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ResponseModification Factor
Prepared by:
Version 1 -Apri l 2011
Ahmed Shaban
Refat Taha
Sulaiman Nayef
Ezzat Hassan
University of Cairo at EgyptWith the support of the
Dr. Osman Ramadan
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Response Modification Factor
1 - Introduction and Objectives
2 - Over-Strength Factor , Rs
3 - Ductility Reduction Factor , R
4 - Summary
5 - Reference
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Response Modification Factor
1 - Introduction and Objectives
2 - Over-Strength Factor , Rs
3 - Ductility Reduction Factor , R
4 - Summary
5 - Reference
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Code Philosophy for Earthquake-Resistant
Design
Objective: -Prevent collapse in the extreme
earthquake likely to occur at a building
site. ( return period =475 years)
Objectives are not to (at extreme EQ) :
- Limit damage
- Maintain function
- Provide for easy repair
-Ensure elastic behavior under a
moderate earthquake ( return period
equal to the life of the structure)
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Design EQ Loads per Egypt Code:
Sd ( T ) = Se ( T ) / R
Where :
Sd the design horizontal response spectrum
Se the elastic horizontal response spectrum
R response modification factor
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R = Rs R Rr
Where :
Rs Over-Strength Factor
R Ductility Reduction Factor
Rr Redundancy Factor
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R response modification factor
Is it allowable to reduce the wind force
by R ?
Why it is allowable to reduce seismic
force by R ?
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H
H
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H
yield
H
yield
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H
failure
H
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H
H
failure
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H
yield
H
yield
failure
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H
failure
H
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H
failure
failure
H
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H
H
yield failure
Time required to failure
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- R = 1 in wind for long time of loading.
-Return period for extreme E.Q = 475 years.
-Return period for extreme wind = 50 years.(short return period)
-Factor of safety is required for short return
period load cases.
-No over strength reaction is allowed
- R = Rs R = 1 x 1 = 1
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Response Modification Factor
1 - Introduction and Objectives
2 - Over-Strength Factor , Rs
3 - Ductility Reduction Factor , R
4 - Summary
5 - Reference
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Over-Strength Factor , Rs :
- Higher actual strength of material than
specified.
- Material reduction factor.- Over load Factor (1.4 D.L )
-Some designers taget demand/capacity ratios
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