• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.379-388
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• 2008

In the bi-directional pile load test (BD PLT) for pile load tests of Mega pile foundations, loading capacity standard is not specified exactly. Therefore there are so many confusions in performing the BD PLT and variations up to maximum 2 times in loading capacity are come out. In this study, standards of bi-directional pile load test (BD PLT) were considered. Based on cases of the bi-directional pile load test performed in domestic areas, maximum equivalent test load, test load increasing ratio, loading capacity increasing ratio and sufficiency ratio of design load were analyzed. It could be known that the loading capacity standard of bi-directional pile load test must be defined as 1-directional loading capacity and also must be established as more than 2 times of design load.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.377-384
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• 2008

In the bi-directional pile load test (BD PLT) for pile load test of Mega foundation, loading capacity specification were not specified exactly. Therefore there are so many confusions and variations of maximum 2 times in loading capacity are come out. In this study, specifications of bi-directional pile load test (BD PLT) were considered. Based on cases of the bi-directional pile load test performed in domestic areas, maximum equivalent test load, test load increasing ratio and sufficiency ratio of design load were analyzed. It can be known that the loading capacity specification of bi-directional pile load test must be defined as 1-directional test load that is established as more than 2 times of design load.

• Earthquakes and Structures
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• v.18 no.5
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• pp.581-598
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• 2020

This paper aims to investigate the seismic behavior and influence parameters of the large-scaled thin-walled reinforced concrete (RC) tubular columns in air-cooled supporting structures of thermal power plants (TPPs). Cyclic loading tests and finite element analysis were performed on 1/8-scaled specimens considering the influence of wall diameter ratio, axial compression ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio and adding steel diagonal braces (SDBs). The research results showed that the cracks mainly occurred on the lower half part of RC tubular columns during the cyclic loading test; the specimen with the minimum wall diameter ratio presented the earlier cracking and had the most cracks; the failure mode of RC tubular columns was large bias compression failure; increasing the axial compression ratio could increase the lateral bearing capacity and energy dissipation capacity, but also weaken the ductility and aggravate the lateral stiffness deterioration; increasing the longitudinal reinforcement ratio could efficiently enhance the seismic behavior; increasing the stirrup reinforcement ratio was favorable to the ductility; RC tubular columns with SDBs had a much higher bearing capacity and lateral stiffness than those without SDBs, and with the decrease of the angle between columns and SDBs, both bearing capacity and lateral stiffness increased significantly.

• Earthquakes and Structures
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• v.12 no.1
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• pp.23-34
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• 2017

Composite steel plate deep beam (CDB) is proposed as a lateral resisting member, which is constructed by steel plate and reinforced concrete (RC) panel, and it is connected with building frame through high-strength bolts. To investigate the seismic performance of the CDB, tests of two 1/3 scaled specimens with different length-to-height ratio were carried out under cyclic loads. The failure modes, load-carrying capacity, hysteretic behavior, ductility and energy dissipation were obtained and analyzed. In addition, the nonlinear finite element (FE) models of the specimens were established and verified by the test results. Besides, parametric analyses were performed to study the effect of length-to-height ratio, height-to-thickness ratio, material type and arrangement of RC panel. The experimental and numerical results showed that: the CDBs lost their load-carrying capacity because of the large out-of plane deformation and yield of the tension field formed on the steel plate. By increasing the length-to-height ratio of steel plate, the load-carrying capacity, elastic stiffness, ductility and energy dissipation capacity of the specimens were significantly enhanced. The ultimate loading capacity increased with increasing the length-to-height ratio of steel plate and yield strength of steel plate; and such capacity increased with decreasing of height-to-thickness ratio of steel plate and gap. Finally, a unified formula is proposed to calculate their ultimate loading capacity, and fitting formula on such indexes are provided for designation of the CDB.

• Earthquakes and Structures
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• v.16 no.1
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• pp.97-107
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• 2019

The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.41-48
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• 2004

Several centrifuge modelling tests were performed to compare sand compaction pile (SCP) with gravel compaction pile (GCP) at the point of bearing capacity. SCP and GCP were installed as 30, 40, 50, 60, 70% of replacement ratio in cylindrical model tank (diameter = 20 cm, height = 40 cm), and the loading tests were carried out to analyze the bearing characteristics of soft clay ground reinforced by SCP and GCP. As a result of loading tests, the bearing capacities of soft grounds reinforced by SCP and GCP increase with increasing replacement ratio of pile, and a GCP reinforced ground has larger bearing capacity than that of a SCP reinforced ground. Several proposed bearing capacity equations for ground reinforced by SCP or GCP were compared with loading test results.

• Steel and Composite Structures
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• v.18 no.1
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• pp.71-90
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• 2015

Axial compression tests have been carried out on 18 rectangular concrete-filled cold-formed steel tubular (CFST) columns with the aim of investigating the axial behaviour of rectangular CFST columns under different loading methods (steel loaded-first and full-section loaded methods). The influence of different loading methods on the ultimate strength of the specimens was compared and the development of Poisson's Ratio as it responds to an increasing load was reported and analysed. Then, the relationship between the constraining factor and the strength index, and the relationship between the constraining factor and ductility index of the specimens, were both discussed. Furthermore, the test results of the full-section loaded specimens were compared with five international code predicted values, and an equation was derived to predict the axial carrying capacity for rectangular CFST columns with a steel loaded-first loading method.

• Steel and Composite Structures
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• v.27 no.3
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• pp.285-295
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• 2018

In this paper, the bearing capacity of a non-eccentric and eccentric tubular, concrete-filled, steel bridge pier was studied through the finite element method. Firstly, to verify the validity of the numerical analysis, the finite element analysis of four steel tube columns with concrete in-fill was carried out under eccentric loading and horizontal cyclic loading. The analytical results were compared with experimental data. Secondly, the effects of the eccentricity of the vertical loading on the seismic performance of these eccentrically loaded steel tubular bridge piers were considered. According to the simulated results, with increasing eccentricity ratio, the bearing capacity on the eccentric side of a steel tubular bridge pier (with concrete in-fill) is greatly reduced, while the capacity on the opposite side is improved. Moreover, an empirical formula was proposed to describe the bearing capacity of such bridge piers under non-eccentric and eccentric load. This will provide theoretical evidence for the seismic design of the eccentrically loaded steel tubular bridge piers with concrete in-fill.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.590-599
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• 2006

In this study, Liquefaction characteristics of saturated sand under various dynamic loadings such as sinusoidal loading, increasing wedge loading, and real earthquake loading were investigated focusing on the dissipated energy. From the results of cyclic triaxial test, liquefaction resistance strength was calculated by the concept of energy according to the type of input loading. Liquefaction resistance strength was expressed in accumulated dissipated energy calculated from stress-strain curve(hysteresis loop). The dissipated energy according to loading type was compared and the energy-based evaluation was proposed. The procedures are presented in terms of normalized energy demand(NED), normalized energy capacity(NEC), and factor of safely, where NED is the load imparted to the soil by the loading(both amplitude and duration), NEC is the demand required to induce liquefaction, and factor of safely is defined as the ratio of NEC and NED.

• 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.