• Earthquakes and Structures
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• 제5권5호
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• pp.607-624
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• 2013

In this study the seismic risk assessments of six- and twelve-story staggered wall system structures with three different structural variations were performed. The performances of staggered wall structures with added columns along the central corridor and the structures with their first story walls replaced by beams and columns were compared with those of the regular staggered wall structures. To this end incremental dynamic analyses were carried out using twenty two pairs of earthquake records to obtain the failure probabilities for various intensity of seismic load. The seismic risk for each damage state was computed based on the fragility analysis results and the probability of occurrence of earthquake ground motions. According to the analysis results, it was observed that the structures with added columns along the central corridor showed lowest probability of failure and seismic risk. The structures with their first story walls replaced by beams and columns showed lowest margin for safety.

• International Journal of Concrete Structures and Materials
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• 제11권2호
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• pp.285-300
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• 2017

This study investigates the seismic performance of a staggered wall structure designed with conventional strength based design, and compares it with the performance of the structure designed by capacity design procedure which ensures strong column-weak beam concept. Then the seismic reinforcement schemes such as addition of interior columns or insertion of rotational friction dampers at the ends of connecting beams are validated by comparing their seismic performances with those of the standard model structure. Fragility analysis shows that the probability to reach the dynamic instability is highest in the strength designed structure and is lowest in the structure with friction dampers. It is also observed that, at least for the specific model structures considered in this study, R factor of 5.0 can be used in the seismic design of staggered wall structures with proposed retrofit schemes, while R factor of 3.0 may be reasonable for standard staggered wall structures.

• 한국전산구조공학회논문집
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• 제25권5호
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• pp.397-404
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• 2012

지진취약도 곡선은 구조물의 피해를 지반가속도에 따른 확률로 나타낸 것으로, 이를 이용하여 구조물의 지진에 대한 손상확률을 추정할 수 있다. 본 연구에서는 6층, 12층 중복도형 격간벽 구조 시스템에 대한 취약도 곡선을 산출하기 위해 22쌍의 지반가속도를 이용하여 증분동적해석(Incremental dynamic analysis)을 수행하고, 다양한 지진강도에 대한 파괴확률을 구하였다. 정형의 격간벽 구조의 해석결과와 1층의 격간벽을 기둥으로 대체한 구조물, 중앙 복도에 기둥이 추가된 구조물의 해석결과를 비교하였다. 취약도 해석결과에 따르면 동일한 수준의 지진하중에 대하여 중앙 복도에 기둥을 추가한 모델이 가장 높은 내진 안전성을 갖는 것으로 나타났다.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.355-371
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• 2016

In this study seismic performance of reinforced concrete staggered wall system structures were investigated and their behavior factors such as overstrength factors, ductility factors, and the response modification factors were evaluated from the overstrength and ductility factors. To this end, 5, 9, 15, and 25-story staggered wall system (SWS) structures were designed and were analyzed by nonlinear static and dynamic analyses to obtain their nonlinear force-displacement relationships. The response modification factors were computed based on the overstrength and the ductility capacities obtained from capacity envelopes. The analysis results showed that the 5- and 9-story SWS structures failed due to yielding of columns and walls located in the lower stories, whereas in the 15- and 25-story structures plastic hinges were more widely distributed throughout the stories. The computed response modification factors increased as the number of stories decreased, and the mean value turned out to be larger than the value specified in the design code.

• 한국지진공학회논문집
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• 제16권3호
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• pp.43-50
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• 2012

FEMA P695은 설계지진하중에 대한 구조물의 붕괴 안전성 및 내진성능계수의 적절성을 검토할 수 있는 방법론을 제시하고 있다. 본 연구에서는 FEMA P695에 제시된 방법에 따라 6층, 12층 중복도 격간벽 구조시스템의 내진성능을 파악하였다. 구조설계기준에 따라 설계된 기본 모델의 해석결과와 중복도 상부 인방보의 춤이나 철근량을 증가시킨 모델의 해석결과를 비교하여 보강 효과를 파악하였다. 두 예제 구조물의 증분 동적해석 결과를 바탕으로 계산된 수정 붕괴 여유비 (ACMR)는 제시된 $ACMR_{20%}$ 한계상태를 만족하여 설계지진하중에 대하여 충분한 내진성능을 보유하고 있는 것으로 나타났다. 인방보의 춤을 증가시킨 모델에 비해 주철근을 증가시킨 모델의 ACMR 증가량이 더 현저하여 보다 효율적인 내진성능 보강방안으로 나타났다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권1호
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• pp.37-50
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• 2016

A large eddy simulation (LES) of a turbulent channel flow is performed by using the third order low-storage Runge-Kutta method in time and second order finite difference formulation in space with staggered grid at a Reynolds number, $Re_{\tau}=590$ based on the channel half width, ${\delta}$ and wall shear velocity, $u_{\tau}$. To reduce the calculation cost of LES, algebraic wall model (AWM) is applied to approximate the near-wall region. The computation is performed in a domain of $2{\pi}{\delta}{\times}2{\delta}{\times}{\pi}{\delta}$ with $32{\times}20{\times}32$ grid points. Standard Smagorinsky model is used for subgrid-scale (SGS) modeling. Essential turbulence statistics of the flow field are computed and compared with Direct Numerical Simulation (DNS) data and LES data using no wall model. Agreements as well as discrepancies are discussed. The flow structures in the computed flow field have also been discussed and compared with LES data using no wall model.

