• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.1-18
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• 2020

For the large deformation of shear walls under vertical and horizontal loads, there are difficulties in obtaining accurate simulation results using the response analysis method, even with fine mesh elements. Furthermore, concrete material nonlinearity, stiffness degradation, concrete cracking and crushing, and steel bar damage may occur during the large deformation of reinforced concrete (RC) shear walls. Matrix operations that are involved in nonlinear analysis using the traditional finite-element method (FEM) may also result in flaws, and may thus lead to serious errors. To solve these problems, a planar four-node element was developed based on vector mechanics. Owing to particle-based formulation along the path element, the method does not require repeated constructions of a global stiffness matrix for the nonlinear behavior of the structure. The nonlinear concrete constitutive model and bilinear steel material model are integrated with the developed element, to ensure that large deformation and damage behavior can be addressed. For verification, simulation analyses were performed to obtain experimental results on an RC shear wall subjected to a monotonically increasing lateral load with a constant vertical load. To appropriately evaluate the parameters, investigations were conducted on the loading speed, meshing dimension, and the damping factor, because vector mechanics is based on the equation of motion. The static problem was then verified to obtain a stable solution by employing a balanced equation of motion. Using the parameters obtained, the simulated pushover response, including the bearing capacity, deformation ability, curvature development, and energy dissipation, were found to be in accordance with the experimental observation. This study demonstrated the potential of the developed planar element for simulating the entire process of large deformation and damage behavior in RC shear walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.30-36
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• 2018

Researches on strengthening and rehabilitation are important since structural capacity is degraded by deterioration or damage of structural members. An effective strengthening scheme such as an externally bonded Carbon Fiber Reinforced Polymers (CFRP) can improve the structural performance of a concrete structure in a cost-effective way. Therefore, many experimental studies on strengthening methods have been widely carried out. In regards to the shear strengthening of a concrete beam, variables of the experimental studies were the amount of CFRP, the angle of the strip, the width of the strip, and the interaction between the materials. However, there are insufficient researches on bi-directional CFRP layout compared to the previous researches. In this study, a total of ten concrete beams were designed and tested to evaluate the shear strengthening effect using CFRP strips. The effectiveness of strengthening was investigated based on the shear contribution of materials, strain distribution of stirrup, and the maximum shear capacity of specimens.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.6
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• pp.3-10
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• 2018

This paper described the shear strengthening effect by deviator location in pre-damaged reinforced concrete (RC) beams strengthened with externally post-tensioning steel rods. Three reinforced concrete beams as control beam and eight post-tensioned beams using external steel rods were tested to fail in shear. The externally post-tensioning material was a steel rod of 22 mm diameter, and it had a 655 MPa yield strength and an 805 MPa tensile strength. Specimens depend on multiple variables, such as the number of deviators, location of deviator, and load pattern. The pre-damaged loads up to about 2/3 of ultimate shear capacities were applied to specimens using displacement control and the diagonal shear crack just occurred at these loading levels. And then, the post-tensioning up to when a strain of steel rod reaches about $2000{\mu}{\varepsilon}$ was continuously applied to beam. A displacement control was changed to a load control during post-tensioning. The post-tensioning resulted in increase of load-carrying capacity and restoration of existing deflection. Also, it prevented the existing diagonal cracks from excessively growing. Two deviators effectively improved the load capacity when compared with in case of test which one deviator at mid-span installed. When deviators were located near region which the diagonal crack occurred on, the strengthening impact by post-tensioning was greater.

• Composites Research
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• v.21 no.2
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• pp.1-7
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• 2008

Composite materials are currently used in aero-space industry, sport and leisure industry but it has many problems such as mechanical properties deterioration by moisture absorption. In this study, we appraised interlaminar shear strength with specimen that immersed/ immersed-dried in water environment(distilled/sea) during $100{\sim}200$days. In the result, properties degradation of resin part and silan part by moisture absorption is judged early on main cause of interlaminar shear strength, and later destruction of mechanical bonding between silan part and fiber by moisture absorption is Judged later main cause of interlaminar shear strength. In conclusion, the recovery of interlaminar shear strength is judged to difficult due to interfacial destruction by moisture when pass over irreversible by moisture in composite material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.327-338
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• 2006

Friction type high tension bolted joints is one of the most common steel structure connections and requires significant concerns on axial force of the bolts. However, its high shear capacity is not appropriately considered in design and hence the number of bolts is over-designed than actually required. It is primarily due to a slip-load-based design method. This study, therefore, suggests a new technology of connection using a shear ring, which may reduce the shortcomings from the friction-typed high tension bolted joints and maximize the advantages from the bearing-typed joints. Experimental and numerical studies were performed to compare the capacity of the suggested method with traditional high tension bolted joints. From the results, it is known that the suggested connections has higher bearing capacity than friction-typed high tension bolted joints due to the higher shear resistance from the ring. For further study, it may be necessary to investigate on design parameters including the depth of shear ring, for increased connection capacity.

