Browsing by Author "Maali, M."

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Effect of Hydrochloric Acid Corrosion and CFRP Coating on the Buckling Behavior of Cylindrical Shells Under External Pressure
(Sharif University of Technology, 2022) Aydin, A.C.; Bilen, M.B.; Maali, M.
Thin-walled cylindrical shells are widely used as silos, liquid tanks, marine structures, and industrial chemical plants. In such applications, the shells are mostly exposed to liquids. Corrosion occurs on surfaces when shells are filled with low-pH liquids. Corroded material loss decreases the thickness of the shells which in turn lessens their buckling capacity. The current study primarily aims to investigate the effects of corrosion on the buckling capacity of thin-walled cylindrical shells subjected to uniform external pressure. The model shells were half- or full- filled with 5% and 10% HCl (Hydrochloric Acid) solutions for corrosion. In order to attenuate the negative effects of corrosion, the cylinders were coated with varying sizes of Carbon Fiber-Reinforced Polymer (CFRP) sheets. A total of 12 models of 800 × 400 × 0:45 mm in dimension were investigated in this research. The perfect non-corroded models were employed to compare the behavior of all models under study. The obtained results indicated that corrosion would cause a significant decrease in the buckling capacity of thin-walled cylindrical shells. It should be noted that the acid ratio, filling rate, and surface area coated with CFRP fabrics considerably affected the buckling capacity of cylinders. To be specific, coating the cylinders with one layer of CFRP moderated the buckling capacity loss. © 2022 Sharif University of Technology. All rights reserved.
Effect of Hydrochloric Acid Corrosion and CFRP Coating on the Buckling Behavior of Cylindrical Shells Under External Pressure
(Sharif University of Technology, 2022) Aydin, A. C.; Bilen, M. B.; Maali, M.
Thin-walled cylindrical shells are widely used as silos, liquid tanks, marine structures, and industrial chemical plants. In such applications, the shells are mostly exposed to liquids. Corrosion occurs on surfaces when shells are filled with low-pH liquids. Corroded material loss decreases the thickness of the shells which in turn lessens their buckling capacity. The current study primarily aims to investigate the effects of corrosion on the buckling capacity of thin-walled cylindrical shells subjected to uniform external pressure. The model shells were half- or full-filled with 5% and 10% HCl (Hydrochloric Acid) solutions for corrosion. In order to attenuate the negative effects of corrosion, the cylinders were coated with varying sizes of Carbon Fiber-Reinforced Polymer (CFRP) sheets. A total of 12 models of 800 x 400 x 0:45 mm in dimension were investigated in this research. The perfect non-corroded models were employed to compare the behavior of all models under study. The obtained results indicated that corrosion would cause a significant decrease in the buckling capacity of thin-walled cylindrical shells. It should be noted that the acid ratio, filling rate, and surface area coated with CFRP fabrics considerably affected the buckling capacity of cylinders. To be specific, coating the cylinders with one layer of CFRP moderated the buckling capacity loss. (c) 2022 Sharif University of Technology. All rights reserved.
Experimental and Numerical Investigation of Semi-Rigid Behavior Top and Seat T-Section Connections with Different Triangular Designed Stiffener Thicknesses
(Elsevier Ltd, 2023) Kiliç, M.; Maali, M.; Maali, M.; Aydin, A.C.
The top and seat T-section connections created using the IPE standard profile and T-shaped elements differ from those in the literature, which utilize welded plates. Thus, the elimination of the problems occurring at the welds of connections, such as fracture points and the inability to perform well in place, is expected. Knowledge of their behavior is needed to recommend the use of weld-less T-section connections. However, T-section connections that use the IPE standard profile are not mentioned or investigated in Eurocode 3. Furthermore, the T-section connections from standard IPE profiles aimed to use residue IPE standard profiles efficiently and back to the consumption cycle. This paper reports the results of 24 new laboratory tests on the moment-rotation curve characteristics of top and seat T-section connections with different triangular-designed stiffener thicknesses under static loading. Additionally, to understand the effects of the web length (T-section connection) and different triangular-designed stiffener thicknesses on the moment-rotation curve characteristics, the web length was chosen according to Eurocode 3 width of the T-section was taken to equal the width of the beam (IPE 160). Furthermore, the T-section ratios of flange thickness (tf) to web thickness (tw) were selected between 1.46 and 1.52 to understand how the effect of this ratio on the characteristics of the moment-rotation curves. The experiments also established and validated the finite-element models (ANSYS-work bench). The test results show that the maximum moment and energy dissipation value increased with increasing tf/tw (flange thicknesses to web thicknesses) ratios from 1.46 to 1.52. Moreover, the stiffness ratio values increased with increasing tf/tw ratios from 1.46 to 1.52, while they decreased with increasing tf/tw ratios from 1.46 to 1.48. Moreover, the number of bolt rows increased from 1 to 2, and the Frye-Morris values became much smaller than the experimental values. Additionally, in the model comparison with the 1 row of bolts T-connection, the stiffener used does not affect the moment capacity of the Frye Morris models. The mean value of the Mexp/MF-M ratio is between 1 and 1.8 for the models with 2 rows of bolts. Therefore, the length of the T-connection used the stiffener effect on the moment capacity of the Frye Morris model with the two rows of bolts. © 2023 Elsevier Ltd
Experimental Evaluation of the Post-Fire Behavior of Steel T-Component in the Beam-To Connection
(Elsevier Ltd, 2018) Maali, M.
