ABSTRACT
The paper presents features of procedures dedicated to assessment of masonry arch bridges (MAB). Two essentially different approaches, i.e. based on the Ultimate Limit State and the Limit Analysis, commonly used in load carrying capacity evaluation of various structural systems are described and their potential and effectiveness in application to MAB are discussed. Various formulations of the methods are presented depicting fundamental differences between them. Basic features of the methods are explained in relation to characteristic structural behaviour of masonry arch barrel determined mainly by its non-tensile-resistant material. Limit criteria governing the methods are defined and commented. The margin of safety that is provided by means of safety factors (partial or global ones) within the corresponding methods is presented and used to show essential differences between the approaches. The theoretical considerations are supplemented with several case studies of advanced numerical analysis of bridges with different geometry realistically simulating behaviour of the structures at the ultimate loading. Carried out analyses are based on finite element models taking into account all crucial features of the bridges including nonlinear material properties as well as geometrical nonlinearities related e.g. to contact problem between structural components. Results of the simulations are referred to criteria of the theoretical assessment methods revealing their advantages and drawbacks in case of such structures. The work is summarised with conclusions giving basis for determination of general assessment procedures that could be included in still missing modern codes for evaluation of existing masonry arch bridges.
