• Journal of Bio-Environment Control
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• v.26 no.1
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• pp.27-34
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• 2017

This study was carried out to estimate structural stabilities in respect of ground footings of plastic greenhouses on reclaimed lands. A 6m-wide multi-span plastic greenhouse with steel spiral piles as well as two 8.2m-wide single-span greenhouses with steel spiral piles and continuous pipe foundation respectively were built up on a reclaimed land with a SPT N-Value of 2 and measured how much the greenhouses were lifted up and subsided. In addition, the uplift capacity of three kinds of spiral piles(${\phi}50$, ${\phi}75$ and ${\phi}100$) was determined on a nearby reclaimed land. The results showed that the greenhouses with spiral piles had a slight vertical displacement like moving up and down but the scales of the rising up and sinking were negligible when compared to that of the greenhouses. The vertical displacement of the multi-span greenhouse ranged from +9.0mm(uplift) to -11.5mm(subsidence). As for the single-span greenhouses with spiral piles and continuous pipe foundation, the measurements showed that it varied from +1.3mm to -7.7mm and from +0.9mm to -11.2mm, respectively. The allowable uplift capacity of spiral piles could all be determined under criteria of ultimate load and accordingly had a value of 0.40kN, 1.0kN and 2.5kN, respectively. It was not entirely certain enough to make a final judgement on structural stabilities in respect of ground footings, it appeared likely however that the greenhouses with steel spiral piles was tentatively observed without any problems on reclaimed lands within the period.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1188-1195
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• 2007

The vertical forces in rail fasteners at areas of bridge transitions near the embankment and on the pier will occur due to different deformations of adjoining bridges caused by the trainloads, the settlement of supports, and the temperature gradients. The up-lifting forces is not large problem in the blast track because the elasticity of blast and rail pad buffs up-lifting effect. But, it is likely to be difficult to ensure the serviceability of the railway and the safety of the fastener in the end in that concrete slab track consist of rail, fastener, and track in a single body, delivering directly the up-lifting force to the fastener if the deck is bended because of various load cases, such as the end rotation of the overhang due to the vertical load, the bending of pier due to acceleration/braking force and temperature deviation, the settlement of embankment and pier, the temperature deviation of up-down deck and front-back pier, and the rail deformation due to wheel loads. The analysis of the rail fastener is made to verify the superposed tension forces in the rail fastener due to various load cases, temperature gradients and settlement of supports. The potential critical fasteners with the highest uplift forces are the fastener adjacent to the civil joint. The main influence factors are the geometry of the bridge such as, the beneath length of overhang, relative position of bridge bearing and fastener, deflection of bridge and the vertical spring stiffness of the fastener.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.165-173
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• 2019

Plate anchors are generally used for structures like transmission towers, mooring systems etc. where the uplift and lateral forces are expected to be predominant. The capacity of anchor plate can be increased by the use of geosynthetics without altering the size of plates. Numerical simulations have been carried out on three different sizes of square anchor plates. A single layer geosynthetic has been used as reinforcement in the analysis and placed at three different positions from the plate. The effects of various parameters like embedment ratio, position of reinforcement, width of reinforcement, frequency and loading amplitude on the pull out capacity have been presented in this study. The load-displacement behaviour of anchors for various embedment ratios with and without reinforcement has been also observed. The pull out load, corresponding to a displacement equal to each of the considered maximum amplitudes of a given frequency, has been expressed in terms of a dimensionless breakout factor. The pull out load for all anchors has been found to increase by more than 100% with embedment ratio varying from 1 to 6. Finally a semi empirical formulation for breakout factor for square anchors in reinforced soil has also been proposed by carrying out regression analysis on the data obtained from numerical simulations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.267-273
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• 2020

Suction anchors are used for floating structures because they have advantages in installation and stability. Recently, the demand for floating structures requiring low allowable displacement has increased. Thus, it is strongly suggested that the displacement of the suction anchor be evaluated. However, conventional studies regarding suction anchors have concentrated on the capacity of the anchor, and research on the displacement of the anchor is limited. In particular, rotation is the primary behavior of a suction anchor subjected to an inclined load, and related information has been insufficient. Therefore, the main objective of this paper is to investigate the rotation behavior of a suction anchor via centrifuge model tests. The experimental parameters are the inclination of the pull-out load, anchor dimensions, and aspect ratio. The rotation values of suction anchors were compared using a series of load-rotation curves. The results show that the inclination of the load has a dominant influence on the rotation behavior of the suction anchor.

