written 5.0 years ago by
teamques10
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modified 5.0 years ago
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- The philosophy of the limit state method of design represents a
definite advancement over the traditional design philosophies.
- Unlike WSM which based calculations on service load conditions
alone, and unlike ULM, which based calculations on ultimate load
conditions alone, LSM aims for a comprehensive and rational
solution to the design problem, by considering safety at ultimate
loads and serviceability at working loads.
- The LSM philosophy uses a multiple safety factor format which
attempts to provide adequate safety at ultimate loads as well as
adequate serviceability at service loads, by considering all possible
'Limit State'.
Limits States
A limit state is a state of impending failure, beyond which a structure
ceases to perform its intended function satisfactorily; in terms of either
safety of serviceability i.e. it either collapses or becomes unserviceable.
There are two types of limit states:
Ultimate limit states (limit states of collapse):- Which deal with
strength, overturning, sliding, buckling, fatigue fracture etc.
Serviceability limit states: - Which deals with discomfort to
occupancy and or malfunction, caused by excessive deflection,
crack width, vibration leakage etc., and also loss of durability etc.