• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.685-695
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• 2020

The connection performance between cross-laminated timber (CLT) walls and support has the greatest effect on the horizontal shear strength. In this study, the horizontal shear performance of CLT walls with reinforced connection systems was evaluated. The reinforcements of metal bracket connections in the CLT connection system was made by attaching glass fiber-based reinforcement to the connection zone of a CLT core lamina. Three types of glass fiber-based reinforcement were used: glass fiber sheet (GS), glass fiber cloth (GT) and fiber cloth plastic (GTS). The horizontal shear strength of the fabricated wall specimens was compared and evaluated through monotonic and cyclic tests. The test results showed that the resistance performance of the reinforced CLT walls to a horizontal load based on a monotonic test did not improve significantly. The residual and yield strengths under the cyclic loading test were 38 and 18% higher, respectively, while the ductility ratio was 38% higher than that of the unreinforced CLT wall. The glass fiber-based reinforcement of the CLT connection showed the possibility of improving the horizontal shear strength performance under a cyclic load, and presented the research direction for the application of real-scale CLT walls.

• 한국지반공학회논문집
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• 제32권12호
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• pp.69-78
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• 2016

최근에 해상 풍력발전기의 기초구조물로 석션 버켓기초가 적용되고 있다. 그런데, 석션기초는 보통 해양 연약지반에 설치되므로 장기 반복하중에 의해 누적변위가 발생할 수 있다. 본 연구에서는 1-g 모형실험을 수행하여 장기 수평 반복하중을 받는 석션 버켓기초의 누적 회전각을 분석하였다. 지반조건은 2가지 밀도의 건조 사질토 지반에 대하여 실험하였다. 모형석션 버켓기초의 근입깊이, 모형지반의 밀도, 반복하중의 크기를 변화시키며 실험을 수행하였다. 수평 반복하중은 일방향 재하로 최대 $10^4$번까지 재하하였다. 실험결과, 석션 버켓기초의 누적회전각은 재하횟수와 재하진폭이 증가에 비례하여 증가하였다. 실험결과를 이용하여 건조 사질토 지반에 근입된 석션 버켓기초의 장기 누적회전각을 산정할 수 있는 경험식을 제안하였다.

• Steel and Composite Structures
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• 제32권6호
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• pp.717-729
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• 2019

A horizontal cyclic test was carried out to study the seismic performance of lightweight aggregate concrete filled steel tube (LACFST). The constitutive and hysteretic model of core lightweight aggregate concrete (LAC) was proposed for finite element simulation. The stress and strain changes of the steel tube and concrete filled inside were measured in the experiment, and the failure mode, hysteresis curve, skeleton curve, and strain curve of the test specimens were obtained. The influence of axial compression ratio, diameter-thickness ratio and material strength were analysed based on finite element model. The results show that the hysteresis curve of LACFST indicated favourable ductility, energy dissipation, and seismic performance. The LACFST failed when the concrete in the bottom first crushed and the steel tube then bulged, thus axial force imposed by prestressing was proved to be feasible. The proposed constitutive model and hysteretic model of LAC under the constraint of its steel tube was reliable. The bearing capacity and ductility of the specimen increase significantly with increasing thickness of the steel tube. The bearing capacity of the member improves while the ductility and energy dissipation performance slightly decreased with the increasing strength of the steel and concrete.

• 한국해양공학회지
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• 제28권2호
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• pp.133-139
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• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.515-518
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• 2010

Horizontal forces may form a major part of the loading system for structures supported on pile groups. It is known that during a strong earthquake, the dynamic behavior of a group-pile foundation is related not only to the inertial force coming from the superstructures but also to the deformation of the surrounding ground. Therefore, it is necessary to understand the behaviors of the group-pile foundations and superstructures during major earthquakes. In this paper, numerical simulation of real-scale group-pile foundation subjected to horizontal cyclic loading is conducted by using a program named as DBLEAVES. In the analysis, nonlinear behaviors of ground and piles are described by cyclic mobility model and axial force dependent model (AFD model). The purpose of this paper is to prove availability of the analysis method by comparing numerical results and test results.

