Design Philosophies of Steel Structures is for achieving the design objectives, the design shall be supported characteristic values for material strengths and applied loads (actions), that take into consideration the probability of variations in the material strengths and in the loads to be supported.
The characteristic values shall be based on statistical information, if available. wherever such data isn’t available, these shall be based on expertise.
Design Philosophies of Steel Structures specifies that the design values are derived from the characteristic values through the use of partial safety factors, each for material strengths and for both. in the absence of special concerns, these factors shall have the values given in this section the material the fabric, the kind of load and the limit state being considered. The dependability of design is ensured by satisfying the requirement:
Design action ≤ design strength
Design Philosophies of Steel Structures
There are 2 types of limit state,
a) Limit state of strength
b) Limit state of serviceability
a) Limit state of strength
The limit states of strength are those related to failures (or imminent failure), under the action of probable and most unfavorable combination of loads on the structure using the appropriate partial safety factors, which can endanger the security of life and property. The limit state of strength includes:
a) Loss of equilibrium of the structure as an entire or any of its components or elements.
b) Loss of stability of the structure (including the impact of sway wherever applicable and overturning) or any of its components together with supports and foundations.
c) Failure by excessive deformation, rupture of the structure or any of its components or elements,
d) Fracture because of fatigue,
e) Brittle fracture.
b) Limit state of serviceability
The limit state of serviceability include:
Deformation and deflections, have an effect on|which can} adversely have an effect on the appearance or effective use of the structure or might cause improper functioning of apparatus or services or may cause damages to finishes and non-structural members.
a) Vibrations in the structure or any of its parts creating discomfort to individuals, damages to the structure, its contents or which can limit its purposeful effectiveness.
Special consideration shall tend to systems at risk of vibration, like massive open floor areas free of partitions to make sure that such vibrations are acceptable for the supposed use and occupancy.
b) Repairable damage or crack because of fatigue.
c) Corrosion, durability.
d) Fire.