• International Journal of Ocean System Engineering
• /
• 제2권2호
• /
• pp.63-70
• /
• 2012

This paper presents a new curvature based kinematic displacement theory and a numerical method to calculate the planar displacement of structures from a geometrical viewpoint. The theory provides an opportunity to satisfy the kinematic equilibrium of a planar structure using a progressive numerical approach, in which the cross sections are assumed to remain plane, and the deflection curve was evaluated geometrically using the curvature values despite being solved using differential equations. The deflection curve is parameterized with the arc-length, and was taken as an assembly of the chains of circular arcs. Fast and accurate solutions of most complex deflections can be obtained with few inputs.

• 대한기계학회논문집A
• /
• 제37권1호
• /
• pp.83-88
• /
• 2013

연쇄붕괴는 충격이나 폭발 등의 비정상 하중에 의하여 구조물의 하중 전달요소가 제거됨으로써 구조물의 일부 또는 전체가 연쇄적으로 붕괴되는 형상을 말한다. 예상외의 하중이 기둥부재에 작용할 경우, 좌굴이 발생하며 내력저하가 급격히 진행되어 붕괴에까지 이르게 된다. 하지만 좌굴 후 에너지를 흡수할 수 있는 잔존내력이 충분하면 붕괴를 막을 수 있다. 따라서, 구조물이 최종 붕괴상태에 도달되는 전 과정에 대한 기둥부재의 하중-변형관계를 명확히 파악할 필요가 있다. 본 논문에서는 비선형유한요소해석을 실시하여 H 형 강재기둥의 단부 구속조건이 고정일 경우 잔존내력의 변화추이를 파악하였다. 또한, 처짐이론을 기반으로 이론식을 도출하여 해석값과의 적합성을 검토하였다.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.65-80
• /
• 2023

To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

• 천문학회지
• /
• 제37권5호
• /
• pp.447-454
• /
• 2004

During the hierarchical formation of large scale structure in the universe, the progressive collapse and merging of dark matter should inevitably drive shocks into the gas, with nonthermal particle acceleration as a natural consequence. Two topics in this regard are discussed, emphasizing what important things nonthermal phenomena may tell us about the structure formation (SF) process itself. 1. Inverse Compton gamma-rays from large scale SF shocks and non-gravitational effects, and the implications for probing the warm-hot intergalactic medium. We utilize a semi-analytic approach based on Monte Carlo merger trees that treats both merger and accretion shocks self-consistently. 2. Production of $^6Li$ by cosmic rays from SF shocks in the early Galaxy, and the implications for probing Galaxy formation and uncertain physics on sub-Galactic scales. Our new observations of metal-poor halo stars with the Subaru High Dispersion Spectrograph are highlighted.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2006년도 추계 학술발표회
• /
• pp.229-240
• /
• 2006

Most of rock slopes contain a lot of discontinuities which have a specific direction and various characteristics. In general, the collapses of the rock slopes occur when the sliding dip of the discontinuity is higher than the internal friction angle and also smaller than the free-air plane of the slope. If a general slope theory is only considered in the case of field exploration of the slopes, there is a possibility that dangerous slopes might be estimated as stable slopes. We mention problems that can easily fail to notice something in field exploration and propose the alternatives to solve the problems through the case studies.

• Structural Engineering and Mechanics
• /
• 제83권5호
• /
• pp.577-591
• /
• 2022

This paper develops a comparatively time-efficient methodology for performing seismic fragility analysis of the reinforced concrete (RC) buildings in the presence of uncertainty sources. It aims to appraise the effectiveness of any variation in the material's mechanical properties as epistemic uncertainty, and the record-to-record variation as aleatory uncertainty in structural response. In this respect, the fuzzy set theory, a well-known 𝛼-cut approach, and the Genetic Algorithm (GA) assess the median of collapse fragility curves as a fuzzy response. GA is requisite for searching the maxima and minima of the objective function (median fragility herein) in each membership degree, 𝛼. As this is a complicated and time-consuming process, the authors propose utilizing the Gene Expression Programming-based (GEP-based) equation for reducing the computational analysis time of the case study building significantly. The results indicate that the proposed structural analysis algorithm on the derived GEP model is able to compute the fuzzy median fragility about 33.3% faster, with errors less than 1%.

