Repair of prestressed concrete bridges : stress distribution and prestressing losses

Abstract: Today we are faced with the problem of a growing number of existing prestressed concrete bridge structures that are in need of repair work. With prestressed concrete in particular, it is difficult to anticipate how the stress distribution in an existing structure will be affected by the removal or addition of concrete due to repair work. With the impending implementation of Eurocode in Europe, the development of suitable calculation methods on how to deal with this problem in accordance with the standard scripture, are compelling. This thesis is part of a larger project, which will develop suitable methods for the evaluation of damages on bridges, and suitable repair work, in accordance with Eurocode. This thesis investigates the effect of repair work on a prestressed concrete bridge beam. The repair work constitutes the removal of old and/or damaged concrete and the addition of new concrete to repair the damage. The consequences of the repair work is investigated and presented by looking closely at the stress distribution in the cross section, and the losses in prestressing over a time-period of 100 years from construction. Concrete creep and shrinkage are taken into account, as well as prestressing steel relaxation. The results indicate that quite extensive repair procedures can be carried out without severe consequences to the structure. The time of the repair procedure is the most crutial to the structure, as large changes in stress are obtained when concrete is removed and replaced. The detrimental effects on the structure are more prominent the more extensive the repair procedure is.