Some structural aspects of top-down demolition of concrete buildings

Abstract

This paper describes the 'top-down' demolition process and then explores the engineering challenges associated with this and how they are commonly addressed. The top-down process as commonly used in UK demolition practice is to support a relatively small plant on the existing floor slabs and demolish the building by using this plant, enclosing the structure in scaffold and disposing of material through vertical drop zones. The main engineering challenges are the assessment of the existing floor plates for the loads from the demolition process (debris, access and plant) and maintenance of overall building stability. The use of larger machinery can be beneficial but requires load-testing processes to validate overloading, with possible reference to failure study and back-analysis. The load-testing approach has potential shortcomings as current floor-testing approaches use relatively high factors against failure but test relatively small areas, generally in flexure rather than shear. Some failure mechanisms are described, and suggestions are made as to what testing could have been adopted to check for these. Notation

Editorial

“…The paper by Lohmann (2018) covers the top-down demolition of buildings in which the floor loads due to debris and plant, and the change in structural form due to demolition create uncertainty. This is controlled destruction as opposed to uncontrolled destruction due to natural hazards.…”