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Height of Building/ Time Period

 
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 2004
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sikandarsiddiqi
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...


Joined: 26 Jan 2003
Posts: 294

PostPosted: Wed Sep 15, 2004 7:32 am    Post subject: Height of Building/ Time Period Reply with quote

Radio Link International E-mail

Dateline
Dhaka - Bangladesh/Asia


IMPORTANT


Dear Engr.Mukesh,> India

Thank you for your e-mail.

In seismic design a slopped roof is incorrect architecture
because it violates the very basic theorem that regulates the seismic design of structure
which is :

All the points of a plan at the same level and at the same moment in
time are in the same phase of displacement,velocity and accleration,
their amplitude being the same.

Example - 1 : Out of 47 earthquake resistant buildings in Fuchu,Japan,only one building
collapsed on June 28,1948.In the opinion of Japanese seismic experts the
collapse was DUE TO INCORRECT DISTRIBUTION of seismic forces
between parts of the building.

Example - 2 : In recent time lot of buildings failed in Bingol,Turkey, during an earthquake
which in the opinion of Turkish Government was due to poor seismic
design standard and faulty construction.



With regards and best wishes.


Engr.Sikandar Hayat Siddiqi
Project & Seismic Design Management Engineer
&
Builder/Developer Selection Consultant
&
Co-ordinator,Earthquake Anti-disaster Defence Management System Initiative





Copy to

Dr.Engr.Sudhir K Jain, IITK, India (skjain@iitk.ac.in)

Engr.Sanjay jha, Government of Delhi (hqadm@hub.nic.in)

Mr.Stacey Martin, Director, ASC (martin@asc-india.org)

Engr.Anup Karanth (anup.karanth@undp.org)













mc.upadhyay@jil.co.in wrote:





Hello
what height of a building should be considered
for the calculation of Time period (as per IS 1893 formula)
in case of Sloping Roofs?

Should it be the maximum point or the average point of sloping part?

Regards

Mukesh Upadhyay













          
---------------------------------

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sikandarsiddiqi
...
...


Joined: 26 Jan 2003
Posts: 294

PostPosted: Wed Sep 15, 2004 8:22 am    Post subject: Height of Building/ Time Period Reply with quote

Radio Link International E-mail

Dateline
Dhaka - Bangladesh/Asia


IMPORTANT


Dear Engr.Mukesh,> India

Thank you for your e-mail.

In seismic design a slopped roof is an incorrect architecture
because it violates the very basic theorem that regulates the seismic design of structure
which is :

All the points of a plan at the same level and at the same moment in
time are in the same phase of displacement,velocity and accleration,
their amplitude being the same.

Example - 1 : Out of 47 earthquake resistant buildings in Fuchu,Japan,only one building
collapsed on June 28,1948.In the opinion of Japanese seismic experts the
collapse was DUE TO INCORRECT DISTRIBUTION of seismic forces
between parts of the building.

Example - 2 : In recent time lot of buildings failed in Bingol,Turkey, during an earthquake
which in the opinion of Turkish Government was due to poor seismic
design standard and faulty construction.



With regards and best wishes.


Engr.Sikandar Hayat Siddiqi
Project & Seismic Design Management Engineer
&
Builder/Developer Selection Consultant
&
Co-ordinator,Earthquake Anti-disaster Defence Management System Initiative


Copy to


Prof. Dr.Engr.Sudhir K Jain, IITK, India (skjain@iitk.ac.in)

Engr.Sanjay jha, Government of Delhi (hqadm@hub.nic.in)

Mr.Stacey Martin, Director, ASC (martin@asc-india.org)

Engr.Anup Karanth (anup.karanth@undp.org)

Engr.Alpa,India ( alpa_sheth@vakilmehtasheth.com )

Engr.Rudra Nevatia,India( rudra_nevatia@yahoo.com)

Engr.Sangeeta,India (sdec@bol.net.in)


















mc.upadhyay@jil.co.in wrote:





Hello
what height of a building should be considered
for the calculation of Time period (as per IS 1893 formula)
in case of Sloping Roofs?

Should it be the maximum point or the average point of sloping part?

Regards

Mukesh Upadhyay


















          
---------------------------------

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aswinpe
SEFI Regulars
SEFI Regulars


Joined: 26 Jan 2003
Posts: 28

PostPosted: Thu Sep 16, 2004 9:56 pm    Post subject: Height of Building/ Time Period Reply with quote

Hello:

It is extremely incorrect to state that  "In seismic design a slopped roof
is incorrect architecture.."  I am an engineer in California which has been
rocked by several earthquakes.  The roof of almost every residential
structure is sloped. According to your theory all these structures should
have failed?

The problem in roof during a seismic event arises when there is two or more
horizontal diaphragm levels (roof) which are not tied together properly to
transfer the shear forces to the vertical resisting system (walls/frames).
For example if there is a mechanical well in the middle of the roof and the
roof diaphragms are not tied together then the load path is affected.  So a
sloped roof is perfectly acceptable and has performed very well if the load
path has been properly detailed to carry the forces to the walls and then to
the foundation.

Now to answer Mr. Mukesh Upadhyay's question of the height.  The formula for
the period of a structure is an approximate method and in a sloped structure
it might be conservative to take the maximum height

Hope it helps.

- Aswin
_____________________________
Aswin Rangaswamy, P.E.
Los Angeles, California

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