• Wind and Structures
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• v.13 no.2
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• pp.207-220
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• 2010

The 'chain reaction' effect of the interaction between wind pressure and windborne debris is likely to be a major cause of damage to residential buildings during severe wind events. The current paper (Part II) concerns the quantification of such pressure-debris interaction in an advanced vulnerability model that integrates the debris risk model developed in Part I and a component-based wind-pressure damage model. This vulnerability model may be applied to predict the cumulative wind damage during the passage of particular hurricanes, to estimate annual hurricane losses, or to conduct system reliability analysis for residential developments, with the effect of windborne debris fully considered.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.445-450
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• 2003

This study was performed 10 develop the accelerated life test method using Weibull-IPL(Inverse Power Law) model for mechanical components. Weibull-IPL model is concerned with determining the assurance life with confidence level and the accelerated life test time From the relation of weibull distribution factors and confidence limit, the testing times on the no number of failure acceptance criteria arc determined. The mechanical components generally represent wear and fatigue characteristics as a failure mode. IPL based on the cumulative damage theory is applied effectively the mechanical components to reduce the testing time and to achieve the accelerating test conditions. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% confidence level for one test sample. According to IPL, because test time call be shorten in case increase test load test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.5
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• pp.494-502
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• 2009

A quantitative model was developed in order to estimate fishery production damage due to anthropogenically induced environmental changes. The model is described in the following equation, $Y_D=\frac{{\phi}_D}{{\phi}_G}[Y_0{\cdot}(t_p-t_0)-\frac{Y_0}{{\phi}_G}(1-e^{-{\phi}_G(t_p-t_0)})]$, where, $Y_D$ is annual amount of fishery production by nuclear power plant. ${\varphi}$ D and ${\varphi}$ G are instantaneous decreasing coefficient of fishery production by nuclear power plant and instantaneous decreasing coefficient of gross fishery production, respectively. $Y_0$ is annual mean fishery production without damages. $t_p$ is the present time, and $t_0$ is the starting time of damages. The model was applied to fishing grounds near a nuclear power plant on the east coast of Korea. Since fishery production damages have become bigger with increasing emission of thermal effluents from generators activities in the power plant, this factor has also been considered as, $\delta_{D_i}=\delta_D\({\sum}\limits_{i=0}^{n}\;W_i/W_T\)$, where, $\delta_{Di}$ is the cumulative damage rate in fishery production from generators, $\delta_D$ is the total cumulative damage rate in fishery production, $W_i$ is the emission amount of thermal effluents by generator i, and n is the number of generators in the nuclear power plant. This model can be used to conduct initial estimates of fishery production damages, before more detailed assessments are undertaken.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.542-548
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• 1997

In this study an evaluation method of fatigue strength of membrane type LNG tank is presented with FEM analysis and experimental approach of seam and raised edge welds. The study contains the following : l)FEM analysis of test specimens 2)Fatigue tests of seam and raised edge welds 3)Estimation of cumulative damage factor of the welds on the basis of safe life design concept complying with the rules of classification society 4)Review of the effect of mean stress on the fatigue strength 5)Modelling of fatigue life of the welds which is changeable by weld heights With the results obtained in this study, a model ${\Delta}{\delta}/h^2=0.13553\;{N_{f}}^{-0.3151}$ for seam and raised edge welds having a given weld height is proposed to be useful for designers and inspectors.

• Journal of Forest and Environmental Science
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• v.39 no.4
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• pp.213-224
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• 2023

As abnormal weather events due to climate change continue to rise, landslide damage is also increasing. Given the substantial time and financial resources required for post-landslide recovery, it becomes imperative to formulate a proactive response plan. In this regard, landslide susceptibility analysis has emerged as a valuable tool for establishing preemptive measures against landslides. Accordingly, this study conducted an annual landslide susceptibility analysis using the history of landslides that occurred over many years in the Jeolla region, and analyzed areas with a high potential for landslides in the Jeolla region. The analysis employed an ensemble model that amalgamated 10 data-based models, aiming to mitigate uncertainties associated with a single-model approach. Furthermore, based on the cumulative data regarding landslide susceptible areas, this research identified regions vulnerable to recurring landslide damage in Jeolla region and proposed specific strategies for utilizing this information at various levels, including local government initiatives, adaptation plan development, and development approval processes. In particular, this study outlined approaches for local government utilization, the determination of adaptation plan types, and considerations for development permits. It is anticipated that this research will serve as a valuable opportunity to underscore the significance of information concerning regions vulnerable to recurring landslide damage.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.103-115
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• 2011

