• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.729-742
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• 2023

It is a recent attraction to the mechanical scientists to investigate state of wave propagation, buckling and vibration in the sport balls to observe the importance of different parameters on the performance of the players and the quality of game. Therefore, in the present study, we aim to investigate the wave propagation in handball game ball in term of mass of the ball and geometrical parameters wit incorporation of the viscoelastic effects of the ball material into account. In this regard, the ball is modeled using thick shell structure and classical elasticity models is utilized to obtain the equation of motion via Hamilton's principle. The displacement field of the ball model is obtained using first order shear deformation theory. The resultant equations are solved with the aid of generalized differential quadrature method. The results show that mass of the ball and viscoelastic coefficient have considerable influence on the state of wave propagation in the ball shell structure.

• Earthquakes and Structures
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• v.25 no.5
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• pp.343-358
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• 2023

The superelastic viscous damper (SVD) is a hybrid passive control device comprising a viscoelastic damper and shape memory alloy (SMA) cables connected in series. The SVD is an innovative damper through which a large amount of seismic energy can dissipate. The current study assessed the seismic collapse induced by steel moment-resisting frames (SMRFs) equipped with SVDs and compared them with the performance of special MRFs and buckling restrained brace frames (BRBFs). For this purpose, nonlinear dynamic and incremental dynamic analysis (IDA) were conducted in OpenSees software. Both 5- and 9-story special MRFs, BRBFs, and MRFs equipped with the SVDs were examined. The results indicated that the annual exceedance rate for maximum residual drifts of 0.2% and 0.5% for the BRBFs and MRFs with SVDs, respectively, were considerably less than for SMRFs with reduced-beam section (RBS) connections and that the seismic performances of these structures were enhanced with the use of the BRB and SVD. The probability of collapse due to residual drift in the SVD, BRB, and RBS frames in the 9-story structure was 1.45, 1.75, and 1.05 times greater than for the 5-story frame.

• Steel and Composite Structures
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• v.49 no.5
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• pp.473-486
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• 2023

A through-railway bridge with an inclined girder has recently been applied to optimize the cross-section of a slender bridge structure in railway bridges. To achieve the additional cross-section optimization effect by the bolted end-plate connection, it is necessary to investigate the application of the bolted end-plate tension connection between the inclined girder and the crossbeam. This basic study was conducted on the application of the bolted end-plate moment connection of crossbeams to half-through girders with inclined webs. The combined behavior of vertical deflection and rotational behavior was observed due to the effect of the web inclination in the inclined girder where the steel crossbeam was connected to the girder by the bolted end-plate moment connection. Therefore, in the experiment, the deflection of the inclined girder was 1.77-2.93 times greater than that of the vertical girder but the lateral deflection of the inclined girder was 0.4 times less than that of the vertical girder. Moreover, the tensile stress of the upper bolts in the inclined girder with low crossbeams was clearly 0.81 times lower than that of the vertical girder. According to the results, the design formula for vertical girders does not reflect the influence of the web inclination. Therefore, this study proposed the design procedures for the inclined girder to apply the bolted end-plate moment connection of the crossbeam to the inclined girder by reflecting the design change factors according to the effect of the web inclination.

• Computers and Concrete
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• v.33 no.5
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• pp.509-518
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• 2024

In this study, we investigated the effect of shear-key placement on the performance of grouted connections in offshore wind-turbine structures. Considering the challenges of height control during installation, we designed and analyzed three grouted connection configurations. We compared the crack patterns and strain distribution in the shear keys under axial loading. The results indicate that the misalignment of shear keys significantly influences the ultimate load capacity of grouted connections. Notably, when the shear keys were positioned facing each other, the ultimate load decreased by approximately 15%, accompanied by the propagation of irregular cracks in the upper shear keys. Furthermore, the model with 50% misalignment in the shear-key placement exhibited the highest ultimate strength, indicating a more efficient load resistance than the reference model. This indicates that tensile-load-induced cracking and the formation of compressive struts in opposite directions significantly affect the structural integrity of grouted connections. These results demonstrate the importance of considering buckling effects in the design of grouted connections, particularly given the thin and slender nature of the inner sleeves. This study provides valuable insights into the design and analysis of offshore wind-turbine structures, highlighting the need for refined design formulas that account for shifts in shear-key placement and their structural implications.

• Advances in Computational Design
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• v.8 no.4
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• pp.327-351
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• 2023

This article explores how multi-objective optimization techniques can be used to design cost-effective and structurally optimal spatial steel structures, highlighting that optimizing performance can be as important as minimizing costs in real-world engineering problems. The study includes the minimization of maximum horizontal displacement, the maximization of the first natural frequency of vibration, the maximization of the critical load factor concerning the first global buckling mode of the structure, and weight minimization as the objectives. Additionally, it outlines a systematic approach to selecting the best design by employing four different evolutionary algorithms based on differential evolution and a multi-criteria decision-making methodology. The paper's contribution lies in its comprehensive consideration of multiple conflicting objectives and its novel approach to simultaneous consideration of bracing system, column orientation, and commercial profiles as design variables.

