Performance of Electromagnetic Covermeters for Nondestructive Assessment of Steel Reinforcement

摘要

Covermeters are electromagnetic devices for locating steel reinforcing bars in concrete structures. An experimental study was carried out to compare the basic characteristics of two types of commercial covermeters (magnetic reluctance and eddy current). Experiments were carried out using single bars and multiple bars with various configurations. One group of single-bar tests studied the relationships between meter reading and cover thickness. Empirical equations were fitted to the data, and the values of the equation parameters were found to be relatively insensitive to the bar size. The other group of single-bar tests examined the relationship between meter reading and horizontal distance between the meter probe and the bar axis (offset). Data were fitted with a bell shaped, quadratic exponential function. The parameter characterizing the decay of the meter reading with offset was found to depend on the cover in a well-defined manner. The parameter was used to characterize the differences in the influence zones of the probes. Tests with multiple, parallel bars were conducted to determine the critical spacings below which the location of the individual bars could not be discerned and below which the meter amplitude exceeded the single-bar value. A simple summation model was used to predict the response based on the individual-bar response.