Concrete slab curls and warps due to the uneven distribution of temperature and moisture and as the result, internal stress develops within the slab. Therefore, environmental loads must be considered in addition to the traffic loads to predict the lifespan of the concrete pavement more accurately. The strength of the concrete slab is gradually decreases to a certain level at which fatigue cracking is generated by the repetitive traffic and environmental loadings. In this study, a new fatigue regression model was developed based on the results from previously performed studies. To verify the model, another laboratory flexural fatigue test program which was not used in the model development, was conducted and compared with the predictions of other existing models. Each fatigue model was applied to analysis logic of cumulative fatigue damage of concrete pavement developed in the study. The sensitivity of cumulative fatigue damage calculated by each model was analyzed for the design factors such as slab thickness, joint spacing, complex modulus of subgrade reaction and the load transfer at joints. As the result, the model developed in this study could reflect environmental loading more reasonably by improving other existing models which consider R, minimum/maximum stress ratio.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.2
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• pp.37-45
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• 2022

A simplified model using the lifetime distribution has been presented to estimate the Mean Residual Life (MRL) of rubble-mound breakwaters, which is not like a stochastic process model based on time-dependent history data to the cumulative damage progress of rubble-mound breakwaters. The parameters involved in the lifetime distribution can be easily estimated by using the upper and lower limits of lifetime and their likelihood that made a judgement by several experts taking account of the initial design lifetime, the past sequences of loads, and others. The simplified model presented in this paper has been applied to the rubble-mound breakwater with TTP armor layer. Wiener Process (WP)-based stochastic model also has been applied together with Monte-Carlo Simulation (MCS) technique to the breakwater of the same condition having time-dependent cumulative damage to TTP armor layer. From the comparison of lifetime distribution obtained from each models including Mean Time To Failure (MTTF), it has found that the lifetime distributions of rubble-mound breakwater can be very satisfactorily fitted by log-normal distribution for all types of cumulative damage progresses, such as exponential, linear, and logarithmic deterioration which are feasible in the real situations. Finally, the MRL of rubble-mound breakwaters estimated by the simplified model presented in this paper have been compared with those by WP stochastic process. It can be shown that results of the presented simplified model have been identical with those of WP stochastic process until any ages in the range of MTT F regardless of the deterioration types. However, a little of differences have been seen at the ages in the neighborhood of MTTF, specially, for the linear and logarithmic deterioration of cumulative damages. For the accurate estimation of MRL of harbor structures, it may be desirable that the stochastic processes should be used to consider properly time-dependent uncertainties of damage deterioration. Nevertheless, the simplified model presented in this paper can be useful in the building of the MRL-based preventive maintenance planning for several kinds of harbor structures, because of which is not needed time-dependent history data about the damage deterioration of structures as mentioned above.

• Earthquakes and Structures
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• v.11 no.4
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• pp.649-664
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• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.

• Earthquakes and Structures
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• v.17 no.5
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• pp.511-519
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• 2019

The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.

• Steel and Composite Structures
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• v.33 no.3
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• pp.433-444
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• 2019

Fatigue failure of a grid structure using bolt-sphere joints is liable to occur in a high-strength bolt due to the alternating and reciprocal actions of a suspension crane. In this study, variable amplitude fatigue tests were carried out on 20 40 Cr steel alloy M30 high-strength bolts using an MTS fatigue testing machine, and four cyclic stress amplitude loading patterns, Low-High, High-Low, Low-High-Low, and High-Low-High, were tested. The scanning electron microscope images of bolt fatigue failure due to variable amplitude stress were obtained, and the fractographic analysis of fatigue fractures was performed to investigate the fatigue failure mechanisms. Based on the available data from the constant amplitude fatigue tests, the variable amplitude fatigue life of an M30 high-strength bolt in a bolt-sphere joint was estimated using both Miner's rule and the Corten-Dolan model. Since both cumulative damage models gave similar predictions, Miner's rule is suggested for estimating the variable-amplitude fatigue life of M30 high-strength bolts in a grid structure with bolt-sphere joints; the S-N fatigue curve of the M30 high-strength bolts under variable amplitude loading was derived using equivalent stress amplitude as a design parameter.