A two-level macroscale continuum description with embedded discontinuities for nonlinear analysis of brick/block masonry

A great proportion of the existing architectural heritage, including historical and monumental constructions, is made of brick/block masonry. This material shows a strong anisotropic behaviour resulting from the specific arrangement of units and mortar joints, which renders the accurate simulation of the masonry response a complex task. In general, mesoscale modelling approaches provide realistic predictions due to the explicit representation of the masonry bond characteristics. However, these detailed models are very computationally demanding and mostly unsuitable for practical assessment of large structures. Macroscale models are more efficient, but they require complex calibration procedures to evaluate model material parameters. This paper presents an advanced continuum macroscale model based on a two-scale nonlinear description for masonry material which requires only simple calibration at structural scale. A continuum strain field is considered at the macroscale level, while a 3D distribution of embedded internal layers allows for the anisotropic mesoscale features at the local level. A damage-plasticity constitutive model is employed to mechanically characterise each internal layer using different material properties along the two main directions on the plane of the masonry panel and along its thickness. The accuracy of the proposed macroscale model is assessed considering the response of structural walls previously tested under in-plane and out-of-plane loading and modelled using the more refined mesoscale strategy. The results achieved confirm the significant potential and the ability of the proposed macroscale description for brick/block masonry to provide accurate and efficient response predictions under different monotonic and cyclic loading conditions.

Development and Calibration of a 3D Micromodel for Evaluation of Masonry Infilled RC Frame Structural Vulnerability to Earthquakes

Within the scope of literature, the influence of openings within the infill walls that are bounded by a reinforced concrete frame and excited by seismic drift forces in both in- and out-of-plane direction is still uncharted. Therefore, a 3D micromodel was developed and calibrated thereafter, to gain more insight in the topic. The micromodels were calibrated against their equivalent physical test specimens of in-plane, out-of-plane drift driven tests on frames with and without infill walls and openings, as well as out-of-plane bend test of masonry walls. Micromodels were rectified based on their behavior and damage states. As a result of the calibration process, it was found that micromodels were sensitive and insensitive to various parameters, regarding the model’s behavior and computational stability. It was found that, even within the same material model, some parameters had more effects when attributed to concrete rather than on masonry. Generally, the in-plane behavior of infilled frames was found to be largely governed by the interface material model. The out-of-plane masonry wall simulations were governed by the tensile strength of both the interface and masonry material model. Yet, the out-of-plane drift driven test was governed by the concrete material properties.

Elastic Properties Estimation of Masonry Walls through the Propagation of Elastic Waves. An Experimental Investigation

Structural identification is one of the most important steps when dealing with historic buildings. Knowledge of the parameters, which define the mechanical properties of these kinds of structures, is fundamental in preparing interventions aimed at their restoration and strengthening, especially if they have suffered damage due to strong events. In particular, by using non-destructive techniques it is possible to estimate the mechanical characteristics of load-bearing structures without compromising the artistic value of the monumental buildings. In this paper, after recalling the main theoretical aspects, the use of elastic waves propagation through impact tests for the characterization of the masonry walls of a monumental building is described. The impact test allowed us to estimate the elastic characteristics of the homogeneous solid equivalent to masonry material. This confirms the great potential of the non-destructive diagnostics suitable for analyzing important structural parameters without affecting the preservation of historical masonry structures.