To evaluate the strength of a connection after exposure to fire, the microstructure/property relationships and influences of these effects on high temperature strength are needed to discuss structural elements exposed to a heat treatment and to determine its mechanical properties. This study focuses on understanding the structural behavior of the connection under post-fire conditions. The aim of the work is also to provide a moment-rotation curve, failure mechanism and microstructure for a connection whose component is exposed to heat treatment. This aim was achieved through five tests that were conducted on a full-scale beam-to-column connection using a T-component obtained from rolled I-profiles by cutting along the web plane. The moment-rotation curves and failure modes of the connection at ambient temperature were compared to the moment-rotation curves and failure modes of the connection whose elements were exposed to high-temperature conditions. The material properties of the specimen element exposed to the heat treatment were also investigated by comparing them to those of the original specimen. The test results show that there are differences between the mechanical properties and microstructures of the heated and original specimens. The differences in these specimens are reflected in the morphology of the fractures. The reason for the fractures is that microstructure-changes contribute to brittle behavior in members. The experimental tests indicated that, post-fire, steel connections can be subjected to large deformations at a lower strength and are more likely to fracture early. © 2018 Elsevier Ltd
Finite Element Evaluation of Seismic Response to RC Interventions in Historical Masonry: Erzurum Stone Granaries
(Elsevier Ltd, 2025) Kocaman, İ.; Maali, M.; Maali, M.; Mercimek, Ö.
This study investigates the seismic behavior of the Erzurum Stone Granaries, a 175-meter-long and 41-meter-wide historical masonry structure located in eastern Türkiye. The building, featuring multi-leaf stone masonry walls with an average thickness of 70 cm, has undergone structural modifications, including the addition of reinforced concrete columns, beams, and slabs during recent restorations. To assess the effects of these additions, two distinct finite element models were developed using ANSYS APDL: the Reinforce Concrete-Model (RC-Model), which includes reinforced concrete interventions, and the M−model, which represents the structure without them. Macro-modeling with SOLID65 elements and the Willam-Warnke failure criterion was employed. Modal analysis results showed that the first mode frequency decreased from 11.41 Hz in the RC-model to 7.62 Hz in the M−model, indicating a reduction in stiffness due to the removal of the concrete elements. Nonlinear time-history analyses using scaled ground motions revealed that displacements in the RC-model remained below 3 mm, while displacements in the M−model exceeded 30 mm in critical regions, leading to partial collapses. These findings demonstrate the significant contribution of reinforced concrete elements to the box effect and enhanced axial loading, ultimately improving the seismic performance of the structure. © 2025 Elsevier Ltd
Installation and Maintenance Principles of Seismic Isolators: Erzurum Health Campus
(Bentham Science Publishers B.V. P.O. Box 294 Bussum 1400 AG, 2018) Maali, M.; Maali, M.; Aydin, A.C.
Background: The objective of isolation is to reduce the seismic forces transmitted through the structure using active and/or passive insulation systems.Seismic isolators, which are passive insulation systems and are placed between the foundation of the structure and the structure, are discussed throughout this study. Isolators consist of rubber layers that have horizontal flexibility, steel layers that increase rigidity and a lead or ball core, which increases vertical stiffness. Installation and maintenance of seismic isolators require great care in order not to exceed the displacements/section forces envisaged at the design of the structure during the earthquake. Objective: Installation and maintenance principles of the friction pendulum type isolators used in Erzurum Health Campus (hospital) are presented throughout this study. While the seismic isolators are anchoraged to directly concrete in the general application, they are placed between two steel plates of type S355J2 in this application, because of cold-weather conditions. To evaluate this condition, it is investigated the models with and without steel plate and compared to each other. Methodology: The models with and without steel plate were formed using finite-element method to compare the stress distributions on the isolator. Conclusion: The results demonstrated that the model with steel plates occur the uniform stress through surface and keep under control deformation of cross-section in the reinforced concrete. © 2018 Sağıroğlu et al.