• Geomechanics and Engineering
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• 제10권1호
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• pp.1-19
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• 2016

This paper presents the results of an intensive experimental investigation on cyclic behavior of various sands and structural materials interface. Comprehensive measurements of the horizontal displacement and shear stresses developed during testing were performed using an automated constant normal load (CNL) cyclic direct shear test apparatus. Two different particle sizes (0.5 mm-0.25 mm and, 2.0 mm-1.0 mm) of sands having distinct shapes (rounded and angular) were tested in a cyclic direct shear testing apparatus at two vertical stress levels (${\sigma}=50kPa$, and 100 kPa) and two rates of displacement ($R_D=2.0mm/min$, and 0.025 mm/min) against various structural materials (i.e., steel, concrete, and wood). The cyclic direct shear tests performed during this investigation indicate that (i) the shear stresses developed during shearing highly depend on both the shape and size of sand grains; (ii) characteristics of the structural materials are closely related to interface response; and (iii) the rate of displacement is slightly effective on the results.

• 한국해양공학회지
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• 제18권6호
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• pp.58-69
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• 2004

In order to investigate the characteristics of the lateral earth pressure at rest, under hysteretic $K_o-loading/unloading$ conditions, seven types of multi-cyclic models have been studied, using dry sand. For this study, the new type of $K_o-oedometer$ apparatus was developed, and the horizontal pressure was accurately measured. The multi-cyclic models consist of primarily 3 cases: (i) $K_o-test$ under the same loading / unloading condition, (ii) multi-cyclic loading / unloading $K_o-test$ exceeding the maximum pre-vertical stress, and (iii) multi-cyclic loading / unloading $K_o-test$ within the maximum pre-vertical stress. Results fromthe multi-cyclic model indicated that a single-cyclic model could be extended if the exponents for the unloading condition $(\alpha\;and\;\alpha^*)$ and the reloading coefficients $(m_r,\;and\;m_r^{\ast})$ were primarily dependent upon the type of model, number of cycles, and the relative density.

• Steel and Composite Structures
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• 제21권3호
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• pp.517-536
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• 2016

Thick steel plate is commonly found with mega steel structures but its properties have not been fully explored. Grade Q345GJ-C steel plate with thickness ranging from 60 mm to 120 mm are studied in this paper. Both the static and cyclic performance of material in different directions (horizontal and through-thickness directions) and locations (outer surface, 1/4 thickness and mid-depth) are experimentally obtained. The accumulative damage during cyclic loading is also calculated by using bilinear mixed hardening (BMH) constitutive relationship together with the Lemaitre's damage model. Results show that the static properties are better at the outer surface of thick steel plates than those at mid-depth. Properties in through-thickness direction are similar to those at mid-depth in the horizontal direction. The cyclic performance at different locations of a given plate is similar within the range of strain amplitude studied. However, when damage parameters identified from monotonic tensile tests are included in the numerical simulation of cyclic loading tests, damage is found accumulating faster at mid-depth than close to outer surface.

• 한국지반공학회지:지반
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• 제11권1호
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• pp.23-40
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• 1995

다주기 Ko-재하/제하 시에 수평응력의 변화특성을 관찰하기 위하여 7종류의 시험모형을 선 정하였고, Ko조건을 크게 만족할 수 있도록 특별히 고안한압밀링 형태의 Ko-시험기를 제작하여 실내 건조된 모래에 대하여 실험을 수행하였다. 시험모형은 동일한 재하/제하 응력의 반복, 최대선행응력을 초과하는 반복 재하/제하, 그리고 최대선행 연직응력 내의 반복 재하/제하 Ko시험으로 구분된다. 실험결과에서 다주기 이력모형도 역시 기존의 단주기 이력모형을 확대하여 사용할 수 있음을 보였다. 여기서, 제하시의 지수 (a 및 a*)와 재재하 시의 계수(mr 및 mr*)는 응력이력의 형태, 반복회수 및 상대밀도에 따라 주로 지배되었다.

• Earthquakes and Structures
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• 제9권3호
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• pp.541-562
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• 2015

This paper aims at developing the knowledge on the seismic behavior of dowel beam-to-column connections, typically employed in precast buildings in Europe. Despite the large diffusion of the industrial buildings, a high seismic vulnerability was exhibited by these structures, mostly due to the connection systems deficiencies, during some recent earthquakes (Emilia 2012, Turkey 2011). An experimental campaign was conducted on a typical dowel connection between an external column and a roof beam. In this paper, the performed cyclic shear test is described. According to the experimental results, the seismic response of the system is evaluated in terms of strength, stiffness and failure mechanism. Moreover, the complete damage pattern of the test is described by means of the instrumentations records. The connection failure occurred due to the concrete cover failure in the column (splitting failure). Such a mechanism corresponds to a negligible energy dissipation capacity of the connection, compared to the overall seismic response of the structure. The experimental results are also compared with the results of a similar monotonic shear test, as well as with some literature relationships for predicting the strength of dowel connections under horizontal (seismic) loads.