Determination of Prestressing Using Crack Reopening Method

Abstract

The level of residual prestressing has a decisive impact on the behaviour of prestressed concrete structures. Therefore, the determination of this crucial factor is a very important but also difficult task. Nowadays, engineers and researchers intend to verify a lot of various techniques which provide the value of residual prestressing force. This paper is focused on the application of the Crack reopening method performed on precast prestressed concrete beams with bonded and unbonded prestressing. The selected method is usually considered one of the Structural response methods. Hence, this approach is based on the observation of the structure’s response to known external load which is applied to it during the testing. In this study, normal stresses and deflections were recorded and evaluated. The analysis aimed to find the level of load that implies the reopening of an already existing crack. Subsequently, the value of the so-called decompression load enabled the calculation of residual prestressing force in precast beams. To avoid the contribution of shear stresses, the four-point bending scheme was chosen. Finally, the obtained results were compared to values provided by the force sensor located in the anchorage area. This sensor monitored real-time prestressing force value, so the evaluation of performed method was precise. The analysis proved, that this method can be an effective tool for civil engineers in practice. However, some issues can be found during its application.