• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.383-393
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• 2007

A simplified model which incorporates the moment-axial tension interaction of the double-span beams in a column-removed steel frame is presented in this paper. To this end, material and geometric nonlinear parametric finite element analyses were conducted for the double-span beams by changing the beam span to depth ratio and the beam size within some practical ranges. The beam span to depth ratio was shown to be the most influential factor governing the catenary action of the double-span beams. Based on the parametric analysis results, a simplified piece-wise linear model which can reasonably describe the vertical resisting force versus the beam chord rotation relationship was proposed. It was also shown that the proposed method can readily be used for the energy-based progressive collapse analysis of steel moment frames.

• Steel and Composite Structures
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• v.23 no.5
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• pp.585-596
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• 2017

Tubular joints have been widely used in offshore platforms and space structures due to their merits such as easy fabrication, aesthetic appearance and better static strength. For existing tubular joints, a grouted sleeve reinforced method was proposed in this paper. Experimental tests on five tubular T-joints reinforced with the grouted sleeve and two conventional tubular T-joints were conducted to investigate their mechanical behaviour. A constant axial compressive force was applied to the chord end to simulate the compressive state of the chord member during the tests. Then an axial compressive force was applied to the top end of the brace member until the collapse of the joint specimens occurred. The parameters investigated herein were the grout thickness, the sleeve length coefficient and the sleeve construction method. The failure mode, ultimate load, initial stiffness and deformability of these joint specimens were discussed. It was found that: (1) The grouted sleeve could change the failure mode of tubular T-joints. (2) The grouted sleeve was observed to provide strength enhancement up to 154.3%~172.7% for the corresponding un-reinforced joint. (3) The initial stiffness and deformability were also greatly improved by the grouted sleeve. (4) The sleeve length coefficient was a key parameter for the improved effect of the grouted sleeve reinforced method.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.137-143
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• 2005

The integrity of steam generator tubes in nuclear power plant should be maintained sufficiently during operation. For sake of this, complicated assessment procedures are required such as fracture mechanics analysis, etc. The integrity assessment of tubes has been performed by using conventional deterministic approaches while there are many uncertainties to carry out a rational evaluation. In this respect, probabilistic integrity assessment is considered as an alternative method for integrity assessment. The objectives of this study are to develop an integrity assessment system based on probabilistic fracture mechanics and to predict the failure probability of steam generator tubes containing an axial through-wall crack. The developed integrity assessment system consists of three evaluation modules, which apply first order reliability method, second order reliability method and Monte Carlo simulation method, respectively. The system has been applied to predict failure probability of steam generator tubes and the estimation results showed a promising applicability of the probabilistic integrity assessment system.

• Advances in concrete construction
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• v.4 no.4
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• pp.319-332
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• 2016

In most cases strengthening reinforced concrete columns exposed to high strain rate is to be expected especially within weak designed structures. A special type of loading is instantaneous loading. Rapid loading can be observed in structural columns exposed to axial loads (e.g., caused by the weight of the upper floors during a vertical earthquake and loads caused by damage and collapse of upper floors and pillars of bridges).Subsequently, this study examines the behavior of reinforced concrete columns under rapid loading so as to understand patterns of failure mechanism, failure capacity and strain rate using finite element code. And examines the behavior of reinforced concrete columns at different support conditions and various loading rate, where the concrete columns were reinforced using various counts of FRP (Fiber Reinforcement Polymer) layers with different lengths. The results were compared against other experimental outcomes and the CEB-FIP formula code for considering the dynamic strength increasing factor for concrete materials. This study reveals that the finite element behavior and failure mode, where the results show that the bearing capacity increased with increasing the loading rate. CFRP layers increased the bearing capacity by 20% and also increased the strain capacity by 50% through confining the concrete.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.313-319
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• 2017

Cylindrical shells are often used in ship structures at deck plating with a camber, side shell plating at fore and aft parts, and bilge structure part. It has been believed that such curved shells can be modelled fundamentally by a part of a cylinder under axial compression. From the estimations with the usage of cylinder models, it is known that, in general, curvature increases the buckling strength of a curved shell subjected to axial compression, and that curvature is also expected to increase the ultimate strength. We conduct series of elasto-plastic large deflection analyses in order to clarify the fundamentals in buckling and plastic collapse behaviour of cylindrical shells under axial compression. From the numerical results, we derive design formula for predicting the ultimate strength of cylindrical shell, based on a series of the nonlinear finite element calculations for all edges, simply supporting plating, varying the slenderness ratio, curvature and aspect ratio, as well as the following design formulae for predicting the ultimate strength of cylindrical shell. From a number of analysis results, fitting curve can be developed to use parameter of slenderness ratio with implementation of the method of least squares. The accuracy of design formulae for evaluating ultimate strength has been confirmed by comparing the calculated results with the FE-analysis results and it has a good agreement to predict their ultimate strength.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.363-372
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• 2001

