• Geomechanics and Engineering
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• v.12 no.4
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• pp.611-626
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• 2017

The research reported herein is concerned with the model testing of piles socketed in soft rock which was simulated by cement, plaster, sand, water and concrete hardening accelerator. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted and the bearing capacity and accumulated deformation characteristics under different static, and cyclic loads were studied by using a device which combined oneself-designed test apparatus with a dynamic triaxial system. The accumulated deformation of the pile head, and the axial force, were measured by LVDT and strain gauges, respectively. Test results show that the static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation, cyclic secant modulus of pile head, and ultimate bearing capacity. The accumulated deformation increases with increasing numbers of cycles, however, its rate of growth decreases and is asymptotic to zero. The cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles, and finally remains stable after 50 cycles. The ultimate bearing capacity of the pile is increased by about 30% because of the cyclic loading thereon, and the axial force is changed due to the applied cyclic shear stress. According to the test results, the development of accumulated settlement is analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to cyclic loading.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.561-566
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• 2005

This study was carried out to amlyze and compare the stability of a 50ton container crane according to various wind load design codes. The wind load was evaluated according to 'The Specification of Port Facilities and Equipments / Specification for the design of crane structures (KS A 1627)' and 'Load Criteria of Building Structures' effected by the ministry of construction & transportation And the uplift forces qf a container crane under this wind load were estimated by amlyzing reaction forces at each supporting point and compared each other. From this study, we noticed that the design wind velocity criteria need to be defined specifically when the wind load is evaluated to design a container crane. And we verified the necessity of the estimation of the uplift forces at each supporting point to analyze a structural stability of a container crane and the maximum compressive force in order to consider the stability of the ground foundation of the berth.

• Computational Structural Engineering
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• v.8 no.4
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• pp.149-158
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• 1995

When hot-rolled wide flanges are used as vertical compressive or bending member, opening web are often to take a space for equipments of pipe or duct. The Web of hot-rolled wide flange steel with opening may be analyzed as a rectangular plate, subjected to in plane force, and the buckling load is governed by the ultimate force of web. The result of the theory showed close agreement with the result of the finite element analysis. It was also shown that the buckling loads of stiffened opening plates could be larger than those of the plate. The stiffened opening plates for the 4-side simply supported case showed more stiffening effect than the Two Opposite Elastic Supports and Two Other Opposite Simply Supports case. In this study, we proposed the effective opening sizes that buckling loads of stiffened opening plate could be greater than those of the plates.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1349-1360
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• 2013

The post-tensioned anchorage zones of normal concrete have larger cross sections because of congested reinforcements to resist high bearing and bursting stresses. The high compressive and tensile strength of newly developed UHPC (Ultra High Performance Concrete) may reduce the cross sectional dimensions and simplify the reinforcement details, if used for post-tensioned members. The Finite Element Analysis was performed to evaluate the mechanical behavior of post-tensioned anchorage zones using UHPC without anchorage plates and confining reinforcements. The results show that the maximum bursting stresses are less than the values given in current design code without failure due to vertical cracks. The location of maximum bursting stresses were at 0.2 times of width of the models. The bursting force from FEA is less than that is obtained using simplified formular in Korean Bridge Design Code.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.261-271
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• 2015

Steel concentrically braced frame is an efficient system that can acquire resistance against the lateral force of buildings with the least amount of quantity. In this study is intended to proceed on the research of schemes for reinforcement by supplementing previously installed H-formed brace with non-welded cold-formed plastic stiffening materials restricting the flexure and buckling and acquire a consistent strength on the tensile and compressive force. As for the measures of supplementing previously-installed inverted V-formed braced frame, stiffening materials in the previous studies were converted to weak-axial supplementing materials to suggest a specific scheme evaluating the structural function through an experiment of members, interpretation of members, and frame-focused experiment. Reinforced brace satisfied the requirement to be prevent AISC brace from being ruptured due to imbalanced strength in the beam.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.52-57
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• 2016

In this study, a restoring viscous damper is introduced for X-type damper system which is designed for the seismic response control of large spatial structures. A nonlinear numerical model for its behavior is developed using the result of dynamic loading tests. The X-type damper system is composed of restoring viscous dampers and connecting devices such as adjustable wire bracing, where the damping capacity of the system is controllable by changing the number of the dampers. The restoring viscous damper is devised to exert main damping force in tension direction, which is effective to prevent the buckling of bracing subjected to compressive axial force. To evaluate the performance of the proposed damper, dynamic cyclic loading tests are performed by using manufactured dampers at full scale. In order to construct the numerical model of the damper system, its model parameters are first identified using a nonlinear curve fitting method with the test data. The numerical simulations are then performed to validate the accuracy of the numerical model in comparison with the experimental test results. It is expected that the proposed system is effectively applicable to various building structures for seismic performance enhancement.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.3
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• pp.9-21
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• 2012

