• International Journal of High-Rise Buildings
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• v.6 no.3
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• pp.217-226
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• 2017

This paper summarizes the structural concept and design of the "Nakanoshima Festival Tower West" in Osaka, Japan, which is 200m high and has a super-high damping system. Its superstructure is mainly composed of a central core and outer tube frames. It has a bottom truss structure at the boundary between the low-rise and mid-rise sections of the building, where the column arrangement is changed. Besides, the high-rise section of the building has a neck truss structure. These truss structures smoothly transfer the axial forces of the columns and reduce the flexural deformations induced by horizontal loads. Oil dampers with extremely high damping capacity are installed in the rigid walls named the "Big Wall Frames" of the low-rise section. Moreover, many braces and damping devices are well arranged in the center core of each story. The damping effects of these devices ensure that all structural members are remain within the elastic range and that story drifts are within 1/150 in large earthquakes. This super-high damping structure in the low-rise section is named the "Damping Layer". The whole structural system is named the "Super Damping Structure". The whole structural systems enhance the building's safety, comfort and Business Continuity Planning (BCP) under large earthquakes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.1-8
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• 1991

Recently the use of steel fibers has been increased in flexural members and columns of concrete structures subjected to cyclic loadings; such as bridge decks, highway roads, runway of airport, buildings, etc.. However only a few experimental tests have been carried out under fatigue loading. In the present study, the reinforced concrete beams with 1% and 2% steel fiber volume fraction are investigated with and without stirrups. It has been found that in fatigue tests, the failure of the beam is usually due to breaking of fibers rather than fiber pull-out. A comparison of experiments and numerical analysis using the nonlinear F.E.M. program (ADINA) is also presented herein.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.104-107
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• 2004

The crack widths of reinforced concrete flexural members are influenced by repetitive fatigue loadings. The bond stress-slip relation is necessary to estimate these crack widths realistically. The purpose of the present study is, therefore, to propose a realistic model for bond stress-slip relation under repeated loading. To this end, several series of tests were conducted to explore the bond-slip behavior under repeated loadings. Three different bond stress levels with various number of load cycles were considered in the tests. The present tests indicate that the bond strength and the slip at peak bond stress are not influenced much by repeated loading if bond failure does not occur. However, the values of loaded slip and residual slip increase with the increase of load cycles. The bond stress after repeated loading approaches the ultimate bond stress under monotonic loading and the increase of bond stress after repeated loading becomes sharper as the number of repeated loads increases. The bond stress-slip relation after repeated loading was derived as a function of residual slip, bond stress level, and the number of load cycles. The models for slip and residual slip were also derived from the present test data. The number of cycles to bond slip failure was derived on the basis of safe fatigue criterion, i.e. maximum slip criterion at ultimate bond stress.

• Steel and Composite Structures
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• v.10 no.1
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• pp.87-108
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• 2010

A Steel Plate Shear Wall (SPSW) is a lateral load resisting system consisting of an infill plate located within a frame. When buckling occurs in the infill plate of a SPSW, a diagonal tension field is formed through the plate. The study of the tension field behavior regarding the distribution and orientation patterns of principal stresses can be useful, for instance to modify the basic strip model to predict the behavior of SPSW more accurately. This paper investigates the influence of torsional and out-of-plane flexural rigidities of boundary members (i.e. beams and columns) on the buckling coefficient as well as on the distribution and orientation patterns of principal stresses associated with the buckling modes. The linear buckling equations in the sense of von-Karman have been solved in conjunction with various boundary conditions, by using the Ritz method. Also, in this research the effects of symmetric and anti-symmetric buckling modes and complete anchoring of the tension field due to lacking of in-plane bending of the beams as well as the aspect ratio of plate on the behavior of tension field and buckling coefficient have been studied.

• Steel and Composite Structures
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• v.15 no.6
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• pp.679-703
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• 2013

This paper presents experimental investigations of the fundamental behavior of concrete filled steel tube (CFT) beam-columns under fire loading. A total of thirteen specimens were tested to determine the axial force-moment-curvature-temperature behavior of CFT beam-columns. The experimental approach involved the use of: (a) innovative heating and control equipment to apply thermal loading and (b) digital image correlation with close-range photogrammetry to measure the deformations (e.g., curvature) of the heated region. Each specimen was sequentially subjected to: (i) constant axial loading; (ii) thermal loading in the expected plastic hinge region following the ASTM E119 temperature-time T-t curve; and (iii) monotonically increasing flexural loading. The effects of various parameters on the strength and stiffness of CFT beam-columns were evaluated. The parameters considered were the steel tube width, width-tothickness ratio, concrete strength, maximum surface temperature of the steel tube, and the axial load level on the composite CFT section. The experimental results provide knowledge of the fundamental behavior of composite CFT beam-columns, and can be used to calibrate analytical models or macro finite element models developed for predicting behavior of CFT members and frames under fire loading.

