• Structural Engineering and Mechanics
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• 제73권5호
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• pp.487-500
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• 2020

Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.

• Steel and Composite Structures
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• 제29권5호
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• pp.659-667
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• 2018

This paper deals with the experimental study on strength the strength and deformation characteristics of short circular Concrete Filled Steel Tube (CFST) columns. Effect of vertical stiffeners on the behavior of the column is studied under axial compressive loading. Intermittently welded vertical stiffeners are used to strengthen the tubes. Stiffeners are attached to the inner surface of tube by welding through pre drilled holes on the tube. The variable of the study is the spacing of the weld between stiffeners and circular tube. A total of 5 specimens with different weld spacing (60 mm, 75 mm, 100 mm, 150 mm and 350 mm) were prepared and tested. Short CFST columns of height 350 mm, outer tube diameter of 165 mm and thickness of 4.5 mm were used in the study. Concrete of cube compressive strength $41N/mm^2$ and steel tubes with yield strength $310N/mm^2$ are adopted. The test results indicate that the strength and deformation of the circular CFST column is found to be significantly influenced by the weld spacing. The ultimate axial load carrying capacity was found to increase by 11% when the spacing of weld is reduced from 350 mm to 60 mm. The vertical stiffeners are found to effective in enhancing the initial stiffness and ductility of CFST columns. The prediction models were developed for strength and deformation of CFST columns. The prediction is found to be in good agreement with the corresponding test data.

• 대한안전경영과학회지
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• 제25권2호
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• pp.187-192
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• 2023

In piping systems, trapeze hangers are subjected to vertical and horizontal seismic loads and stiffeners are used. In this study, monotonic compression tests were conducted with the removable stiffeners using three variables: stiffener clamp fixing position, section length, and installation direction. The maximum load reinforced with stiffeners could withstand a compressive load of 11kN by applying a safety factor of 10%. It could be estimated that the fixing clamp spacing or the length of shape and load had a proportional relationship. And the stiffener must be fixed in the direction of the strong axis on hinge parts. Also the stiffener buckiling load design proposes to use a method of calculate the flexural buckling compressive strength of and unreinforced full threaded bolt.

• 대한조선학회 특별논문집
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• 대한조선학회 2011년도 특별논문집
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• pp.21-24
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• 2011

Oil Tight Bulkhead (O. T. Bulkhead) is one of the most important structural members of oil tankers in the views of vessel's strength and safety. Therefore O.T. bulkhead's strength should be sufficient against relevant loadings, which is normally verified by local scantling requirement and structural strength analysis defined in CSR (Common Structure Rules for Double Hull Oil Tankers). However, there is a weak-able situation when the vertical stiffeners are cut due to the penetration of cargo pipes through O. T. Bulkhead. In addition, CSR does not define how to prove the strength of this case. Therefore it is necessary to verify the structural adequacy in case that several vertical stiffeners are discontinued. This article intends to prove the strength of O. T. Bulkhead with five (5) vertical stiffeners discontinued due to pipes' penetration using the grillage analysis and the finite element analysis and to provide proper reinforcement.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.121-130
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• 2002

This paper presents the tensile behavior of a Concrete-Filled Square Steel Tubular (CFT) column to H-beam welded connections. These connections were externally reinforced with T-shaped stiffeners at the junction of CFT column and beam. The tensile loading tests of eighteen tee-joint connections and finite element analysis using ANSYS were carried out. The main parameters of tests are as follows: 1) the thickness of Square Steel Tubular Column : 6 mm, 9 mm, 2) the strength ratios of tensile strength of horizontal stiffeners to tensile strength of beam flange : 70 %, 100 %, 150 %, 3) the strength ratios of shear strength of vertical stiffeners to tensile strength of beam flange : 80 %, 115 %, 160 %. The results of the tests demonstrate that overall behavior and failure modes of all the specimens are governed mainly by the horizontal stiffeners rather than the vertical stiffeners, and the vertical stiffener played only a role in transferring load introduced from beam to column.

