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Seismic Analysis and Design

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies.    www.sefindia.org Forum Index -> Past Discussions Year 2006
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kajal.chopra
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Joined: 26 Jan 2003
Posts: 102

PostPosted: Thu Nov 09, 2006 2:43 pm    Post subject: Seismic Analysis and Design Reply with quote

 
Could anyone help me with the following questions pertaining to Seismic Analysis and Design:

Consider the equivalent lateral force method:

Now, if we determine the inertial forces by  the equivalent lateral  force method and design the structural members based on consequent linear elastic analysis.Right?

Based on Seismic Design Philosophy the structural is in the inelastic range under the action of seismic forces.Right?

It is possible , that , during the earthquake (wherein the structural is in the inelastic range) the  bending moment at a certain section of the beam is less than that obtained from liner elastic analysis (due to redistribution of moments that occur after the material enters the inelastic range) but the consequent capacity of the section is more (as the section is designed based on outputs from linear elastic analysis).Right?

Designing such a section based on outputs from linear elastic analysis would obviously result in the overstrength of the section.Right?

This could cause a consequent brittle failure at another section,Right?

Then, how is it justified to adopt equivalent lateral force method and consequent linera elastic analysis without considering redistribution of moments?

Please help!!

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SaurabhPurandare at co...
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PostPosted: Fri Nov 10, 2006 11:10 am    Post subject: Seismic Analysis and Design Reply with quote

Kajal,

The structure is designed for "1/R" times the seismic forces in the equivalent lateral force method using elastic analysis.

Actual seismic forces would be "R" times larger, and hence the structure would be in  the inelastic range for such high magnitude of forces. There is no question of overstrength....as the structure is designed for much much lower forces!!

Regards,
Saurabh

-----Original Message-----
Message From  kajal.chopra[AT]red... [mailto:kajal.chopra[AT]red...]
Sent: 09 November 2006 20:13
To: Saurabh Purandare
Subject: Seismic Analysis and Design

 
Could anyone help me with the following questions pertaining to Seismic Analysis and Design:

Consider the equivalent lateral force method:

Now, if we determine the inertial forces by  the equivalent lateral  force method and design the structural members based on consequent linear elastic analysis.Right?

Based on Seismic Design Philosophy the structural is in the inelastic range under the action of seismic forces.Right?

It is possible , that , during the earthquake (wherein the structural is in the inelastic range) the  bending moment at a certain section of the beam is less than that obtained from liner elastic analysis (due to redistribution of moments that occur after the material enters the inelastic range) but the consequent capacity of the section is more (as the section is designed based on outputs from linear elastic analysis).Right?

Designing such a section based on outputs from linear elastic analysis would obviously result in the overstrength of the section.Right?

This could cause a consequent brittle failure at another section,Right?

Then, how is it justified to adopt equivalent lateral force method and consequent linera elastic analysis without considering redistribution of moments?

Please help!!

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