• Steel and Composite Structures
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• v.13 no.2
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• pp.171-185
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• 2012

The calculation of fire resistance for a composite structural element comprises the calculation of the temperature within its cross-section and of the load bearing capacity, considering the evolution of the steel and concrete mechanical properties, function of the temperature. The paper proposes a method to calculate the bending capacity under ISO fire, for Slim Floor systems using asymmetric steel beams, with a wider lower flange or a narrow upper flange welded onto a half hot-rolled profile. The temperatures in the cross-section are evaluated by means of empirical formulas determined through a parametrical analysis, performed with the special purpose non-linear finite element program SAFIR. Considering these formulas, the bending capacity may be calculated, using an analytical approach to determine the plastic bending moment, for different fire resistance demands. The results obtained with this simplified method are validated through numerical analysis.

• Plant Resources
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• v.8 no.1
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• pp.32-35
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• 2005

This study was conducted to investigate the influence of $K_{2}O$ fertilizer application on growth, yield and lodging resistance of rice. Culm length and panicle length were lowest at the treatment of fertilizer level, $N-P_{2}O_{5}-K_{2}O=16-8-8$ plot but number of panicle, percentage of fruitful culm, $1{\ell}$ grain weights of paddy rice and brown rice, 1,000 grains weight of brown rice, brown rice ratio, yields of paddy rice and brown rice were highest at the treatment of fertilizer level, $N-P_{2}O_{5}-K_{2}O=16-8-8$ kg/10a plot. Bending moment, breaking strength and lodging index were lowest at the treatment of fertilizer level, $N-P_{2}O_{5}-K_{2}O=16-8-8$ kg/10a plot. Judging from the results reported above, an optimum fertilizer level of rice for lodging resistance is most likely be $N-P_{2}O_{5}-K_{2}O=16-8-8$ kg/10a treatment.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.53-56
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• 2004

Recently, post tension flat plate slab system is widely used for a new slab structural system. Slab-column connections may fail in brittle manner by punching shear. Flat plate slabs have been widely used for gravity load resisting system in buildings. Lateral resistance usually provided by shear walls or moment resisting frames. Since plat plates move together with lateral loading system during earthquake or wind, it is important to evaluate the gravity resistance under a drift experienced by lateral force resisting system during either design earthquake or wind. Thus, this study investigated post tension flat plate slab systems whether they have sufficient strength and deformability to resist gravity loads during specified drift levels. Experimental research was carried out.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.1-8
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• 2018

Shake table tests performed on five 1:3 reduced scale two story RC moment resisting frames having construction defects, have shown severe joint damageability in deficient RC frames, resulting in joint panels' cover spalling and core concrete crushing. Haunch retrofitting technique was adopted herein to upgrade the seismic resistance of the deficient RC frames. Additional four deficient RC frames were built and retrofitted with steel haunch; both axially stiffer and deformable with energy dissipation, fixed to the beam-column connections to reduce shear demand on joint panels. The as-built and retrofitted frames' seismic response parameters are calculated and compared to evaluate the viability of haunch retrofitting technique. The haunch retrofitting technique increased the lateral stiffness and strength of the structure, resulting in the increase of structure's overstrength. The retrofitting increased response modification factor R by 60% to 100%. Further, the input excitation PGA was correlated with the lateral roof displacement to derive structure response curve that have shown significant resistance of retrofitted models against input excitations. The technique can significantly enhance the seismic performance of deficient RC frames, particularly against the frequent and rare earthquake events, hence, promising for seismic risk mitigation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.355-362
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• 2009

Many of residential buildings, which have pilotis in lower stories to meet the architectural needs, are recently constructed in Korea. Usually, infill walls located in the upper stories of these buildings may cause a soft first story, which is very weak from the earthquake resistance. In the design of the buildings, the infill walls of upper stories are usually considered as non-structural elements and thus they are not included in the analytical model. However, the infill walls may affect the seismic behavior of the residential buildings. Therefore, the differences in seismic behaviors of RC buildings with and without masonry infill walls are required to be investigated. In this study, seismic fragility analyses were performed for masonry infilled low-rise RC moment-resisting frames. And seismic behaviors of RC moment-resisting frame with/without masonry infill walls were evaluated. Two types of structural system with the same frame and different allocation of infill walls are used to evaluate the influence of masonry infill walls on seismic behavior of RC moment-resisting frames. The infill walls were modeled as bi-equivalent diagonal struts. The fragility analyses show that the seismic performance of RC moment-resisting frames with soft story is below the desirable building seismic performance level recommended by current seismic codes, indicating high vulnerability of RC moment-resisting frames with soft story.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.629-636
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• 2011

