Browsing by Author "Sagiroglu, Merve"

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Analyzing of Bolted Joints for Connecting Rectangular Hollow Sections in Reticulated Shells
(Taylor & Francis Ltd, 2023) Maali, Mahyar; Orhan, Suleyman Nazif; Sagiroglu, Merve; Cirpici, Burak Kaan
This paper investigates a novel joint method for connecting rectangular hollow section (RHS) members in reticulated shells. It is proposed to overcome the problem of connecting rectangular tubes using the traditional joint (cast steel joint) under dead and snow load. A case study is a structure in the eastern region of Turkey that was built on August 20, 2019. This museum-style structure is 40 meters long and 20 meters wide, with an oval shape. In the middle of the building, five tree-shaped columns were used. ANSYS is used to create a refined 3D solid model of the RHS joint. The moment-rotation results show that the proposed RHS joint (plate steel joint) for connecting rectangular hollow section members can be considered a semi-rigid connection and preferred due to its lower cost and weight. Moreover, the dissipated energy capacity has been raised by approximately 3.22 times when the plate steel type model has been used instead of the cast steel type. The stress ratios indicate that the connection stress in the Cast steel type model is lower than the stress in the Plate steel type model. As a result, the Cast steel type model is determined to be incredibly safe and more rigid than plate steel. Furthermore, since the resulting stress rates are lower than those of S355 steel, both models (cast and plate steel type models) can be used for connecting RHS.
Buckling Behavior of Double-Layered Composite Cylindrical Shells
(Elsevier Sci Ltd, 2021) Maali, Mahyar; Bayrak, Baris; Kilic, Mahmut; Sagiroglu, Merve; Aydin, Abdulkadir Cuneyt
Composite shells of revolution are widely used as pressure vessels, reservoirs and tanks, rocket, spacecraft parts and in different elements of the building. The aim of this study is to investigate the buckling and post-buckling behavior of the cylindrical shell made of mild steel filled with melted waste polymer, polypropylene, filled with the silicon and the steel adhesive. Furthermore, seven thin-walled cylindrical shell specimens with different composite cover subject to hydrostatic pressure were tested in the present work. The results of testing under different theories and codes are compared. Also, one specimen was without composite cover (perfect model), which used to check other specimens. This study shows that the initial buckling value of all other specimen tests was higher than the perfect specimen and double layer CFRP coiling have a significant effect on the initial buckling value. However, using material between two cylinders instead of CFRP wrapping increased initial buckling value compared to the perfect specimen. The use of melted PP was more effective than other materials (silicone, steel adhesive glue and waste polymer).
Cold-Formed Steel Beam-to Screw Connections Exposed to High Temperatures Reinforced with CFRP
(Springer Int Publ Ag, 2023) Sagiroglu, Merve; Maali, Mahyar; Kar, Mert; Bilen, Mahmut Bugra
This study uses eight tests to show the experimental behavior of cold-formed steel beam-to-column screw connections exposed to high temperatures reinforced with CFRP. The structural beam members were heated from room temperature to 600 degrees C, held at that temperature for 5 h, and then cooled to room temperature before being reinforced with CFRP (carbon fiber-reinforced polymer). The joint's energy dissipation capacity, moment-rotation behavior, and ductility under high-temperature conditions were investigated using different beam thicknesses, gusset thicknesses, and stiffeners. The results demonstrate that increasing the gusset thickness reduced the moment, stiffness, and rotational values of the connection for beams without stiffeners but increased the beam's ductility. Using stiffeners reduced the beam's ductility but increased its energy dissipation capacity. In addition, increasing the profile thickness decreased the energy dissipation capacity. The collapse modes under high-temperature reinforced with CFRP conditions were compared to ambient temperature and post-fire conditions. The findings show that the buckling of models is affected by the thickness of the beam's wall. When the thickness of the beam wall exceeds the thickness of the gusset plate, collapse mode occurs, resulting in screw breakage. Beam buckling does not appear in beams that have stiffeners at the connection. This means that the beam will not buckle no matter how many stiffeners are employed in the connection. In addition, beam buckling was too common in beams exposed to high temperatures. Furthermore, the use of CFRP in the beam reduced buckling. All connection collapses are induced by the screw when the beam thickness divided by the gusset thickness is less than one; otherwise, they are caused by the gusset yield with screw rupture.
Design and Analysis of Non-Linear Space Frames with Semi-Rigid Connections
(Techno-press, 2015) Sagiroglu, Merve; Aydin, Abdulkadir Cuneyt
Semi-rigid connections are the actual behavior of beam-to-column connections in steel frames. However, the behavior of semi-rigid connections is not taken into account for the simplicity in the conventional analysis and design of steel frames. A computer-based analysis and design has been studied for the three-dimensional steel frames with semi-rigid connections. The nonlinear analysis which includes the effects of the flexibility of connections is used for this study. It is designed according to the buckling and combined stress constraints under the present loading after the joint deformations and the member end forces of the space frame are determined by the stiffness matrix method. The semi-rigid connection type is limited to the top and bottom angles with a double web angle connection. The Frye-Morris polynomial model is used to describe the non-linear behavior of semi-rigid connections. Various design examples are presented to demonstrate the efficiency of the method. The results of design and analysis of unbraced semi-rigid frames are compared to the results of unbraced rigid frames under the same design requirements.
