Rock slope stability analyses using extreme learning neural network and terminal steepest descent algorithm

The analysis of rock slope stability is a classical problem for geotechnical engineers. However, for practicing engineers, proper software is not usually user friendly, and additional resources capable of providing information useful for decision-making are required. This study developed a convenient tool that can provide a prompt assessment of rock slope stability. A nonlinear input–output mapping of the rock slope system was constructed using a neural network trained by an extreme learning algorithm. The training data was obtained by using finite element upper and lower bound limit analysis methods. The newly developed techniques in this study can either estimate the factor of safety for a rock slope or obtain the implicit parameters through back analyses. Back analysis parameter identification was performed using a terminal steepest descent algorithm based on the finite-time stability theory. This algorithm not only guarantees finite-time error convergence but also achieves exact zero convergence, unlike the conventional steepest descent algorithm in which the training error never reaches zero

Application of neural network to rock slope stability assessments

It is known that rock masses are inhomogeneous, discontinuous media composed of rock material and naturally occurring discontinuities such as joints, fractures and bedding planes. These features make any analysis very difficult using simple theoretical solutions. Generally speaking, back analysis technique can be used to capture some implicit parameters for geotechnical problems. In order to perform back analyses, the procedure of trial and error is generally required. However, it would be time-consuming. This study aims at applying a neural network to do the back analysis for rock slope failures. The neural network tool will be trained by using the solutions of finite element upper and lower bound limit analysis methods. Therefore, the uncertain parameter can be obtained, particularly for rock mass disturbanc

Limit Analysis of Complex 3D Steel Structures Using Second-Order Cone Programming

International audienceThe modelling of complex steel structures under static loading using rigid perfectly plastic material is presented within the framework of second-order cone programming (SOCP). The classic upper and lower bound principles of yield analysis, naturally written as optimization problems, are formulated as a pair of dual second-order cone programs which are then solved using a state-of-the art primal-dual interior point method (IPM). The IPM shows good robustness and efficiency along with reduced computational times especially for limit analysis. The whole process is illustrated first with basic steel structures checks of fillet welds or beams under biaxial bending moment, and second with complex 3D steel assemblies. The results show good agreement with the failures modes and resistance values presented in the Eurocode and allows us to obtain a reliable estimate of the ultimate resistance within a reasonable time

Numerical Yield Design Analysis of High-Rise Reinforced Concrete Walls in Fire Conditions

International audienceThe present contribution aims at developing a numerical procedure for predicting the failure of high rise reinforced concrete walls subjected to fire loading conditions. The stability of such structures depends, on the one hand, on thermal strains inducing a curved deformed configuration and, on the other hand, on a local degradation of the constitutive material strength properties due to the increase of temperature across the wall thickness. A three step procedure is proposed, in which the yield design (limit analysis) method is applied on two separate levels. First, an up-scaling procedure on the wall unit cell is considered as a way for assessing the generalized strength properties of the curved wall, modelled as a shell, by taking into account reduced strength capacities of the constitutive materials. Secondly, the overall stability of the wall in its fire-induced deformed configuration is assessed using lower and upper bound based on shell finite elements and the previously determined temperature-dependent strength criterion. Second-order cone programming problems are then formulated and solved using state-of-the-art solvers. Different illustrative applications are presented to investigate the sensitivity of the wall stability to geometrical parameters. Finally, the influence of imperfect connections between panels is also considered using a simple joint behaviour