• Structural Engineering and Mechanics
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• v.91 no.3
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• pp.301-313
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• 2024

Plastic buckling of tubular columns has been attributed to rotational instability of plastic hinges. The present study aimed to characterize the plastic hinges for two different grades of strain-hardening, examined in mild-steel (MS) and stainless-teel (SS) tubes with un-strengthened and strengthened conditions. At the primary stage, the formerly tested experimental specimens were simulated using full-scale FE models considering nonlinear response of the materials, then to estimate the characteristics of the plastic hinges, a meso model was developed from the critical region of the tubes and the moment-rotation diagrams were depicted under pure bending conditions. By comparison of the relative rotation diagram obtained by the full-scale models with the critical rotation under pure bending, the length and critical rotation of the plastic hinges under eccentric axial load were estimated. The stress and displacement diagrams indicated the mechanism of higher energy absorption in the strengthened tubes, compared to unstrengthened specimens, due to establishment of stable wrinkles along the tubes. The meso model showed that by increasing the critical rotation in the strengthened MS tube equal to 1450%, the energy absorption of the tube has been enhanced to 2100%, prior to collapse.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.473-479
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• 2020

In this study, the structural experiment was conducted with two types of specimens to investigate the mechanical behavior of the column-rafter-purlin connection of an arch-type greenhouse under monotonic loading. Based on the experimental results, the flexural performance was analyzed for two types of connections, and connection classification was attempted. Type B showed 77% of flexural performance compared to Type A, and both types showed that the rigidity and flexural strength did not reach the level of the full rigid. The behavior of the column-rafter-purlin connection was dominated by local buckling due to deformation of the weld and fasteners. As a result of connection classification by AISC standard, both Type A and B connections showed a result that did not meet the rigid connection performance assumed during design, and were classified as simple connection. Therefore, the connection performance evaluation and classification results show that the greenhouse design should be made in consideration of connection performance and in order to design a reliable greenhouse structure, a study on establishing clear design standards for the greenhouse connection is necessary.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.645-653
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• 2008

Welded built-up square tubes are manufactured by flare welding at the center of the column width for cold-formed L-shaped four-piece plates and improved composite effect of concrete and steel by vertical inner anchor. Also, the axial resistance of concrete is increased by the thinness of the steel column, and the composite effect of concrete and steel prevents the steel column from local buckling. In this study, we introduced a manufacturing method of built-up square column steel square concrete-filled tubular column with vertical inner anchor and superior structural performance of the square stub column verified by the structural test for 15 specimens with parameters of shape of tube (built-up square tube, general steel tube), width over thickness of the steel tube (B/t=50, 58, 67) and the strength of concrete (f'c=10MPa, 50MPa).

• Journal of the Korea Institute of Building Construction
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• v.13 no.3
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• pp.272-281
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• 2013

Concrete filled tube (CFT) columns, which consist of a steel tube filled with concrete, combine the benefits of the two materials. The steel tube provides a confining pressure to the concrete, while the local buckling of steel plate can be prevented by the concrete core. CFT columns also have a high fire resistance due to the heat storage effect of concrete under fire. For this reason, it is possible to develop CFT columns without fire protection measures. CFT columns without fire protection have many advantages, including quality control, cost reduction, better space efficiency and a shorter construction period. Due to these advantages, studies on the development of CFT columns without fire protection measures have been performed. However, CFT columns lose their bearing capacity under fire because the steel tube is exposed to the outside. As a result, the structure is collapsed, causing significant damage. In this research, we made a CFT column using high strength concrete (100 MPa) and high strength steel (800 MPa). We use steel fiber and nylon fiber with concrete to provide fire resistance. We perform the fresh concrete experiment and investigate the fire resistance of the CFT column (${\Box}400{\times}400{\times}15{\times}3000mm$) under loading. To investigate the effect of steel fiber on increasing fire resistance, we compare the fire resistance time according to the steel fiber. Through the test, it was found that the CFT specimen with steel fiber had better fire resistance performance than other cases.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.443-450
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• 2012

In this study, This study investigates the axial load behavior of concrete-filled steel columns using seismic rectangular steel tube with the width-to-thickness and slenderness ratio. Due to cold-roll forming and cold-press forming of steel tube, the flat part and the corner part of the rectangular steel tubes are changed in the material properties compared to SN-steel plate. It was showed the tendency to increase yield strength, tensile strength and upper limit of yield ratio This phenomenon affects the nonlinear behavior after local buckling of the steel tube. Therefore, the coupon test was performed by the processing of rectangular steel tube, in order to assess forming performance. And a total of 6 CFT-columns were tested under monotonic loading condition. Main parameters were the width-thickness ratio and the slenderness ratio.