• Earthquakes and Structures
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• 제11권4호
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• pp.723-740
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• 2016

Reinforced concrete corbels are generally used to transfer loads within a structural system, such as buildings, bridges, and facilities in general. They commonly present low aspect ratio, requiring an accurate model for shear strength prediction in order to promote flexural behavior. The model described here, originally developed for walls, was adapted for corbels. The model is based on a reinforced concrete panel, described by constitutive laws for concrete and steel and applied in a fixed direction. Equilibrium in the orthogonal direction to the shearing force allows for the estimation of the shear stress versus strain response. The original model yielded conservative results with important scatter, thus various modifications were implemented in order to improve strength predictions: 1) recalibration of the strut (crack) direction, capturing the absence of transverse reinforcement and axial load in most corbels, 2) inclusion of main (boundary) reinforcement in the equilibrium equation, capturing its participation in the mechanism, and 3) decrease in aspect ratio by considering the width of the loading plate in the formulation. To analyze the behavior of the theoretical model, a database of 109 specimens available in the literature was collected. The model yielded an average model-to-test shear strength ratio of 0.98 and a coefficient of variation of 0.16, showing also that most test variables are well captured with the model, and providing better results than the original model. The model strength prediction is compared with other models in the literature, resulting in one of the most accurate estimates.

• 한국강구조학회 논문집
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• 제9권1호통권30호
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• pp.139-147
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• 1997

본 논문은 단조하중(monotonic loading)하의 강재 보-기둥의 절점의 패널 영역 거동을 연구한 논문(Kim 1997)의 후속 논문으로 주기하중에 대한 패널영역의 거동을 해석하기 위한 이력법칙(hysteretic rules)에 관한 것이다. 제안된 이력법칙은 실험결과와 합당한 상관관계를 보여주었고, 이 이력법칙을 사용한 패널영역요소의 해석 결과가 실험결과와 잘 일치하는 것으로 나타났다. 한편 보강판(a doubler plate)을 갖는 패널영역에 대한 해석과 실험결과로 부터 보강판이 패널영역전달력 (panel zone shear force)을 저항하는데 있어 부분적인 효과만 있다는 것을 알 수 있었다. 제안된 패널영역요소는 구조물의 전체 거동과 국부 변형을 기존의 패널영역요소(bilinear panel zone element)보다 정확하게 예측 할 수 있었다.

• 대한토목학회논문집
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• 제28권3A호
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• pp.367-373
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• 2008

국내/외에서 설계되는 강곡선거더교 복부판의 전단강도는 복부판의 4변을 단순지지라는 가정 하에서 산정되는 탄성전단좌굴강도로 제안하고 있다(AASHTO Guide Specifications, 2003). 그러나, Lee et al.(1996, 1999)과 Bradford(1996)의 최근 연구에서 실제의 설계범위를 갖는 직선이나 곡선 복부판에서 어느 정도의 강성을 갖는 플랜지에 의해서 접하는 변의 경계조건은 단순지지 보다는 고정지지에 더 근접하며, 복부판의 형상비에 따라서는 AASHTO의 탄성좌굴강도가 60%이상 낮게 평가되고 있음을 발표하였다. 특히 강곡선복부판의 전단좌굴강도는 곡률의 영향으로 AASHTO Guide Specifications(2003)의 탄성전단좌굴강도보다 최대 38%이상 증가하고 있음이 Lee and Yoo(1999)의 연구에서 조사되었다. 본 논문에서는 선형좌굴해석을 이용하여 곡률과 경계조건이 동시에 고려된 강곡선 복부판의 전단좌굴계수를 합리적으로 추정할 수 있는 산정식을 제안하고자 한다.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.105-117
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were experimentally performed on one unreinforced beam-column specimen and two reinforced specimens with L-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of L-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D except for the equation to predict the concrete breakout failure strength at the concrete side, principally agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.

• 대한토목학회논문집
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• 제26권4A호
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• pp.727-734
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• 2006

강곡선복부판의 전단설계에서 Guide Specifications(AASHTO, 2003)에서는 여전히 후좌굴강도를 반영하고 있지 않다. 그러나 최근 강곡선 복부판의 전단거동에 관한 해석 및 실험연구를 통해서 탄성좌굴 후에 직선교 복부판과 같이 후좌굴강도를 발현하고 있으며, 일반적인 설계범위에서 직선교 복부판과 유사한 크기의 극한전단강도를 나타내고 있는 것으로 조사되었다. 본 연구에서는 강곡선복부판의 극한전단강도를 조사하기 위하여 유한요소해석과 실험연구를 수행하였다. 연구결과를 통해서 일반적으로 설계가 수행되는 기하학적인 범위 내에서 강곡선복부판은 후좌굴강도를 발현하며, 그 크기는 동일한 재료를 적용한 직선복부판과 유사하다는 것을 알 수 있었다. 그러므로 강도한계상태에서 강곡선복부판도 Lee and Yoo(1998)가 제안한 직선복부판의 극한전단강도를 이용하여 설계할 수 있음을 본 연구를 통해서 제안하였다.

