Jan Arve Øverli

Experimental and numerical investigation of slabs on ground subjected to concentrated loads

An experimental program is presented where a slab on ground is subjected to concentrated loading at the centre, the edges and at the corners. Analytical solutions for the ultimate load capacity fit well with the results obtained in the tests. The non-linear behaviour of the slab is captured by performing nonlinear finite element analyses. The soil is modelled as a no-tension bedding and a smeared crack approach is employed for the concrete. Through a parametric study, the finite element model has been used to assess the influence of subgrade stiffness and shrinkage. The results indicate that drying shrinkage can cause severe cracking in slabs on grade.

Reliability Assessments of Large Reinforced Concrete Structures Using Non-linear Finite Element Analyses: Challenges and Solutions

The use of non-linear finite element analyses for reliability assessments of reinforced concrete structures has gained much attention during the last decade, particularly with the introduction of semi-probabilistic methods in fib Model Code 2010. In a recent PhD project, the topic has been elaborated on with a special focus on the applicability to large concrete structures like dams and offshore platforms. Such structures usually require the use of relatively large solid finite elements and large load steps in order to reduce the computational cost. In this paper, the main findings from the project, including a proper material model for concrete, quantification of the modelling uncertainty and treatment of uncertainties from different sources, will be discussed. Unanswered questions that has been raised during the project will be highlighted.

Non-linear finite element analyses applicable for the design of large reinforced concrete structures

Abstract In order to make non-linear finite element analyses applicable during assessments of the ultimate load capacity or the structural reliability of large reinforced concrete structures, there is need for an efficient solution strategy with a low modelling uncertainty. A solution strategy comprises choices regarding force equilibrium, kinematic compatibility and constitutive relations. This contribution demonstrates four important steps in the process of developing a proper solution strategy: (1) definition, (2) verification by numerical experiments, (3) validation by benchmark analyses and (4) demonstration of applicability. A complete solution strategy is presented in detail, including a fully triaxial material model for concrete, which was adapted to facilitate its implementation in a standard finite-element software. Insignificant sensitivity to finite element discretisation, load step size, iteration method and convergence tolerance were found by numerical experiments. A low modelling uncertainty, denoted by the ratio of experimental to predicted capacity, was found by comparing the results from a range of experiments to results from non-linear finite element predictions. The applicability to large reinforced concrete structures is demonstrated by an analysis of an offshore concrete shell structure.