• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2003년도 학술발표논문집
• /
• pp.451-454
• /
• 2003

This study was mainly conducted to derive the design drought rainfall by the consecutive duration using probability weighted moments with rainfall in the regional drought frequency analysis. Selecting the drought rainfall series by the consecutive durations of drought observed for the long period all over the regions in Korea, optimal regionalization of the drought rainfall was classified by the climatologically and geographically homogeneous regions. Using the L-moment ratio and Kolmogorov- Smimov test, resonable frequency distribution for the drought rainfall was selected by the regions and consecutive periods of drought. Design drought rainfalls by the regions and consecutive durations were derived and compared by at-site and regional drought frequency analysis using the method of L-moments.

• 한국군사과학기술학회지
• /
• 제22권3호
• /
• pp.353-359
• /
• 2019

In this study, a aerodynamic loads prediction to design a deploying device of folded fin was introduced. In general, resultant flow conditions around the fin are used to obtain deploying moments and required energy. However, when it comes to the air vehicles launched from a mobile platform, more specific flow conditions can be provided. With the conditions, the design criteria can be calculated more realistically. In this study, therefore, aerodynamic moments induced by aerodynamic loads and energy required in deployment were calculated using wind-over-deck(WOD) velocity, combination of a platform velocity and a wind velocity. For the calculation, wind tunnel test was conducted on various angle of attack, side slip angles, and folding angles. It was found that the aerodynamic moments and the energy required in deployment using the non-uniform flow due to the velocity components were less than those using the uniform flow without the components.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2002년도 학술발표회 발표논문집
• /
• pp.229-232
• /
• 2002

This study was conducted to estimate the design flood by the determination of best fitting order of LH-moments of the annual maximum series at six and nine watersheds in Korea and Australia, respectively. Adequacy for flood flow data was confirmed by the tests of independence, homogeneity, and outliers. Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Pareto (GPA), and Generalized Logistic (GLO) distributions were applied to get the best fitting frequency distribution for flood flow data. Theoretical bases of L, L1, L2, L3 and L4-moments were derived to estimate the parameters of 4 distributions. L, L1, L2, L3 and L4-moment ratio diagrams (LH-moments ratio diagram) were developed in this study.

• Steel and Composite Structures
• /
• 제19권4호
• /
• pp.897-916
• /
• 2015

A procedure for critical buckling moment of a tapered beam is proposed with the application of potential energy calculations using Ritz method. Respective solution allows to obtain critical moments initiating lateral buckling of the simply supported, modestly tapered steel I-beams. In particular, lateral-torsional buckling of beams with simultaneously tapered flanges and the web are considered. Detailed, numerical, parametric analyses are carried out. Typical engineering, uniformly distributed design loads are considered for three cases of the load, applied to the top flange, shear centre, as well as to the bottom flange. In addition simply supported beam under gradient moments is investigated. The parametric analysis of simultaneously tapered beam flanges and the web, demonstrates that tapering of flanges influences much more the critical moments than tapering of the web.

• Wind and Structures
• /
• 제1권3호
• /
• pp.255-269
• /
• 1998

Second-order moments of considerable magnitude arise in tall and slender RC chimneys and towers subject to along-wind loading, on account of eccentricities in the distributed self-weight of the tower in the deflected profile. An accurate solution to this problem of geometric nonlinearity is rendered difficult by the uncertainties in estimating the flexural rigidity of the tower, due to variable cracking of concrete and the 'tension stiffening' effect. This paper presents a rigorous procedure for estimating deflections and second-order moments in wind-loaded RC tubular towers. The procedure is essentially based on a generalised formulation of moment-curvature relationships for RC tubular towers, derived from the experimental and theoretical studies reported by Schlaich et al. 1979 and Menon 1994 respectively. The paper also demonstrates the application of the proposed procedure, and highlights those conditions wherein second-order moments become too significant to be overlooked in design.

• Advances in Computational Design
• /
• 제4권3호
• /
• pp.273-294
• /
• 2019

In this paper is presented the minimum cost (optimal design) for reinforced concrete circular isolated footings based on an analytic model. This model considers a load and two moments in directions of the X and Y axes, and the pressure has a variation linear, these are the effects that act on the footing. The minimum cost (optimal design) and the Maple program are shown in Flowcharts. Two numerical experiments are shown to obtain the minimum cost design of the two materials that are used for a circular footing supporting an axial load and moments in two directions in accordance to the code of the ACI (American Concrete Institute), and it is compared against the current design (uniform pressure). Also, the same examples are developed through the normal procedure to verify the minimum cost (optimal design) presented in this document, i.e., the equations of moment, bending shear and punching shear are used to check the thickness, and after, the steel areas of the footing are obtained, and it is compared against the current design (uniform pressure). Results section show that the optimal design is more accurate and more economical than to any other model. Therefore, it is concluded that the optimized design model presented in this paper should be used to obtain the minimum cost design for the circular isolated footings.

