Action effects in post-tensioned concrete box-girder bridges obtained from high-frequency monitoring

In this paper, an investigation into the action effect behaviour on two post-tensioned concrete highway box-girder bridges is performed. The focus is on the determination of the action effects induced in the bridges’ structural elements resulting from both traffic and thermal loading. Long-term monitoring campaigns were carried out, generating over 3 years of measured data. The strain cycles in the reinforcement bars were determined using measurements of the reinforcement bars themselves with strain gauges as well as indirectly through measurement of crack widths. The seasonal effects in the measurements are presented for both cases and thermal strain behaviour is described. The influence of the seasonal behaviour of action effects at an element level is used to demonstrate the differing fatigue damage throughout the year for specific elements. The concept of the average daily damage curve is introduced for fatigue verification based on short-term measurements to accurately account for the seasonal effects.