• Journal of Korean Society of Steel Construction
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• v.23 no.5
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• pp.535-546
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• 2011

In this paper, semi-rigid elasto-plastic post-buckling analysis of a space frame was performed using various explicit arc-length methods. Various explicit arc-length methodsand a large-deformation and small-strain elasto-plastic 3D space frame element with semi-rigid connections and plastic hinges were developed. This element can be appliedto both explicit and implicit numerical algorithms. In this study, the Dynamic Relaxation method was adopted in the predictor and corrector processesto formulate an explicit arc-length algorithm. The developed "explicit-predictor" or "explicit-corrector" were used in the elasto-plastic post-buckling analysis. The Eulerian equations for a beam-column with finite rotation, which considers the bowing effects, were adopted for the elastic system and extended to theinelastic system with a plastic hinge concept. The derived tangent stiffness matrix was asymmetrical due to the finite rotation. The joint connection elements were introduced for semi-rigidity using a static condensation technique. Semi-rigid elasto-plastic post-buckling analyses were carried out to demonstrate the potential of the developed explicit arc-length method and advanced space frame element in terms of accuracy and efficiency.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.58-64
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• 2010

GLI model was verified to consider the interaction between a ground and a tunnel lining and to rationally reduce the ground load acting on the secondary lining(concrete lining) of a tunnel. In this study, the economy and the construction condition of tunnel concrete linings designed by a conventional frame model at Lot O of OO line were highly enhanced through a field design change using GLI model. For a few safe considerations, not only about 50% saving of reinforcing steel could reduce the material cost but also the wide space between bars could make it easy to pour concrete mix without voids. There was large saving effect of reinforcing steel for poor ground conditions because Terzaghi's load used in the conventional frame model produces too much high loads for those conditions.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.04b
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• pp.7-7
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• 2002

Recently social demand to achieve low fuel consumption and clean emission requires the development of new generation vehicle beyond the conventional vehicle concept. In this point, new generation vehicle is newly designed as electric vehicle, hybrid electric vehicle, fuel cell electric vehicle or 3 liter car etc. In order to develop new generation vehicle, it is very important to develop new materials and process technologies now. In this paper these new technologies are presented focusing on weight reduction specially. Steel body can be achieved 20-25% weight reduction by adoption of high strength steel and new process technologies, i.e tailored blank and hydroforming. Aluminium body can be achieved 40-50% weigt down by use of all aluminium monocoque body or aluminium space frame with aluminium panel. Plasitic composite body can be achieved 30% weight reduction comparing with conventional steel body.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.45-52
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• 2003

A finite element procedure to estimate ultimate strength of space frames considering spread of plasticity is presented. The improved displacement field is introduced based on inclusion of second order terms of finite rotations. All the nonlinear terms due to bending and torsional moment as well as axial force are precisely considered. The concept of plastic hinge is introduced and the incremental load/displacement method is applied for the elasto-plastic analysis. The initial yield surface is defined based on the residual stress and the full plastification surface is considered under the combined action of axial force, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for ultimate strength of space frames are compared with available solutions and experimental results.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.683-694
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• 2004

Advanced analysis and optimal design of semi-rigid space steel frames were presented. The advanced analysis can predict the combined nonlinear effects of connection, geometry, and material on the behavior and strength of semi-rigid frames. The Kishi-Chen power model was used to describe the nonlinear behavior of semi-rigid connections. Geometric nonlinearity was determined using stability functions. Material nonlinearity was determined using the Column Research Council (CRC) tangent modulus and the parabolic function. The direct search method proposed by Choi and Kim was used as optimization technique. One by one, the member with the largest unit value evaluated using the LRFD interaction equation were placed adjacent to a larger member selected from the database. The objective function was assumed to be the weight of steel frame, while the constraint functions were load-carrying capacities, deflections, inter-story drifts, and the ductility requirements. The member sizes determined using the proposed method were compared to those derived from the conventional LRFD method.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.299-311
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• 2003

This paper presents a finite element procedure to estimate the ultimate strength of space frames considering spread of plasticity. The improved displacement field is introduced based on the inclusion of second-order terms of finite rotations. All the non-linear terms due to bending moment, torsional moment, and axial force are precisely considered. The concept of plastic hinges is introduced and the incremental load/displacement method is applied for elasto-plastic analyses. The initial yield surface is defined based on the residual stress, and the full plastification surface is considered under the combined action of axial forces, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for the ultimate strength of space frames are compared with available solutions and experimental results.

