Innovative technique for identification of prestressing tendons layout in post-tensioned bridges using a probe with MEMS accelerometer

Abstract

Post-tensioned concrete bridges are currently often constructed engineering structures. In this type of bridges it is crucial that geometrical layout of prestressing system complies with the design requirements. Unfortunately, major errors still occur during assembly of tendon routes. This has often negative effects. In a local aspect, it may cause a local damage, such as spalling of concrete cover. In a global aspect, prestressing may produce distribution of forces in the bridge structure different from the expected. That is why numerous methods have been developed to control the accuracy of executed tendon routs. Some of them, e.g. geodetic measurements with levelers, require direct access to tendon sheaths. Other methods, which can be used after casting of concrete (mainly NDT methods) have a series of resolution, efficiency and accessibility limitations. Hence, the paper presents a proposal of an alternative method for control of tendons routing using a special probe with Micro Electro-Mechanical Systems capacitive accelerometer. The paper presents a concept of tests performed with the probe, evaluation of the probe application in the view of a random process and finally assessment of the results obtained with the use of the constructed measurement system in trial laboratory conditions.

Keywords:

• Post tensioning
• bridges
• concrete
• cables & tendons
• non-destructive testing
• random processes
• assessment
• measurement