Concrete filled steel tube (CFT) columns have been widely used in moment resisting frame structures both in seismic zones. This paper discusses the design of such members based on the advanced methods introduced in the 2005 AISC Specification and the 2005 Seismic Provisions. This study focuses particularly on design following both linear and nonlinear methods utilizing equivalent static and dynamic loads for low-rise moment frames. The paper begins with an examination of the significance of pseudo-elastic design interaction equations and the plastic ductility demand ratios due to combined axial compressive force and bending moment in CFT members. Based on advanced computational simulations for a series of five-story composite moment frames, this paper then investigates both building performance and new techniques to evaluate building damage during a strong earthquake. It is shown that 2D equivalent static analyses can provide good design approximations to the force distributions in moment frames subjected to large inelastic lateral loads. Dynamic analyses utilizing strong ground motions generally produce higher strength ratios than those from equivalent static analyses, but on more localized basis. In addition, ductility ratios obtained from the nonlinear dynamic analysis are sufficient to detect which CFT columns undergo significant deformations.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.1-13
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• 2007

As girders and towers in cable-stayed bridges are subject to bending moments as well as axial forces, the conventional load rating equation, which considers only the single force effect, cannot be used to evaluate the rating factors of cable-stayed bridges. The load rating equation for components in cable-stayed bridges is not currently established yet. In this paper, we propose load rating equations for girders and towers in cable-stayed bridges using the interaction equations for beam-column members. Moving load analyses were performed for the cases of a maximum axial compressive force, maximum positive moment and maximum negative moment for each component in cable-stayed bridges and detailed procedures to apply proposed equations were presented. The Dolsan Grand Bridge was used to verify the validity of proposed equations. The conventional load rating equation overestimates rating factors of girders and towers in the Dolsan Grand Bridge, whereas proposed equations properly reflect the axial-flexural interaction behaviour of girders and towers in cable-stayed bridges.

• Tribology and Lubricants
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• v.36 no.5
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• pp.253-261
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• 2020

In this paper, we present an experimental investigation of the frequency characteristics and a visual inspection of an oxidizer pump with a modified rear-floating ring seal for a 7-tonf turbopump. An oxidizer pump typically operates at high rotational speeds and under cryogenic conditions. Despite its low hydraulic efficiency, the floating ring seal is frequently employed as a leakage control solution for turbomachinery because it effectively reduces abrasion by friction. When the oxidizer pump starts up, the floating ring moves excursively but locks up stably against the pump casing when the contact pressure increases. The compressive force on the floating ring depends on the hydrodynamic forces induced by the flow through the floating ring. This force is controlled by the nose position of the floating ring. Based on a validation test for a 7-tonf turbopump with two types of floating rings, we concluded that the floating ring with a small diameter nose can move easily with a low contact pressure in the cooling path. This leads to instability of the pressure fluctuation around the floating ring. In contrast, a floating ring with a large diameter nose has a high contact pressure and attaches strongly to the casing, which causes wear and frictional oxidation between the contact surfaces of the impeller and the floating ring.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.72-81
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• 2014

Even though two-hands lifting/lowering activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting/lowering are also very common at the industrial site, forestry, farming, and daily life. The objective of this study was to compare one-hand lowering activity to lifting activity in terms of biomechanical stress for the range of lowering heights from knuckle height to 10cm above floor level with two workload 7.5kg and 15.0kg. Eight male subjects with LMM were asked to perform lifting/lowering tasks using both a one-handed (left-hand and right-hand) as well as a two-handed technique. Spinal loading was estimated through an EMG-assisted free-dynamic biomechanical model. The biomechanical stress of one-hand lowering activity was shown to be 43% lower than that of one-hand lifting activity. It was claimed that the biomechanical stress for one-hand lifting/lowering activity is almost twice (194%) of the one for two-hands lifting/lowering activity. It was also found that biomechanical stress by one-hand lowering/lifting activity with the half workload of two-hands lowering/lifting activity was greater than that of the two-hands lowering/lifting activity. Therefore, it might be a risk to consider the RWL of one-hand lowering/lifting activity to simply be a half of the RWL of two-hands lowering/lifting activity recommended by NIOSH.