ISSN:2630-5763
Journal of Structural Engineering & Applied Mechanics
ARTICLES
Korhan Özgan
Sebahat Şimşek
Volkan Kahya
While numerous methodologies for identifying structural damages through finite element (FE) model updating and optimization algorithms have been developed and validated for accuracy, certain unresolved issues necessitate further investigation. The establishment of a numerical model is imperative for damage assessment through model updating, particularly for complex engineering structures with numerous elements, such as trusses, which demand substantial effort. Utilizing commercial software can offer significant convenience in this context. To cope with this challenge, we propose a FE model update strategy employing the SAP2000 Open Application Programming Interface (OAPI) and Teaching-Learning-Based Optimization (TLBO) for evaluating damages in complex truss structures. The FE model of the monitored structure is, first, constituted via SAP2000 software. Subsequently, the damage assessment of the structure is formulated as an unconstrained optimization problem. An objective function is defined as a weighted linear combination of three modal parameters: frequency, Coordinate Modal Assurance Criterion (COMAC), and flexibility. For the identification and quantification of stiffness degradation induced by damage, the optimization problem is addressed through TLBO. The iterative optimization process is automated by establishing a linkage between MATLAB and SAP2000 through the OAPI feature of SAP2000. The efficacy of the proposed approach is demonstrated through two numerical test examples, accounting for measurement noise and sparse measured data.
https://doi.org/10.31462/jseam.2024.04219237
Kazim Ahmet Hasim
In this study, an isogeometric finite element originally developed for piezolaminated plates has been extended and named FGL-IGA to perform the static analysis of thick and thin functionally graded piezoelectric plates. Unlike most of the isogeometric finite element models in literature that neglect thickness stretching when analyzing through-the-thickness functionally graded plates, FGL-IGA integrates Reddy’s layerwise theory into the electromechanically coupled constitutive and equilibrium equations, enabling precise displacement and stress results relying on the displacement-based virtual work principle. Additionally, unlike standard finite elements, the utilization of high-order continuous NURBS functions for discretizing geometry and kinematic variables allows both direct and exact retrieval of geometry from CAD software, as well as faster convergence of results. The accuracy and reliability of FGL-IGA have been tested and validated for two cases with exact solutions from literature, considering various span-to-thickness ratios and electromechanical loading scenarios.
https://doi.org/10.31462/jseam.2024.04238258
Suhail Alabsi
Ayşe T. Daloğlu
Sameer Alabsi
This study aims to improve the parameters of the modified fractional derivative constitutive model (MFDCM) for viscoelastic dampers (VEDs), as these parameters are extremely important in reducing and resisting structural responses to dynamic loads, such as seismic and wind loads. The MFDCM, with its nonlinear and frequency-dependent characteristics, is a complex model, which directly affects the storage modulus (G_s) and loss factor (η) of VEDs, leading to great difficulty in accurately predicting the damper behavior under different conditions. The problem studied is inherently multi-objective, involving trade-offs between errors in the storage modulus〖 (G〗_s) and loss factor (η). First, a multi-objective approach is employed to identify a set of potential solutions and generate a Pareto front, which provides insights into the trade-offs between competing objectives. Precise weights are then determined from the Pareto front to transform the multi-objective problem into a single-objective problem, allowing further refinement using single-objective optimization techniques. Four advanced meta-heuristic optimization techniques—Non-dominated Sorting Genetic Algorithm II (NSGA-II), Teaching–Learning-Based Optimization (TLBO), Particle Swarm Optimization (PSO), and Harmony Search Algorithm (HSA)—are employed to systematically reduce the error rates in the storage modulus (G_s) and loss factor (η) predictions compared to experimental data. The results of this study demonstrate that, by incorporating multiple optimization techniques, the prediction accuracy of the MFDCM can be significantly enhanced. This improved modeling ability thus enables better design of VEDs, improving their performance and reliability in practical engineering applications. Comparative analysis of different algorithms provides insights into their effectiveness and efficiency, offering valuable guidance for choosing appropriate optimization strategies in engineering optimization problems.
