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Computation of upper and lower bounds in limit analysis using second-order cone programming and mesh adaptivity

机译:利用二阶锥规划和网格自适应计算极限分析的上下界

摘要

Limit analysis is relevant in many practical engineering areas such as the design of mechanical structures or the analysis of soil mechanics. Assuming a rigid, perfectly-plastic solid subject to a static load distribution, the problem of limit analysis consists of finding the minimum multiple of this load distribution that will cause the body to collapse. This collapse multiplier results from solving an infinite dimensional saddle point problem, where the internal work rate is maximized over an admissible set of stresses -defined by a yield condition- and minimized over the linear space of kinematically admissible velocities for which the external work rate equals the unity. When strong duality is applied to this saddle point problem, the well-known convex (and equivalent) static and kinematic principles of limit analysis arise. In this thesis, an efficient procedure to compute strict upper and lower bounds for the exact collapse multiplier is presented, with a formulation that explicitly considers the exact convex yield condition. The approach consists of two main steps. First, the continuous problem, under the form of the static principle, is discretized twice (one per bound) by means of different combinations of finite element spaces for the stresses and velocities. For each discretization, the interpolation spaces are chosen so that the attainment of an upper or a lower bound is guaranteed. The second step consists of solving the resulting discrete nonlinear optimization problems. Towards this end, they are reformulated into the canonical form of Second-order Cone Programs, which allows for the use of primal-dual interior point methods that optimally exploit the convexity and duality properties of the limit analysis
机译:极限分析与许多实际工程领域相关,例如机械结构设计或土壤力学分析。假设刚性,完美塑性的实体承受静态载荷分布,则极限分析的问题在于找到该载荷分布的最小倍数,该最小倍数将导致车身坍塌。该塌陷系数是由解决无穷维鞍点问题导致的,在该问题中,内部工作率在一组可允许的应力(由屈服条件定义)上最大化,而在运动上允许的速度的线性空间上被最小化,外部运动速率等于团结。当强对偶应用于该鞍点问题时,就会出现众所周知的凸(和等效)极限分析的静态和运动学原理。本文提出了一种有效的程序,可以计算精确的塌陷乘数的严格上限和下限,其公式应明确考虑确切的凸屈服条件。该方法包括两个主要步骤。首先,在静态原理的形式下,连续问题通过应力和速度的有限元空间的不同组合被离散两次(每个边界一个)。对于每个离散化,选择插值空间,以便确保达到上限或下限。第二步包括解决由此产生的离散非线性优化问题。为此,它们被重新构造为二阶圆锥程序的规范形式,从而允许使用原始对偶内点方法,以最佳方式利用极限分析的凸性和对偶性

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