• 한국전산구조공학회논문집
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• 제25권1호
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• pp.19-26
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• 2012

본 논문에서는 강판벽이 설치된 골조 구조물의 연쇄붕괴 거동을 비선형 정적 pushdown 해석을 이용하여 평가하였다. 해석모델은 중력하중에 대해서 설계된 2층 2경간 철골구조물이며, 중앙 기둥을 제거하고 하중을 서서히 증가시키며 하중-변위 관계를 구하였다. 구조물의 전체적인 거동뿐만 아니라 부분적인 응력과 변형을 파악하기 위하여 ABAQUS를 이용한 유한요소해석을 수행하였다. 해석을 통해서 구조물의 경간 길이 및 설치된 강판의 두께의 변화에 따른 연쇄붕괴 거동을 평가하였으며, 샛기둥을 이용하여 강판을 분할하고 분할된 강판의 위치에 따른 연쇄붕괴 성능의 변화를 관찰하였다. 해석결과에 따르면 경간의 길이가 증가할수록 연쇄붕괴를 방지하기 위하여 요구되는 강판의 두께 또한 증가하며, 분할된 강판의 수가 증가할수록 연쇄붕괴에 대한 저항성능이 약간 증가하지만 그 영향은 그리 크지 않은 것으로 나타났다. 또한 개구부로 인하여 일부 경간에만 강판이 설치된 경우에도 연쇄붕괴 저항성능이 어느 정도 증가하는 것으로 나타났다.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Steel and Composite Structures
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• 제24권2호
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• pp.151-176
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• 2017

This paper deals with general equations of motion for free vibration analysis response of thick three-layer doubly curved sandwich panels (DCSP) under simply supported boundary conditions (BCs) using higher order shear deformation theory. In this model, the face sheets are orthotropic laminated composite that follow the first order shear deformation theory (FSDT) based on Rissners-Mindlin (RM) kinematics field. The core is made of orthotropic material and its in-plane transverse displacements are modeled using the third order of the Taylor's series extension. It provides the potentiality for considering both compressible and incompressible cores. To find these equations and boundary conditions, Hamilton's principle is used. Also, the effect of trapezoidal shape factor for cross-section of curved panel element ($1{\pm}z/R$) is considered. The natural frequency parameters of DCSP are obtained using Galerkin Method. Convergence studies are performed with the appropriate formulas in general form for three-layer sandwich plate, cylindrical and spherical shells (both deep and shallow). The influences of core stiffness, ratio of core to face sheets thickness and radii of curvatures are investigated. Finally, for the first time, an optimum range for the core to face sheet stiffness ratio by considering the existence of in-plane stress which significantly affects the natural frequencies of DCSP are presented.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.485-488
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• 2008

The structure supporting road sign is a road information facility for ensuring the safe transportation and smooth traffic. But, lots of road information facilities were damaged by the typhoon "Maemi" in 2003. Such damaged facilities should be rehabilitated and could increase economic loss by causing traffic accident. Therefore, in this study, behavior that reduce wind load and improve wind resistance of the structure supporting road sign are studied about wind load beyond design specification by abnormal climate as below. The first is wind load reducing technique such that shear key resist wind load that is not greater than design wind speed but in case that it is over the design wind limit, column member is rotated on the inner steel pipe axis by the brittle failure of shear key. The second is the technique such that fail-safe the overturning of road sign panel by equipment installation in the vertical member. The third is the technique of installing stiffening plate inside the vertical member to relieve stress concentration.

• Steel and Composite Structures
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• 제51권1호
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• pp.53-61
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• 2024

Aluminum foams sandwich panel (AFSP) has been used in engineering field, where cyclic loading is used in most of the applications. In this paper, the fatigue life of AFSP prepared by the bonding method was investigated through a three-point bending test. The mathematical statistics method was used to analyze the influence of different plate thicknesses and core densities on the bending fatigue life. The macroscopic fatigue failure modes and damage mechanisms were observed by scanning electron microscopy (SEM). The results indicate that panel thickness and core layer density have a significant influence on the bending fatigue life of AFSP and their dispersion. The damage mechanism of fatigue failure to cells in aluminum foam is that the initial fatigue crack begins the cell wall, the thinnest position of the cell wall or the intersection of the cell wall and the cell ridge, where stress concentrations are more likely to occur. The fatigue failure of aluminum foam core usually starts from the semi-closed unit of the lower layer, and the fatigue crack propagates layer by layer along the direction of the maximum shear stress. The results can provide a reference for the practical engineering design and application of AFSP.