https://doi.org/10.31462/jseam.2024.04259283
Baris Gunes
Turgay Cosgun
Kamran Samadi
Turhan Bilir
Barış Sayın
This study investigates slab damage, the underlying causes of these damages, and the post-damage performance of a five-story reinforced concrete building with shear walls under construction. Deflections and visible cracks resulting from these deflections were observed in the slabs and beams of the building under investigation. To assess the risk and progression potential of the existing damage, the vertical structural elements in the 1st normal floor of the building and the beams and slabs in the ceiling were modeled in Midas Gen finite element software. This model was subjected to the loads from structural elements, construction loads, coating loads, material loads intended to correct the existing slab slope, and live loads. Additionally, an in-situ loading test was conducted to evaluate the post-damage performance of the slabs under vertical loads, and this test was incorporated into the numerical analysis. To represent the structure’s behavior under loads during the construction process, the time-dependent change in concrete strength was considered. For the cracked section analysis of the slabs, the EN 1992-1-1 standard was considered, and cracked section stiffness was applied for each mesh element representing the slab. When cracking occurred, the effective moment of inertia was calculated in both directions, and displacements for the cracked section were determined based on this moment of inertia. The analysis model contains approximately 3,000 meshes representing the slabs. Instead of employing a single effective moment of inertia for the entire slab, the effective moment of inertia is calculated separately for each mesh segment. The analyses, which considered five different load combinations, revealed that the slab displacements in service conditions exceeded the limit values specified in the applicable codes, indicating that the slabs require strengthening.
https://doi.org/10.31462/jseam.2024.04284298
Muneeb Jadallah
Cem Cicos
Adem Doğangün
Turkey is a region known for its high seismic activity, and unfortunately, many of its existing buildings are not well-prepared to withstand earthquakes. This study delves into the consequences of removing ground floor columns, either due to architectural modifications or damage from earthquakes to the structural integrity of buildings. To investigate this, a model simulating a cantilevered structure was developed, allowing for a detailed analysis of potential collapse mechanisms. The structural model, designed using STA4CAD software, represents a seven-story building with a ground floor height of 4.2 meters and a typical floor height of 3.2 meters. The building has a cantilever length of 1.5 meters, with 5-meter spacing between axes in both the X and Y directions. A uniform slab thickness of 150 mm and the load-bearing system is composed of columns and beams. These designs were then transferred into the Extreme Loading Structures (ELS) software, where further analysis was conducted. In the ELS program, models were created with varying concrete classes of C10, C15, and C20, incorporating specific cross-section dimensions and reinforcements. The primary focus of the analysis was to assess the buildings' vulnerability to progressive collapse, particularly when critical ground-floor columns were removed. The evaluation followed the guidelines set out in the "Design of Buildings to Resist Progressive Collapse" (UFC 4-023-03) code. The findings of this study are significant. Buildings constructed with C10-grade concrete were found to be highly susceptible to collapse when either interior or corner columns were removed. On the other hand, buildings with stronger C15 and C20 concrete demonstrated greater resilience, only suffering damage rather than complete collapse upon the removal of corner columns. These results underscore the importance of both material strength and architectural design in ensuring the seismic safety of buildings in earthquake-prone areas.
https://doi.org/10.31462/jseam.2024.04299314
Ali Juma Noorzad
Hakan Dilmaç
The strengthening of reinforced concrete columns using fiber-reinforced polymer (FRP) composites has garnered significant attention in recent years due to its numerous advantages. RC columns primarily support axial compression loads and often require strengthening to improve their axial strength and ductility. This research investigates the analytical structural axial behavior of rectangular RC columns retrofitted externally with FRP, internally strengthened with transverse steel reinforcement (TSR), or strengthened using a combination of FRP and TSR techniques, applied externally and internally, respectively. The research also aims to identify precise stress-strain models that accurately represent the mechanical behavior of rectangular RC columns which experience irregular stress variations due to their geometry, in three different confinement configurations: FRP, TSR, and combined confinement of FRP and TSR, under pure axial compression loads. Furthermore, five rectangular and square cross-sectional RC columns with various dimensions and confinement configurations have been analyzed using three confinement methods under pure axial compressive load, and all influential parameters were investigated analytically with the proposed models. The results show that the stress-strain relationships obtained from the suggested models are in good agreement with experimental data taken from the literature and previous studies. Based on the findings, combined confinement reinforcement using FRP and TSR demonstrates greater benefits than individual methods in improving the structural axial behavior of rectangular RC columns under axial loads, making this technique particularly effective for enhancing axial load-bearing capacity and ductility.
https://doi.org/10.31462/jseam.2024.04315342