• Wind and Structures
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• v.13 no.2
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• pp.145-167
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• 2010

By using the 'failure' model approach, the effects of wind direction on the flight of sheathing panels from the roof of a model house in extreme winds was investigated. A complex relationship between the initial conditions, failure velocities, flight trajectories and speeds was observed. It was found that the local flow field above the roof and in the wake of the house have important effects on the flight of the panels. For example, when the initial panel location is oblique to the wind direction and in the region of separated flow near the roof edge, the panels do not fly from the roof since the resultant aerodynamic forces are small, even though the pressure coefficients at failure are high. For panels that do fly, wake effects from the building are a source of significant variation of flight trajectories and speeds. It was observed that the horizontal velocities of the panels span a range of about 20% - 95% of the roof height gust speed at failure. Numerical calculations assuming uniform, smooth flow appear to be useful for determining panel speeds; in particular, using the mean roof height, 3 sec gust speed provides a useful upper bound for determining panel speeds for the configuration examined. However, there are significant challenges for estimating trajectories using this method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.8
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• pp.757-766
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• 2004

This paper focuses on the formulation and validation of an automatic strategy to select the optimal location and direction of strain gauges for the measurement of the modal response. These locations and directions are important to render the strain measurements as robust as possible when a random mispositioning of the gauges and gauge failures are expected. The approach relies on the evaluation of the signal-to-noise ratios of the gauge measurements from strain data of finite element. The multi-step optimization strategy including genetic algorithm is used to find the strain gauge locations-directions that maximize the smallest modal strain signal-to-noise ratio in the absence of gauge failure or its expected value when gauge failure is possible. A flat Plate is used to prove the applicability of the proposed methodology and to demonstrate the effects of the essential parameters of the problem such as the mispositioning level, the probability of gauge failure, and the number of gauges.

• Steel and Composite Structures
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• v.23 no.6
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• pp.647-656
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• 2017

This paper presents an experimental study on the behaviour of steel beams with different types of web openings. Steel beams with web openings became progressively more accepted as a well-organized structural form in steel construction since their existence. Their complicated design and profiling method provides better flexibility in beam proportioning for strength, depth, size and location of holes. The objective of this study is to carry out the experiments on steel beams with different types of web openings and performed non-linear finite element (FE) analysis of the beams that were considered in the experimental study in order to determine their ultimate load capacity and failure modes for comparison. Ten full scale models of steel beam with web openings have been tested in the experimental investigation. The finite element method has been used to predict their entire response to increasing values of external loading until they lose their load carrying capacity. FE model of each specimen that is utilized in the experimental studies is carried out. These models are used to simulate the experimental work to verify test results and to investigate the nonlinear behaviour of failure modes such as local buckling, lateral torsional buckling, web-post buckling, shear buckling and Vierendeel bending of beams.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.1
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• pp.101-110
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• 2000

In case heavy rainfall is a key factor of slope failure, the failure zone is usually developed within the depth of 3~5m from the ground surface regardless of the location of the watertable. If rainfall is taken into consideration, it is general that the slope stability analysis is carried out under the assumption that the cut slope is saturated to the slope surface or the watertable elevates to a certain height so that ${\gamma}_{sat}$, the unit weight of saturated soil, is used. However, the analysis method mentioned above can't exactly simulate the variation of pore water pressure in the slope and yields different failure shape. The applicability of slope stability analysis method considering the distribution of pore water pressure within the slope with heavy rainfalls, was checked out after the stability analysis of a lage-scale cut slope in a highway construction site, where surface failure occurred with heavy rainfalls. An appropriate slope stabilization method is proposed on the base of the outcome of the analysis.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.109-118
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• 2019

The movement of soil along a slope during rainfall can cause serious economic damage and can jeopardize human life. Accordingly, predicting slope stability during rainfall is a major issue in geotechnical engineering. Due to rainwater penetrating the soil, the negative pore water pressure will decrease, in turn causing a loss of shear strength in the soil and ultimately slope failure. More seriously, many constructions such as houses and transmission towers built in/on slopes are at risk when the slopes fail. In this study, the numerical simulation using 2D finite difference program, which can solve a fully coupled hydromechanical problems, was used to evaluate the effects of soil properties, rainfall conditions, and the location of a foundation on the slope instability and slope failure mechanisms during rainfall. A slope with a transmission tower located in Namyangju, South Korea was analyzed in this study. The results showed that the correlation between permeability and rainfall intensity had an important role in changing the pore water pressure via controlling the infiltrated rainwater. The foundation of the transmission tower was stable during rainfall because the slope failure was estimated to occur at the toe of the slope, and did not go through the foundation.

