L. Simões da Silva

A component model for the behaviour of steel joints at elevated temperatures

Abstract Recent experimental evidence has shown that steel joints exhibit a distinct change in their moment–rotation response under increasing temperature. In terms of cold design, the component method is currently the widely accepted procedure for the evaluation of the various design values. It is the purpose of the present paper to extend the component method to the prediction of the response of steel joints under fire loading. Using typical mechanical models consisting of extensional springs and rigid links, whereby the springs exhibit a non-linear force deformation response (here taken as a bi-linear approximation), an analytical procedure is proposed capable of predicting the moment–rotation response under fire conditions that incorporates the variation of yield stress and Young’s modulus of the various components as the temperature increases. An application to a cruciform flush end-plate beam-to-column steel joint is presented and compared to the experimental results obtained under various loading conditions.

Post-limit stiffness and ductility of end-plate beam-to-column steel joints

Abstract A procedure for the evaluation of ductility in steel joints is presented. Using the component method as background, a non-linear analysis for a number of end-plate beam-to-column joints is performed that is capable of identifying the “yield” sequence of the various components and the failure of the joint. Each component is characterised using a bi-linear approximation for the force–displacement relation. Comparing these results with the corresponding experimental results leads to a proposal of the post-limit stiffness of the various components. A component ductility index is proposed for each component as a means of classification with respect to ductility, using the three ductility classes currently proposed in the literature. A joint ductility index is also proposed, which can be used to verify available rotation against the structure required rotation.

Experimental behaviour of end-plate beam-to-column composite joints under monotonical loading

An experimental research program on end-plate beam-to-column composite joints under monotonical loading is presented. The major focus relates to the identification of the contribution of the concrete confinement in composite columns to the behaviour of the joint, coupled with a thorough assessment of the various loading possibilities, ranging from symmetric and anti-symmetric loading on internal nodes to external nodes under hogging and sagging moments, typical in seismic regions. Comparison with current methodologies in the analysis of composite joints is also presented.

A ductility model for steel connections

A model for the evaluation of the ductility of steel connections loaded in bending is presented in this paper. In the context of the component method, whereby a joint is modelled as an assembly of springs (components) and rigid links, using an elastic post-buckling analogy to the bi-linear elastic‐plastic behaviour of each component, a general analytical model is proposed that yields the maximum rotation of the connection. Despite the complexity of the various connection types, the proposed model is able to provide analytical solutions for the moment‐rotation response of a steel connection by using appropriate transformation criteria for assemblies of components in series and in parallel. The model is applied to typical beamto-column connections, showing good agreement with numerical results.

A probabilistic decision-making approach for the sustainable assessment of infrastructures

Sustainable development is a multidimensional concept that usually implies a simultaneous concretization of contradictory aspects. Multi-criteria decision approaches are often used for the management of conflicting perspectives. In life cycle approaches, uncertainties are unavoidable and a decision making approach dealing with life-cycle based criteria cannot disregard the uncertainties associated with the evaluation of criteria. It is the purpose of this paper to introduce a decision-making approach, based on PROMETHEE and AHP, to address both of these important issues. Moreover, the proposed approach aims to address two other types of uncertainties, inherent to the use of PROMETHEE and AHP, which arise from the selection of the generalized criterion functions and the selection of preference values, respectively. The proposed approach enhances the robustness of the decision-making approach and enables decisions to be made on a more reliable base. The approach is applied to a case study: the comparative assessment of alternatives bridges taking into account environmental, economical and social criteria evaluated over the complete life-cycle of the bridges.

An analytical evaluation of the response of steel joints under bending and axial force

Abstract This paper presents an equivalent elastic model where each bi-linear spring is replaced by two equivalent elastic springs using an energy formulation and in the context of a post-buckling stability analysis. Such a model yields analytical solutions for the evaluation of the behaviour of steel joints under compressive forces, combined axial force and bending moment, which enables the reproduction of their full non-linear behaviour. The resulting formulation is applied to a simple beam-to-column welded connection initially loaded in pure compression. Subsequent loading of the joint in combined bending and various levels of axial force clearly shows the reduction in moment capacity.

Database for the semi-rigid behaviour of beam-to-column connections in seismic regions

The behaviour of steelwork connections has long been recognised as complex. A database of test results for connection behaviour constitutes an essential step towards the development of design methodologies, allowing more researchers to investigate in this field without the financial burden of carrying out experimental work, avoiding being misled by incomplete or incorrect data, and opening the way to design assisted by testing. A database of experimental results for steel and steel-concrete composite connections is presented which encompasses graphical treatment of data, numerical manipulation and statistical treatment of groups of results, allowing easy comparison of connection behaviour. Simplified constitutive models for the hysteretic behaviour of connections are presented and included in the database for comparison and calibration with experimental results. The database SERIWWW was developed according to the following specifications: Possibility to introduce test results for any type of connection in free form format, irrespective of the type of connection (existent or not); Possibility to deal with any material; Possibility to deal with dynamical tests; Possibility to deal with numerical simulations; Easy interchange (import-export) with any commercial program (EXCEL, ACCESS, etc.); INTERNET on-line implementation. and implemented as independent modules which correspond to different levels of utilisation, as shown in Table 1. An experimental project of beam-to-column composite connection cyclic and dynamic tests currently under execution is presented where both con

Influence of climate change on the energy efficiency of light-weight steel residential buildings

This paper addresses the influence of the climate change scenarios predicted by the Intergovernmental Panel for Climate Change (IPCC) for Southern Europe and the Mediterranean region on the energy efficiency of light-weight steel residential buildings. A performance-based approach is adopted to carry out this assessment using advanced dynamic simulation of the operational energy performance. Based on a typical Portuguese cold-formed steel residential building, a representative numerical model is calibrated against normative requirements for dynamic simulation of thermal behaviour and sophisticated computational fluid dynamics models. Considering climate change scenarios predicted by the IPCC, a parametric study is carried out to assess the influence of climate change on the energy efficiency of light-weight steel residential buildings representative of a warm temperate summer dry climatic region.

Equivalent post-buckling models for the flexural behaviour of steel connections

Abstract Analytical solutions for the evaluation of the behaviour of steel connections are presented which are able to reproduce their full non-linear behaviour. Because usual models for the analysis of steel connections consist of translational springs and rigid links whereby the springs exhibit a non-linear force–deformation response, usually taken as a bi-linear approximation, they require an incremental non-linear analysis. Using a substitute elastic post-buckling model where each bi-linear spring is replaced by two equivalent elastic springs in the context of a post-buckling stability analysis using an energy formulation, closed-form solutions are obtained for a connection loaded in bending. Application to a beam-to-column welded connection using the component (spring) characterisation of code regulations yields the same results in terms of moment resistance and initial stiffness, being additionally able to trace the full unstiffening response.

Reliability assessment of the post-limit stiffness and ductility of steel joints

Abstract Steel joints must exhibit sufficient ductility for safe structural behaviour. This is especially true for partial-strength steel joints, whereby the nonlinear response of the joint plays an important part in the overall response of the structure. Uncertainty in joint response, particularly beyond the elastic limit of the moment–rotation curve, naturally leads to a probabilistic treatment of the ductility of steel joints. It is the objective of the present paper to compare a direct probabilistic approach with simulation techniques using the Monte-Carlo method both at the component and joint level, in the context of the component method, with the aim of establishing safe limits for the ductile behaviour of the steel joints.