Paulo Providência

Multiple equilibria for unlinked and weakly-linked cellular structural forms

Abstract It is demonstrated that a structural form comprising n unlinked or weakly-linked separate identical cells can, by its nature, suffer an explosion of unstable post-buckling states, associated with an n -fold compound critical point. Examples of rigid-link models, and atomic matrix cellular models employing a Lennard-Jones potential, are included. Attention is paid to criteria for the appearance of homogeneous, localized but distributed, and thoroughly-localized solutions. For the atomic models, generalized coordinates that exploit local and global symmetries of unlinked cells are introduced in a block diagonalization context, to clarify the bifurcation structure. A discretized Lagrangian formulation is introduced to untangle the paths for weakly-linked cells.

Sustainability and Lifecycle Assessment of Timber-Concrete Composite Bridges

AbstractOver the last few years there has been a renewed interest on the use of timber-concrete composite (TCC) structures in bridge decks, possibly because of their cost competitiveness and environmental friendliness. Accordingly, this paper investigates the sustainability of TCC bridge decks under a threefold environmental, economic, and sociocultural perspective. Two different types of decks, which represent the overall characteristics of TCC bridges constructed around the world, are first described. Next, the paper presents a comparative sustainability assessment of two existing concrete bridges and their TCC deck potential alternatives (of the types previously mentioned); a lifecycle methodology, based on standards from the International Organization for Standardization (ISO) and other publications, is followed. The main conclusions are that, when compared with concrete decks, TCC solutions cause less environmental impact and are cost-competitive. Regarding sociocultural impacts, this analysis reveal...

Lateral-Torsional Stability Boundaries for Polygonally Depth-Tapered Strip Cantilevers Under Multi-Parameter Point Load Systems—An Analytical Approach

This paper reports an analytical study on the elastic lateral-torsional buckling behavior of strip cantilevers (i) whose depth is given by a monotonically decreasing polygonal function of the distance to the support and (ii) which are subjected to an arbitrary number of independent conservative point loads, all acting in the same “downward” direction. The study is conducted on the basis of a one-dimensional (beam) mathematical model. A specialized model problem, consisting of a two-segment cantilever acted by two loads, applied at the free end and at the junction between segments, is first considered in detail for it “contains all the germs of generality”. It is shown that the governing differential equations can be integrated in terms of confluent hypergeometric functions or Bessel functions (themselves special cases of confluent hypergeometric functions). This allows us to establish exactly the characteristic equation for this structural system, which implicitly defines its stability boundary. Moreover, it is shown that the methods used to solve the model problem also apply to the general problem. A couple of parametric illustrative examples are discussed. Some analytical solutions are compared with the results of shell finite element analyses—a good agreement is found.