In maintenance operations involving a vacuum tower approximately 50 meters in height, additional scaffolding is necessary. This scaffolding introduces increased wind loads, which, in turn, can elevate compressive stresses at the base of the tower. Such elevated stresses may lead to potential buckling or localized high stresses within the tower, as well as potential circumferential instability.
The primary objective was to evaluate whether the vacuum tower continued to comply with the Stoomwezen design code in light of the additional wind loads induced by the scaffolding. DRG was engaged to conduct this assessment, ensuring the analysis was completed efficiently and accurately.
Analysis Methodology
To ensure the vacuum tower’s compliance with the Stoomwezen design code, DRG carried out a comprehensive analysis. The process involved several critical steps:
Global Strength and Stability Check: The overall strength and stability of the tower under the influence of the additional wind load from the scaffolding were evaluated using design-by-rules calculations in accordance with the Stoomwezen design code.
Local Strength and Stability Check: The local impacts at the connection points where radial and torsion scaffolding supports were attached to the tower were analyzed using the FEMAP finite element program. This analysis involved checking the stresses induced by the scaffolding loads against permissible values.
Circumferential Stability Assessment: The stability of the tower under the simultaneous application of multiple radial supports on a single vacuum ring was examined using FEMAP’s stability module. This assessment involved determining the safety margin between applied loads and the buckling load threshold.
Results
The analysis confirmed that, even with the additional wind load from the scaffolding, the vacuum tower remained compliant with the Stoomwezen design code. Consequently, no modifications were required for the scaffolding design provided by the client. Additionally, evaluations of the foundation and anchor bolts indicated they were adequately capable of supporting the increased wind loads.
DRG also recommended several modifications to the scaffolding connection method. These changes were proposed to ensure that stress magnitudes at the connection points where scaffolding wind loads were transferred to the tower remained within acceptable limits.
Conclusion
DRG’s thorough analysis demonstrated that the vacuum tower, with the additional scaffolding loads, adhered to the Stoomwezen design code. The collaborative efforts between DRG and the scaffolding supplier facilitated a prompt and effective assessment, ensuring structural integrity and compliance with safety standards.
