Page - 710 - in Book of Full Papers - Symposium Hydro Engineering

Owners who can tolerate a higher risk may elect for either partial replacement, or indeed for no further post-tensioning at all, and some type of “observation” strategy. Step 5. Once the “High Risk” projects have been evaluated thus, then the same process can be applied to the “Moderate Risk” projects. Such projects may also afford the possibility of conducting lift-off tests provided the free length is sheathed, the anchor head is accessible, and the field testing will not adversely affect the structural performance of the locking assembly (especially for wedges for strands) or its corrosion integrity. This process is summarized in the flow diagram (Figure 2) which focuses on high risk legacy anchors. Thus, a project which scores “high-high-high-high- high” in each risk category will have a more urgent need of further action/evaluation, than one which scores, for example, “high-high-high-moderate- low.” This figure only shows the flow path for the highest risk anchors. Fig. 2 Flow chart for screening portfolio risk assessment of aging anchors. REFERENCES [1] BRUCE, D.A., AND J. WOLFHOPE (2007). “Rock Anchors for North American Dams: The National Research Program Bibliography and Database,” Institution of Civil Engineers, Ground Anchorages and Year of installation? Up to 1998 High Is the free length sheathed? No High Quality and intensity of pregrouting? None/poor High Quality of head protection? None High Importance of Anchors to Dam Stability Vital High Important High Redundant Low Grease High Concrete Moderate Excellent Moderate Yes Moderate 1989-1998 Moderate 1999 Onward LowRisk 1 Risk 2 Risk 3 Risk 4 Risk 5 STEP 1 STEP 2 STEP 3 710