• Steel and Composite Structures
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• v.52 no.4
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• pp.419-434
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• 2024

A flat slab is a structural system where columns directly support it without the presence of beam elements. However, despite its wide advantages, this structural system undergoes a major deficiency where stresses are concentrated around the column perimeter, resulting in the progressive collapse of the entire structure as a result of losing the shear transfer mechanisms at the cracked interface. Predicting the punching shear capacity of RC flat slabs is a challenging problem where the factors contributing to the overall slab strength vary broadly in their significance and effect extent. This study proposed a new expression for predicting the slab's capacity in punching shear using a nonuniform concrete tensile stress distribution assumption to capture, as well as possible, the induced strain effect within a thick RC flat slab. Therefore, the overall punching shear capacity is composed of three parts: concrete, aggregate interlock, and dowel action contributions. The factor of the shear span-to-depth ratio (a_v/d) was introduced in the concrete contribution in addition to the aggregate interlock part using the maximum aggregate size. Other significant factors were considered, including the concrete type, concrete grade, size factor, and the flexural reinforcement dowel action. The efficiency of the proposed model was examined using 86 points of published experimental data from 19 studies and compared with five code standards (ACI318, EC2, MC2010, CSA A23.3, and JSCE). The obtained results revealed the efficiency and accuracy of the model prediction, where a covariance value of 4.95% was found, compared to (13.67, 14.05, 15.83, 19.67, and 20.45) % for the (ACI318, CSA A23.3, MC2010, EC2, and JSCE), respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.22-32
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• 2015

This study intended to analyze an influence of the structure elements on the optimal location for one-outrigger system in tall building by using MIDAS-Gen. In this investigation, the analysis parameters were the outrigger position and the stiffness of main structure elements such as shear walls, outrigger systems, exterior columns connected in outrigger system and frames not to be connected in outrigger system. For the objective of finding out the optimal location for one-outrigger system in high-rise building, we studied the lateral displacement in top level of 80 stories building. The results of this study indicated that the outrigger location and the stiffness of main structure elements such as shear walls, outrigger systems, exterior columns connected in outrigger system and frames not to be connected in outrigger system had an influence on the optimal location of one-outrigger system. In addition, it is showed that the research results can be very useful in obtaining the structure design data for looking for the optimal location of one-outrigger system in high-rise building.

• Earthquakes and Structures
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• v.12 no.2
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• pp.165-175
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• 2017

This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it's observed that as the soil and foundation become stiffer, the soil uncertainty is found to be less important in influencing the response variability. On the other hand, the soil uncertainty becomes more important as the foundation-structure system is expected to experience nonlinear behavior to more sever degree. Since full probabilistic analysis methods like MC commonly are very time consuming, the feasibility of simple approximate methods' application including First Order Second Moment (FOSM) method and ASCE41 proposed approach for the soil uncertainty considerations is investigated. By comparing the results of the approximate methods with the results obtained from MC, it's observed that the results of both FOSM and ASCE41 methods are in good agreement with the results of MC simulation technique and they show acceptable accuracy in predicting the response variability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.121-127
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• 2012

This paper investigates the response of frame structures with the consideration of tunnel construction (ground loss) conditions. The response of four-story open frame structure and block-infilled frame structures, which are subjected to tunnelling-induced ground movements, has been investigated in different construction (ground loss) conditions using numerical analysis. The open frame structure has been modelled as an elastic structure, while the block-infilled frame structure has been modelled to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of the two different frame structures has been investigated in terms of construction (ground loss) conditions considering the magnitude of deformations and cracks in structures. In addition, the damage levels, which are possibly induced in the structures, has been provided in terms of construction (ground loss) conditions using the state of strain damage estimation criterion (Son and Cording, 2005). The results of this study will provide a background for better understandings for controlling and minimizing building damage on nearby frame structures due to tunnelling-induced ground movements.

• The Journal of the Petrological Society of Korea
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• v.6 no.3
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• pp.244-244
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• 1997

The Janggunbong area(this study area) at the central-south part in the North Sobaegsan Massif, Korea, consists mainly of Precambrian(Wonnam and Yulri Formations)-Paleozoic [Joseon Supergroup(Jangsan Quarzite, Dueumri Formation and Janggum Limestone) and Pyeongan Group(Jaesan and Dongsugok Formations)] metasedimentary rocks and Mesozoic granitoid(Chunyang granite.) This study is to interpret geological structure of the North Sobaegsan Massif in the Jang-gunbong area by analysing rock-structure and microstructure of the constituent rocks. It indicates that its geological structure was formed at least by four phases of deformation after the formation of gneissosity(S0) in the Wonnam Formation and bedding plane(S0) in the Paleozoic metasedimentary rocks. The first phase deformation(D1) formed tight isoclinal fold(F1). Its axial plane(S1) strikes east-west and steeply dips north. Its axis (L1) subhorizontally plunges east-west. The second phase deformation(D2), which was related to ductile shear deformation, formed stretching lineation(L2) and shear foliation(S2). The sense of the shear movement indicates dextral strike-slip shearing(top-to-the east shearing). The third phase deformation(D3) formed open inclined fold(F3). Its axial plane(S3) strikes east-west and moderately or gently dips north. Its axis(L3) subhorizontally plunges east-west. The F3 fold reoriented the original north-dipping S1 foliation and D2 shear sense into south-dipping S1 foliation(top-to-the west shear sense on this foliation) at its a limb. The four phase of deformation(D4) formed asymmetric-type open inclined fold(F4) of NE-vergence with NW striking axial plane(S4) and NW-NNW plunging axis(L4). The F4 fold partly reoriented pre-D4 structural elements with east-west trend into those with north-south trend. Such reorientation is recognized mainly in the Paleozoic metasedimentary rocks.