• Steel and Composite Structures
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• v.13 no.3
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• pp.225-238
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• 2012

Steel structural elements with web-tapered I cross section, are usually made of welded thin plates. Due to the nonrectangular shape of the element, thin web section may be obtained at the maximum cross section height. The buckling strength is directly influenced by lateral restraining, end support and initial imperfections. If no lateral restraints, or when they are not effective enough, the global behaviour of the members is characterized by the lateral torsional mode and interaction with sectional buckling modes may occur. Actual design codes do not provide a practical design approach for this kind of elements. The paper summarizes an experimental study performed by the authors on a relevant number of elements of this type. The purpose of the work was to evaluate the actual behaviour of the web tapered beam-columns when applying different types of lateral restraints and different web thickness.

• Wind and Structures
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• v.20 no.2
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• pp.275-292
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• 2015

The presence of traffic on a slender long-span bridge deck will modify the cross-section profile of the bridge, which may influence the flutter derivatives and in turn, the critical flutter wind velocity of the bridge. Studies on the influence of vehicles on the flutter derivatives and the critical flutter wind velocity of bridges are rather rare as compared to the investigations on the coupled buffeting vibration of the wind-vehicle-bridge system. A typical streamlined cross-section for long-span bridges is adopted for both experimental and analytical studies. The scaled bridge section model with vehicle models distributed on the bridge deck considering different traffic flow scenarios has been tested in the wind tunnel. The flutter derivatives of the modified bridge cross section have been identified using forced vibration method and the results suggest that the influence of vehicles on the flutter derivatives of the typical streamlined cross-section cannot be ignored. Based on the identified flutter derivatives, the influence of vehicles on the flutter stability of the bridge is investigated. The results show that the effect of vehicles on the flutter wind velocity is obvious.

• Structural Engineering and Mechanics
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• v.52 no.4
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• pp.723-738
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• 2014

Prestressing is the most commonly employed technique in bridges and long span beams in commercial buildings as prestressing results in slender section with higher load carrying capacities. This work is an attempt to study the performance of a minimum weight prestressed concrete beam adopting a non-prismatic section so that there will be a reduction in the volume of concrete which in turn reduces the self-weight of the structure. The effect of adopting a non-prismatic section on parameters like prestressing force, area of prestressing steel, bending stresses, shear stresses and percentage loss of prestress are established theoretically. The analysis of non-prismatic prestressed beams is based on the assumption of pure bending theory. Equations are derived for dead load bending moment, eccentricity, and depth at any required section. Based on these equations an algorithm is developed which does the stress checks for the given section for every 500 mm interval of the span. Limit state method is used for the design of beam and finite difference method is used for finding out the deflection of a non-prismatic beam. All the parameters of nonprismatic prestressed concrete beams are compared with that of the rectangular prestressed concrete members and observed that minimum weight design and economical design are not same. Minimum weight design results in the increase in required area of prestressing steel.

• Steel and Composite Structures
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• v.24 no.2
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• pp.201-211
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• 2017

This study evaluates the reliability of present European codes in predicting the collapse load of columns made with perforated cold-formed steel (CFS) profiles under combined axial load and bending. To this aim, a series of experimental tests on slender open-section specimens have been performed at varying load eccentricity. Preliminarily, stub column tests have also been performed to calculate the effective section properties of the investigated profile. By comparison of experimental data with code-specified M-N strength domains, the authors demonstrate that present code formulations may underestimate the collapse load of thin-walled perforated open sections. The study is the first step of a wider experimental and numerical study aimed at better describing strength domains of perforated CFS open sections.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.120-125
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• 2000

A heddle frame is the major part of a loom that produces woven cloth by insertion of weft yarns between warp yams. Warp yarns are manipulated by many heddles fixed in a heddle frame. Recently, the up and down speed of heddle frames has been increased much for the increase of productivity, which induces higher inertial stresses and vibrations in the heddle frame. The heddle frame has the rectangular cross-section. For the design of box type beams of rectangular cross-section, extensional stiffness EA, flexural stiffness El, and torsional stiffness GJ as well as the vibration characteristics are important and should be simultaneously considered. Tn this paper, the vibration characteristics of the composite and the composite sandwich beams for high-speed heddle frame were tested by impulse frequency response.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.3-10
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• 1999

