Limit state principles for soil reinforcement are of two types. These are:
a. Ultimate limit state
b. Serviceability limit state
Here we will discuss about ultimate limit state. In the next post we will learn about serviceability limit state. Ultimate limit state:
This principles includes
-similar other types of structural failure
This states are reached for certain modes of failure. This failure occur when restoring forces become less or equal to disturbing forces.
The collapse that are considered in limit state, should be opposed by sufficient safety margins. The safety margins are:
-Partial material factors
-Partial load factors
Partial factors assumed should be equal or greater than unity.
Disturbing forces are increased by using prescribed multiplication factors discussed above to derive design load.
Material factors, prescribed, are used to derive desire strength. Here restoring forces are decreased by dividing actual material strength by material factors.
It is believed that when design strength equal to or greater than design loads, sufficient safety margin is provided against the collapse assumed in ultimate limit states.