Temporary Works Toolkit. Part 19: An introduction to the demolition of large stuctures

Many modern office towers are of steel-composite constructione. However, the lightweight nature of steel means a lower modal mass – and vibrations from active sources (e.g. footfall) need be considered carefully during the design stage. This article discusses vibration performance and mitigation based on recent experience in Singapore.

Last month’s article in the series covered the theory and detailed methods recommended for calculating backpropping loads. This article continues by discussing some of the design issues and preconceptions related to backpropping, and gives worked examples.

The permanent works designer (PWD) has a major influence on the temporary works and can, for example:

• eliminate temporary works, e.g. through the use of steel decking rather than timber falsework
• minimise the use of temporary works, e.g. by using the permanent capping beam as a waling in basement construction
• design the permanent works so that simple temporary works solutions can be used.