by Dr. Albert T Yeung, Civil Engineering
Mar 16, 2016
The research results of field and laboratory investigations on the engineering performance of the fir log scaffolding platform being used for slope site investigation in Hong Kong conducted by Ir Dr. Albert T. Yeung have been published by the Hong Kong Construction Association in a book.
Temporary fir long scaffolding platforms are often required for slope site investigation works. The structural members of the platform are fir logs of diameters ranging from 100 to 125 mm. The fir logs are held together by the friction between them at the connections and the tensions in nylon ties to construct the temporary platform. The platform is required to support the construction workers working on the platform, the drilling rig and associated equipment, the dynamic impacts inducted by in-situ tests, in particular the SPT, and the reaction load induced on the platform during maneuvering of site investigation equipment and extraction of temporary steel casing. In addition to dead loads and live loads, the platform has to resist other natural forces, such as wind load. In particular, the foundation of the platform can be scoured by rapid running water during heavy rainstorms. Nonetheless, there is no established procedure for the structural analysis of these scaffolding platforms built of fir logs. The lack of analysis procedure poses a technical difficulty for any Independent Checking Engineer to make a quantitative assessment of the stability and structural conditions of the platform, not mention to certify its structural and stability adequacy with reasonable professional skill and confidence, as required contractually by Government infrastructure construction contracts. The Study was conducted in an attempt to break through the impasse by a technically feasible and practical approach.
The test platform
A full-scale field evaluation of the engineering performance of an existing platform configuration was conducted at a test site of the Kadoorie Research Institute of The University of Hong Kong in Shek Kong, New Territories. The instrumented platform was loaded to support a live load of 10 tonnes, four times the normal live load on the platform. Laboratory tests were performed on nylon ties, fir logs and connection joints in the laboratories of the Department of Civil Engineering to develop a better understanding of the engineering behavior of these structural components of the fir log scaffolding platform. It has been concluded that the empirical rules of thumb for the design and the state-of-practice for the construction routinely adopted by experienced and skilled scaffolders are satisfactory. Acceptance criteria should be developed on the basis of these aspects for the best benefits of the industry, the safety of construction workers, and public safety.
Testing of the fir log
The purpose of the document is to provide practical guidance for practitioners undertaking the erection, use, alteration, dismantling and independent checking of these fir log scaffolding platforms. It is hoped that the book will serve as a standard reference for practitioners and promote continuing improvement to the industry.
Testing of longitudinal connection joint