Non Destructive Evaluation of Bridges

A bridge is a very complex mega structure with many different components composed of different materials. NDE plays a very important role in the testing of bridge structures in service. Non-destructive evaluation (NDE) has offered unprecedented utilize for bridge management body to monitor structural health. NDE of bridges is based on multiple non-destructive testing methods, and the final conclusion is a combination of those evaluations. In most of the cases, the response of one evaluation method implies the presence of a defect among the multiple defects to which the evaluation method is sensitive. There are lots of nondestructive evaluations available for concrete inspection, but, unfortunately a few number is in practical use in structural evaluation. The commonly used NDE methods for deck evaluation are visual inspection, chain drag, Impact echo, Ground penetration radar, Infrared thermography and Half-cell potential. None of these methods can provide all required damage information alone, because evaluation methods are of different principles (acoustic, electromagnetic, electrochemical) that restrict a degree of capability in evaluation addressing different types of damage in attention. Non-destructive techniques (NDT) can assess the state of health of structures, but they can only provide an indirect approach to their performances.   Combination of NDE is required because, in majority of cases, response of one evaluation method does not specify particular damage; rather it provides prediction among a number of defects to which the signal is sensitive. While one evaluation method fails to screen a particular type of damage, the other could easily identify it. In addition, the use of third evaluation method can yield quantitative evaluation for the damage. That is why combination of NDE is recommended to bring reliability in assessment in conjunction with detailed information of defect or crack. However combination of NDE does not refer to employ all available...