THEORETICAL JUSTIFICATION OF INCREASING THE EFFICIENCY OF REINFORCEMENT OF FLEXIBLE CELLULAR CONCRETE STRUCTURES

Aerated concrete is actively used in energy efficient construction, mainly as a masonry material for vertical load-bearing structures. At the same time, the creation of a closed thermal contour of the building, which is the basis of modern energy saving requirements, is rational by the use of aerated concrete in load-bearing horizontal structures that require reinforcement. Traditionally bar reinforcement is ineffective in aerated concrete due to low specific adhesion at the contact of the reinforcement with concrete and significantly less than that of heavy concrete, the distribution capacity of concrete around a rod, which evenly transforms concrete stress to bar extension, the consequence of which is the significant bar understress while pulling it in concrete. The authors’ research in the field of rationalization of reinforcing elements that are effective in cellular concrete, aimed at increasing the contact surface of the reinforcing element with concrete while maintaining the original steel consumption, makes it possible to recommend tape reinforcement for use in reinforced aerated concrete structures. Punched steel tapes equal to the bar reinforcement of the cross-sectional area, but having developed lateral surface, provide an increase in the adhesion strength of the reinforcement and preventing its pulling. The article presents the results of a numerical study of stress-strain state in reinforced aerated concrete beam with rectangular section, reinforced with the proposed tape reinforcement in comparison with traditional bar reinforcement

Research on the Inspection Method of Chimney Appearance and Masonry Material Performance

As a high-rise structure, the safety of chimneys has always been a public concern. In this paper, the damage condition, tilting, and the strength of load-bearing materials of the chimney were inspected, and the inspection conclusions and maintenance suggestions were given based on the inspection results. The inspection method can provide relevant reference for the inspection of similar structures.

Physical-Mechanical Properties of Stone Masonry of Gjirokastër, Albania

In addition to reinforced concrete and steel buildings, a large part of the existing building stock in Europe is made of stone masonry. Prediction of the structural behavior requires the development of a systematic material characterization of the mechanical properties and structural details (units, arrangement, bonding, inter-connection). This study aims to analyze the mechanical and physical behavior of building stones in the historical city of Gjirokastër, Albania, known also as the Stone City. A thorough investigation of the regional stone quarries was performed, and the collected samples were cut into regular prismatic specimens for further analysis. The experimental campaign consisted of the determination of flexural strength and compressive strength, water absorption, porosity, specific gravity as well as structural analysis of the masonry material, using the MQI (Masonry Quality Index) method. The test results showed that there is a large scattering in the values of the mechanical and physical stone properties such as compressive strength varying from 20 to 115 MPa and flexural strength from 8 to 25 MPa. However, the analysis of the masonry material revealed a satisfactory structural performance, based on a frequent, systematic respect of the good construction practices (i.e., the rules of the art) in Gjirokastër.

Assessment of Building Vulnerability with Varying Distances from Outlet Considering Impact Force of Debris Flow and Building Resistance

Studies have been conducted to understand the physical characteristics of debris flows and quantitatively assess the vulnerability of the buildings nearby to mitigate damage from debris flow disasters. However, there remains a paucity of research on vulnerability assessments that discuss the impact force of debris flow and building resistance within certain sections, where debris flows spread from an outlet. In this regard, the study assesses the vulnerability of buildings to debris flows while considering the distance from an outlet. For this purpose, it selects the two sites of Chuncheon-shi in Gangwon-do and Cheongju-shi in Chungcheongbuk-do in South Korea, which are widely known for having experienced debris flow damage in 2011 and 2017, respectively. For the sites, the study conducts an inverse analysis through debris flow simulation to understand the physical characteristics of debris flows, including flow depth, flow velocity, and impact force. Then, the study assesses vulnerability by estimating the resistance of the materials of the buildings placed in the range where debris flows spread, which allows the calculation of a vulnerability index that a building material may have and the estimation of a safety distance from the outlet for each material of the buildings in the study sites. The result shows that with an increasing distance from the outlet, the flow depth, velocity, and impact force, which represent debris flow properties, tend to decrease. This again results in vulnerability being gradually reduced. The study also suggests that buildings are exposed to the risk of debris flow disasters at a sections 40 to 60 m from an outlet for wood material construction, 70 to 110 m for brick-masonry material construction, and all sections from an outlet for prefabricated material construction. Based on this result, the vulnerability index is estimated for the wood material (0.85), brick-masonry material (0.58), and prefabricated material (0.003).