Ryan_Berry
Member
Hi everyone. I am bored, I know that is sad on a friday night, so thought I would see what everyones views are on the application of limit state approach to scaffolding.
What are everyones thoughts on the application of limit state approach to the design of scaffolding as this ties in with the Eurocodes system which we have adopted (albeit not fully)? The eurocode suite is based fully on limit state and cannot be adopted effectively without the use of EU 0.
I am just doing some designs (trials if you like) to see what the impact will be on the design of scaffolds using limit state when compared with permissible stress. The results seem to be going in favour of LS at the minute. "The permissible stress method is not used widely in most engineering disciplines due to overcomplication of the design process and also leads to more conservative solutions. In addition to this, the quality of material production has increased and safety margin decreased. The assumption that stress is proportional to strain became unjustifiable making it impossible to estimate the true factors of safety". As suggested by Arya C. ‘Design of Structural Elements: Concrete, Steelwork, Masonry and Timber Design to British Standards and Eurocodes’. 2nd Edition.
On the other hand, Limit state approach is a more comprehensive approach than permissible stress and load factor approaches. It is a combination of the two which takes account of both in appropriate ways. Most modern codes of practice require limit state approach, including BS EN12811-1. We do not engineer scaffolds to limit state as many published figures for scaffolding materials are given in permissible stress values giving a safety factor of 1.65 to 1, as opposed to BS EN 12811-1 that requires limit state approach. Limit state applies a partial safety factor of 1.5 to 1 for live loads and 1.1 for dead load giving a single factor of 1.5 x 1.1 = 1.65 similar to permissible stress.
The consensus of most seem to be against the idea but if adopting it can assist the industry as an whole then maybe it isn't such a bad thing - just a different look. I think it is long overdue as it is the only area of engineering which has not adopted it yet. Even timber, which is not homogeneous, uses the limit state approach. I personally think that limit state would bring us into the modern world of engineering and even save some kit for the scaffolders.
what are your thoughts on this?
What are everyones thoughts on the application of limit state approach to the design of scaffolding as this ties in with the Eurocodes system which we have adopted (albeit not fully)? The eurocode suite is based fully on limit state and cannot be adopted effectively without the use of EU 0.
I am just doing some designs (trials if you like) to see what the impact will be on the design of scaffolds using limit state when compared with permissible stress. The results seem to be going in favour of LS at the minute. "The permissible stress method is not used widely in most engineering disciplines due to overcomplication of the design process and also leads to more conservative solutions. In addition to this, the quality of material production has increased and safety margin decreased. The assumption that stress is proportional to strain became unjustifiable making it impossible to estimate the true factors of safety". As suggested by Arya C. ‘Design of Structural Elements: Concrete, Steelwork, Masonry and Timber Design to British Standards and Eurocodes’. 2nd Edition.
On the other hand, Limit state approach is a more comprehensive approach than permissible stress and load factor approaches. It is a combination of the two which takes account of both in appropriate ways. Most modern codes of practice require limit state approach, including BS EN12811-1. We do not engineer scaffolds to limit state as many published figures for scaffolding materials are given in permissible stress values giving a safety factor of 1.65 to 1, as opposed to BS EN 12811-1 that requires limit state approach. Limit state applies a partial safety factor of 1.5 to 1 for live loads and 1.1 for dead load giving a single factor of 1.5 x 1.1 = 1.65 similar to permissible stress.
The consensus of most seem to be against the idea but if adopting it can assist the industry as an whole then maybe it isn't such a bad thing - just a different look. I think it is long overdue as it is the only area of engineering which has not adopted it yet. Even timber, which is not homogeneous, uses the limit state approach. I personally think that limit state would bring us into the modern world of engineering and even save some kit for the scaffolders.
what are your thoughts on this?