Investigation on fluctuations of electrical resistance of permanent anchors (AGB2001/489)
Overview
Background & policy context:
Measurement of corrosion protection of tense anchors with insulated electrical resistance has been introduced in Switzerland in 1990. The experience with this measuring method are generally good.
However, there are always measuring results that give cause for debate. On the one hand occur in individual anchors on successive electrical resistance, the material safely or are system dependent. On the other hand, occur also unexplained variations in the measurements that need to be measured for technical reasons. Especially the second set of measurements often affects the confidence of builders in the method.
Objectives:
The main objective is to clarify the reason(s) for the fluctuations of the electrical resistances in certain anchors.
An additional desired goal is to determine if the successive drop of the resistance values at individual anchors is material technically or constructive or execution due to technical reasons.
Physical explanation for the causes of fluctuations of the electrical resistance of isolated, post-tensioned anchors.
Clarification of the causes for the gradual decline of electrical resistance of certain anchors.
Elaboration of rules for the execution and the valuation of the measurement of the electrical resistance of isolated permanent anchors.
Eventually proposal for improvements of anchor systems (construction, material, execution).
Methodology:
The research objectives to be achieved by three strategies:
a) Statistical evaluation of all available measurements of electrical resistance values of isolated anchors.
b) continuous measurements of the electrical resistance of three anchors with striking variations in the electrical resistance over a representative period with simultaneous registration of all possible influencing factors (temperature, humidity, etc.).
c) laboratory tests to those used for electrical insulation materials as a function of temperature, water content and humidity.
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