• Fire Science and Engineering
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• v.28 no.3
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• pp.49-54
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• 2014

Beams play an important role to transfer an applied load on the floor into columns. However, if the beams affected by a fire the length will be changed longer or shorter and the structural stability decreased gradually and resulted in structural failure. Therefore, the fire regulation requires that structural beam has to satisfied with a constant fire resistance. The fire resistance conducted by a constant size and boundary condition in an horizontal furnace. But this is not enough to adopt a beam made of high structural steels having various lengths. In this study, in order to suggest structural behaviors of beams made of high structural steels at high temperature, mechanical properties at high temperature and heat stress analysis were used and the surface temperature, expansion, displacement and variance of maximum load according to lengths of the beam were compared with those of SM 400.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.113-119
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• 2016

In this study, the method to predict the lateral response by using strain data is presented on the steel moment frame. For this, the reliability of the proposed method by applying the example of five-story frame structure were verified. Using the strain value of columns, it predicted the lateral response of structure. It is assumed that all of four strain sensors for one column set up and the strain responses of both end of the column are utilized. The lateral response of member is calculated by using the slope deflection method. Also, using the acceleration response of the one layer, the stiffness of the rotation spring located in the supporting point is predicted. As a result, it was effective to understand the lateral displacement and acceleration responses and to predict local damage and location.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.13-21
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• 2016

A hybrid precast concrete beam system with a simple rigid connection was proposed to compensate the limitations and shortcomings of the conventional bolt connection associated with the H-beams embedded into concrete beams. Three beam specimens with fixed both ends were tested under one-point top cyclic loading to explore the effectiveness of the developed hybrid beam system in transferring externally applied flexure to a column. The main parameter considered was the length ($L_s$) of H-beam, which was selected to be $0.25L_I$, $0.5L_I$, and $1.0L_I$, where $L_I$ is the distance from the support to the point of inflection. All beam specimens showed a better displacement ductility ratio than the reinforced concrete beams with the same longitudinal reinforcement index, indicating that the cyclic load-deflection curve and ductility were insignificantly affected by $L_s$. The continuous strain distribution along the beam length and the prediction of the ultimate load based on the collapse mechanism ascertained the structural adequacy of the developed rigid connection.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.769-782
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• 2006

As the ambient vibration test (AVT) of railway bridges has a limited range of speed, it has a limitation in examining the dynamic behavior of bridges accordingto speed. Thus, in order to analyze the correlation between the speed of a train passing over a bridge and the bridge's dynamic response, we conducted a speed-increasing experiment using a real diesel locomotive. To analyze the acceleration response characteristics, we attached seven vertical accelerometers at equal intervals throughout the entire section of the bridge except the supports, and one horizontal accelerometer to the middle span. Linear variable differential transformers (LVDT) were installed at the bridge's center in both vertical and horizontal directions to investigate the vertical and horizontal behaviors. The test train was statically loaded at the center and at the end of the bridge. And its speed was increased from 5 km/h to 90 km/h. With data obtained from the experiment, the vibration level was evaluated in each direction by the filtering frequency, and the level of horizontal vibration was examined in comparison with vertical vibration. The displacement and wheel load variation was analyzed by speed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2D
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• pp.159-166
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• 2012

During concrete placement, the formwork structure supports the weight of concrete mass. The complexity of the operation can cause concentrated workloads, which in turn brings about a collapse of the temporary structure. As a countermeasure, the operation needs to be constantly monitored to maintain safety and prevent accidents. This paper presents a USN (Ubiquitous Sensor Network)-based safety monitoring system for formwork construction. The system takes advantage of ubiquitous technology in monitoring the behavior of the formwork structure such as deflection, load weight, and tilting. The collected data are sent to the host computer wirelessly for real time monitoring. The data can be then compared with the allowed limits on guidelines. The comparison can indicate whether the concrete placement operation is executed in a safe condition.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.328-334
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• 2015

Building insulation materials use for the purpose of energy saving. Insulation materials can be classified inorganic and organic insulation materials. Inorganic insulation is used for fire resistive performance parts and organic insulation is used for thermal performance parts. Meanwhile, organic insulation is due to toxic gas emission in fire. Inorganic insulation is too heavy and low thermal performance than organic materials. This study is focused on evaluation of the physical properties of inorganic foam material using industrial by-products such as waste glass powder and fly ash. From the test result, inorganic foam materials for the applicability of fire-resistance and insulation light-weight materials.

• Computational Structural Engineering
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• v.10 no.4
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• pp.315-325
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• 1997

This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.45-53
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• 2014

In strength limit states design, it is assumed that after cracking, reinforcement carries all tension in the tension zone of reinforced concrete members. However, it can be seen the concrete between cracks will contribute to carrying a part of the tension stress in actual concrete members particularly at service load levels, this effect is referred as tension stiffening effect. In this study, tension stiffening models and high strength concrete beam flexural test results were verified through comparison. The relationship between moment-curvature and load-deflection was evaluated by result of tension stiffening model and test result values. The analysis results showed that ACI 318 and Owen & Damjanic generally shows good agreement.

• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.141-151
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• 2013

In this paper, lateral-torsional buckling(LTB) strength of HSB800 steel plate girder under uniform bending moment was estimated by the nonlinear analysis. Doubly symmetric sections with slender, noncompact and compact webs were considered and the LTB strength in the inelastic range was estimated by taking initial imperfection and residual stress into account. For the numerical analysis, single-panel model and three-panel model were considered and analysis of SM490 steel plate girder was performed to judge the validity of the constructed models by comparing the results with AASHTO, AISC, Eurocode and KHBDC(LSD) codes. By using the same models, LTB strength of HSB800 girder was evaluated and it was acknowledged that the current codes can be applied to HSB800 girders with doubly symmetric section in the inelastic LTB range.

• Journal of the Korea Convergence Society
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• v.12 no.10
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• pp.129-136
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• 2021

Radiation shields used in medical institutions mainly use lead to manufacture products and fitments. Although lead has excellent processability and economic efficiency, its use is being reduced due to environmental issues when it is disposed of. In addition, when used for a long time, there is a limit to using it as a shielding film, shielding wall, medical device parts, etc. due to cracking and sagging due to gravity. To solve this problem, copper, tin, etc. are used, but tungsten is mostly used because there is a difficulty in the manufacturing process to control the shielding performance. However, it is difficult to compare with other shielding materials because the characteristics according to the type of tungsten are not well presented. Therefore, in this study, a medical radiation shielding sheet was manufactured in the same process using pure tungsten, tungsten carbide, and tungsten oxide, and the particle composition and shielding performance of the sheet cross-section were compared.As a result of comparison, it was found that the shielding performance was excellent in the order of pure tungsten, tungsten carbide, and tungsten oxide.