It has been suggested that buildings designed for strong ground motions will also have improved resistance to air blast loads. As an initial attempt to quantify this behavior, the responses of a ten story steel building, designed for the 1994 building code, with lateral resistance provided by perimeter moment frames, is considered. An analytical model of the building is developed and the magnitude and distribution of blast loads on the structure are estimated using available computer software that is based on empirical methods. To obtain the relationship between pressure, time duration, and standoff distance, these programs are used to obtain an accurate model of the air blast loading. A hemispherical surface burst for various explosive weights and standoff distances is considered for generating the air blast loading and determining the structural response. Linear and nonlinear analyses are conducted for these loadings. Air blast demands on the structure are compared to current seismic guidelines. These studies present the displacement responses, story drifts, demand/capacity ratio and inelastic demands for this structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.108-116
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• 2017

In this study, the prototype structure of seismically designed steel moment frame was analyzed statically and dynamically in order to demonstrate the applicability of energy-based approximate analysis with the dynamic effect of sudden column loss in the evaluation of the collapse resistance and a method for assessing the sensitivity to progressive collapse was proposed. For the purpose of comparing the structural behavior of buildings with different structural systems, the sensitivity of the structure to the sudden removal of vertical members can be used as a significant measure. The energy-based approximate analysis prediction for the prototype structure considered in the study showed good agreement with the dynamic analysis result. In the sensitivity evaluation, the structural robustness index that indicates the ability of a structure to resist collapse induced by abnormal loads was used. It was confirmed that the proposed methods can be used conveniently and rationally in progressive collapse analysis and design.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.109-117
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• 2012

This study seeks to devise a design application for a beam structure with partially restrained composite connection to a CFT column. A cost-efficient and stable component is applied by adjusting the stiffness ratio of the column connection through partially restrained composite connection. Based on a review of the structure's stability, it was confirmed that in the case of a low-rise building as a moment frame, resistance without bracing is feasible because stiffness increased by virtue of the partial restrained composite connection by composite action. In the case of a high-rise building, lateral resistance load of moment frame was approximately 10% when proper partial restrained rate was at around 60%. With considerations related to economic efficiency, the partial restriction effect of the beam component was significantly activated by the uniform load, but that of the beam activated by concentrated load was not significantly indicative. The analysis indicated that 60% partial restrained girder at the connection was the most economical in the case of uniform load. It also showed that end moments can be reduced by approximately 25%.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.335-343
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• 2008

In order to improve the workability in erecting Precast Concrete (PC) members and enhance the seismic resistance capacity of the joints in PC moment frames, a new PC column and its construction process are introduced in this paper. This column is manufactured by centrifugal force in keeping the hollow tube inside; the hollow is little bit wide and the grout can be poured from top to bottom after erection at site so that more compact grouting is possible in horizontal joint. The repeated cyclic loading test for four full scaled specimens was conducted to evaluate the seismic resistance capacity of the joint designed by the proposed system. For the continuity of main reinforcements in column, two connecting methods are used in designing specimens; one is to use mechanical connector and other is lab splice. From the cyclic lateral loading test, it was found that the seismic capacity of the developed PC column joint is comparable to that of monolithic joint.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.187-194
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• 2016

It is necessary to determine reliability indexes of existing railway bridges prior to setting up a proper target reliability index that can be used to introduce a reliability based limit state design method to design practice. Reliability is evaluated for a six PSC-I girder railway bridge, which is one of many representative types of double-track railway bridges. The reliability assessment is carried out for an edge girder subjected to bending moment. In the assessment, the flexural resistance and the fixed-load effect were obtained using existing statistical values from previous research on the introduction of limit state design to road bridge design. On the other hand, the live-load effect was determined using statistical values obtained from field measurement for the Joong-ang corridor, on which heavy freight trains are frequently passing. The reliability assessment is performed by AFOSM(Advanced First Order Second Moment method) for the limit state equation, and a sensitivity analysis for the reliability is performed for each factor of the load and resistance effects.