CE 3320 Design of steel structural systems Faculty: Arul Jayachandran 1
Load Simplification
q kN/m2
qL N/m
qB N/m B L
Purlin design q kN/m2
S-Purlin spacing
L y
Sag rod design
L y
Rafter Design
Q kN/m2
Evolving a pre-engineered Building system
Loads on PEBs • Dead
Loads
Dead load is the weight of all permanent construction materials, such as roofing, framing, and other structural elements
Normally: 50 to 100 kg/m2
Loads on PEBs •
Collateral Loads or Super-imposed dead loads (SIDL)
Collateral or superimposed dead load is a specific type of dead load that
includes the weight of any materials other than the permanent construction. It may account for the weight of mechanical ducts, pipes, sprinklers, electrical work, future ceilings, and reroofing.
Ceilings: 5 to 15 kg/m2
Lighting:
0.5 to 5 kg/m2
Heating, ventilating, air conditioning ducts : 5 kg/m2
Sprinklers:
7.5 kg/m2 for dry systems, 15 kg/m2 for wet systems
In Total
25- kg/m2 collateral load is sufficient to account for the effect of most superimposed dead loads
Loads on PEBs • Live
loads
This load is supposed to due loads that may move.
Normally: Access provided
75 kg/m2
Access not provided 50 kg/m2
Loads on PEBs • Wind
Loads
IS:875 – Part 3 •
Earthquake Loads IS:1893 – Part 1
When do we do dynamic analysis? When the natural frequency of a structure is very close to the excitation frequency then pre“dynamic amplifications” becomes dominant and hence dynamic analysis is needed If the natural frequency is well away then we can treat them by “equivalent static” analysis. For wind sensitive structures the critical frequency is 1Hz