• Steel and Composite Structures
• /
• 제30권2호
• /
• pp.109-121
• /
• 2019

This paper presents the second part of the modeling for the strap combined footings, this part shows a mathematical model for design of strap combined footings subject to axial load and moments in two directions to each column considering the soil real pressure acting on the contact surface of the footing for one and/or two property lines of sides opposite restricted, the pressure is presented in terms of an axial load, moment around the axis "X" and moment around the axis "Y" to each column, and the methodology is developed using the principle that the derived of the moment is the shear force. The first part shows the optimal contact surface for the strap combined footings to obtain the most economical dimensioning on the soil (optimal area). The classic model considers an axial load and a moment around the axis "X" (transverse axis) applied to each column, i.e., the resultant force from the applied loads is located on the axis "Y" (longitudinal axis), and its position must match with the geometric center of the footing, and when the axial load and moments in two directions are presented, the maximum pressure and uniform applied throughout the contact surface of the footing is considered the same. A numerical example is presented to obtain the design of strap combined footings subject to an axial load and moments in two directions applied to each column. The mathematical approach suggested in this paper produces results that have a tangible accuracy for all problems and it can also be used for rectangular and T-shaped combined footings.

• 대한토목학회논문집
• /
• 제9권1호
• /
• pp.33-40
• /
• 1989

철근 콘크리트 뼈대구조는 설계변수가 많고, 목적함수의 제약조건이 복잡하여 주로 반복적인 재해석에 의하여 최적해에 접근하는 방법이 사용되고 있다. 본 연구에서는 다단계분할(multilevel decomposition)에 의하여 최적화 문제를 형성하여 재해석과정을 줄이고 효과적으로 설계변수를 취할 수 있도록 하였다. 최적화의 단계는 첫째 단계에서 비선형거동에 의한 재분배모멘트의 설계공간을 계산하여 설계모멘트에 대한 제약조건식을 형성하고, 둘째 단계에서는 재분배 모멘트를 최적화하였으며, 셋째 단계에서는 설계단면을 최적화하였다. 이때 재분배 모멘트의 최적화에 따른 첫째 단계의 모멘트의 설계공간의 변화는 부재력 변화량 추정(force approximation technique)에 의하여 수정하도록 하며, 변수를 단계별로 줄여 수렴을 가속화시킬 수 있도록 하였다. 최적화 문제의 목적함수로는 경비함수를 취하였으며 영국 CP110의 한계상태설계법을 이용하여 부재의 응력제약조건식을 유도하고, 설계예를 통하여 본 연구의 타당성과 효율성을 구명하였다.

• Computers and Concrete
• /
• 제18권6호
• /
• pp.1113-1134
• /
• 2016

A methodology using neural networks has been proposed for rapid prediction of inelastic bending moments in reinforced concrete continuous beams subjected to service load. The closed form expressions obtained from the trained neural networks take into account cracking in concrete at in-span and at near the internal supports and tension stiffening effect. The expressions predict the inelastic moments (considering the concrete cracking) from the elastic moments (neglecting the concrete cracking) at supports. Three separate neural networks are trained since these have been postulated to represent all the beams having any number of spans. The training, validating, and testing data sets for the neural networks are generated using an analytical-numerical procedure of analysis. The proposed expressions are verified for example beams of different number of spans and cross-section properties and the errors are found to be small. The proposed expressions, at minimal input data and computation effort, yield results that are close to FEM results. The expressions can be used in preliminary every day design as they enable a rapid prediction of inelastic moments and require a computational effort that is a fraction of that required for the available methods in literature.

• 한국안전학회지
• /
• 제17권4호
• /
• pp.189-195
• /
• 2002

I-단면 곡선보 (curved beam)의 모멘트 하중 하에서 비틀림(warping)을 포함한 평면외 (out-of-plane)의 좌굴을 미분구적법 (DQM)을 이용하여 해석하였다. 다양한 경계조건(boundary conditions) 및 굽힘각(opening angles)에 따른 임계모멘트 (critical moments)를 계산하고, DQM의 해석결과는 해석적 해답 (exact solution) 과 비교 분석하였다. DQM은 적은 요소(grid points)를 사용하여 정확한 해석결과를 보여주었고, 두 경계조건 (고정-고정, 고정-단순지지)하에서 새로운 결과 또한 제시하였다.