The objective of this study is to evaluate the $P-{\Delta}$ effect in the case of weak beam unbraced frames by experimental approach. To evaluate $P-{\Delta}$ effect, four specimens were tested under monotonic loading condition. The parameters of tests are the stiffness of column and the axial load ratio. The results show that the value of axial load affects frame stability because $P-{\Delta}$ effects promote the yielding of beam. The maximum lateral load increases in proportion to the increment of column stiffness and rotational stiffness of supports, The collapse mechanism of weak beam unbraced frames is stably formed in the condition of low axial load ratio. The $B_2$ factor of limit state design code does not properly consider the $P-{\Delta}$ effect in inelastic region.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.169-184
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• 2006

A close form solution of the maximum deflection for cracked columns with rectangular cross-sections was developed and thus the elastic buckling behavior and ultimate bearing capacity were studied analytically. First, taking into account the effect of the crack in the potential energy of elastic systems, a trigonometric series solution for the elastic deflection equation of an arbitrary crack position was derived by use of the Rayleigh-Ritz energy method and an analytical expression of the maximum deflection was obtained. By comparison with the rotational spring model (Okamura et al. 1969) and the equivalent stiffness method (Sinha et al. 2002), the advantages of the present solution are that there are few assumed conditions and the effect of axial compression on crack closure was considered. Second, based on the above solutions, the equilibrium paths of the elastic buckling were analytically described for cracked columns subjected to both axial and eccentric compressive load. Finally, as examples, the influence of crack depth, load eccentricity and column slenderness on the elastic buckling behavior was investigated in the case of a rectangular column with a single-edge crack. The relationship of the load capacity of the column with respect to crack depth and eccentricity or slenderness was also illustrated. The analytical and numerical results from the examples show that there are three kinds of collapse mechanisms for the various states of cracking, eccentricity and slenderness. These are the bifurcation for axial compression, the limit point instability for the condition of the deeper crack and lighter eccentricity and the fracture for higher eccentricity. As a result, the conception of critical transition eccentricity $(e/h)_c$, from limit-point buckling to fracture failure, was proposed and the critical values of $(e/h)_c$ were numerically determined for various eccentricities, crack depths and slenderness.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.258-265
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• 2002

The recent earthquakes in worldwide have caused extensive damage to highway bridge structures. In particular, it has been demonstrated that concrete columns with inadequate lateral reinforcement contributed to the catastrophic collapse of many bridges. The poor detailing of the starter bars in these columns compounded the problem of seismic deficiency. Therefore, this study has been performed to verify the effect of lap spliced longitudinal steel and confinement steel type for the seismic behavior of reinforced concrete bridge piers. Eight concrete columns were constructed with existing scale as diameter, 1.2m and height, 4.8m. 4 confinement steel types were adopted for seismic performance evaluation. All specimens were rested under inelastic cyclic loading while simultaneously subjected to a constant axial load. The longitudinal steel lap-splice is highly effective in seismic performance deterioration of reinforced concrete bridge piers.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.241-245
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• 2012

In this study, one type of circular shaped composite tube was used, combined with reinforcing foam and without foam. Furthermore, CFRP (Carbon Fiber Reinforced Plastic) circular member manufactured from CFRP prepreg sheet for lightweight design. CFRP is an anisotropic material which is the most widely adapted lightweight structural member. The crashworthy behavior of circular composite material tubes subjected to static axial compression under same conditions is reported in this paper. The collapse mode during the failure process were observed and analyzed. The behavior of polymeric foams to the tubes crashworthiness were also investigated.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.3
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• pp.27-34
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• 2010

Unbraced vinyl house frame that is economically installed is certainly easy to collapse under the influence of excess snow load. To make it more cheaply in putting up as well as more efficiently in withstanding the applied snow load, it is essential to insert additional bracing into the existing unbraced vinyl house frame. On the other hand, there are varieties of possible bracing shapes that can be formed. However, their efficiencies are different. Therefore, it is important to identify the most effective bracing shape. In this study, 2 different kinds of bracing shapes, horizontal and inclined bracing, are used to additionally install in the ordinary single frames in order to show the effect of the bracing resisting the applied snow load and compare the bending moment, axial force, combined stress and vertical displacement of the vinyl house frame.