The Shear and Flexural Behavior of Cold-Formed Steel Composite I and U Beams
(Sharif University of Technology, 2021) Aydin, A.C.; Bayrak, B.; Maali, M.; Mete, E.; Çebi, K.; Kiliç, M.
Recycling and re-usability of waste materials are of great importance in terms of ecological order. Furthermore, cold-formed steel has recently drawn considerable attention. The objective of the present study was to investigate the bending and shear behavior of the composite formed by pouring waste polymer into the cold-formed I and U profile melds after homogenous pulping. The best results for shear and bending strengths were obtained using melted polypropylene (PP). The enhanced adherence between the steel and molted PP increased both shear and bending capacity. Moreover, it was reinforced by Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) bars to increase the bending and shear behavior of I and U profiles filled with melted waste polymer. Changing the cross-sectional area in I and U beams under the bending moment had a considerable effect on the load at yielding, ultimate strength, displacement values corresponding to these loads, ductility, and energy dissipation capacity. Addition of CFRP to I beams could also significantly increase displacement capacity in free end regions under the shear force. Addition of GFRP bars, rather than CFRP bars, with a higher elongation capacity in I and U beams caused ductile behavior. © 2021 Sharif University of Technology. All rights reserved.
The Shear and Flexural Behavior of Cold-Formed Steel Composite I and U Beams
(Sharif University of Technology, 2021) Aydin, A. C.; Bayrak, B.; Maali, M.; Mete, E.; Cebi, K.; Kilic, M.
Recycling and re-usability of waste materials are of great importance in terms of ecological order. Furthermore, cold-formed steel has recently drawn considerable attention. The objective of the present study was to investigate the bending and shear behavior of the composite formed by pouring waste polymer into the cold-formed I and U profile melds after homogenous pulping. The best results for shear and bending strengths were obtained using melted polypropylene (PP). The enhanced adherence between the steel and molted PP increased both shear and bending capacity. Moreover, it was reinforced by Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) bars to increase the bending and shear behavior of I and U profiles filled with melted waste polymer. Changing the cross-sectional area in I and U beams under the bending moment had a considerable effect on the load at yielding, ultimate strength, displacement values corresponding to these loads, ductility, and energy dissipation capacity. Addition of CFRP to I beams could also significantly increase displacement capacity in free end regions under the shear force. Addition of GFRP bars, rather than CFRP bars, with a higher elongation capacity in I and U beams caused ductile behavior. (C) 2021 Sharif University of Technology. All rights reserved.
Web Hole Diameter Optimization for Enhancing Bending Capacity of Steel Beams: Experimental and Numerical Analysis
(Springer India, 2025) Sadid, M. S.; Cinar, N.; Maali, M.; Yaman, Z.; Bilen, M. B.; Sahin, F. Z.; Maali, M.
This study examines the flexural behavior of cellular beams in the context of the size and placement of web openings. Cellular beams are widely used in construction due to their advantages such as weight reduction and versatility. However, the diameter and spacing of web openings significantly impact the flexural capacity of these beams. Therefore, the flexural behavior of steel beams with various web opening diameters and spacings was investigated using both experimental and numerical methods. In the experimental work, four-point bending tests were conducted on steel beams with three different web opening diameters (137 mm, 148 mm, and 160 mm) and various spacing configurations. The numerical analyses were performed using nonlinear finite element analysis in ABAQUS software. The numerical models were validated against experimental results and subsequently utilized in a parametric study. The results showed that increasing the web opening diameter reduced the flexural capacity by up to 64%, while wider spacing increased it by 10-20%. Additionally, when the ratio of beam height to web opening diameter is 1.75, the beam exhibits the highest load capacity and the lowest energy absorption loss. These findings underscore the importance of optimizing web opening configurations in the design of steel structures, both in practical and theoretical terms. The study highlights the need for future research to refine current design codes and integrate new technologies to achieve more efficient designs.