• Computers and Concrete
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• v.18 no.5
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• pp.999-1018
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• 2016

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams.

• Structural Monitoring and Maintenance
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• v.7 no.3
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• pp.233-259
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• 2020

Using bonded fiber-reinforced polymer laminates for strengthening wooden structural members has been shown to be an effective and economical method. In this research, properties of suitable composite materials (sika wrap), adhesives and two ways of strengthening beams exposed to bending moment are presented. Passive or slack reinforcement is one way of strengthening. The most effective way of such a strengthening was to place reinforcement laminates in the stretched part of the wooden beam (lower part in our case), in order to investigate the effectiveness of externally bonding FRP to their soffits. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the wooden beam, the sika wrap composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. This research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-wooden hybrid structures. The results showed that the use of the new strengthening system enhances the performance of the wooden beam when compared with the traditional strengthening system.

• Structural Engineering and Mechanics
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• v.67 no.6
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• pp.629-641
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• 2018

The paper describes the development of a two-dimensional (2D) co-rotational nonlinear beam finite element that includes advanced path-following capabilities for detecting bifurcation instability in elasto-plasticity of steel elements subjected to fire without introducing imperfections. The advantage is twofold: i) no need to assume the magnitude of the imperfections and consequent reduction of the model complexity; ii) the presence of possible critical points is checked at each converged time step based on the actual load and stiffness distribution in the structure that is affected by the temperature field in the elements. In this way, the buckling modes at elevated temperature, that may be different from the ones at ambient temperature, can be properly taken into account. Moreover, an improved displacement predictor for estimating the displacement field allowed significant reduction of the computational cost. A co-rotational framework was exploited for describing the beam kinematic. In order to highlight the potential practical implications of the developed finite element, a parametric analysis was performed to investigate how the beam element compares both with the EN1993-1-2 buckling curve and with experimental tests on axially compressed steel members. Validation against experimental data and numerical outcomes obtained with commercial software is thoroughly described.

• Computational Structural Engineering
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• v.8 no.2
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• pp.115-121
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• 1995

The object of this study is to propose a rational method of resistance strength and flexural deformation for structures using high strength concrete(400-700kgf/cm/sup 2/). The material property(stress-strain relationship) is to be modelize using regression analysis of experimental result. And the applicability of trapezoidal stress model is to be verified. An analytical method is used by the moment-curvature relationship which is based on stress-strain relationships of material for discreted element of section. The evaluation method of moment-curvature of high strength concrete structures is also proposed by using the Monte Carlo Simulation based on a probabilistic concept that could minimize an error due to iterated calculations and random variable of material properties.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.13-22
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• 2000

This paper describes the results obtained from 11 direct tension tests to explore the influence of concrete strength on tension stiffening behavior in reinforced concrete axial members. Three different concrete compressive strengths, 250, 650, and 900kgf/$\textrm{cm}^2$, were included as a main variable, while the ratio of cover thickness-to-rebar diameter was kept constant to be 2.62 to prevent from splitting cracking. As the results, it was appeared that, as higher concrete strength was used, less tension stiffening effect was resulted, and the residual deformation upon unloading was larger. In addition, the spacing between adjacent transverse cracks became smaller with higher concrete strength. The major cause for those results may be attributed to the fact that nonuniform bond stress concentration at both loaded ends and crack sections becomes severer as higher concrete is used, thereby local bond failure becomes more susceptible. From these findings, it would be said the increase in flexural stiffness resulting from using high-strength concrete will be much smaller than that predicted by the conventional knowledge. Finally, a factor accunting for concrete strength was introduced to take account for the effect of HSC on tension stiffening. This proposed equation predicts well the tension stiffening for the effect of HSC on tension stiffening. This proposed equation predicts well the tension stiffening behavior of these tests.