Field Investigation Results

There were no visual observations made of the roof system that indicated that there has been a loss of integrity. There were observations made that selected columns have experienced some corrosion – related deterioration, but were not impacting the roof’s integrity.

Visual Observations

Prestressing Wires.

Figure 7 shows a typical condition of the prestressing wires exposed at each tendon opening. The wires generally appeared to be in good condition with only evidence of minor surface corrosion. The dark color of the wires is discoloration principally from the mastic. This minor surface corrosion did not appear “fresh” as would have been evidenced by a bright orange corrosion product. There were no significant corrosion pits indicative of area loss.

The paper wrap, which acts as the unbonded PT duct, has experienced some deterioration as observed in Figure 7. The bitumen mastic that was used to protect the wires from corrosion was variable in thickness and coverage. However, as long as the roofing material prevents water intrusion, the deterioration of the paper duct and presence variable mastic is not considered overly significant.

Figure 7. Typical condition of prestressing wires.


The condition of the exposed coupler along the strong axis tendon is observed in Figure 8. There was little evidence of corrosion of the metal duct that was split open to observe the coupler, threaded rod or anchors. Also note that the “buttons” of each wire are intact and show no evidence of corrosion.

Figure 8. Condition of exposed coupler.


Figure 9 shows the representative condition observed at the exposed anchorages of the PT tendons. The field investigation at the selected anchorages clearly indicated that there has been no significant corrosion of the prestressing wires, bearing plate or transfer plates.

Figure 9. Typical condition of exposed anchorage.