Relating Corroded Seven-Strand, Posttensioned Cable Cross-Sectional Properties to Load Capacity

Abstract

Multistrand anchors have seen widespread use, providing strength and stability at hydraulic Corps facilities. However, these steel tendons are subject to strength reduction as an effect of corrosion. Methods for evaluating the corroded cable strength do not exist to accurately estimate the time until tendon cables would have to be replaced (at great expense). The following five research tasks are used to address this deficiency: laboratory accelerated corrosion; pull-tests on pristine and laboratory corroded cables; optical scanning; data collection correlated with cross-sectional properties of cables; and development of a method to relate this data to the field. The pull-tests provide measured capacities for seven-strand, posttensioned (PT) cables. An optical scan of the corroded cables provides cross-sectional properties of individual wires within the pulled cables. Trendlines are established for the related peak cable capacities and cross-sectional properties in an effort to determine their correlations. Trendlines for minimum wire area and second-moment short axis diameter are found with low error, making them good predictors of loaded cable capacity. This pull-test dataset has been related back to cable failure in the field, assuming a linear rate of corrosion loss for the cross-sectional properties and required PT capacity.

Corroded Anchor Structure Stability/Reliability (CAS_Stab-R) software for hydraulic structures

“…When the multi-strand anchor cables lose enough material to reduce the capacity of the cable below the tension force that was applied at installation, the anchor will fail, thereby reducing the stability of the structure. A series of unprecedented pull-test experiments conducted at the Engineer Research and Development Center (ERDC) with results published by Ebeling et al (2016) and Haskins et al (2016b) provided statistical relationships of reduced cable capacity to the reduced cross-section area and to the cross-section minimum short axis diameter of failed cable strands with varying levels of corrosion.…”

“…A series of experiments were conducted at the ERDC in 2013 to measure the loading capacity of seven-strand wire cables. The laboratory experiments and statistical processing of the resulting (reduced) strength data were discussed in Ebeling et al (2016) and summarized in Haskins et al (2016b). The seven strands were arranged with a center "king" wire surrounded by six "outer" wires that spiraled along the length of the king wire.…”

Strength reduction curves for corroded seven‐wire strands

“…The behaviour of corroded strands, collected from existing bridges, has been studied in [1]- [4]. Experimental results of artificial corroded strands are available in [5]- [7], where also analytical modelling of corrosion introducing a damage constitutive model is reported. In addition, [8] introduces a constitutive model for corroded strands, taking into account the pit type morphologies proposed by [1] comparing the results of the model with experimental tensile tests.…”