• Interaction and multiscale mechanics
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• v.3 no.1
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• pp.55-79
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• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.

• Korean Institute of Interior Design Journal
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• v.21 no.3
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• pp.128-135
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• 2012

The purpose of this study is to investigate and analyze the compositional elements of plan of art museums by selecting architectural works, which have strong symbolic meaning when evaluating value, from architectural works by Louis Kahn. First, the centrality of artworks, which are being displayed at the Yale Art Gallery, is complex. It includes three patterns of Void (spatial) Centrality+Symbolic Centrality+Functional Centrality among the five patterns suggested in this study. Second, the ratio system of interior space, which is expressed in the extension of the Yale Art Gallery, can be classified into the floor and walls. The floor used the square 1:1 ratio system. The ceiling used the grid patterns of equilateral triangles (regular tetrahedrons). It was applying a geometric ratio system when creating forms by using one side as a beam and the other sides as decorations of the ceiling. Third, the contours of interior space, which were expressed in Kahn's works, used the method of forming separate space according to the contouring rule (structural unit) defined by columns, and they were used in constructing the entire space through the integration of separate spaces. Fourth, according to the characteristics that were expressed by artworks displayed within the Yale Art Gallery Extension, the concept of accessibility was not as clear as that of residential buildings, because an approach of respecting existing architecture and context was used, rather than the starting point of interior space, or differentiated circulation, which has the function of a determined position.

• Journal of the Korea Furniture Society
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• v.20 no.5
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• pp.467-479
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• 2009

The high-tech computer technology developments have greatly affected the area of design education. Starting from the mid 80s, innovations in visual presentation methods have heightened with 2D computer graphic programs, CAD & 3D modeling, and Rapid Prototype that allows dimensional generation. The specialty and quality in design studio education have advanced due to the development in presentation methods such as Power Point and Keynote. But there are many problems with the current method of presenting the visual outcome in a data format using beam projectors, which is a vertical presenting method compared to the old studio study method of conducting discussions and reviews based on the substantial outcome. The essence of studio study that allows for comparisons and analysis by horizontally opening up the various work outcomes is being offset. Also the requirement for manual idea sketching work that plays an important role in the initial design phase continuing to decrease due to the digital working process dependence and cumbersome procedures in the presentation. In order to resolve this problem, the CALM system (Class Applied LCD Modular System) has been developed that replaces the method of attaching the sketches or renderings on the wall with a digital multi-display system. In a nutshell, individuals will upload the outcomes online and display them on the CALM system studio that is composed of 32 LCD (Columns: 4 $\times$ Rows: 8) monitors that are 19 inches in size so that various personnel can openly study the design outcomes. Also the central 42 inch PDP monitor that offers touch pad capability allows each design outcome to be described and examined by expanding. The concept phase of this development process has elevated to the production of an operating prototype that is being reviewed of its practicality. It is considered that the development of this system will decrease the extreme tendency of depending on digital operation but achieve revitalization of a more realistic and opened studio study environment compared to the individual consulting method of the old study approach.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1287-1294
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• 2005

The purpose of this paper is to investigate free vibrations and critical loads of the Beck's columns with a tip spring, which carry a tip mass. The ordinary differential equation governing free vibrations of Beck's column subjected to a follower force is derived based on the Bernoulli-Euler beam theory Both the divergence and flutter critical loads are calculated from the load-frequency corves that are obtained by solving the differential equation numerically. The critical loads are presented in the figures as functions of various non-dimensional system parameters such as the subtangential parameter, mass ratio and spring parameter.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.201-208
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• 2010

Information on the distribution characteristics of construction errors is very important to determine the member factors, which are to be introduced in a new Korean design code for reinforced concrete structures. The new design code, which is under development for reinforced concrete structures, is based on the performance design concept. The construction errors of reinforced concrete members are mainly caused by the firmness and dimensional accuracy of forms, the arranging condition of reinforcing bars, the pouring and compaction methods of concrete, the skills of field workers, and the experience of supervisors. To find out the construction errors of reinforced concrete structures already built in Korea, a field survey for cover thickness, effective depth of reinforcement, the thickness of slabs and walls, and the dimension of beams and columns has been performed. Based on the survey, which is the first time in Korea, the analysis results are presented. The measuring methods for the construction errors, which have been established through the laboratory tests, are also presented. In addition, the measured construction errors from the survey are compared with the allowable tolerances in the current domestic and foreign specifications.