Recently, It is proceeding the project of offshore structures in the many contury. A hybrid boundary-integral method is developed for computing wave forces on floating bodies. In this method, using the cylindric boundary for deviding elements, it is convenient to analysis but is difficult to apply to the rectangular or slender bodies. Thus, in this paper, I propose the new method by using the fictitious vertical cylinder of arbitary cross-section and shows results of the numerical analysis for testing.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.04a
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• pp.80-85
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• 1992

A nonlinear second-order analysis program that properly describes the nonlinear behavior of concrete was developed by using the layering technique. As the slenderness ratio of column is increased, the peaks of P-M curve lie remote from the section interaction diagram for the same eccentricities. But the peaks of P-M curve lie rather close to the section interaction diagram for very large eccentricities. In this study , the effects of compressive strength of concrete, longitudinal steel ratio, and yield strength of steel on second-order moment of concrete columns were analyzed. As the compressive strength of concrete and the yield strength of steel are increased, the ratio of peak axial force to maximum axial strength for concentrically loaded short column( Pu/Po) is decreased. But as the longitudinal steel ratio is increased, the ratio , Pu/Po increases.

• Steel and Composite Structures
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• v.2 no.2
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• pp.129-146
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• 2002

This paper describes a series of compression tests carried out on concrete filled double skin tubes (CFDST). Both outer and inner tubes are cold-formed circular hollow sections (CHS). Six section sizes were chosen for the outer tubes with diameter-to-thickness ratio ranging from 19 to 57. Two section sizes are chosen for the inner tubes with diameter-to-thickness ratio of 17 and 33. The failure modes, strength, ductility and energy absorption of CFDST are compared with those of empty single skin tubes. Increased ductility and energy absorption have been observed for CFDST especially for those having slender outer tubes with larger diameter-to-thickness ratio. Predictions from several theoretical models are compared with the ultimate strength of CFDST stub columns obtained in the tests. The proposed formula was found to be in good agreement with the experimental data.

• Earthquakes and Structures
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• v.9 no.4
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• pp.831-849
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• 2015

Seismic-design procedures for walls require that the confinement in the critical (plastic hinge) regions should extend over a length in the compression zone of the cross section at the wall base where concrete strains in the Ultimate Limit State (ULS) exceed the limit of 0.0035. In a performance-based framework, confinement is linked to required curvature ductility so that the drift demand at the performance point of the structure for the design earthquake may be met. However, performance of flexural walls in the recent earthquakes in Chile (2010) and Christchurch (2011) indicates that the actual compression strains in the critical regions of many structural walls were higher than estimated, being responsible for several of the reported failures by toe crushing. In this study, the method of estimating the confined region and magnitude of compression strain demands in slender walls are revisited. The objective is to account for a newly identified kinematic interaction between the normal strains that arise in the compression zone, and the lumped rotations that occur at the other end of the wall base due to penetration of bar tension yielding into the supporting anchorage. Design charts estimating the amount of yield penetration in terms of the resulting lumped rotation at the wall base are used to quantify the increased demands for compression strain in the critical section. The estimated strain increase may exceed by more than 30% the base value estimated from the existing design expressions, which explains the frequently reported occurrence of toe crushing even in well confined slender walls under high drift demands. Example cases are included in the presentation to illustrate the behavioral parametric trends and implications in seismic design of walls.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.159-166
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• 2022

In this study, slender reinforced concrete columns subjected to high temperatures and eccentric axial loads are evaluated by finite element analysis employing Abaqus (a finite element analysis program). Subsequently, the analysis results are compared and assessed. The sequentially coupled thermal stress analysis provided by Abaqus was employed to reflect the condition of an axially loaded column exposed to fire. First, heat transfer analysis was performed on the column cross-section. After verifying the results, another analysis was conducted: the cross-section was transformed into a three-dimensional element and then structural analyzed. In the analysis process, the column was modeled by accounting for the effects of tension stiffening and initial imperfection that could affect convergence and accuracy. The analysis results were compared with 74 experimental records, and an average error of 6% was observed based on the fire exposure and resistance. The foregoing indicates that the fire resistance performance of reinforced concrete columns can be predicted through finite element analysis.