Articles
Soil Dynamics and Earthquake Engineering (02677261)199
This study presents a comprehensive, time-resolved investigation into the effects of localised damage and subsequent restoration on the dynamic behaviour of a semi-circular brick-and-gypsum masonry arch, representative of Persian architectural heritage. Using Operational Modal Analysis (OMA) with Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI), dynamic responses were evaluated across intact, under three distinct damage scenarios, and following restoration. The findings reveal that both damage location and symmetry significantly influence the arch's dynamic properties. Localised damage led to substantial reductions in natural frequencies, with mode two exhibiting up to 26.6 % reduction in initial damage and 43.5 % in the most severe scenario. Symmetric damage reduced sensitivity in fundamental modes, underscoring the need for multi-modal assessment. Average modal damping ratios increased by up to 107.2 providing more consistent and reliable detection compared to EFDD. Restoration using traditional gypsum mortar significantly improved dynamic characteristics, with natural frequencies recovering by approximately 13.5 % EFDD and 13 % SSI relative to the damaged state. Modal parameters stabilised within 24 h post-restoration; however, certain modes showed incomplete recovery, especially near sensor locations indicating residual stiffness deficits. Damage detection indices of Modal Assurance Criterion (MAC), Normalised Modal Difference (NMD), and Coordinate Modal Assurance Criterion (COMAC) have effectively identified damage, reinforcing their critical role in heritage structural health monitoring. The research highlights the importance of considering restoration as a time-dependent, evolving process, and advocates for integrated and multi-parameter monitoring frameworks. The results offer practical insights for optimising the conservation strategies of historic masonry structures, with recommendations for future work addressing environmental effects, numerical modelling, and advanced restoration materials. © 2025 Elsevier Ltd
International Journal for Numerical Methods in Engineering (00295981)126(14)
In this study, the bending, buckling, and free vibration analysis of bi-directional functionally graded porous microbeams with variable thickness are investigated. By utilizing the modified strain gradient theory (MSGT) in conjunction with a sinusoidal shear deformation theory, governing equations are derived using Hamilton's principle within the framework of the non-uniform rational B-spline (NURBS)-based isogeometric analysis (IGA). In addition, the C2-continuity requirement can be easily achieved by increasing the order of the NURBS basis functions. The MLSPs and the material properties of microbeams vary along with both thickness and axial directions based on the rule of mixture scheme. To consider the effects of porosity, two even and uneven distributions are considered. After verifying the accuracy of the presented approach, the influence of the aspect ratio, gradient indices, different boundary conditions, porosity parameters, variable MLSPs, and thickness on the bending, buckling, and free vibration characteristics of microbeams are investigated. © 2025 John Wiley & Sons Ltd.
Thin-Walled Structures (02638231)211
In this paper, the isogeometric analysis (IGA) is extended to study the size-dependent behavior of bending, buckling and free vibration of in-plane bi-directional functionally graded porous microplates with variable thickness. In order to capture the effect of size, the modified strain gradient elasticity theory, which has three length scale parameters, is used. Regarding to the third-order shear deformation theory, the equations of motions are derived by using the Hamilton's principle and then are discretized based on the IGA approach. The material properties vary continuously through in-plane directions by employing the rule of mixture and the porosity distribution is considered an even type. The C2-continuity requirement can be easily achieved by increasing the order of the non-uniform rational B-spline (NURBS) basis functions larger than two. The influences of the size effect, aspect ratios, boundary conditions, thickness variations, material gradations, and porosity distributions on the deflections, the fundamental natural frequencies, and the buckling load values of the rectangular, circular and elliptical microplates are studied. The obtained results are compared with the previously published studies to show the performance and efficiency of the present research. © 2025 Elsevier Ltd
Structural Engineering and Mechanics (12254568)89(2)pp. 181-197
A numerical method is presented in this paper, for buckling analysis of thin arbitrary stiffened composite cylindrical shells under axial compression. The stiffeners can be placed inside and outside of the shell. The shell and stiffeners are operated as discrete elements, and their interactions are taking place through the compatibility conditions along their intersecting lines. The governing equations of motion are obtained based on Koiter's theory and solved by utilizing the principle of the minimum potential energy. Then, the buckling load coefficient and the critical buckling load are computed by solving characteristic equations. In this formulation, the elastic and geometric stiffness matrices of a single curved strip of the shell and stiffeners can be located anywhere within the shell element and in any direction are provided. Moreover, five stiffened composite shell specimens are made and tested under axial compression loading. The reliability of the presented method is validated by comparing its numerical results with those of commercial software, experiments, and other published numerical results. In addition, by using the ANSYS code, a 3-D finite element model that takes the exact geometric arrangement and the properties of the stiffeners and the shell into consideration is built. Finally, the effects of Poisson's ratio, shell length-to-radius ratio, shell thickness, cross-sectional area, angle, eccentricity, torsional stiffness, numbers and geometric configuration of stiffeners on the buckling of stiffened composite shells with various end conditions are computed. The results gained can be used as a meaningful benchmark for researchers to validate their analytical and numerical methods. Copyright © 2024 Techno-Press, Ltd.
This study includes extensive compression tests on clay brick units, gypsum mortar, and masonry configurations, incorporating both gypsum and cement mortar, across four distinct scales 1:1, 1:2, 1:4, and 1:6. It investigates the relationship between compressive strength and modulus of elasticity, with the aim of providing precise estimation tools for these important mechanical properties. Systematic experimentation is employed, and scatter diagrams illustrate the dynamic interplay between modulus of elasticity and compressive strength. The derived coefficients, validated against experimental data, verify the accuracy of the proposed relationships. Specifically, the derived coefficient η, representing the ratio of modulus of elasticity to compressive strength, exhibits scale-dependent variations. For brick units, η ranges from 104 for the 1:1 scale to 126 for the 1:6 scale, emphasising the impact of size. Additionally, the coefficient η for gypsum mortar demonstrates a 20% increase with a rise in the water-to-gypsum ratio. Regarding masonry configurations, the coefficient η in the BS method varies from 91 for the 1:6 scale to 139 for the 1:2 scale. In the RILEM method, the coefficient η ranges from 48 for the 1:6 scale to 105 for the 1:1 scale. The proposed relationships display a negligible deviation from experimental results, affirming their robustness. Furthermore, a relationship is introduced for estimating masonry compressive strength based on the compressive strength of both the brick and the mortar at different scales. The accuracy of this relationship is verified by its minor deviation from experimental results. © 2024 Institution of Structural Engineers
