• Journal of Korean Association for Spatial Structures
• /
• v.20 no.4
• /
• pp.169-176
• /
• 2020

When an unexpected excessive seismic load is applied to the base isolation of arch structure, the seismic displacement of the base isolation may be very large beyond the limit displacement of base isolation. These excessive displacement of the base isolation causes a large displacement in the upper structure and large displacement of upper structure causes structural damage. Therefore, in order to limit the seismic displacement response of the base isolation, it is necessary to install an additional device such as an anti-uplift device to the base isolation. In this study, the installation direction of the base isolation and the control performance of the base isolation installed anti-uplift device were investigated. The installation direction of the base isolation of the arch structure is determined by considering the horizontal and vertical reaction forces of the arch structure. In addition, the separation distance of the anti-uplift device is determined in consideration of the design displacement of the base isolation and the displacement of the arch structure.

• Geomechanics and Engineering
• /
• v.11 no.1
• /
• pp.141-160
• /
• 2016

This study elucidates the uplift behaviors of the straight-sided and belled shafts. The field uplift load tests were carried out on 18 straight-sided and 15 belled shafts at the three collapsible loess sites under an arid environment on the Loess Plateau in Northwest China. Both the site conditions and the load tests were documented comprehensively. In general, the uplift load-displacement curves of the straight-sided and belled shafts approximately exhibited an initial linear, a curvilinear transition, and a final linear region, but did not provide a well defined peak or asymptotic value of the load, and therefore their uplift resistances should be interpreted from the load test results using an appropriate criterion. Nine representative uplift resistance interpretation criteria were used to define the "interpreted failure load" for each of the load tests, and all of these interpreted uplift resistances were normalized by the failure threshold, $T_{L2}$, obtained using the $L_1-L_2$ method. These load test data were compared statistically and graphically. For the straight-sided and belled shafts, the normalized uplift load-displacement curves were respectively established by the plots that related the mean interpreted uplift resistance ratio against the mean displacement at the corresponding interpreted criteria, and the comparisons of the normalized load-displacement curves were made. Specific recommendations for the designs of uplift belled and straight-sided shafts in the loess were given, in terms of both capacity and displacement.

• Geomechanics and Engineering
• /
• v.11 no.2
• /
• pp.211-234
• /
• 2016

A total of 99 full-scale field load tests at 22 sites were compiled for this study to elucidate several issues related to the load-displacement behaviour of belled piers under axial uplift loading, including (1) interpretation criteria to define various elastic, inelastic, and "failure" states for each load test from the load-displacement curve; (2) generalized correlations among these states and determinations to the predicted ultimate uplift resistances; (3) uncertainty in the resistance model factor statistics required for reliability-based ultimate limit state (ULS) design; (4) uncertainty associated with the normalized load-displacement curves and the resulting model factor statistics required for reliability-based serviceability limit state (SLS) design; and (5) variations of the combined ULS and SLS model factor statistics for reliability-based limit state designs. The approaches discussed in this study are practical and grounded realistically on the load tests of belled piers with minimal assumptions. The results on the characterization and uncertainty of uplift load-displacement behaviour of belled piers could be served as to extend the early contributions for reliability-based ULS and SLS designs.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.10
• /
• pp.5-16
• /
• 2012

Geotechnical buried structures with relatively light weight have been suffering from uplift damage due to liquefaction in the past earthquakes. The factor of safety approach by Koseki et al. (1997a), which is widely used in seismic design, predicts the triggering of uplift. However, a method for "quantitative" estimates of the uplift displacement has yet to be established. Estimation of the uplift displacement may be an important factor to be considered for designing underground structures under the framework of performance-based design (ISO23469, 2005). Therefore, evaluation of the uplift displacement of buried structure in liquefied ground during earthquakes is needed for a performance-based design as a practical application. In order to predict the uplift displacement quantitatively, a simplified method is derived based on the equilibrium of vertical forces acting on buried structures in backfill during earthquakes (Tobita et al., 2012). The method is verified through comparisons with results of centrifuge model tests and damaged sewerage systems after the 2004 Niigata-ken Chuetsu, Japan, earthquake. The proposed flow diagram for performance-based design includes estimation of the uplift displacement as well as liquefaction limit of backfill.

• Earthquakes and Structures
• /
• v.15 no.5
• /
• pp.555-564
• /
• 2018

Allowing structures to uplift in earthquakes can significantly reduce or even avoid the development of plastic hinges within the structure. The permanent deformations in the structure can thus be minimized. However, uplift of footings can cause additional horizontal movements of a structure. With an increase in movement relative to adjacent structures, the probability of pounding between structures increases. This experimental study reveals that the footing mass can be used to control the vertical displacement of footing and thus reduce the horizontal displacements of an upliftable structure. A four storey model structure with plastic hinges and uplift capability was considered. Shake table tests using ten different earthquake records were conducted. Three different footing masses were considered. It is found that the amplitude of footing uplift can be greatly reduced by increasing the mass of the footing. As a result, allowing structural uplift does not necessary increase the horizontal displacement of the structure. The results show that with increasing footing weight, the interaction between structural and footing response can increase the contribution of the higher modes to the structural response. Consequently, the induced vibrations on secondary structure increase.

