Pre-stressed and Post Tensioned Concrete
Designers Knowledge Base
In specifying the use of pre-stressed or post tensioned concrete in his design the designer should be aware of, and assess the risks from, the following principal hazards.
Hazards and risks
- falls from height: operatives falling during fixing or stressing operations
- possibility of collapse and crushing: caused by the instability of units during temporary storage; duct support failure causing duct to float or strand breakages during stressing. Considerations should also be given to the hazard of collapse of elements during demolition due to inadequate support or failure of compression zone.
- unsafe access to work area and unsafe place of work
- falls of materials or tools from height
Consider the following; the need to protect materials, to provide safe access for fixing and stressing and the provision of stressing protection. There should be a grouting procedure, handling points should be provided and transport considered. Consider the hazards of demolition. The design assumptions should be clearly stated.
Possible design options
- consider element manufacture off site
- provide adequate design guidance to contractor
- ensure design sequence allows for safe access
- design duct supports
- ensure adequate anchorage spacing and avoid dead-end anchorages
- specify installation and inspection procedures
- specify protection of materials, installation and completed work
- detail control procedures before, during, and after tendon stressing