• Title/Summary/Keyword: upper bound theorem

Search Result 54, Processing Time 0.021 seconds

Collapse mechanism of tunnel roof considering joined influences of nonlinearity and non-associated flow rule

  • Yang, X.L.;Xu, J.S.;Li, Y.X.;Yan, R.M.
    • Geomechanics and Engineering
    • /
    • v.10 no.1
    • /
    • pp.21-35
    • /
    • 2016
  • Employing non-associated flow rule and Power-Law failure criterion, the failure mechanisms of tunnel roof in homogeneous and layered soils are studied in present analysis. From the viewpoint of energy, limit analysis upper bound theorem and variation principle are introduced to study the influence of dilatancy on the collapse mechanism of rectangular tunnel considering effects of supporting force and seepage force. Through calculation, the collapsing curve expressions of rectangular tunnel which are excavated in homogeneous soil and layered soils respectively are derived. The accuracy of this work is verified by comparing with the existing research results. The collapsing surface shapes with different dilatancy coefficients are draw out and the influence of dilatancy coefficient on possible collapsing range is analyzed. The results show that, in homogeneous soil, the potential collapsing range decreases with the decrease of the dilatancy coefficient. In layered soils, the total height and the width on the layered position of possible collapsing block increase and the width of the falling block on tunnel roof decrease when only the upper soil's dilatancy coefficient decrease. When only the lower soil's dilatancy coefficient decrease or both layers' dilatancy coefficients decrease, the range of the potential collapsing block reduces.

Failure Mechanism for Pull-Out Capacity of Headed Reinforcement (Head Reinforcement 인발강도를 위한 파괴 메캐니즘)

  • 홍성걸;최동욱;권순영
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2002.05a
    • /
    • pp.233-238
    • /
    • 2002
  • This study presents failure mechanisms for the pull-out strength of headed reinforcement for upper bound solution based on the limit theorem. The failure mechanisms to be presented follow the failure surface pattern of punching shear failure found in the joints of slab with a column. Several failure surfaces of the mechanisms have different characteristics for dissipation works and these mechanisms are able to interpret the role of bar details surrounding headed reinforcement.

  • PDF

ON THE HOMOLOGY OF SCHUR COMPLEXES

  • Choi, Eun-J.;Kim, Young-H.;Kyoung, Il-H.;Won, Seung-J.
    • Communications of the Korean Mathematical Society
    • /
    • v.17 no.3
    • /
    • pp.389-401
    • /
    • 2002
  • We give an upper bound for the degrees of the nonvanishing homology modules of the Schur complex L$\sub$λ/${\mu}$/ø in terms of the depths of the determinantal ideals of ø). Using this fact, we obtain the acyclic theorem for L$\sub$λ/ø and the information concerning the support of the homology modules of L$\sub$λ/${\mu}$/ø.

Determination of Composite Strength Parameter Using Elasto-Plastic Theory (탄소성이론을 이용한 복합지반의 대표 강도정수 예측)

  • 이주형;김영욱;박용원
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2002.03a
    • /
    • pp.93-100
    • /
    • 2002
  • Vertical reinforcement of soft soils using the deep mixing method has received increasing applications. In this study, the theory of elasticity and plasticity including the upper bound theorem of limit analysis were used to derive the equations for obtaining composite elastic properties and shear strength parameters. The developed equations were validated using the finite element computer program SAGE CRISP. The analysis involved 4 different cases-two different type of soil and replacement ratios. Tile results of the analysis show that the proposed equations could determine the properties of composite material for practical applications.

  • PDF

Prediction of seismic displacements in gravity retaining walls based on limit analysis approach

  • Mojallal, Mohammad;Ghanbari, Ali
    • Structural Engineering and Mechanics
    • /
    • v.42 no.2
    • /
    • pp.247-267
    • /
    • 2012
  • Calculating the displacements of retaining walls under seismic loads is a crucial part in optimum design of these structures and unfortunately the techniques based on active seismic pressure are not sufficient alone for an appropriate design of the wall. Using limit analysis concepts, the seismic displacements of retaining walls are studied in present research. In this regard, applying limit analysis method and upper bound theorem, a new procedure is proposed for calculating the yield acceleration, critical angle of failure wedge, and permanent displacements of retaining walls in seismic conditions for two failure mechanisms, namely sliding and sliding-rotational modes. Also, the effect of internal friction angle of soil, the friction angle between wall and soil, maximum acceleration of the earthquake and height of the wall all in the magnitude of seismic displacements has been investigated by the suggested method. Two sets of ground acceleration records related to near-field and far-field domains are employed in analyses and eventually the results obtained from the suggested method are compared with those from other techniques.