• 한국언론정보학보
• /
• 제33권
• /
• pp.7-52
• /
• 2006

본 연구의 목적은 역사적으로 한국언론에 나타난 교육위기담론의 의미구성방식과 주체 구성방식을 분석함으로써 한국사회의 진보-보수 언론이 갖는 대립적 입장과 이데올로기적 특성들을 드러내는 데 있다. 이를 위해 미셀 페쇠의 담론이론에서 제시된 언어체계의 선택과 조합방식들-선구성과 절합 메커니즘-, 그리고 이데올로기의 주체구성 방식을 이론적으로 검토한 후, 실제 사례분석에 들어가고자 한다. 사례분석의 대상은 조선일보와 한겨레신문이고, 두 신문의 진보와 보수라는 상징적 적대성을 근거로 선정했다. 이와 함께 "교실붕괴"나 "학교붕괴" 등의 교육위기 담론을 현장진술, 원인과 책임규명 그리고 사후대책의 범주 속에서 분석하고자 한다.

• Steel and Composite Structures
• /
• 제42권4호
• /
• pp.501-511
• /
• 2022

Earthquake Resistant Design Philosophy seeks (a) no damage, (b) no significant structural damage, and (c) significant structural damage but no collapse of normal buildings, under minor, moderate and severe levels of earthquake shaking, respectively. A procedure is proposed for seismic design of low-rise reinforced concrete special moment frame buildings, which is consistent with this philosophy; buildings are designed to be ductile through appropriate sizing and reinforcement detailing, such that they resist severe level of earthquake shaking without collapse. Nonlinear analyses of study buildings are used to determine quantitatively (a) ranges of design parameters required to assure the required deformability in normal buildings to resist the severe level of earthquake shaking, (b) four specific limit states that represent the start of different structural damage states, and (c) levels of minor and moderate earthquake shakings stated in the philosophy along with an extreme level of earthquake shaking associated with the structural damage state of no collapse. The four limits of structural damage states and the three levels of earthquake shaking identified are shown to be consistent with the performance-based design guidelines available in literature. Finally, nonlinear analyses results are used to confirm the efficacy of the proposed procedure.

• 한국공간구조학회논문집
• /
• 제2권4호
• /
• pp.61-76
• /
• 2002

The structure system that is discreterized by continuous shells is usually used to make a large space structures and these structures show the collapse mechanisms that are captured at over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. Moreover, resist force of structure can be reduced by initial condition and initial imperfection significantly. In order to investigate the instability of shell structures, the finite deformation theory can be applied and it becomes a nonlinear mathematics in which use equation of tangential stiffness incrementally. With an initial imperfection, using simple example and Flow Truss Dome, the buckling characteristics of space truss is main purpose of this paper, and unstable behavior is studied by proposed the numerical method. Also, by using MIDAS, this research work analyzes displacements and inner forces as the design load of model, and the ratio of buckling load of design load is investigated.

• Steel and Composite Structures
• /
• 제28권4호
• /
• pp.427-438
• /
• 2018

Static stability is a decisive factor in the design of domes. Stability-related external factors, such as load and supports, are incorporated into structural vulnerability theory by the definition of a relative rate of joint well-formedness ($r_r$). Hence, the instability mechanism of domes can be revealed. To improve stability, an optimization model against instability, which takes the maximization of the lowest $r_r$ ($r_{r,min}$) as the objective and the discrete member sections as the variables, is established with constraints on the design requirements and steel consumption. Optimizations are performed on two real-life Kiewitt-6 model domes with a span of 23.4 m and rise of 11.7 m, which are initially constructed for shaking table collapse test. Well-formedness analyses and stability calculation (via arc-length method) of the models throughout the optimization history demonstrate that this proposed method can effectively enhance $r_{r,min}$ and optimize the static stability of shell-like structures. Additionally, seismic performance of the optimum models subjected to the same earthquake as in the shaking table test is checked. The supplemental simulations prove that the optimum models are superior to the original models under earthquake load as well.