• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.589-593
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• 2015

The demand of high cycle fatigue behavior on plate material is increasing because of its various applications. However, the high-cycle fatigue life data of the plate material is very rare compared to the rod material. Thus, in this study, a plate specimen is designed for the ultrasonic fatigue test because it is time efficient as compared to the conventional fatigue test. To apply the ultrasonic fatigue test, the specimen design is required to resonate at 20 kHz. Therefore, the dynamic elastic modulus was determined by measuring the resonance frequency with a piezoelectric element and laser doppler vibrometer (LDV). As a result, the plate specimen is designed and demonstrated using the ultrasonic fatigue testing machine. The ultrasonic fatigue test results were compared with the hydraulic fatigue test results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.114-115
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• 2018

This paper studies a mechanism for cost-effective analysis of big data in the cloud environment. Recently, as a storage of electronic medical records can be managed outside the hospital, there is a growing demand for cloud-based big data analysis in small-and-medium hospitals. This paper firstly analyze the Amazon Elastic MapReduce which is a popular cloud framework for big data analysis, and proposes a cost model for analyzing big data using Amazon EMR with less cost. Using the proposed model, the user can construct a cost-effective computing cluster, which maximize the effectiveness of the analysis per operational cost.

• Structural Engineering and Mechanics
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• v.90 no.3
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• pp.273-285
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• 2024

Tapered girders emerged as an economical remedy for the challenges associated with constructing long-span buildings. From an economic standpoint, these systems offer significant advantages, such as wide spans, quick assembly, and convenient access to utilities between the beam's shallow sections and the ceiling below. Elastic-local buckling is among the various failure modes that structural designers must account for during the design process. Despite decades of study, there remains a demand for efficient and comprehensive procedures to streamline product design. One of the most pressing requirements is a better understanding of the tapered web plate girder's local buckling behavior. This paper conducts a comprehensive numerical analysis to estimate the critical buckling coefficient for simply supported tapered steel web plates, considering loading conditions involving compression and bending stresses. An eigenvalue analysis was carried out to determine the natural frequencies and corresponding mode shapes of tapered web plates with varying geometric parameters. Additionally, the study highlights the relative significance of various parameters affecting the local buckling phenomenon, including the tapering ratio of the panel, normalized plate length, and ratio of minimum to maximum compressive stresses. The regression analysis and optimization techniques were performed using MATLAB software for the results of the finite element models to propose a separate formula for each load case and a unified formula covering different compression and bending cases of the elastic local buckling coefficient. The results indicate that the proposed formulas are applicable for estimating the critical buckling coefficient for simply supported tapered steel web plates.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.167-173
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• 2015

This paper attempts to estimate the electricity demand function in Korea with quarterly data of average temperature, GDP and electricity price over the period 2005-2013. We apply lagged dependent variable model and ordinary least square method as a robust approach to estimating the parameters of the electricity demand function. The results show that short-run price and income elasticities of the electricity demand are estimated to be -0.569 and 0.631, respectively. They are statistically significant at the 1% level. Moreover, long-run income and price elasticities are estimated to be 1.589 and -1.433, respectively Both of results reveal that the demand for electricity is price- and income-elastic in the long-run. The relationship between electricity consumption and temperature is supported by many of references as a U-shaped relationship, and the base temperature of electricity demand is about $15.2^{\circ}C$. It is shown that power of explanation and goodness-of-fit statistics are improved in the use of the lagged dependent variable model rather than conventional model.

• Earthquakes and Structures
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• v.7 no.2
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• pp.201-216
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• 2014

In this paper the vulnerability of the confined masonry buildings is evaluated analytically. The proposed approach includes the nonlinear dynamic analysis of the two-story confined masonry buildings with common plan as a reference structure. In this approach the damage level is calculated based on the probability of exceedance of loss vs a specified ground motion in the form of fragility curves. The fragility curves of confined masonry wall buildings are presented in two levels of limit states corresponding to elastic and maximum strength versus PGA based on analytical method. In this regard the randomness of parameters indicating the characteristics of the building structure as well as ground motion is considered as likely uncertainties. In order to develop the analytical fragility curves the proposed analytical models of confined masonry walls in a previous investigation of the authors, are used to specify the damage indices and responses of the structure. In order to obtain damage indices a series of pushover analyses are performed, and to identify the seismic demand a series of nonlinear dynamic analysis are conducted. Finally by considering various mechanical and geometric parameters of masonry walls and numerous accelerograms, the fragility curves with assuming a log normal distribution of data are derived based on capacity and demand of building structures in a probabilistic approach.

