Interactive assessment of masonry arch bridges

The paper outlines an interactive approach for masonry arch bridge assessments which applies 'first principles' and allows engineers to retain control on assumptions and 'feel' towards convergence whilst utilising computer's power for solving equations which arise at each stage. This is achieved by manual intervention between computer iterations in which plastic hinges are progressively inserted in the arch ring by altering the input file for the elastic analysis program. Such an interactive approach requires a little longer time being spent by the engineer than using a fully computerised approach. This is, however, still better than engineers not fully appreciating the underlying assumptions and/or not controlling the 'workings' of the analytical method which can lead to errors of interpretation with possible professional liability consequences.