• Explosives and Blasting
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• v.38 no.4
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• pp.26-36
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• 2020

With the increase of expansion and use of the underground space, the possibility of an underground explosion by terrorists is increasing. In this study, after modeling a circular tunnel excavated at a depth of 50m, an explosion load was applied to the inside of the tunnel. As for the explosion load, the explosion load of the maximum explosive amount for six types of vehicle booms proposed by ATF (Bureau of Alcohol, Tobacco, and Firearms) was calculated. For the rock mass around the circular tunnel, three types of rock grades were selected according to the support pattern suggested in the domestic tunnel design. Nonlinear dynamic analysis was performed to evaluate the influence of the ground structure by examining the surface displacement using the explosion load and rock mass characteristics as parameters. As a result of the analysis, for grade 1 rock, the influence on the uplift of the surface should be considered, and for grade 2 and 3 rocks, the influence on a differential settlement should be considered. In particular, for grade 3 rocks, detailed analysis is required for ground-structure interaction within 40m. Also, it is considered that the influence of Young's modulus is the main factor for the surface displacement.

• Earthquakes and Structures
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• v.9 no.1
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• pp.127-143
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• 2015

In conventional seismic design, structures are assumed to be fixed at the base. To reduce the impact of earthquake loading, while at the same time providing an economically feasible structure, minor damage is tolerated in the form of controlled plastic hinging at predefined locations in the structure. Uplift is traditionally not permitted because of concerns that it would lead to collapse. However, observations of damage to structures that have been through major earthquakes reveal that partial and temporary uplift of structures can be beneficial in many cases. Allowing a structure to move as a rigid body is in fact one way to limit activated seismic forces that could lead to severe inelastic deformations. To further reduce the induced seismic energy, slip-friction connectors could be installed to act both as hold-downs resisting overturning and as contributors to structural damping. This paper reviews recent research on the concept, with a focus on timber shear walls. A novel approach used to achieve the desired sliding threshold in the slip-friction connectors is described. The wall uplifts when this threshold is reached, thereby imparting ductility to the structure. To resist base shear an innovative shear key was developed. Recent research confirms that the proposed system of timber wall, shear key, and slip-friction connectors, are feasible as a ductile and low-damage structural solution. Additional numerical studies explore the interaction between vertical load and slip-friction connector strength, and how this influences both the energy dissipation and self-centring capabilities of the rocking structure.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.307-311
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• 2007

In the case of the railway bridges, uplift forces were occurred at the edge of the segments when vehicular loads were applied. These forces made the compressive and tensile forces occur in the fastening system. Therefore, the structural analysis was performed to investigate the safety of fastening system which was modeled as one directional spring element. In this case, the stiffness of the spring element was obtained from experimental study which was conducted by compressive load. For that reason, to perform rational and exact structural analysis, the translational stiffness of the fastening system obtained from the experimental study applied the tensile load and the rotational stiffness should be considered because it was occurred the tensile force as well as the compressive force in fastening system. In this study, an elastic and inelastic experimental study was performed for six specimens. The translational stiffness along the vertical axis of rail and the rotational stiffness along the strong axis of rail were investigated. Also structural behavior of the fastening system was analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.21-30
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• 1989

In this study, the dynamic behavior of a continuous bridge under moving load is studied considering roughness of the road surface. Vehicle model includes the spring effects of axes, and due to these effects, equations of motions for the vehicle and bridge are derived in coupled form. And then iteration method is used to solve the equations. In experimental study a bridge model is constructed considering the similarity rule in order that the model exhibits dynamic behavior similar to that of prototype. Three types of roughness such as uneven random roughness, uplift on the approach and piece-wise constant roughness are used to describe road roughness. Through the numerical analysis and experiments, the effects of surface roughness, sprung mass, and velocity on the dynamic behavior of the bridge are examined.

• Earthquakes and Structures
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• v.21 no.6
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• pp.641-652
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• 2021

Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. In this study, a new type of digging well foundation with prefabricated roots was proposed to reduce earthquake damage of these bridges. Quasi-static tests were conducted to investigate the failure mechanism of the root digging well foundation, and then to analyze seismic behaviors of the new type well foundation. The testing results indicated that these prefabricated roots could effectively limit the rotation and uplift of the digging well foundation and increase the lateral bearing capacity of the digging well foundation. The elastic critical load and ultimate load can be increased by 69% and 36% if prefabricated roots were added in the digging well foundation. The prefabricated roots drived more soil around the foundation to participate in working, the stiffness of the bridge pier with root digging well foundation was improved. Moreover, the root participation could improve the energy dissipation capacity of soil-foundation-pier interaction system. The conclusions obtained in this paper had important guiding significance for the popularization and application of the digging well foundation with prefabricated roots in earthquake-prone zones.

• Geotechnical Engineering
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• v.12 no.3
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• pp.63-72
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• 1996

Plate anchors are often used for various types of offshore construction and maintenance works. When the plates are embedded in soft clay and subjected to sustanined allowable loads, creep may develop. This paper presents some results from laboratory model test designed to study the creep effect that develops with time for a shallow circular anchor subjected to sustained net loads that are less than the net ultimate uplift capacity. Based on the model test results, relationships among the net load, the rate of strain, and time are developed.