• Geomechanics and Engineering
• /
• 제10권1호
• /
• pp.95-107
• /
• 2016

Deep soil mixing with cement and cement-lime mixtures has been widely used for decades to improve the strength of soils. In this study, small-scale laboratory model tests of polymer columns in soft clayey soil were conducted to evaluate the feasibility of using various polymeric compounds as binders in deep soil mixing. Floating and end bearing polymer columns were used to examine the load-settlement relationship of improved soft clayey soils for various area replacement ratios. The results indicate that polymer columns show good promise for use in deep mixing applications.

• Structural Engineering and Mechanics
• /
• 제65권1호
• /
• pp.81-89
• /
• 2018

Stone column installation is a convenient method for improvement of soft ground. In very soft clays, in order to increase the lateral confinement of the stone columns, encasing the columns with high stiffness and creep resistant geosynthetics has proved to be a successful solution. This paper presents the results of three dimensional finite element analyses for evaluating improvement in behaviour of ordinary stone columns (OSCs) installed in soft clay by geotextile encasement under monotonic and cyclic loading by a comprehensive parametric study. The parameters include length and stiffness of encasement, types of stone columns (floating and end bearing), frictional angle and elastic modulus of stone column's material and diameter of stone columns. The results indicate that increasing the stiffness of encasement clearly enhances cyclic behaviour of geotextile encased stone columns (GESCs) in terms of reduction in residual settlement. Performance of GESCs is less sensitive to internal friction angle and elasticity modulus of column's materials in comparison with OSCs. Also, encasing at the top portion of stone column up to triple the diameter of column is found to be adequate in improving its residual settlement and at all loading cycles, end bearing columns provide much higher resistance than floating columns.

• Earthquakes and Structures
• /
• 제22권2호
• /
• pp.203-218
• /
• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.

• 한국지반공학회논문집
• /
• 제35권3호
• /
• pp.5-16
• /
• 2019

최근 도시 인구의 밀집으로 대형구조물의 건설이 증가하고 있으며 이와 더불어 대형구조물의 기초도 발전하고 있다. 2000년대 말에 일본의 기술을 도입하여 PHC말뚝은 많은 구조물에 사용되고 있다. 최근 PHC말뚝의 장점을 이용하여 흙막이 벽체로의 사용에 대한 연구가 많이 진행되고 있으며, 이 연구에서는 PHC-W 흙막이 벽체를 이용한 건축물 지하증설벽체에서 PHC-W말뚝을 주열식으로 시공하여 연직 압축정재하시험을 실시하였으며, 하중전이 측정을 통하여 PHC-W말뚝의 선단지지력을 산정하였다. 풍화암에 근입된 PHC-W말뚝의 지지력은 기존 PHC말뚝의 지지력과는 차이를 보였으므로, 주열식으로 시공된 PHC-W말뚝의 선단지지력 산정식을 제안하였다. 풍화암에 근입된 PHC-W말뚝의 단위극한선단지지력 산정식으로 주열식 군PHC-W말뚝과 단일PHC-W말뚝에서 각각 $q_b=6.8N_b$와 $q_b=13.3N_b$로 제안할 수 있었다.

• 한국지반환경공학회 논문집
• /
• 제2권3호
• /
• pp.71-80
• /
• 2001

쇄석말뚝-매트로 구성된 기초시스템은 지지력이 여러 인자에 의해 영향을 받게 되어 기초지반과 말뚝체의 상호작용을 정량적으로 평가하기에 어려움이 있다. 복합지반의 지지력은 말뚝-흙 경계면의 측방응력에 의해 발생되므로 쇄석말뚝의 거동을 규명하기 위해서는 경계면에서 발생하는 수평저항력에 영향을 미치는 인자들에 대한 평가가 필요하다. 또한, 말뚝간격과 근입비, 파괴각 등 기하학적 요인들도 영향을 미치는 것으로 알려져 있다. 따라서, 본 논문에서는 쇄석말뚝-매트로 구성된 기초시스템의 선단지지 단일말뚝과 군말뚝에 대한 실내모형실험을 통하여 쇄석말뚝의 한계깊이를 측정하고 파괴각에 영향을 미치는 인자들을 평가하였다. 또한, 실내실험결과를 이론식과 비교하였으며 유한요소해석을 통해 파괴거동을 평가하여 실내모형실험의 타당성을 검증하였다.

• Steel and Composite Structures
• /
• 제29권3호
• /
• pp.391-404
• /
• 2018

Researchers have been long studying new building implementation methods to improve the quality of construction, reduce the time of assembly, and increase productivity. One of these methods is the use of modular pre-fabricated structural forms that are composed of a beam, column, short column, pyramidal end block, and connection plates. In this study, a new geometry for the pyramidal end block was proposed that helps facilitate the assembly procedure. Since the proposed configuration affects the performance of this form of connection, its behavior was evaluated using finite element method. For this purpose, the connection was modeled in ABAQUS and then validated by comparing the outputs with experimental results. The research proceeded through analyzing 16 specimens under monotonic and cyclic loading. The results indicated that using the pyramidal end block not only makes the assembly process easier but also reduces the out-of-plane displacement of the short column webs and the vertical displacement of beam end. By choosing appropriate section properties for column and beam, the connection can bear a rotation up to 0.01 radians within its inelastic region and a total of 0.04 radians without any significant reduction in its bearing capacity.

