Question about PS69 seismic force

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Jeong Sik Kim	Wednesday 10 November 2010 8:19:42 am Hi I am korean structural engineer. I have a question about PS69 modified in 1982. According to ACI 318-08, the load combination of Seismic Force(E) is applied with 1.0. It means that the load combination "1.2D+1.0E+1.0L+0.2S" is applied in reinforced concrete design. Where E, the load effects of earthquake, is based on service-level seismic force, 1.4E shall be used in place of 1.0E. In thesedays, I have performed the Morocco PJ. According to PJ ITB, the seismic force must be estimated with PS69 rules and the ACI 318-08 code must be applied in Reinforced concrete design. So I just want to know that the seismic force estimated with PS69 is service-level seismic force or ultimate-level seismic force. And one more question I have. Could you inform us the return period of PS69 seismic foece? Best regards Kim Jeong Sik
yves GUILLON	Wednesday 01 December 2010 12:08:20 pm For your appraisal, you have to take into account the fact that PS69 French seismic code was to be used with elastic limit states construction codes (ie not ultimate limite state with safety factors on materials and on load case). As far as I remember, for concrete structures, CCBA 68 specified that "second genre" elastic limit states were to be used. That is elastic tress were to be computed in each section with a maximum of 90% of quasi-elastic strength in concrete and 100% of elastic strength in reinforcement. Some uncalculated ductility was provided (as resulting from material specific construction codes mandatory without seismic considerations) in the design spectra to be considered for the various structural types. Correspondence with present ultimate limit codes is not straightforward. Some interpretation may be inhered from comparison with PS92 french code which was (it is to be replaced by Eurocode 8) consistent with service or ultimate limit states and based on the same seismic zone definition in France. However, this code specified complementary construction rules more trustable ductility. Application of PS69-82 loads as a service load for ACI318 without any load magnification factor, and with limited allowable stress (with a small margin below elastic limit), may lead to a design roughly equivalent to the french seventies design, although the french philosophy both for PS69 an PS92 was to consider earthquake as and accidental rare case (France is not so seismic except in some overseas islands). Design specification should, in the near future, be adjusted to modern regulations, with clear definition of limit states (on strength check side - Eurocode 2 for concrete Eurocode 3 for metal ...), and of design loads and combination (Eurocode 0 for basic combination, Eurocode 1 for usual loads and Eurocode 8 for seismic loads). yves GUILLON

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Jeong Sik Kim

Wednesday 10 November 2010 8:19:42 am

Hi
I am korean structural engineer.

I have a question about PS69 modified in 1982.
According to ACI 318-08, the load combination of Seismic Force(E) is applied with 1.0.
It means that the load combination "1.2D+1.0E+1.0L+0.2S" is applied in reinforced concrete design.
Where E, the load effects of earthquake, is based on service-level seismic force, 1.4E shall be used in place of 1.0E.

In thesedays, I have performed the Morocco PJ.
According to PJ ITB, the seismic force must be estimated with PS69 rules and the ACI 318-08 code must be applied in Reinforced concrete design.

So I just want to know that the seismic force estimated with PS69 is service-level seismic force or ultimate-level seismic force.

And one more question I have.
Could you inform us the return period of PS69 seismic foece?

Best regards

Kim Jeong Sik

yves GUILLON

Wednesday 01 December 2010 12:08:20 pm

For your appraisal, you have to take into account the fact that PS69 French seismic code was to be used with elastic limit states construction codes (ie not ultimate limite state with safety factors on materials and on load case).

As far as I remember, for concrete structures, CCBA 68 specified that "second genre" elastic limit states were to be used. That is elastic tress were to be computed in each section with a maximum of 90% of quasi-elastic strength in concrete and 100% of elastic strength in reinforcement.
Some uncalculated ductility was provided (as resulting from material specific construction codes mandatory without seismic considerations) in the design spectra to be considered for the various structural types.

Correspondence with present ultimate limit codes is not straightforward. Some interpretation may be inhered from comparison with PS92 french code which was (it is to be replaced by Eurocode 8) consistent with service or ultimate limit states and based on the same seismic zone definition in France. However, this code specified complementary construction rules more trustable ductility.

Application of PS69-82 loads as a service load for ACI318 without any load magnification factor, and with limited allowable stress (with a small margin below elastic limit), may lead to a design roughly equivalent to the french seventies design, although the french philosophy both for PS69 an PS92 was to consider earthquake as and accidental rare case (France is not so seismic except in some overseas islands).

Design specification should, in the near future, be adjusted to modern regulations, with clear definition of limit states (on strength check side - Eurocode 2 for concrete Eurocode 3 for metal ...), and of design loads and combination (Eurocode 0 for basic combination, Eurocode 1 for usual loads and Eurocode 8 for seismic loads).

yves GUILLON

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Question about PS69 seismic force