Abstract
ASME STS-1 provides guidelines for the design, fabrication, and erection of steel stacks, however there are no specific guidelines for the assessment of guyed steel stacks already in service. For example, drift (i.e., displacement) acceptance criteria are only provided for initial installation. Furthermore, existing literature regarding the proper re-tensioning of guy wires is scarce or nonexistent. This procedure is particularly important for stacks that experience significant thermal growth. This effect is further exacerbated by differential wind cooling effects on both the guy wires and on the stack itself. This paper investigates the effect of guy wire spacing, position, tension pattern, and operating and shutdown tension settings on the structural response of a guyed steel stack. Field thermography readings, ultrasonic testing (UT) thickness data, guy wire tension measurements, and laser scans are used to refine a finite element model of the stack. Using elastic-plastic nonlinear “pushover” analyses based on API 579 – 1 Level 3 fitness-for-service methodology and FEMA 356 rehabilitation guidelines, a performance-based methodology resulting in a “watch circle” approach for lateral displacement is provided to guide fitness-for-service assessments and mitigation implementation. Example application of this methodology and recommendations regarding guy wire tensioning are provided for an incinerator stack with 9 guy wires (3 levels – 3 guy wire configuration).
