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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