Goscote House: Top Down Demolition of LPS Structure

Scope of Work

The demolition of this structure required a range of temporary works design and specialised demolition engineering.

The temporary works and demolition engineering delivered by Andun included:

Ballasted Tower Crane Base – Design and CAT 2 check of the tower crane base with a mini pile solution.

Plant Justification – Calculations to justify the plant operating on the slab and detailing of backpropping. 

Design Panel Propping arrangements – Raking propping to ensure the lateral stability of wall panels and vertical propping to support floor slabs once released and ready to lift.

Panel lifting assessments – Structural assessment to ensure the stability of each panel type during the lifts and checks on lifting equipment.

Specification of proprietary toast rack – The rack was used to store the removed panels at ground level standing ‘on end’ to save room on the congested site. The rack was also designed to enable mechanical demolition of the panels on the rack.

Global Stability Checks – Engineering assessments were conducted to plan and detail sequence and verify stability at each phase.

Andun Engineering Consultants also conducted scaffold and good hoist checks as part of the temporary works package delivered. 

Site Constraints and Challenges

The key challenge was the building being an LPS structure.

LPS structures come with the risk of latent defects and lack of structural robustness, which can lead to disproportionate/pancake collapse if not appropriately planned. 

These risks were key drivers for the demolition methodology and required extensive site investigation to determine panel-to-panel connections and the capacity of the structure. We were able to understand the structural form of the building through the site investigation, which enabled us to predict the behaviour during demolition.

In addition to the considerations required for any LPS structure, the site also had a small site footprint with residential properties and a health centre on the boundary.

Demolition Methodology

The chosen demolition methodology was a floor-by-floor deconstruction; removing panels sequentially using a tower crane. Supplementary mechanical demolition was available using small plant operating on the slab.

First, the lateral and vertical propping was installed before the tower crane removed the slabs and walls in sequence. This process is repeated floor by floor until the structure is reduced to the point when demolition can be completed by breaking down the structure using a large excavator operating from ground level.

The panel removal strategy of the floor-by-floor demolition methodology can be seen in the video above.  

Tower Crane Base Design

Toast Rack Design

Additional Resources