Seismic collapse prediction of frame structures by means of genetic algorithms

Abstract

This paper presents an automatic approach for the evaluation of the plastic load and failure modes of planar frames. The method is based on the generation of elementary collapse mechanisms and on their linear combination aimed at minimizing the collapse load factor. The minimization procedure is efficiently performed by means of genetic algorithms which allow to compute an approximate collapse load factor, and the correspondent failure mode, with sufficient accuracy in a very short computing time. A user-friendly original software in the agent-based programming language Netlogo, here employed for the first time with structural engineering purposes, has been developed showing its great versatility and advantages. Many applications have been performed both with reference to the classical plastic analysis approach, in which all the loads increase proportionally, and with a seismic point of view considering a system of horizontal forces whose magnitude increases while the vertical loads are assumed to be constant. In this latter case a parametric study has been performed aiming at evaluating the influence of some geometric, mechanical and load distribution parameters on the ultimate collapse load of planar frames.The problem of plastic analysis and design of frame structures has been deeply analysed by many researchers since the middle of the past century [1] by means of two different approaches. The first of these is the finite element method in which the global stiffness matrix of the system is computed and the response of the structure is obtained solving iteratively a set of non linear equations [2]. In this analysis the history of loading is applied incrementally until the failure of the structure, therefore the analysis can be very time-consuming.The second approach is directly based on the kinematic theorem of limit analysis; by analysing all the possible collapse mechanisms of a structure and the related collapse loads, the correct ultimate load is determined seeking the absolute lowest value among the considered mechanisms. This method therefore does not require the direct computation of stiffness matrix and it is not necessary to apply the complete history of loading.Many contributions can be found in the literature aiming at solving plastic collapse problems for example by means of linear programming [3][4][5] or at the optimal plastic design of beams [6] or frames considering as constraint the minimum weight of the structure [7-10] or a generic cost function of design variables [11].In the limit analysis kinematic approach, one of the most frequently used method is that first developed by Neal and Symonds [8,9] in which only the elementary mechanisms are analysed and these are combined to obtain a final collapse mechanism whose load factor is lower than all the possible

A New Agent-Based Methodology for the Seismic Vulnerability Assessment of Urban Areas

“…The methodology here proposed adopts the SOC earthquake engine of the OFC model in the context of agent-based simulations. Agent-based (or multi-agent) simulations are a powerful computational tool that has been extensively applied in several fields to model complex phenomena [27][28][29][30][31][32][33][34][35][36]. This approach has been here implemented by means of a new software, called ABES (Agent-Based Earthquake Simulator) and realized within the programmable multi-agent environment NetLogo [37], with the purpose of assessing the seismic vulnerability of urban areas in the critical state.…”

Optimization of plastic analysis of moment frames using modified dolphin echolocation algorithm

“…Kaveh et al carried out plastic analyzes of planar frames with the use of colliding bodies optimization (COD) algorithms and its developed version (Kaveh and Ghafari, 2015; Kaveh and Ilchi Ghazaan, 2014). The latest studies also include Greco et al in 2017, which investigated the prediction of seismic failure of frame structures with genetic optimization algorithm. In this study, in order to simulate the seismic state of structures, a constant uniform gravity load and an incremental lateral load are applied to the floors.…”

“…In this study, in order to simulate the seismic state of structures, a constant uniform gravity load and an incremental lateral load are applied to the floors. A push-over analysis in Sap2000 is applied in order to verify the results of investigated frames, and little error is observed in load factor determination and also the location of hinge formations (Greco et al, 2017).…”

Parametric analysis of collapse load factor of planar frames

“…Furthermore, the effects of various base restraints have been investigated on the nonlinear inelastic static and seismic responses of steel frames [19]. Greco et al used a genetic algorithm to predict the seismic collapse of frame structures [20]. Moreover, a robust predictive model was presented by Aminian et al based on the shear of steel frame structures using hybrid genetic programming [21].…”