• Interaction and multiscale mechanics
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• v.3 no.2
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• pp.192-211
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• 2010

In most framed structures the nonlinearities and the damages are localized, extending over a limited length of the structural member. In order to capture the details of the local damage, the segments of a member that have entered the nonlinear range may need to be analyzed using the three-dimensional element (3D) model whereas the rest of the member can be analyzed using the simpler one-dimensional (1D) element model with fewer degrees of freedom. An Element-Coupling model was proposed to couple the small scale solid 3D elements with the large scale 1D beam elements. The mixed dimensional coupling is performed imposing the kinematic coupling hypothesis of the 1D model on the interfaces of the 3D model. The analysis results are compared with test results of a reinforced concrete pipe column and a structure consisting of reinforced concrete columns and a steel space truss subjected to static and dynamic loading. This structure is a reduced scale model of a direct air-cooled condenser support platform built in a thermal power plant. The reduction scale for the column as well as for the structure was 1:8. The same structures are also analyzed using 3D solid elements for the entire structure to demonstrate the validity of the Element-Coupling model. A comparison of the accuracy and the computational effort indicates that by the proposed Element-Coupling method the accuracy is almost the same but the computational effort is significantly reduced.

• Explosives and Blasting
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• v.36 no.4
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• pp.48-61
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• 2018

This case study is concerned with the project of the explosive demolition for the KOGAS office building located in Bundang district in Seongnam city. Since the office building was a kind of long-span beam structures, a mechanical demolition method using jacking support systems was considered in the beginning of the project. With consideration of the excessive reinforcement cost, uncertainty of safety, and prolonged construction period, however, the original plan was later changed to use an explosive demolition method. For the purpose of protecting nearby buildings and facilities during the collapse process, the explosive initiation sequence was elaborately designed to bring down the building structure towards its front left corner. A total of over 550 electronic detonators (Unitronic 600) was used to sequentially initiate the explosives installed at appropriate columns in the first, second, and fifth floors. To diminish dust production, water bags of small and large sizes were respectively installed at each column and on the floors to be blasted. As such, every effort was exercised to mitigate overall noise, dust, and shock vibrations that could be generated during the explosive demolition process for the office building.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.427-435
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• 2020

Modular structures are relatively lightweight compared to reinforced-concrete or steel structures. However, it is difficult to achieve structural integrity between the columns of unit modules in a modular structure, which causes undesirable effects on the lateral force resistance capacity against wind and earthquake loads. This is more prominent in modular structures whose overall heights are greater. Hence, a post-tensioned modular structural system is proposed herein to improve the lateral force resistance capacity of a typical modular structure. A post-tensioned column-base connection, which is the main component of the proposed modular structural system, is configured with shapes and characteristics that allow inducing self-centering behaviors. Finite element analysis was then performed to investigate the hysteretic behaviors of the post-tensioned column-base connection. The analysis results show that the hysteretic behaviors are significantly affected by the initial tension forces and beam-column connection details at the base.

• Advances in nano research
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• v.13 no.3
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• pp.285-295
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• 2022

Creation of plastic deformation under seismic loads, is one of the most serious subjects in RC structures with steel bars which reduces the life threatening risks and increases dissipation of energy. Shape memory alloy (SMA) is one of the best choice for the relocating plastic hinges. In a challenge to study the seismic response of concrete moment resisting frame (MRF), this article investigates numerically a new type of concrete frames with nano fiber reinforced polymer (NFRP) and shape memory alloy (SMA) hinges, simultaneously. The NFRP layer is containing carbon nanofibers with agglomeration based on Mori-Tanaka model. The tangential shear deformation (TASDT) is applied for modelling of the structure and the continuity boundary conditions are used for coupling of the motion equations. In SMA connections between beam and columns, since there is phase transformation, hence, the motion equations of the structure are coupled with kinetic equations of phase transformation. The Hernandez-Lagoudas theory is applied for demonstrating of pseudoelastic characteristics of SMA. The corresponding motion equations are solved by differential cubature (DC) and Newmark methods in order to obtain the peak ground acceleration (PGA) and residual drift ratio for MRF-2%. The main impact of this paper is to present the influences of the volume percent and agglomeration of nanofibers, thickness and length of the concrete frame, SMA material and NFRP layer on the PGA and drift ratio. The numerical results revealed that the with increasing the volume percent of nanofibers, the PGA is enhanced and the residual drift ratio is reduced. It is also worth to mention that PGA of concrete frame with NFRP layer containing 2% nanofibers is approximately equal to the concrete frame with steel bars.