Eco-friendly Ductile Cementitious Composite (EDCC) is evaluated through Finite Element Modelling (FEM). EDCC is a sustainable material composed mostly by fly-ash and sand, with low cement content, used to repair masonry structures: it has excellent ductile behaviour due to the presence of polymeric fibres. Numerical models that can accurately simulate EDCC-reinforced masonry behaviour under compressive, flexural and shear loads were validated using previous experimental tests. A literature review was completed about the parameters defined for the component materials, interfaces and strategies that can be implemented to model structural masonry walls accurately, with the finite element method. Subsequently, the models were calibrated, comparing the results of stress vs strain or force vs displacement diagrams of experimental tests with numerical simulations. The models were able to simulate the masonry behaviour, with consistent results and failure modes. Parametric modelling was implemented to develop a formula capable of predicting the compressive load capacity of masonry walls strengthened with EDCC.

A damage-plasticity based interface model for simulating in-plane/out-of-plane response of masonry structural panels

A coupled damage-plastic based constitutive model using a traction-separation law is developed in this study to simulate the behaviour of mortar joints in masonry structural panels subjected to in-plane (2D) and out-of-plane (3D) loading. A smooth hyperbolic failure surface is used to develop the interface material model, which is implemented numerically using a fully implicit backward Euler integration technique is unconditionally stable. To further improve the accuracy and robustness of the interface model, an adaptive sub-stepping scheme and associated consistent tangent operator are formulated considering the effects of damage and plastic deformations. This is beneficial for simulating full-scale masonry structures because the size of load step for some locations with higher deformations can be significantly larger than other locations. The model is first validated using a single cohesive element within a finite-element modelling platform, to assess its behaviour under all possible deformation modes: tensile, compressive with shear and tensile-shear mix-mode behaviour. The cyclic response of a masonry couplet is then simulated to assess model performance in the unloading scenario. Finally, the model is applied to masonry structural walls for simulating their failure response under in-plane and out-of-plane loads, and a good correlation with the experimental results is observed.

Numerical and Experimental Assessment of an Improved Design Detail for Partially Grouted Reinforced Masonry Wall Structures

AbstractReinforced masonry buildings predominantly are partially grouted in areas of low or moderate seismicity in North America. The walls in such structures typically contain widely spaced separa...

A nonlinear BE formulation for analysis of masonry walls considering orthotropy: Fundamentals

In this work, a non-linear Boundary Element (BE) formulation with damage model is extended for numerical simulation of structural masonry walls. The original formulation was presented by other researchers to investigate the concrete material in 2D stress analysis. The formulation proposal is written in terms of domain strain variables and it is based on the consistent tangent operator. A simple damage model is used to represent the material behavior of masonry components and internal variables and cell discretization of the domain are considered. However, for brick masonry it is necessary to take into account the orthotropy in this type of structure. The orthotropy is considered by expressing a residual elastic tensor as the difference of the orthotropic and the isotropic elastic property tensors. The complete integral formulation, using isotropic fundamental solution, and algebraic procedure are developed.

Experimental investigation of axial compressive behavior of square and rectangular confined concrete-masonry structural wall boundary elements

Reinforced masonry boundary elements (RMBEs) are critical components in determining the lateral response of reinforced masonry structural walls with boundary elements. Fundamental interpretation of the effect of various influential parameters on the RMBEs′ behavior is essential to enhance their stress–strain response. This study investigates, experimentally, the influence of various design parameters and construction procedures on the axial compressive behavior of fully grouted RMBEs built with C-shaped concrete-masonry blocks. Thirty-eight unreinforced and RMBEs were constructed and tested under concentric axial loading till failure. The effect of five parameters, namely, the vertical reinforcement ratio, the volumetric ratio of confinement reinforcement, cross-section configuration, stack pattern and running-bond, and pre-wetting of dry masonry shell before grouting, was investigated. The test results showed that increasing the vertical reinforcement ratio of the RMBEs resulted in a significant increase in the peak compressive stress and a considerable reduction in the corresponding strain ductility. Moreover, as the RMBEs volumetric ratio of transverse reinforcement doubled, the strain ductility witnessed a remarkable enhancement, whereas the peak compressive stress experienced an inconsistent trend. RMBEs built with rectangular C-shaped cross-sections exhibited comparable peak stress, smaller drop following the face shell spalling, and better strain ductility than square RMBEs. The running-bond pattern had a negative effect on both the peak stress and the strain ductility of dry RMBEs, although it exhibited comparable or even enhanced response in wet RMBEs compared to those built in the stack pattern. Pre-wetting of dry masonry shell before grouting was found to boost the peak compressive stress of unreinforced and RMBEs significantly. However, it adversely affected their strain ductility. Wet RMBEs showed a steeper post-peak descending branch compared to their dry counterparts. Indeed, the vertical reinforcement ratio and pre-wetting of dry masonry shell were the most critical parameters affecting the RMBEs peak compressive stress, whereas the confinement ratio mostly influenced the strain ductility. This study sheds light on the most critical parameters influencing the stress–strain components (i.e., strength and ductility) of RMBEs.

Out-of-plane behaviour of masonry wall structures strengthened with steel-bar truss system

An experimental study was performed to investigate the effect of external prestressed truss steel-bar units installed on an unreinforced masonry (URM) wall under out-of-plane loadings. The key components of this new retrofitting method are prestressed vertical and diagonal bars. The prestressed vertical bars induce a prestressing force onto the horizontal section of the URM wall and the diagonal bars resist lateral loadings. Reverse cyclic tests were conducted on a full-scale URM wall as a control specimen and URM walls retrofitted in-plane and/or out-of-plane (parallel to short intersecting walls). The test results showed that the specimen strengthened using the new technique was superior to the control specimen in terms of seismic performance, including lateral load resistance, stiffness, energy dissipation and restrained slip of the entire specimen. Two units installed on short intersecting walls exhibited the same shear strength as four units installed on the in-plane and in-plane retrofitted masonry walls. The out-of-plane masonry specimen demonstrated the best performance. It was confirmed that aligning the retrofitting method based on the loading direction was effective, despite the lower axial load level.