• Computers and Concrete
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• v.30 no.1
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• pp.19-32
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• 2022

This paper presents an investigation into the failure of RC columns under impact loadings. A numerical simulation of 19 identical RC columns subjected to single and repeated impact loadings was performed. A free-falling hammer was dropped at midspan with the same total kinetic energy input but varying mass and momentum. The specimens under the repeated impact test were struck two times at the same location. The colliding index, defined as the impact energy-momentum ratio, was proposed to explain the different impact responses under equal-energy impacts. The increase of colliding index from low to high indicates the transition of the impact response from static to dynamic and failure mode from flexure to shear. This phenomenon was more evident when the column had a greater axial load and was impacted with a high colliding index. The existence of the axial load had an inhibitory effect on the crack development and increased the shear resistance. The second impact changes the failure mode from flexural to brittle shear as found in the specimen with 20% axial load subjected to high a colliding index. Moreover, a deflection prediction equation based on the impact energy and force was limited to the low colliding index impact.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3493-3505
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• 2023

Reactor containment buildings serve as the last barrier to prevent radioactive leakage due to accidents and their safety is crucial in overpressurization conditions. Thus, the Regulatory Guide (RG) 1.216 has mentioned the global strain as one of failure criteria in the free-field for cylindrical prestressed concrete containment vessels (PCCV) subject to internal pressure. However, there is a limit that RG 1.216 shows the free-field without the specific locations of failure criteria and also the global strain corresponding to only azimuth 135° has been mentioned in NUREG/CR-6685, regardless of the elevations of the structure. Therefore, in order to reevaluate the failure criteria of the 1:4 scaled PCCV, the high fidelity simulation model based on the experimental test was significantly validated in this study, and it was interesting to find that the experimental and numerical result was very close to each other. In addition, for the consideration of the material uncertainties, the Latin hypercube method was used as a statistical approach. Consequently, it was revealed that the radial displacements of various azimuth area such as 120°, 135°, 150°, 180° and 210° at elevations 4680 mm and 6,200 mm can represent as the global deformation at the free-field, obtained from the statistical approach.

• Structural Monitoring and Maintenance
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• v.4 no.1
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• pp.69-84
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• 2017

Delamination is the most common failure mode in layered composite materials. The author have found that the electrical potential change (EPC) technique using response surfaces method is very effective in assessment delamination in basalt fiber reinforced polymer (FRP) laminate composite pipe by using electrical capacitance sensor (ECS). In the present study, the effect of the electrodes number on the method is investigated using FEM analyses for delamination location/size detection by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Three cases of electrodes number are analyzed here are eight, twelve and sixteen electrodes, afterwards, the delamination is introduced into between the three layers [$0^{\circ}/90^{\circ}/0^{\circ}$]s laminates pipe, split into eight, twelve and sixteen scenarios for cases of eight, twelve and sixteen electrodes respectively. Response surfaces are adopted as a tool for solving inverse problems to estimate delamination location/size from the measured EPC of all segments between electrodes. As a result, it was revealed that the estimation performances of delamination location/size depends on the electrodes number. For ECS, the high number of electrodes is required to obtain high estimation performances of delamination location/size. The illustrated results are in excellent agreement with solutions available in the literature, thus validating the accuracy and reliability of the proposed technique.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.567-576
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• 2017

Structural failures are undesirable events that devastate the construction industry resulting in loss of life, injury, huge property loss, and also affect the economy of the region. Roof truss failures occur mainly due to excessive loading, improper fabrication, deterioration, inadequate repair, etc. Although very rare, a roof truss may even fail due to inappropriate location of supports. One such case was reported from the recent failure of a steel roof truss used in an indoor stadium at Kargil in India. Kargil region, being mountainous in nature, receives heavy snowfall and hence the steel roof trusses are designed for heavy snow loads. Due to inappropriate support location, the indoor stadium's steel roof truss had failed under heavy snow load for which it was designed and became an interesting structural engineering problem. The failure observed was primarily in terms of yielding of the bottom chord under the supports, leading to partial collapse of the roof truss. This paper summarizes the results of laboratory tests and analytical studies that focused on the validation of the proposed remedial measure for rehabilitating this distressed steel roof truss. The study presents the evaluation of (i) significant reduction in strength and stiffness of the distressed truss resulting in its failure, (ii) desired recovery in both strength and stiffness of the rectified truss contributed by the proposed remedial measure. Three types of models i.e., ideal truss model, as build truss model and rectified truss model were fabricated and tested under monotonic loading. The structural configuration and support condition varied in all the three models to represent the ideal truss, distressed truss and the rectified truss. To verify the accuracy of the experimental results, an analytical study was carried out and the results of this analytical study are compared with the experimental ones.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.1
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• pp.25-33
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• 1999

Since concrete is an inhomogeneous material consisting of larger aggregates and sand embedded in a cement paste matrix, it relatively shows a complex failure mechanism. In order to assure the reliability of concrete structure. microscopic fracture behavior and internal damage progress of concrete under the loading should be fully understood. In this study, an acoustic emission(AE) technique has been used to clarify microscopic failure mechanism and their corresponding AE signal characteristics of concrete under three-point bending test. In addition 2-dimensional AE source location has been performed to monitor the progress of an internal damage and the successive crack growth behavior during the loading. The relationship between AE signal characteristics and microscopic fracture mechanism is discussed.