M.R.T. Arruda

Static and dynamic physically non-linear analysis of concrete structures using a hybrid mixed finite element model

A new hybrid-mixed stress finite element model for the static and dynamic non-linear analysis of concrete structures is presented and discussed in this paper. The main feature of this model is the simultaneous and independent approximation of the stress, the strain and the displacement fields in the domain of each element. The displacements along the static boundary, which is considered to include inter-element boundaries, are also directly approximated. To define the approximation bases in the space domain, complete sets of orthonormal Legendre polynomials are used. The adoption of these functions enables the use of analytical closed form solutions for the computation of all linear structural operators and leads to the development of very effective p-refinement procedures. To represent the material quasi-brittle behaviour, a physically non-linear model is considered by using damage mechanics. A simple isotropic damage model is adopted and to control strain localisation problems a non-local integral formulation is considered. To solve the dynamic non-linear governing system, a time integration procedure based on the use of the @a-HHT method is used. For each time step, the solution of the non-linear governing system is achieved using an iterative algorithm based on a secant method. The model being discussed is applied to the solution of two-dimensional structures. To validate the model, to illustrate its potential and to assess its accuracy and numerical efficiency, several numerical examples are discussed and comparisons are made with solutions provided by experimental tests and with other numerical results obtained using conventional finite elements (CFE).

Finite element analysis of steel structures – a review of useful guidelines

Purpose – Since the use of advanced finite element analysis (FEA) in the design of steel structures has been increasing its popularity in order to avoid unsafe or highly conservative designs, a solid know-how in computer-aided design (CAD) and engineering (CAE) codes is necessary. Therefore the purpose of this paper is to provide an extensive review of useful guidelines concerning modelling, simulation and result validation for the accurate performance of those analyses. Design/methodology/approach – Such guidelines are obtained from international steel design codes like Eurocode 3 and DNV, publications from experienced CAE engineers and renowned FE software companies like Ansys and Altair. Topics like mesh independence, the effect of the load sequence on the load bearing capacity and steel fracture criteria are underlined. Findings – Since the use of advanced FEA in the design of steel structures is becoming more and more traditional due to the increase of its competitiveness when compared to the use of ...

On a mixed time integration procedure for non-linear structural dynamics

Purpose – The purpose of this paper is to report the implementation of an alternative time integration procedure for the dynamic non-linear analysis of structures. Design/methodology/approach – The time integration algorithm discussed in this work corresponds to a spectral decomposition technique implemented in the time domain. As in the case of the modal decomposition in space, the numerical efficiency of the resulting integration scheme depends on the possibility of uncoupling the equations of motion. This is achieved by solving an eigenvalue problem in the time domain that only depends on the approximation basis being implemented. Complete sets of orthogonal Legendre polynomials are used to define the time approximation basis required by the model. Findings – A classical example with known analytical solution is presented to validate the model, in linear and non-linear analysis. The efficiency of the numerical technique is assessed. Comparisons are made with the classical Newmark method applied to the ...

Structural Assessment of Reinforced-Concrete Arch Underpasses Subjected to Vehicular Overloads

In most countries, the maximum dimensions and weights of vehicles that circulate on national roads and highways are legally reg- ulated. However, several economic activities imply the circulation of exceptional vehicles or overloads, raising concerns not only about road surface deterioration but also about the structural safety of the bridges that are to be crossed. In a previous publication, the authors proposed a methodology for permit checking of vehicular overloads applicable to girder bridge decks that involves a comparison of code design-load effects with those resulting from the special vehicle being analyzed. The software developed therein (Bridge Investigation for Special Trucks (BIST))performsastructuralsafetyanalysisof thebridgesthataretobecrossed,providingsimplifiedsafetyfactors associatedwithaparticular overload, based on which the permit decision is made. This paper presents an update of the BIST software that extends the permit-checking methodology to underpass arch bridges. The first part of the paper describes the general methodology of BIST and its application to RC underpass arch bridges. Extension of the methodology involved the development of two- and three-dimensional finite-element (FE) models of a wide range of arch underpasses that were validated and calibrated based on full-scale experimental tests and the assumption of a set of proper conservative simplifications. The second part of the paper presents a study carried out to evaluate the conservativeness and accuracy of the method proposed by comparing the safety factors provided by BIST with those obtained from numerical models of real arch underpasses subjectedtoawiderangeofrealvehicularoverloads.ThesafetyfactorsprovidedbytheBIST softwarewerealwaysconservativeandreasonably accurate,therebyvalidatingthemethodologyproposedandenablingfast,economical,andsafepermitdecisionmaking.DOI:10.1061/(ASCE) CF.1943-5509.0000410.