Optimal design of steel frames accounting for buckling

Abstract

A formulation of a special design problem devoted to elastic perfectly plastic steel frame structures subjected to different combinations of static and dynamic loads is presented. In particular, a minimum volume design problem formulation is presented and the structure is designed to be able to elastically behave for the assigned fixed loads, to elastically shakedown in presence of serviceability load conditions and to prevent the instantaneous collapse for suitably chosen combinations of fixed and ultimate seismic loadings as well as of fixed and wind actions. The actions that the structure must suffer are evaluated by making reference to the actual Italian seismic code. The dynamic response of the structure is performed by utilizing a modal technique. In order to prevent other undesired collapse modes further constraints are introduced in the relevant optimization problem taking into account the risk of element buckling. Different applications devoted to flexural frames conclude the paper. The sensitivity of the structural response has been investigated on the grounds of the determination and interpretation of the Bree diagrams of the obtained optimal structures

Optimization of structures with unrestricted dynamic shakedown constraints

“…(41). Actually, it is known (see, e.g., Benfratello et al 2013aBenfratello et al , 2013bBenfratello et al , 2014Palizzolo et al 2014Palizzolo et al , 2015 that the instantaneous collapse conditions for a structure subjected to a load arbitrarily varying within a given domain defined through suitably assigned basic loads (vertices of the load domain) have the same form of the relevant shakedown limit conditions but for each basic load an independent field of free selfstresses (or analogously an independent field of free plastic deformations) must be considered.…”

“…In the present paper a very current and widespread problem, both in the scientific research field and in the practical engineering application one, is studied: the optimal design problem of structures mainly subjected to seismic loads (see, e.g., Baratta and Corbi 2004;Benfratello et al 2013aBenfratello et al , b, 2014Ghasemi and Farshchin 2014;Kaveh and Nasrollahi 2014;Palizzolo et al 2014Palizzolo et al , 2015. In such a topic it is a wellestablished practice to consider the ductility features of the structure and, as a consequence, to take into account its residual resistance capacity beyond the elastic limit, which is often very high (see, e.g., Atkočiūnas 2011;Giambanco et al 1994;Lógó 2002, 2006;König 1975;Massonet and Save 1965;Palizzolo 2004;Se-Hyu and Seung-Eock 2002;Tin-Loi 2000).…”

“…Furthermore, by means of a natural extension of the unrestricted dynamic shakedown to the case of the limit analysis it is possible to formulate the appropriate safety criterion even against the impending instantaneous collapse (see, e.g., Benfratello et al 2013aBenfratello et al , b, 2014.…”

An efficient framework for the elasto-plastic reliability assessment of uncertain wind excited systems

“…Under these conditions, the goal is to understand whether an elasto-plastic structure subject to loads varying within a specified domain will eventually respond in a purely elastic manner after a finite amount of plastic deformation and is based on the well-known Bleich-Melan and Koiter theorems. In the last decades, many applications have been treated with this approach [35][36][37][38], including recent applications where both the loads and the strength parameters have been considered as uncertain [39,40]. When dynamic effects are important, dynamic shakedown analysis becomes necessary.…”

Seismic shakedown design of frames based on a probabilistic approach

“…Most of the effected study are related to a deterministic approach (see, e.g. [14][15][16]), even if some paper exists accounting for the randomness of the load, but limiting to the structure elastic behaviour (see, e.g. [17,19]).…”