Performance-Based Wind Design for the Integrated Waste Management Facilities Phase 1 at Shek Kwu Chau, Hong Kong
Posted on March 30, 2022
The proposed Integrated Waste Management Facilities (IWMF) Phase 1 developed by the Environmental Protection Department of Hong Kong Government is the first such facility in Hong Kong that will adopt the state-of-the-art technologies to substantially reduce the bulk size of mixed municipal solid waste, to generate energy and to recover useful resources. The IWMF Phase 1 will comprise an advanced thermal incineration plant with a tall chimney tower and a mechanical sorting and recycling plant located at an artificial island to the south of Shek Kwu Chau in Hong Kong. An artist’s impression of the IWMF Phase 1 is shown in Figure 1.
Figure 1. An Artist Impression of the Proposed IWMF Phase 1 Development (image from https://iwmfhk.com/en/)
The proposed chimney tower has a complex aerofoil prismatic cross-section and will be equipped with a complex cladding system to achieve the visual appearance of a sail-like profile. The wind performance of this unusual and asymmetrical chimney tower cannot be predicted by the analytical approach provided in the “Code of Practice on Wind Effects in Hong Kong 2004” or other international wind codes. Especially the potential vortex shedding and localised wind effects on the cladding elements can only be assessed reliably through a wind tunnel study. Furthermore, as illustrated in Figure 1, there is significant topography near the project site and a topographical model wind tunnel study was undertaken to assess the impact of this topography on the wind climate at the site.
As emphasises in the recently released Prestandard for Performance-Based Wind Design (2019) by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE), “wind tunnel testing is the only approach consistent with reliable application of performance-based design principles and shall be used to determine the local wind pressures and global wind-induced structural loads and responses”. Similarly, in the ASCE Manual of Practice No. 143 it states: “Wind tunnel testing . . . is the only current method that allows the designer to determine aerodynamic characteristics for specific shapes and over a full range of wind speeds”. Hence, with the view of designing an optimised, economical and safe chimney tower, Windtech has been appointed by Arcadis (the design consultant) on behalf of Zhen Hua / Keppel Seghers Joint Venture (the main contractor) to carry out a purposely designed boundary layer wind tunnel study to accurately determine the wind loads for the structural and façade cladding.
The wind tunnel study was carried out in two stages to allow the design team to improve the efficiency of the structural and façade cladding systems by using the results from the first stage wind tunnel test to modify and optimise the external geometry, the structural arrangement, and the design of the façade cladding elements. The wind performance of the optimised design was then verified through the second stage wind tunnel test.
A pressure model wind tunnel test was adopted to determine both the structural wind loads through High-Frequency Pressure Integration (HFPI) technique and the façade cladding pressures. HFPI technique is the preferred technique in the Prestandard for Performance-Based Wind Design for the determination of structural wind loads and responses as it obtains a more accurate distribution of the mean and background responses.
It was expected the chimney tower will experience significant aerodynamic damping effects due to its height and shape, and an aero-elastic model wind tunnel study was also carried out to determine the amount of aerodynamic damping for the structure. The wind tunnel results illustrated that the chimney tower exhibits positive aerodynamic damping for the critical wind directions for the peak response along the X and Y axes, which helps to reduce the peak structural wind loads and allow the design team to further improve the efficiency of the structural system.
We would like to congratulate the team made up of Arcadis, China Harbour Engineering Company, Zhen Hua / Keppel Seghers Joint Venture, Aecom, Environmental Protection Department, and many others for delivering a great design for this unique and innovative project, which could not have been achieved without the esteemed team.
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