Damage Tolerant Design

The damage tolerant design approach deals with the problems that arise when one or more structural members lose their capacity to resist loads. This approach is based on the idea that explicit redistribution of the load path is possible in a redundant system. Damage-tolerant design originated from blast loading and progressive collapse limit state considerations.
The idea of damage tolerant design is that the structure shown here won't collapse even though several of its key columns are rendered useless.

The focus of the design is on the critical elements for a particular load path and the ability of the structure to redistribute loads. Damage tolerant design is expressed in European codes as a "progressive collapse" limit state, and is explicitly stated in Japanese seismic codes. In the U.S., a dual system such as a moment frame and braced frame or moment frame and shear walls can provide a "backup" system that provides the necessary redundancy.