• Earthquakes and Structures
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• v.5 no.4
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• pp.439-459
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• 2013

Main objective of the present study is to determine the statistical properties and suitable probability distribution functions of spectral displacements from nonlinear static and nonlinear dynamic analysis within the frame work of Monte Carlo simulation for typical low rise and high rise RC framed buildings located in zone III and zone V and designed as per Indian seismic codes. Probabilistic analysis of spectral displacement is useful for strength assessment and loss estimation. To the author's knowledge, no study is reported in literature on comparison of spectral displacement including the uncertainties in capacity and demand in Indian context. In the present study, uncertainties in capacity of the building is modeled by choosing cross sectional dimensions of beams and columns, density and compressive strength of concrete, yield strength and elastic modulus of steel and, live load as random variables. Uncertainty in demand is modeled by choosing peak ground acceleration (PGA) as a random variable. Nonlinear static analysis (NSA) and nonlinear dynamic analysis (NDA) are carried out for typical low rise and high rise reinforced concrete framed buildings using IDARC 2D computer program with the random sample input parameters. Statistical properties are obtained for spectral displacements corresponding to performance point from NSA and maximum absolute roof displacement from NDA and suitable probability distribution functions viz., normal, Weibull, lognormal are examined for goodness-of-fit. From the hypothesis test for goodness-of-fit, lognormal function is found to be suitable to represent the statistical variation of spectral displacement obtained from NSA and NDA.

• Earthquakes and Structures
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• v.11 no.2
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• pp.265-280
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• 2016

Environmental and operational benefits of green roofs are manifolds; however, their main disadvantages are cost and weight. New technology enabled the use of plastics to reduce the weight of green roof systems to promote their installation. To maximize their potential benefits, green roofs can be installed on existing structures. This study evaluates the influence of green roofs on the seismic response of 3, 6, and 8 storey reinforced concrete ductile moment resisting frames, which were designed according to current seismic standards, however, not designed for green roofs. For each frame, three different types of roofs are considered: gravel flat roof, extensive green roof, and intensive green roof. Nonlinear dynamic time history analysis using an ensemble of twenty real earthquake records was performed to determine the inter-storey drift demand and roof drift demand for each frame. Eigenvalue analysis was also performed to determine the impact of green roofs weight on the elastic and cracked periods of the structure. Results from the analysis demonstrated that intensive and extensive green roofs do not affect the seismic performance of reinforced concrete frame structures.

• Steel and Composite Structures
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• v.4 no.6
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• pp.437-452
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• 2004

A simplified seismic design procedure for steel structures with buckling-restrained braces (BRB) was proposed based on the energy balance concept and the equal energy assumption. The input seismic energy was estimated from a design spectrum, and the elastic and hysteretic energy were computed using energy balance concept. The size of braces was determined so that the hysteretic energy demand was equal to the hysteretic energy dissipated by the BRB. The validity of using equivalent single-degree-of-freedom systems to estimate seismic input and hysteretic energy demand in multi story structures with BRB was investigated through time-history analysis. The story-wise distribution pattern of hysteretic energy demands was also obtained and was applied in the design process. According to analysis results, the maximum displacements of the 3-story structure designed in accordance with the proposed procedure generally coincided with the target displacements on the conservative side. The maximum displacements of the 6- and 8-story structures, however, turned out to be somewhat smaller than the target values due to the participation of higher vibration modes.

• Earthquakes and Structures
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• v.22 no.6
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• pp.585-595
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• 2022

Using the nonlinear static procedures has become very common in seismic codes to achieve the nonlinear response of the structure during an earthquake. The capacity spectrum method (CSM) adopted in ATC-40 is considered as one of the most known and useful procedures. For this procedure the seismic demand can be approximated from the maximum deformation of an equivalent linear elastic Single-Degree-of-Freedom system (SDOF) that has an equivalent damping ratio and period by using an iterative procedure. Data from the results of this procedure are plotted in acceleration- displacement response spectrum (ADRS) format. Different improvements have been made in order to have more accurate results compared to the Non Linear Time History Analysis (NL-THA). A new procedure is presented in this paper where the iteration process shall not be required. This will be done by estimation the ductility demand response spectrum (DDRS) and the corresponding effective damping of the bilinear system based on a new parameter of control, called normalized yield strength coefficient (η), while retaining the attraction of graphical implementation of the improved procedure of the FEMA-440. The proposed procedure accuracy should be verified with the NL-THA analysis results as a first implementation. The comparison shows that the new procedure provided a good estimation of the nonlinear response of the structure compared with those obtained when using the NL-THA analysis.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.5
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• pp.93-101
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• 2010

The demand for elastic pavement, providing comfort for pedestrians is expected to increase continuously but the lack of a standard for materials mixing ratio, that is, the optimal mixing ratio between ERDM chip and polyurethane binder, is still in a trial and error stage. This study aimed at recommending an optimal mixing ratio for elastic landscape pavement through a coherence and resilience test depending on ratio. The test result is outlined as follows. In a tensile strength test, samples B and C indicated a close positive relationship between the binder mixing ratio and tensile strength, indicating that the higher the mixing ratio the higher the tensile strength. In a hardness test, none of samples A, B or C indicated a statistical interrelationship between the binder mixing ratio and hardness. That is, the hardness of the elastic pavement material remained unchanged, irrespective of the binder mixing ratio. In a resilience lest, Samples A and B indicated a close negative interrelation between mixing ratio and resilience, indicating that the higher the mixing ratio, the lower the resilience. Upon analyzing the optimal mixing ratio based on test results, an increase in tensile strength began to slow at a 20% mixing ratio, while resilience began to reduce rapidly at 22%, Thus the optimal range for a mixing ration appeared to be 20~22%. The outcome of this study could to provide guidance for improving the elasticity and stability of elastic pavement.