Design Optimization of Semi-Rigid Space Steel Frames with Semi-Rigid Bases Using Biogeography-Based Optimization and Genetic Algorithms
(Techno-Press, 2019) Shallan, Osman; Maaly, Hassan M.; Sagiroglu, Merve; Hamdy, Osman
This paper performs for the first time a simultaneous optimization for members sections along with semi-rigid beam-to-column connections for space steel frames with fixed, semi-rigid, and hinged bases using a biogeography-based optimization algorithm (BBO) and a genetic algorithm (GA). Furthermore, a member's sections optimization for a fully fixed space frame is carried out. A real and accurate simulation of semi-rigid connection behavior is considered in this study, where the semi-rigid base connections are simulated using Kanvinde and Grilli (2012) nonlinear model, which considers deformations in different base connection components under the applied loads, while beam-to-column connections are modeled using the familiar Frye and Morris (1975) nonlinear polynomial model. Moreover, the P-Delta effect and geometric nonlinearity are considered. AISC-LRFD (2016) specification constraints of the stress and displacement are considered as well as section size fitting constraints. The optimization is applied to two benchmark space frame examples to inspect the effect of semi-rigidity on frame weight and drift using BBO and GA algorithms.
The Effect of Longitudinal Imperfections on Thin-Walled Conical Shells
(Elsevier, 2018) Maali, Mahyar; Aydin, Abdulkadir Cuneyt; Showkati, Hossein; Sagiroglu, Merve; Kilic, Mahmut
The load carrying capacity as well as the buckling and post-buckling behavior of conical thin-walled shells exposed to pressure loads are very sensitive to imperfections in the initial geometry. In this study, comprehensive work on the overall longitudinal imperfections created by welding and their effects on external pressure load carrying capacity has been performed by using finite-element models. The models were modified to include either one or two-line imperfection with amplitudes of six different magnitudes. The results presented here have confirmed some of the existing theories and provided new information concerning buckling of thin-walled conical shells. The load carrying capacity from buckling analysis was double the result from the Jawad theory for perfect models (without imperfection). In this research, increasing the cone height increased the imperfections' weakening effect. In nonlinear analyses, the presence of an imperfection increased the buckling load capacity. However, increasing the number of imperfections resulted in less buckling load capacity than the model with one imperfection.
Experimental Assessment of the Semi-Rigid Connections Behavior with Angles and Stiffeners
(Elsevier Sci Ltd, 2015) Aydin, Abdulkadir Cuneyt; Kilic, Mahmut; Maali, Mahyar; Sagiroglu, Merve
Experimental investigations were done on statically loaded beam-to-column connections that were designed with top-and-seat angles in minor column axes. This study was undertaken to analyze the influence of angles with and without stiffeners on the behavior of the beam-to-column connections. The aim was to provide necessary data to improve the Eurocode 3. While the rotation stiffness and capacity of the entire stiffener used beams decreased, the resistance moment increased. Moreover, the rotation capacity increased with the increased thickness of the top-and-seat angles. (C) 2015 Elsevier Ltd. All rights reserved.
Experimental Behavior of Cold-Formed Stainless Steel Screwed Beam-Column Connections at Post-Fire Condition
(Springer International Publishing AG, 2021) Cirpici, Burak Kaan; Orhan, Suleyman Nazif; Kilic, Mahmut; Maali, Mahyar; Sagiroglu, Merve
Herein this paper, the experimental behavior of the cold-formed stainless steel screwed beam-column connection with the post-fire condition is presented by performing eight experiments. The beam structural members have been heated beginning from room temperature to 600 degrees C remaining at this temperature for 5-h and letting them cool down back to the room temperature. Energy dissipation capacity, moment-rotation behavior and ductility of the joint under the post-fire condition have been examined by various beam thickness, gusset thickness and with and without stiffeners. The obtained results show that energy dissipation, and rotation decrease due to the sudden breakage of the screws with the increase in gusset plate thickness. Contrast to this outcome, stiffness had a decrease trend, whereas rotation increases when using stiffeners. With the increase of beam thickness, rotation had an increase behavior. Failure modes under the post-fire condition have been compared with the ambient temperature condition. The results indicate that the pre-heating before loading influences the screws' strength more causing a laceration around the screws hence the total collapse of the connection. As using stiffeners increases the strength of the beam at ambient temperature condition, it also gives an advantage under fire condition. Therefore, rare screw deformation has been obtained depending on the beam thickness and gusset plate thickness while wrinkle of the gusset plate and torsion of the beam has been observed.
