Analytical and finite element modelling of the elastic–plastic behaviour of metallic strands under axial–torsional loads

In this work a new formulation for modelling the elastic–plastic behaviour of metallic strands subjected to axial–torsional loads is presented. Simple and accurate cross sectional constitutive equations a rederived, fully accounting for the evolution of plastic deformations in the wires, starting from a description of the internal structure of the strand. The proposed approach is suitable both for straightforward analytical calculations as well as for implementation into finite elements for the large-scale structural analyses of cable structures. A full three-dimensional(3D) finite element(FE) model, based on a parametric description of the strand internal geometry, is also developed. The results of both the FE model and the analytical formulation are validated with reference to a well-documented physical testing campaign and a well-established linearly elastic literature model. Additional analyses are then performed to carefully assess the validity of the proposed mechanical formulation, for a wide range of strand construction parameters, by means of systematic comparisons against the results of the 3DFE modeland of a recent linearly elastic literature model

Performance-based seismic design of steel structures accounting for fuzziness in their joint flexibility

This paper presents a performance-based earthquake engineering framework to explicitly take into account fuzziness in the design parameters, with application to steel structures. Semi-rigidity of column-to-foundation and beam-to-column connections is considered as a relevant example of design parameters that can be conveniently modelled using fuzzy variables. Without lack of generality, their fixity factors are described by means of triangular membership functions, fully defined by lower and upper values of admissibility and their most likely value, i.e. their reference value. For demonstration purposes, the procedure is applied to analyse two different case studies, namely a 5-storey single-bay plane frame and an industrial 3D modular structure. The analyses are performed accounting for the fuzziness of the connections, which is then propagated onto representative engineering demand parameters, within a general performance-based design (PBD) approach

Performance-based seismic design of a modular pipe-rack

Aimed at demonstrating the benefits of using a robust PBD (performance-based design) framework in the engineering construction industry, the seismic analysis of a typical pipe-rack module is presented in this paper, comparing prescriptive and performancebased approaches. The case-study steel frame is 6 m long, 8 m wide and 10 m tall, and is representative of this type of structures in the oil and gas industry. The hazard analysis is used to select a representative set of recorded accelerograms for increasing values of the seismic intensity measure (IM), chosen as the spectral ordinate at the fundamental period of vibration of the structure. Nonlinear time-history analyses are carried out with the commercial software SAP2000 to establish the fragility curves relevant to the pipe rack. The process is automated through MATLAB coding and a range of EDPs (engineering demand parameters) are statistically characterised, namely internal forces, deformations and absolute accelerations, which in turn are associated with various DMs (damage measures)

Performance-based engineering for industrial modular structures

Performance-based engineering for industrial modular structure