• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.115-130
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• 2013

In this study, lateral-torsional buckling (LTB) strength of high-strength H-beams built up from 800MPa tensile-strength steel was experimentally and analytically evaluated according to current lateral stability provisions (KBC 2009, AISC-LRFD 2010). The motivation was to evaluate whether or not current LTB provisions, which were originally developed for ordinary steel with different stress-strain characteristics, are still applicable to high-strength steel. Two sets of compact-section specimens with relatively low (Set A) or high (Set B) warping stiffness were prepared and tested under uniform moment loading. Laterally unbraced lengths of the test specimens were controlled such that inelastic LTB could be induced. All specimens exhibited LTB strength exceeding the minimum limit required by current provisions by a sufficient margin. Moreover, some specimen in Set A reached a rotation capacity required for plastic design, although its laterally unbraced length belonged to the inelastic LTB range. All the test results indicated that extrapolation of current provisions to high-strength steel is conservative. In order to further analyze the test results, the relationship between inelastic moment and laterally unbraced length was also derived in explicit form for both ordinary- and high-strength steel based on the effective tangent modulus of inelastic section. The analytical relationship derived again showed that extrapolation of current laterally unbraced length limit leads to a conservative design in the case of high-strength steel and that the laterally unbraced length to control the inelastic LTB behavior of high-strength steel beam should be specified by including its unique post-yield strain-hardening characteristics.

• Computational Structural Engineering
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• v.4 no.4
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• pp.79-89
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• 1991

New design method of R/C slab system based on finite element method has been presented. The proposed method can substitute inaccurate existing method, which has limitation in its application, and provide accurate and efficient design results for any type of slab system. Isoparametric plate element used in the slab design has been efficiently formulated to save computational time. Reinforcement has been determined by strength design method and compared with code minimum values. Graphical output through comprehensive contour map for resulting moments and designed steel areas has considerably facilitated design process. Accurate shear results from isoparametric plate element enabled to check punching shear in a proper manner. In addition to strength design criteria, serviceability has also been checked by utilizing newly developed inelastic deflection multiplier method. An example for circular slab with opening showed that the proposed method could be applied to design of irregular slab without any difficulty.

• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.85-93
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• 2008

This study summarizes the results of a research project aimed at investigating the inelastic rotation capacity of beam-column joints of reinforced concrete special moment frames. All of the test specimens were classified as special moment frame (SMF), based on the design and detailing requirements of the ACI 318-02 provisions. The acceptance criteria, originally defined for steel moment frame connections in the 1997 edition of the AISC Seismic provisions, were used to evaluate the beam-column joints of the reinforced concrete moment frames. A total of 39 test specimens were examined in detail. Most of the joints that satisfy the design requirements for special moment frame structures were found to be ductile up to a plastic rotation of 3% without any major degradation in strength. This is mainly due to the stringent ACI 318-02 requirements for special moment frame joints. The presence of transverse beams increases confinement and shear resistance of joints, which results in better performance than for joints without transverse beams. All of the SMF connections that satisfy the ACI 318-02 limitations on joint shear stress turned out to meet the acceptance criteria.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.149-160
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• 2012

Corrugated steel plates have several advantages such as high resistance for shear without stiffeners, minimization of welding process, and high fatigue resistance. To take advantage of these benefits, several researchers have attempted to use corrugated steel plate as a web of I-girders. The lateral-torsional buckling is the major design aspect of such I-girders. However, lateral-torsional buckling of the I-girder with corrugated steel webs still needs to be investigated especially for a real loading condition such as non-uniform bending. This paper investigated the lateral-torsional buckling strength of the I-girder with corrugated steel webs under linear moment gradient by using finite element analysis. From the results, it was found that the buckling behavior of the I-girder with corrugated steel webs differed depending on the number of periods of the corrugation. Also, a simple equation for the moment gradient correction factor of the I-girder with corrugated steel webs was suggested. The inelastic lateral-torsional buckling strength of the I-girder with corrugated steel webs was then discussed based on current design equations for ordinary I-girders and the results of finite element analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.2
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• pp.59-68
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• 2009

For safe and economical design to provide strong earthquake resistance, the moment redistribution and plastic rotation of structures and their members needs to be evaluated. To achieve this, an earthquake design method was developed using secant stiffness analysis. To address the variation of member stiffness due to plastic rotation and moment redistribution, a structure was modeled with a beam-column element with non-rigid end connections (NREC element). Secant stiffness for the NREC element was determined based on the ductility demands of the structure and members. By performing a conventional linear analysis for the secant stiffness model, redistributed moments and plastic rotations of the members were computed. The proposed method was applied to a moment frame and two dual systems. The design results were verified using detailed nonlinear analyses.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.185-194
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• 2004

To evaluate seismic performance of reinforced concrete piers two procedures for capacity spectrum method are presented. The capacity spectrum procedures include the reduction factor-ductility-period($R_{\mu}-{\mu}-T$)relationship in order to construct the inelastic demand spectra from the elastic demand spectra. Application of the procedures are illustrated by example analysis. Maximum displacements estimated by the procedures are compared to those by inelastic time history analysis for several artificial earthquakes. The results show that the maximum displacements estimated by the procedures are, on overall, smaller than those by the inelastic time history analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.175-176
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• 2009

An improved column shortening analysis method which can be used in designing the horizontal members has been proposed. If you use this analysis method which is used effective modulus method by EMM or AEMM, you will get more exactly moments on the horizontal members.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.406-413
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• 2001

The energy dissipation or damage prevention capability of structure can be greatly enhanced by employing hysteretic dampers. According to recent studies by the authors, the ratio of hysteretic damper stiffness to structural story stiffness has been identified as one of the most important parameters for characterizing the performance of this damper In this study the method for determining appropriate properties of hysteretic dampers to satisfy the given performance objectives is developed based on the concept of capacity spectrum method. The comparison with the results from inelastic time history analysis proves that the hysteretic dampers designed from the proposed method restrains the displacement well within the target displacement.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.214-224
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• 1999

The design response spectrum has been widely used in seismic design to estimate force and deformation demands of structures imposed by Earthquake Ground Motion (EQGM). Inelastic Design Response Spectra (IDRS) to specify design yielding strength in seismic codes are obtained by reducing the ordinates of Linear Elastic Design Response Spectrum (LEDRS) by strength reduction factor (R). Since a building is designed using reduced design spectrum (IDRS) rather than LEDRS in current seismic design procedures it allows structures behave inelastically during design level EQGM. Inelastic Response Spectra (IRS) depend not only on the characteristics of the expected ground motion at a given site, but also on the dynamic properties and nonlinear characteristics of a structure. However, it has not been explicitly investigated the effect of different hysteretic models on IRS. In this study, the effect of hysteretic models on IRS is investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.207-214
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• 1997

Current seismic design code is based on the assumption that the designed structures would be behaved inelastically during a severe earthquake ground motion. For this reason, seismic design forces calculated by seismic codes are much lower than the forces generated by design earthquakes which makes structures responding elastically. Present procedures for calculating seismic design forces are based on the use of elastic spectra reduced by a strength reduction factors known as "response modificaion factor". The effect of hysteretic behavior, as well as maximum ductility ratio and period on the inelastic strength demand is investigated. Special emphasis is given to the effects of the hysteretic characteristics such as strength degradation or pinching. Results indicate that inelastic strength demands are strongly dependent on level of inelastic deformation, period and hysteretic behavior.