• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.297-298
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• 1998

Prototype portal imaging device (EPID) based on CCD camera, which has a $20\times20cm^2$ field of view (FOV), has been developed and then tested by acquiring phantom images for 6 MV x-ray beam. While, among the captured images, each frame suffered notorious quantum noise, the frame averaging largely enhanced the image quality against quantum noise. Over 60 frames averaging, the signal-to-noise ratio (SNR) was increased by $\sim20$ times and contrast was increased about 2 times in the skull-region of the acquired head-phantom image.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.191-198
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• 1997

The subject of this thesis is the vibration response of framed structure for buildings of "damed beam" type. In steel rigid frame with damped beams, web plate in mid span of beams is perforated to form a rectangular opening, only upper and lower flanges being remained. When the frame is subjected to horizontal seismic forces, dominant shearing deformation takes place in the opening part of the beams. Energy absorber in stalled in the opening is driven by relative displacement caused by the shearing deformation and provide the frame with damping force. First, static deformation of portal frames having a beam with the web opening is discussed and formulas of elastic deformation is derived.s derived.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.76-84
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• 1997

At the initial design stage, for rapid evaluation of strength of ship structures, finite element analysis using beam elements is carried out in general. In beam modeling of ship structures, brackets are usually represented by rigid elements to simplify the analysis. Extent of rigid ends, which is called as a span point, can be determined from the three kinds of view points, i.e., bending, shearing and axial deformation. In this paper, a 2-dimensional novel beam element is developed and a method to replace the 3-dimensional analysis with 2-dimensional analysis is proposed. The developed novel beam element named rigid-ended beam element can consider the effect of three kinds of span points within one element, which was impossible in modeling with the ordinary beam element. Calculated results for the portal frame using the rigid-ended beam element agree with the results using membrane elements. And also, the proposed semi 3-dimensional analysis method which includes two step analysis using influence coefficients shows good accuracy. Structural analysis using the rigid-ended beam element and the semi 3-dimensional method is revealed to have good computing efficiency due to unnecessity of elements corresponding to the brackets and simplification of 3-dimensional analysis.

• Structural Engineering and Mechanics
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• v.3 no.5
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• pp.475-495
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• 1995

In the past, physical models have been proposed, in compliance with the concept of the compressive-force path, for the realistic design of various statically determinate structural concrete members. The present work extends these models so as to encompass indeterminate RC structural forms. Pilot tests conducted on continuous beams and fixed-ended portal frames have revealed that designing such members to present-day concepts may lead to brittle types of failure. On the other hand, similar members designed on the basis of the proposed physical models attained very ductile failures. It appears that, unlike current design approaches, the compressive-force path concept is capable of identifying those areas where failure is most likely to be triggered, and ensures better load redistribution, thus improving ductility. The beneficial effect of proper detailing at the point of contraflexure in an indeterminate RC member is to be noted.

• Coupled systems mechanics
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• v.2 no.2
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• pp.175-190
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• 2013

Pounding damage has been observed frequently in major earthquakes in the form of aesthetic, minor or major structural cracks and collapse of buildings. Studies have identified a building located at one end of a row of buildings as very vulnerable to pounding damage, while buildings in the interior of the same row are assumed to be safer. This study presents the results of a shake table investigation of pounding between two and three buildings in a row. Two steel portal frames, one stiffer and another more flexible, were subjected to pounding against a frame with eight other configurations. Three pounding arrangements were considered, i.e., the reference frame (1) on the right of the second frame, (2) in the middle of two identical frames, and (3) on the right of two identical frames. Zero seismic gap was adopted for all tests. Five different ground motions are applied from both directions (right to left and left to right). The amplification of the maximum deflection due to pounding was calculated for each configuration. The results showed that, for the stiffer building in a row, row building pounding is more hazardous than pounding between only two buildings. The location of the stiffer frame, whether at the end or the middle of the row, did not have much effect on the degree of amplification observed. Additionally, for all cases considered, pounding caused less amplification for stronger ground motions, i.e., the ground motions that produced higher maximum deflection without pounding than other ground motions.

• Advances in Computational Design
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• v.1 no.1
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• pp.105-117
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• 2016

The objective of this work is to study the restraining effect in fire resistance of framed structures and to evaluate the global response of reinforced concrete frames when exposed to fire based on advanced finite element method. To study the response a single portal frame is analyzed. The effect of floor slab on this frame is studied by modeling a beam-column-slab assembly. The evolution of temperature distribution, internal stresses and deformations of the frame subjected to ISO 834 standard fire curve for both the frames are studied. The thermal and structural responses are evaluated and a comparison of results of individual members and entire structure is done. From the study it can be seen that restraining forces has significant influence on both stresses and deflection and overall response of the structure when compared to individual structural member. Among the various structural elements, columns are the critical members in fire and failure of column causes the failure of entire structure. The fire rating of various structural elements of the frame is determined by various failure criteria and is compared with IS456 2000 tabulated fire rating.

• Steel and Composite Structures
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• v.7 no.6
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• pp.421-440
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• 2007

An optimal design method in cooperated with nonlinear inelastic analysis is presented. The proposed nonlinear inelastic method overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional LRFD method. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are used to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are load-carrying capacity, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.707-725
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• 2004

An optimal design method with nonlinear elastic analysis is presented. The proposed nonlinear elastic method overcomes the drawback of the conventional LRFD method that accounts for nonlinear effect by using the moment amplification factors of $B_1$ and $B_2$. The genetic algorithm used is a procedure based on Darwinian notions of survival of the fittest, where selection, crossover, and mutation operators are employed to look for high performance ones among sections in the database. They are satisfied with the constraint functions and give the lightest weight to the structure. The objective function taken is the total weight of the steel structure and the constraint functions are strength, serviceability, and ductility requirement. Case studies of a planar portal frame, a space two-story frame, and a three-dimensional steel arch bridge are presented.

• Structural Engineering and Mechanics
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• v.33 no.1
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• pp.79-93
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• 2009

This paper investigates the possibility of controlling the response of typical portal frame structures to blast loading using a combination of semi-active and passive control devices. A one storey reinforced concrete portal frame is modelled using non-linear finite elements with each column discretised into multiple elements to capture the higher frequency modes of column vibration response that are typical features of blast responses. The model structure is subjected to blast loads of varying duration, magnitude and shape, and the critical aspects of the response are investigated over a range of structural periods in the form of blast load response spectra. It is found that the shape or length of the blast load is not a factor in the response, as long as the period is less than 25% of the fundamental structural period. Thus, blast load response can be expressed strictly as a function of the momentum applied to the structure by a blast load. The optimal device arrangements are found to be those that reduce the first peak of the structural displacement and also reduce the subsequent free vibration of the structure. Semi-active devices that do not increase base shear demands on the foundations in combination with a passive yielding tendon are found to provide the most effective control, particularly if base shear demand is an important consideration, as with older structures. The overall results are summarised as response spectra for eventual potential use within standard structural design paradigms.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.281-290
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• 2003

A series of connection tests of portal frames which were composed of cold-formed steel studs and rafters was carried out to study the moment-rotation relation, the rotational rigidity, and the yield and the ultimate moment of the connections. The main factors of the tests were the thickness, the shape of the connecting members which were made of mild steel, and the torsional restraints of the test specimens. The test results were compared with those obtained through the non-linear analysis, for verification. The secant stiffness estimated from the experimental moment-rotation curve was proposed for the rotational rigidity of semi-rigid connections, and its validity was verified in the structural frame analysis.