Experimental Behavior of Screwed Beam-to Connections in Cold-Formed Steel Frames
(Springer Heidelberg, 2018) Maali, Mahyar; Sagiroglu, Merve; Solak, M. Semih
In this study, a beam-to-column connection in cold-formed steel structure has been examined using self-drilling screw. An experimental study is carried out for the full-scale specimens of the connection. The beam has different thickness to determine the structural behavior of the connection. The behavior of connections is represented by their moment-rotation curve. So, this study focuses on evaluating the moment-rotation curves and whose characteristic values. The aim of the work is also to provide failure mechanism for the connection whose fastener is self-drilling screws. The failures of the connected members and screws are observed in the knee joint configuration. This was performed through cantilever tests of full-scale beam-to-column joints. Experiment results were evaluated by comparing to the results of other experiments with different combination thickness. The experimental results showed that plastic and maximum deformation decreases while maximum moment and stiffness increases when the profile thickness of the beam increased.
Experimental Evaluation of the Post-Fire Behavior of Steel T-Component in the Beam-to Connection
(Elsevier Sci Ltd, 2018) Sagiroglu, Merve
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.
Experimental Investigation of Sinus Beams with End-Plate Connections
(Elsevier Sci Ltd, 2015) Aydin, Abdulkadir Cuneyt; Maali, Mahyar; Kilic, Mahmut; Sagiroglu, Merve
Using high-strength steel with reduced weight in buildings and industry is important because, as the weight of the buildings is reduced, the behavior of steel in various situations becomes important. In this study, moment-rotation curves of sinusoidal beams were investigated using fixed end-plate connections. Use of a new sinusoidal beam model is proposed. Results were compared with experiments performed not only with IPE profile but also with similar manufactured profile. In the result, weight was reduced for sinusoidal 70 degrees beams, showing improvements in terms of moment resistance. (C) 2015 Elsevier Ltd. All rights reserved.
Experimental Model for Predicting the Semi-Rigid Connections' Behaviour with Angles and Stiffeners
(Sage Publications Inc, 2017) Maali, Mahyar; Kilic, Mahmut; Sagiroglu, Merve; Aydin, Abdulkadir Cuneyt
This article presents the experimental results of nine specimens of steel bolted beam-to-column connections with top-and-seat angle and stiffener. All of the connections have the angles and beams reinforced with stiffeners in the extended parts. The results are analysed on the basis of the global moment-rotation curves. The main parameters observed are the failure modes, the evolution of the resistance, the stiffness, the rotation capacity, the ductility of a joint and the energy dissipation. The aim was to provide necessary data to improve the Eurocode 3. While the stiffness decreased with the increased thickness of beam stiffeners of 5-10 mm, the maximum bending moment (M-j.max) increased with the increased length of top-and-seat angle.
Investigation of Innovative Steel Runway Beam in Industrial Building
(Indian Acad Sciences, 2015) Maali, Mahyar; Aydin, Abdulkadir Cuneyt; Sagiroglu, Merve
The design of a runway beam for overhead cranes is of great importance when constructing steel structures, as is the lateral-torsional buckling (LTB) value obtained for I-beam sections. Therefore, engineers must always consider the optimal design of these beams under overhead cranes loads. In this study, runway beams of three overhead crane groups were analyzed for LTB, and a sinusoidal runway beam body was developed. These runway beams with different sinusoidal angles were analyzed by using the finite element method (ABAQUS) and compared to each other and other runway IPE-IPN beam sections; furthermore, all models were compared with the Canadian Institute of Steel Construction standard. As a result, a new method was proposed for developing sinusoidal runway beams for overhead cranes. The sinusoidal runway beam has lower weight than runway IPE-IPN beam sections. Ultimately, a sinusoidal beam body was developed practically with a scale of 1:1.
A Novel Approach for Bolted T-Stub Connections
(Korean Soc Steel Construction-KSSC, 2018) Sagiroglu, Merve; Maali, Mahyar; Kilic, Mahmut; Aydin, Abdulkadir Cuneyt
This paper reports an investigation into new connection types and their behaviors determined using full-scale experiments. T-shaped connections were created using the IPE standard profile. The aim of this study was to analyze the influence of T connections based on the IPE standard profile, height of beam to height of T-stub joint (H) of T-stub joints, and lengths (X) of T-stub joints on the behavior of steel connections, in order to provide the necessary data for improving Eurocode 3 and enable efficient use of residue IPE standard profiles and back to the consumption cycle. While the moment resistance values increased with an increase in H from H-min to H-max in model groups with X of 126 mm, and the energy dissipation increased with an increase in H from H-min to H-max and also with an increase in the lengths (X) of T-stub joints from 54 to 126 mm.