• Earthquakes and Structures
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• 제23권3호
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• pp.297-313
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• 2022

Composite steel plate shear wall (CSPSW) is a relatively novel structural system proposed to improve the performance of steel plate shear walls by adding one or two layers of concrete walls to the infill plate. In addition, the buckling of the infill steel plate has a significant negative effect on the shear strength and energy dissipation capacity of the overall systems. Accordingly, in this study, using the finite element (FE) method, the performance and behavior of composite steel shear walls using T-shaped stiffeners to prevent buckling of the infill steel plate and increase the capacity of CSPSW systems have been investigated. In this paper, after modeling composite steel plate shear walls with and without steel plates with finite element methods and calibration the models with experimental results, effects of parameters such as several stiffeners, vertical, horizontal, diagonal, and a combination of T-shaped stiffeners located in the composite wall have been investigated on the ultimate capacity, web-plate buckling, von-Mises stress, and failure modes. The results showed that the arrangement of stiffeners has no significant effect on the capacity and performance of the CSPSW so that the use of vertical or horizontal stiffeners did not have a significant effect on the capacity and performance of the CSPSW. On the other hand, the use of diagonal hardeners has potentially affected the performance of CSPSWs, increasing the capacity of steel shear walls by up to 25%.

• Structural Engineering and Mechanics
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• 제43권4호
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• pp.449-458
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• 2012

Finite element buckling analysis of insulated transition flue ducts is carried out to determine the critical buckling load multipliers when subjected to axial compression for design process. Through this investigation, the results of numerical computations to examine the buckling strength for different possible duct shapes (cylinder, and circular-to-square) are presented. The load multipliers are determined through detailed buckling analysis taking into account the effects of geometrical construction and duct plate thickness which have great influence on the buckling load. Enhancement in the buckling capacity of such ducts by the addition of horizontal and vertical stiffeners is also investigated. Several models with varying dimensions and plate thicknesses are examined to obtain the linear buckling capacities against duct dimensions. The percentage improvement in the buckling capacity due to the addition of vertical stiffeners and horizontal Stiffeners is shown to be as high as three times for some cases. The study suggests that the best location of the horizontal stiffener is at 0.25 of duct depth from the bottom to achieve the maximum buckling capacity. A design equation estimating the buckling strength of geometrically perfect cylindrical-to-square shell is developed by using regression analysis accurately with approximately 4% errors.

• Steel and Composite Structures
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• 제22권1호
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• pp.183-201
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• 2016

Perforated steel beams can be optimised by increased beam depth and the moment of inertia combined with a reduced web thickness, favouring the use of original I-section beams. The designers are often confronted with situations where optimisation cannot be carried out effectively, taking account of the buckling risk at web posts, moment-shear transfers and local plastic deformations on the transverse holes of the openings. The purpose of this study is to suggest solutions for reducing these failure risks of tested optimal designed beams under applying loads in a self-reacting frame. The design method for the beams is the hunting search optimisation technique, and the design constraints are implemented from BS 5950 provisions. Therefore, I have aimed to explore the strengthening effects of reinforced openings with ring stiffeners, welded vertical simple plates on the web posts and horizontal plates around the openings on the ultimate load carrying capacities of optimally designed perforated steel beams. Test results have shown that compared to lateral stiffeners, ring and vertical stiffeners significantly increase the loadcarrying capacity of perforated steel beams.

• 국제초고층학회논문집
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• 제7권3호
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• pp.223-232
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• 2018

Two novel types of construction detailings, including using the distributive beam and the inner ring diaphragm in the joint between large-section CFT columns and outrigger truss to enhance the transferring efficiency of huge vertical load, and using the T-shaped stiffeners in the steel tube of large-section CFT columns to promote the local buckling capacity of steel tubes, were tested to investigate their working mechanism and design methods. Experimental results show that the co-working performance between steel tube and inner concrete could be significantly improved by setting the distributive beam and the inner ring diaphragm which can transfer the vertical load directly in the large-section CFT columns. Meanwhile, the T-shaped stiffeners are very helpful to improve the local bulking performance of steel tubes in the column components by the composite action of T-shaped stiffeners together with the core concrete under the range of flange of T-shaped stiffeners. These two approaches can result in a lower steel cost in comparison to normal steel reinforced concrete columns. Finally, a practical engineering case was introduced to illustrate the economy benefits achieved by using the two typical detailings.

• 한국공간구조학회논문집
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• 제4권4호
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• pp.137-144
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• 2004

Recently, as steel structures become higher and more long-spanned, application of high-strength steels is increasing gradually. However, criteria and example for design of high-strength steel are not built up. exiting criteria for structural steels is not proper for economical design of high-strength steel. Moreover, exiting criteria will be decrease the fatigue performance of steel bridge using high-strength steel. Therefore, criterion for application of high-strength steel must be established. In this paper, the behavior of plate girder using high-strength vertical stiffeners was clarified by carrying out layer elastic-plastic finite element analysis using finite deformation theory. In order to optimize the design and construction of plate girder using high-strength vertical stiffener, criterion for application of high-strength vertical stiffener is proposed.