Interpretation of the preannouncernent behaviour of prestressed concrete bridges by applying the "crack-before-collapse-criterion" - Proposals for further proceeding with critical bridges

Due to extending lifetimes of prestressed concrete bridges the importance of the durability increases. With numerical calculations and investigations of structures according to DIN 1076 it is intended to recognize and prevent possible failure of the structures in time and to minimize the risk for the owner during the remaining lifetime. Especially older prestressed concrete bridges with tension wires endangered to stress-corrosion-cracking need to be numerically investigated and judged concerning their preannouncement behaviour according to the "crack-before-collapse-criterion". According to the numerical results of the "crack-before-collapse- criterion" and supplemental calculations it is possible to evaluate the existing risk for the owner concerning failure of the structures. The design of the concerned structures will be discussed. Based on results of performed investigations proposals for further proceeding with older critical bridges will be given along with recommendations how to limit the remaining risks. For newer bridges the analysis according to the "crack-before-collapse-criterion " is a measure of a sufficient sturdiness.