• Journal of Bio-Environment Control
• /
• v.10 no.3
• /
• pp.148-154
• /
• 2001

The uplift capacity of a pile for improving the wind resistance of the 1-2 W type plastic film pipe on greenhouses was tested using the plane and corrugated piles with various shapes and diameters. First, the resistant uplift capacity was measured by using the uplift loading on plane piles. As the uplift loading on plane piles increased, the resistant uplift capacity also increased until the loading was reached to ultimate uplift capacity. After ultimate uplift capacity was appeared the uplift displacement, the uplift capacity was decreased gradually. Secondly, the resistant uplift capacity was measured by using the uplift loading on corrugated piles. After the uplift capacity was reached the uplift displacement, the uplift capacity was continually increased or decreased. In general, the ultimate uplift capacity was independent of pile shapes, pile diameter length, and embedded pipe depth. However, the ultimate uplift capacity of a corrugated pile was twice more than that of a plane pile without regard to its diameter and embedded depth. The ultimate uplift capacity per unit pile area was increasing in deeper embedded depth. However, the longer a pile diameter was, the less ultimate uplift capacity. The uplift capacity of a plane pile, used in conjunction with the design wind velocity (26.9m.s$^{-1}$ ) of the project area, was unsatisfiable without regard to diameters and embedded depths of piles, while most of corrugated piles were well appeared uplift capacity under various experimental conditions.

• Structural Engineering and Mechanics
• /
• v.77 no.3
• /
• pp.369-381
• /
• 2021

The seismic responses of elevated tanks considering liquid-structure interaction are presented under horizontal earthquake. The scaled model tank is fabricated to study the dynamic responses of anchored tank and newly designed uplift tank with replaced dampers. The natural frequencies for structural mode are obtained by modal analysis. The dynamic responses of tanks are completed by finite element method, which are compared with the results from experiment. The displacement parallel and perpendicular to the excitation direction are both gained as well as structural acceleration. The strain of tank walls and the axial strain of columns are also obtained afterwards. The seismic responses of liquid storage tank can be calculated by the finite element model effectively and the results match well with the one measured by experiment. The aim is to provide a new type of tank system with vertical constraint relaxed which leads to lower stress level. With the liquid volume increasing, the structural fundamental frequency has a great reduction and the one of uplift tank are even smaller. Compared with anchored tank, the displacement of uplift tank is magnified, the strain for tank walls and columns parallel to excitation direction reduces obviously, while the one perpendicular to earthquake direction increases a lot, but the values are still small. The stress level of new tank seems to be more even due to uplift effect. The new type of tank can realize recoverable function by replacing dampers after earthquake.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.40 no.4
• /
• pp.109-119
• /
• 1998

Recently pipe-framed greenhouses are widely constructed on domestic farm area. These greenhouses are extremely light-weighted structures and so are easily damaged under strong wind due to the lack of uplift resistance of foundation piles. This experiment was carried out by laboratory soil tank to investigate the displacement be haviors of cylindrical pile foundations according to the uplift loads. Tested soils were sampled from two different greenhouse areas. The treatment for each soil type are consisted of 3 different soil moisture conditions, 2 different soil depths, and 3 different soil compaction ratios. Each test was designed to be repeated 2 times and additional tests were carried out when needed. The results are summarized as follows : 1. When the soil moisture content are low and/or pile foundations are buried relatively shallow, ultimate uplift capacity of foundation soil was generated just after begining of uplift displacement. But under the high moisture conditions and/or deeply buried depth, ultimate up-lift capacity of foundation soil was generated before the begining of uplift displacement. 2. For the case of soil S$_1$, the ultimate uplift capacity of piles depending on moisture contents was found to be highest in optimum moisture condition and in the order of air dryed and saturated moisture contents. But for the case of soil S$_2$, the ultimate uplift capacity was found to be highest in optimum moisture condition and in the order of saturated and air dryed moisture contents. 3. Ultimate uplift capacities are varied depending on the pile foundation soil moisture conditions. Under the conditions of optimum soil moisture contents with 60cm soil depth, the ultimate uplift capacity of pile foundation in compaction ratio of 80%, 85%, and 90% for soil 51 are 76kg, 115kg, and 155kg, respectively, and for soil S$_2$are 36kg, 60kg, and 92kg, respectively. But considering that typical greenhouse uplift failure be occurred under saturnted soil moisture content which prevails during high wind storm accompanying heavy rain, pile foundation is required to be designed under the soil condition of saturated moisture content. 4. Approximated safe wind velosities estimated for soil sample S$_1$and S$_2$are 32.92m/s and 26.58m/s respectively under the optimum soil condition of 90% compaction ratio and optimum moisture content. But considering the uplift failure pattern under saturated moisture contents which are typical situations of high wind accompanying heavy rain, the safe wind velosities for soil sample S$_1$and S$_2$are not any higher than 20.33m/s and 22.69m/s respectively.

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.3
• /
• pp.99-106
• /
• 2020

If an excessive displacement occurs in the base isolation system, the structure will be damaged due to overturning of the upper structure. In this study, we analyze the behavior of base isolation by applying earthquake to base isolation with anti-uplift device. In the case of structures that generate horizontal reaction forces such as arch structures, horizontal reaction forces must be considered in the design of the base isolation and structural members. And anti-uplift device for preventing the excessive displacement of the base isolation system is needed.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2002.10a
• /
• pp.125-128
• /
• 2002

The uplift capacity and displacement of an earth anchor for improving the wind resistance of the 1-2W type plastic film pipe on greenhouse was tested using the steel circular vertical earth anchor with various diameters and embedded depths (L) in dry sand. The diameter (B) of the model anchor is 90mm, 120mm, 150mm, respectively. The model tests were performed embedded depth ratios (L/B) ranging from $1{\sim}3$ in loose density. In the case of diameter 90mm, as the uplift loading increased, the uplift capacity also increased until the loading was reached to ultimate uplift capacity. After that, the uplift capacity was continually increased or decreased until the experiment was finished. In general, the ultimate uplift capacity was different depending upon the anchor diameter and embedded depth ratios.