http://hydroreview.hotims.com RS #41
1. Calculating the strain that corresponds to the reported maximum
vertical defection of 23 mm at beam A3; then
2. Calculating the necessary load to reach the strain level from Step 1.
A strain of 0.13% was found to be required to cause a vertical
deformation of 23 mm at the center of beam A3.
For the deformation load estimation, the maximum operating load
was incrementally increased to reproduce the observed confguration.
It was determined that for a vertical defection of 23 mm, a load 2. 4
times the maximum operating load is required.
To determine the acceptability of the spillway gate for protection
against plastic collapse, a FFS assessment was carried out.
An elastic-plastic stress analysis was performed on the as-deformed
model with corrosion damage. Te acceptability of the spillway gate
using an elastic-plastic analysis was determined by satisfying the
following criteria: global collapse and local failure.
Global collapse criterion
To satisfy the global collapse criterion, the fnite element model was
subjected to a load factor of 3. 6 and is required to reach the converged
solution. Te load factor was determined based on Equation 1, in which
the remaining strength factor (RSF), defned as the ratio of the limit
load of the damaged component to the limit load of the undamaged
component, is 0.9 (see Figure 2 on page 36).
Load factor coefcient ( ) = 4.0 x RSF
Te as-deformed model of the spillway gate subjected to a load
factor of 3. 6 reached a converged solution. Terefore, the as-deformed
model with corrosion damage satisfed the global criterion for protection
against plastic collapse following the ASME FFS- 1 guidelines.
Local failure criterion
In accordance with the local failure criterion guidelines found in the
ASME FFS- 1 standard, the model that included the permanent
deformation and surface corrosion is required to satisfy the failure
criterion against the applied loading condition with a load factor of
1. 5. High-stressed locations were identifed for the assessment.
For the component to satisfy the local failure criterion, the total
equivalent plastic strain must be less than the limiting triaxial strain
(εL). Total equivalent plastic strain at the assessed locations was
extracted from the results of the elastic-plastic analysis with a load
factor of 1. 5.
Te limiting triaxial strain was calculated based on the guidelines
Deflection was discovered at the bottom of Spillway Gate No. 2 at the
Karapiro facility in late 2014.
Table 1: Thickness measurement results
Plate nominal thickness: 15.875 mm (5/8 in.)
Location Thickness Readings (mm) Minimum Thickness Readings (mm)
A 11. 42 11. 36 11.71 11. 36
B 13. 24 13. 15 13. 7 13. 15
C 14.63 14.68 14. 9 14.63
D 15.73 15.82 15. 9 15.73