“Pocket-Monitoring” for the fatigue safety verification of bridge members in steel and reinforced concrete

The fatigue safety of the reinforced concrete deck slab of a sixty-year-old steel-concrete road viaduct as well as the riveted steel girders of a 130 year old railway bridge was questioned based on the results of conventional assessment consisting in "re-calculation" using traffic models given by codes. Subsequently, examination of the fatigue action effect was performed using data obtained from "pocket-monitoring" which is a rational and ready-to-use, cost-effective monitoring device. The "pocket-monitoring" concept for the determination of fatigue action effects in the two present cases revealed fatigue relevant stresses that were lower than the fatigue limit of the critical fatigue details. Consequently, there is no fatigue damage in these details, and the fatigue relevant element of the two bridge structures is safe for a next long service duration of unrestricted traffic loads. The large discrepancy in the results between the presented monitoring method and conventional assessment is attributed to over-conservative code provisions.