• Structural Engineering and Mechanics
• /
• 제73권6호
• /
• pp.613-620
• /
• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• Earthquakes and Structures
• /
• 제20권4호
• /
• pp.417-430
• /
• 2021

Due to functional requirements, SRC column-RC beam abnormal joints with characteristics of strong beam weak column, variable column section, unequal beam height and staggered height exist in the Steel reinforced concrete (SRC) frame-bent main building structure of thermal power plant (TPP). This paper presents the experimental results of these abnormal joints through cyclic loading tests on five specimens with scaling factor of 1/5. The staggered height and whether adding H-shaped steel in beam or not were changing parameters of specimens. The failure patterns, bearing capacity, energy dissipation and ductile performance were analyzed. In addition, the stress mechanism of the abnormal joint was discussed based on the diagonal strut model. The research results showed that the abnormal exterior joints occurred shear failure and column end hinge flexural failure; reducing beam height through adding H-shaped steel in the beam of abnormal exterior joint could improve the crack resistance and ductility; the abnormal interior joints with different staggered heights occurred column ends flexural failure; the joint with larger staggered height had the higher bearing capacity and stiffness, but lower ductility. The concrete compression strut mechanism is still applicable to the abnormal joints in TPP, but it is affected by the abnormal characteristics.

• 콘크리트학회논문집
• /
• 제21권3호
• /
• pp.291-302
• /
• 2009

현행 기준식에 따르면 초고강도콘크리트에서는 철근 인장이음길이보다 압축이음길이가 더 길어지는 현상이 발생된다. 초고강도콘크리트의 경제적 실용화를 위해 합리적인 압축이음강도의 평가가 필요하다. 이를 위해 압축이음의 거동 특성을 분석하고 영향인자를 도출하였으며, 설계강도 40, 60 MPa 콘크리트에 대한 압축이음 실험을 수행하였다. 압축이음강도는 부착과 지압으로 구성되고, 부착과 지압의 복합 거동에 의해 발현되므로, 압축이음 거동특성 및 강도평가를 위해서는 부착과 지압이 함께 존재하는 상태에서의 연구가 수행되어야한다. 인장이음과 달리 압축이음은 이음길이가 짧고 지압의 존재로 인해 콘크리트 강도의 영향이 크다. 실험결과 압축이음강도는 콘크리트의 제곱근에 비례하는 것으로 평가되었다. 부착과 지압 모두 주변 콘크리트의 응력상태에 따라 결정되는데, 콘크리트의 축방향 응력이 높기 때문에 철근 순간격 증가에 따른 이음강도 증가는 거의 없다. 지압강도는 이음길이와 철근 순간격에 무관하며, 콘크리트 강도의 제곱근의 함수로 표현할 수 있다. 파괴양상이 측면파열파괴와 유사하므로 지압강도는 앵커의 측면파열파괴 강도식을 활용하여 평가가 가능하다. 부착에 의해 발현되는 강도는 인장이음의 경우와 유사하므로, 인장이음강도에 비해 향상된 압축이음강도는 단부 지압효과로 설명될 수 있다.

• Structural Engineering and Mechanics
• /
• 제63권5호
• /
• pp.617-628
• /
• 2017

In order to study the failure mode and seismic behavior of the interior-joint in steel traditional-style buildings, a single beam-column joint and a double beam-column joint were produced according to the relevant building criterion of ancient architectural buildings and the engineering instances, and the dynamic horizontal loading test was conducted by controlling the displacement of the column top and the peak acceleration of the actuator. The failure process of the specimens was observed, the bearing capacity, ductility, energy dissipation capacity, strength and stiffness degradation of the specimens were analyzed by the load-displacement hysteresis curve and backbone curve. The results show that the beam end plastic hinge area deformed obviously during the loading process, and tearing fracture of the base metal at top and bottom flange of beam occurred. The hysteresis curves of the specimens are both spindle-shaped and plump. The ultimate loads of the single beam-column joint and double beam-column joint are 48.65 kN and 70.60 kN respectively, and the equivalent viscous damping coefficients are more than 0.2 when destroyed, which shows the two specimens have great energy dissipation capacity. In addition, the stiffness, bearing capacity and energy dissipation capacity of the double beam-column joint are significantly better than that of the single beam-column joint. The ductility coefficients of the single beam-column joint and double beam-column joint are 1.81 and 1.92, respectively. The cracks grow fast when subjected to dynamic loading, and the strength and stiffness degradation is also degenerated quickly.