• Architectural research
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• v.25 no.1
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• pp.1-9
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• 2023

Structural ageing influences the structural performance in a negative way by reducing the seismic resilience of the structure which makes it a major concern around the world. Retrofitting is considered to be a pragmatic and feasible solution to address this issue. Numerous retrofitting techniques are devised by researchers over the years. The viability of using steel bracings as retrofitting component is evaluated on a G+30 storied building model designed according to ACI318-14 and ASCE 7-16. Four different types of steel bracing arrangements (V, Inverted V/ Chevron, Cross/ X, Diagonal) are assessed in the model developed in commercial nu-merical analysis software while considering both material and geometric nonlinearities. Reducing displacement and cost in the structures indicates that the design is safe and economical. Therefore, the purpose of this article is to find the best bracing system that causes minimum displacement, which indicates maximum lateral stiffness. To evaluate the seismic vulnerability of each system, incremental dynamic analysis was conducted to develop fragility curves, followed by the formation of collapse margin ratio (CMR) as stipulated in FEMA P695 and finally, a cost estimation was made for each system. The outcomes revealed that the effects of ge-ometric nonlinearity tend to evoke hazardous consequences if not considered in the structural design. Probabilistic seismic and economic probes indicated the superior performance of V braced frame system and its competency to be a germane technique for retrofitting.

• Journal of architectural history
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• v.9 no.3 s.24
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• pp.51-69
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• 2000

This study tries to analyze the development of architectural technologies appeared in several tall buildings and large spatial structures from 1955 to 1999 in Korea. We suppose that these buildings represent the development of technology in Korean modern architecture. By the detailed analysis of these buildings, we can arrive at a conclusion as such; During the years 1955-1999, there existed a great changement in the eighties. We can find this fact very well in the domain of structural system and curtain wall system. In large spatial structures, the structural-system of shell and steel truss dome was replaced by that of space frame, space truss and cable truss with membrane. In tall building, the structural system of rigid frame and shear wall was replaced by tubular system, core and outrigger system. Korean architects introduced the aluminum curtain wall in the sixties, but its low technological level caused many problems in reality. Therefore, precast concrete curtain wall appeared from seventies as the main method for an outer wall in tall building. With the augmentation of height after 1980, PC curtain wall was replaced by the aluminum curtain wall of unit type and structural glass wall system. These systems help to stress the transparency in a tall building.

• Smart Structures and Systems
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• v.15 no.1
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• pp.99-117
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• 2015

The Stonecutters Bridge (SCB) in Hong Kong is the third-longest cable-stayed bridge in the world with a main span stretching 1,018 m between two 298 m high single-leg tapering composite towers. A Wind and Structural Health Monitoring System (WASHMS) is being implemented on SCB by the Highways Department of The Hong Kong SAR Government, and the SCB-WASHMS is composed of more than 1,300 sensors in 15 types. In order to establish a linkage between structural health monitoring and maintenance management, a Structural Health Rating System (SHRS) with relevant rating tools and indices is devised. On the basis of a 3D space frame finite element model (FEM) of SCB and model updating, this paper presents the development of an SHR-oriented 3D multi-scale FEM for the purpose of load-resistance analysis and damage evaluation in structural element level, including modeling, refinement and validation of the multi-scale FEM. The refined 3D structural segments at deck and towers are established in critical segment positions corresponding to maximum cable forces. The components in the critical segment region are modeled as a full 3D FEM and fitted into the 3D space frame FEM. The boundary conditions between beam and shell elements are performed conforming to equivalent stiffness, effective mass and compatibility of deformation. The 3D multi-scale FEM is verified by the in-situ measured dynamic characteristics and static response. A good agreement between the FEM and measurement results indicates that the 3D multi-scale FEM is precise and efficient for WASHMS and SHRS of SCB. In addition, stress distribution and concentration of the critical segments in the 3D multi-scale FEM under temperature loads, static wind loads and equivalent seismic loads are investigated. Stress concentration elements under equivalent seismic loads exist in the anchor zone in steel/concrete beam and the anchor plate edge in steel anchor box of the towers.

• Steel and Composite Structures
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• v.21 no.1
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• pp.93-107
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• 2016

Seismic fragility analysis is a probabilistic decision-making framework which is widely implemented for evaluating vulnerability of a building under earthquake loading. It requires ingredient named probabilistic model and commonly developed using statistics requiring collecting data in large quantities. Preparation of such a data-base is often costly and time-consuming. Therefore, in this paper, by developing generic seismic drift demand model for regular-multi-story steel moment resisting frames is tried to present a novel application of the probabilistic decision-making analysis to practical purposes. To this end, a demand model which is a linear function of intensity measure in logarithmic space is developed to predict overall maximum inter-story drift. Next, the model is coupled with a set of regression-based equations which are capable of directly estimating unknown statistical characteristics of the model parameters.To explicitly address uncertainties arise from randomness and lack of knowledge, the Bayesian regression inference is employed, when these relations are developed. The developed demand model is then employed in a Seismic Fragility Analysis (SFA) for two designed building. The accuracy of the results is also assessed by comparison with the results directly obtained from Incremental Dynamic analysis.