Work performed
- Structural inspection of the collapsed section and desk study
- Development of the methodology
- Stabilization
- Demolition and clearing of waste material
Scope
A cement manufacturer suffered property damage when one of its cement mill roofs collapsed. As part of the emergency response, TALOS was engaged to inspect the collapsed section and the remaining roof, prevent further collapse and remove the debris.
A drone inspection was the safest way to approach a structure with difficult access and potential hazards, providing photographic evidence from every angle. The data collected led to the proposal to approach the collapsed section from a mobile crane with a man-basket.
Access
Because of the high risk, the structure was first approached by drone, which allowed the technical team to plan where to start and which areas to avoid. A man-basket was used to approach the collapsed section, while a second mobile crane with chain and nylon slings removed the debris.
Solution
TALOS conducted a visual inspection of the collapsed section and analysed the structural integrity of the remaining roof. The inspection confirmed that the primary support component had to be supported and braced: a 250 t mobile crane was stationed supporting the girder truss, while scaffolding supported the other trusses and protected the mill's essential equipment.
Technicians approached in the man-basket while a rigger directed the second crane; loose sections were attached and hoisted away, taking great care not to pull the wrong sections and disturb the equilibrium, which could have caused a second collapse. Large sections were cut to size with torches or angle grinders, and a wheel loader and dump truck kept the plant clear throughout.
Results
The TALOS investigation identified the most probable cause of the collapse: accumulated cement on the roof adding dead weight, combined with modifications to the roof trusses and bracing made when large equipment was installed inside the mill building. Cement plant roofs should be cleaned periodically, and new equipment installations must not compromise the structural integrity of the building.