• Steel and Composite Structures
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• 제31권1호
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• pp.1-12
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• 2019

Steel-concrete composite walls have been proposed and developed for applications in various types of structures. The double-skin profiled composite walls, as a natural development of composite flooring, provide structural and architectural merits. However, adequate intermediate fasteners between profiled steel plates and concrete core are required to fully mobilize the composite action and to improve the structural behavior of the wall. In this research, two new types of fasteners (i.e., threaded rods and vertical plates) were proposed and three specimens with different fastener types or fastener arrangements were tested under axial compression. The experimental results were evaluated in terms of failure modes, axial load versus axial displacement response, strength index, ductility index, and load-strain relationship. It was found that specimen with symmetrically arranged thread rods sustained more stable axial strain than that with staggered arranged threaded rods. Meanwhile, vertical plates are more suitable for practical use since they provide stronger confinement to profiled steel plate and effectively prevent the steel plate from early local buckling, which eventually enhance the composite action and increase the axial compressive capacity of the wall. The calculation methods were then proposed and good agreement was observed between the test results and the predicted results.

• Wind and Structures
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• 제29권1호
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• pp.65-75
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• 2019

A heated square cylinder (with height $A^*$) is kept parallel to the cold wall at a fixed gap height $0.5A^*$ from the wall. Another adiabatic rectangular cylinder (of same height $A^*$ and width $0.5A^*$) is placed upstream in an inline tandem arrangement. The spacing between the two cylinders is fixed at $3.0A^*$. The inlet flow is taken as Couette-Poiseuille flow based non-linear velocity profile. The conventional fluid (also known as base fluid) is chosen as water (W) whereas the nanoparticle material is selected as $Al_2O_3$. Numerical simulations are performed by using SIMPLE algorithm based Finite Volume approach with staggered grid arrangement. The dependencies of hydrodynamic and heat transfer characteristics of the cylinder on non-dimensional parameters governing the nanofluids and the fluid flow are explored here. A critical discussion is made on the mechanism of improvement/reduction (due to the presence of the upstream cylinder) of heat transfer and drag coefficient, in comparison to those of an isolated cylinder. It is observed that the heat transfer increases with the increase in the non-linearity in the incident velocity profile at the inlet. For the present range studied, particle concentration has a negligible effect on heat transfer.

• Steel and Composite Structures
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• 제42권1호
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• pp.107-121
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• 2022

Past studies have shown that the aspect ratio (width-to-height) of a steel plate shear wall (SPSW) can significantly affect its seismic response. SPSWs with lower aspect ratio (narrow SPSW) may experience low lateral stiffness and flexure dominated drift response. As the height of the frame increases, the narrow SPSWs prove to be uneconomical and demonstrate inferior seismic response than their wider counterparts. Moreover, the thicker web plates required for narrow SPSWs exerts high inward pull on the VBEs. The present study suggests the limiting values of the aspect ratio for an SPSW system by evaluating the seismic collapse performance of 3-, 6- and 9-story SPSW systems using FEMA P695 methodology. For this purpose, nonlinear models are developed. These models are validated with the past quasi-static experimental results. Non-linear static analyses and Incremental dynamic analyses are then carried. The results are then utilized to conservatively suggest the limiting values of aspect ratios for SPSW system. In addition to the conventional-SPSW (Conv-SPSW), the collapse performance of staggered-SPSW (S-SPSW) is also explored. Its performance is compared with the Conv-SPSW and the use of S-SPSW is suggested in the cases where SPSW with lower than recommended aspect ratio is desired.

• Wind and Structures
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• 제26권5호
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• pp.331-341
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• 2018

A numerical study on the flow over a square cylinder in the vicinity of a wall is conducted for different Couette-Poiseuille-based non-uniform flow with the non-dimensional pressure gradient P varying from 0 to 5. The non-dimensional gap ratio L (=$H^{\ast}/a^{\ast}$) is changed from 0.1 to 2, where $H^{\ast}$ is gap height between the cylinder and wall, and $a^{\ast}$ is the cylinder width. The governing equations are solved numerically through finite volume method based on SIMPLE algorithm on a staggered grid system. Both P and L have a substantial influence on the flow structure, time-mean drag coefficient ${\bar{C}}_D$, fluctuating (rms) lift coefficient ($C_L{^{\prime}}$), and Strouhal number St. The changes in P and L leads to four distinct flow regimes (I, II, III and IV). Following the flow structure change, the ${\bar{C}}_D$, $C_L{^{\prime}}$, and St all vary greatly with the change in L and/or P. The ${\bar{C}}_D$ and $C_L{^{\prime}}$ both grow with increasing P and/or L. The St increases with P for a given L, being less sensitive to L for a smaller P (< 2) and more sensitive to L for a larger P (> 2). A strong relationship is observed between the flow regimes and the values of ${\bar{C}}_D$, $C_L{^{\prime}}$ and St. An increase in P affects the pressure distribution more on the top surface than on bottom surface while an increase in L does the opposite.