The wind load capacity of two natural-draft cooling towers within a power plant located in a hurricane-prone region was analyzed for the as-designed and existing condition scenarios. The existing condition scenario incorporated a) repairs to columns, ring beam, and bottom 12 lifts of the veil and b) condition of the exterior of the veil based on an assessment of one of the cooling tower veils conducted by others. Columns, ring beam and veil of the natural-draft cooling towers were modeled using finite element software packages SAP and ANSYS. The model in SAP was linear elastic. The maximum wind speed obtained from the SAP analysis at which the structure appeared to be adequate was designated the design wind speed for the purpose of this study. The model using finite element software ANSYS, on the other hand, was a non-linear (material and geometric nonlinear behavior) failure analysis that provided wind speeds at ultimate wind load capacity. The maximum wind speed at which the structure was unable to resist additional wind pressure was designated the failure wind speed. Design wind speeds expressed as 3-second gust for the as-designed and the existing condition scenarios were found to be within the range of Category 3 hurricanes on the Saffir/Simpson scale. For wind speeds consistent with Category 3 hurricanes, extensive cracking and yielding of reinforcement could be expected on the windward face of the veil. Failure wind speeds expressed as 3-second gust obtained were found to be consistent with Category 5 hurricanes in the as-designed scenario and Category 4 in the existing condition scenario. Under these circumstances, catastrophic failure of the tower could be expected with crippling of the veil and concrete crushing below the veil throat. In the event of a Category 3 hurricane or higher, it would be prudent to evacuate the vicinity of the cooling towers.
展开▼