Convergence rate of a test statistics observed by the longitudinal data with long memory

  • Kim, Yoon Tae;Park, Hyun Suk
    • Communications for Statistical Applications and Methods
    • /
    • v.24 no.5
    • /
    • pp.481-492
    • /
    • 2017
  • This paper investigates a convergence rate of a test statistics given by two scale sampling method based on $A\ddot{i}t$-Sahalia and Jacod (Annals of Statistics, 37, 184-222, 2009). This statistics tests for longitudinal data having the existence of long memory dependence driven by fractional Brownian motion with Hurst parameter $H{\in}(1/2,\;1)$. We obtain an upper bound in the Kolmogorov distance for normal approximation of this test statistic. As a main tool for our works, the recent results in Nourdin and Peccati (Probability Theory and Related Fields, 145, 75-118, 2009; Annals of Probability, 37, 2231-2261, 2009) will be used. These results are obtained by employing techniques based on the combination between Malliavin calculus and Stein's method for normal approximation.

NUMERICAL SIMULATION OF PLASTIC FLOW BY FINITE ELEMENT LIMIT ANALYSIS

  • Hoon-Huh;Yang, Wei-H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1992.03a
    • /
    • pp.159-176
    • /
    • 1992
  • Limit analysis has been rendered versatile in many problems such as structural problems and metal forming problems. In metal forming analysis, a slip-line method and an upper bound method approach to limit solutions is considered as the most challenging areas. In the present work, a general algorithm for limit solutions of plastic flow is developed with the use of finite element limit analysis. The algorithm deals with a generalized Holder inequality, a duality theorem, and a combined smoothing and successive approximation in addition to a general procedure for finite element analysis. The algorithm is robust such that from any initial trial solution, the first iteration falls into a convex set which contains the exact solution(s) of the problem. The idea of the algorithm for limit solution is extended from rigid/perfectly-plastic materials to work-hardening materials by the nature of the limit formulation, which is also robust with numerically stable convergence and highly efficient computing time.

  • PDF

Design charts for yield acceleration and seismic displacement of retaining walls with surcharge through limit analysis

  • Aminpoor, Mohamad Mahdi;Ghanbari, Ali
    • Structural Engineering and Mechanics
    • /
    • v.52 no.6
    • /
    • pp.1225-1256
    • /
    • 2014
  • Calculating the seismic displacement of retaining walls has an important role in the optimum design of these structures. Also, studying the effect of surcharge is important for the calculation of active pressure as well as permanent displacements of the wall. In this regard, some researchers have investigated active pressure; but, unfortunately, there are few investigations on the seismic displacement of retaining walls with surcharge. In this research, using limit analysis and upper bound theorem, permanent seismic displacement of retaining walls with surcharge was analyzed for sliding and overturning failure mechanisms. Thus, a new formulation was presented for calculating yield acceleration, critical angle of failure wedge, and permanent displacement of retaining walls with surcharge. Also, effects of surcharge, its location and other factors such as height of the wall and internal friction angle of soil on the amount of seismic displacements were investigated. Finally, designing charts were presented for calculating yield acceleration coefficient and angle of failure wedge.

Collapse analysis of shallow tunnel subjected to seepage in layered soils considering joined effects of settlement and dilation

  • Yang, X.L.;Zhang, R.
    • Geomechanics and Engineering
    • /
    • v.13 no.2
    • /
    • pp.217-235
    • /
    • 2017
  • The stability prediction of shallow buried tunnels is one of the most difficult tasks in civil engineering. The aim of this work is to predict the state of collapse in shallow tunnel in layered soils by employing non-associated flow rule and nonlinear failure criterion within the framework of upper bound theorem. Particular emphasis is first given to consider the effects of dilation on the collapse mechanism of shallow tunnel. Furthermore, the seepage forces and surface settlement are considered to analyze the influence of different dilation coefficients on the collapse shape. Two different curve functions which describe two different soil layers are obtained by virtual work equations under the variational principle. The distinct characteristics of falling blocks up and down the water level are discussed in the present work. According to the numerical results, the potential collapse range decreases with the increase of the dilation coefficient. In layered soils, both of the single layer's dilation coefficient and two layers' dilation coefficients increase, the range of the potential collapse block reduces.