Earthquake resistance to Eurocode 8 1

My points ,
- EN 1998 has 6 parts and 1998 Part 1: General rules, seismic actions and rules for buildings ..
- There is a near collapse (NC) limit state concept . It is used as a conservative approximation of structural collapse and in Eurocode 8, Part 3, the NC limit state is defined as follows:
LS of Near Collapse (NC). The structure is heavily damaged, with low residual lateral
strength and stiffness, although vertical elements are still capable of sustaining vertical
loads. Most non-structural components have collapsed. Large permanent drifts are
present. The structure is near collapse and would probably not survive another
earthquake, even of moderate intensity.
- NC limit state is typically based on a mean return period of 2475 years (2% probability of being exceeded in 50 years).

The standards are minimum requirements IMO , provide legal shield for the designer. Moreover , the client / owner has the right to ask more to design with more stringent requirements. Sometimes the owner may ask for designing with higher importance factor .

Suggest you to look to the following doc. (Performance Based Design , performance requirements )

HTURKAK said:

My points ,
- EN 1998 has 6 parts and 1998 Part 1: General rules, seismic actions and rules for buildings ..
- There is a near collapse (NC) limit state concept . It is used as a conservative approximation of structural collapse and in Eurocode 8, Part 3, the NC limit state is defined as follows:
LS of Near Collapse (NC). The structure is heavily damaged, with low residual lateral
strength and stiffness, although vertical elements are still capable of sustaining vertical
loads. Most non-structural components have collapsed. Large permanent drifts are
present. The structure is near collapse and would probably not survive another
earthquake, even of moderate intensity.
- NC limit state is typically based on a mean return period of 2475 years (2% probability of being exceeded in 50 years).

The standards are minimum requirements IMO , provide legal shield for the designer. Moreover , the client / owner has the right to ask more to design with more stringent requirements. Sometimes the owner may ask for designing with higher importance factor .

Suggest you to look to the following doc. (Performance Based Design , performance requirements )

Click to expand...

Hi,

Thanks for your insight.
Part 3 is for existing building. Does it applicable in my case where we are designing a completely new structure? or it is a good practices to take into account of the provision of Part 3?
Also, I get confused as following:-
No collapse is 475year while near collapse is 2475years seem confusing as no collapse should require a more critical case but 475 years of return period sound required lesser support than return period of 2,475years?

Agent Coconut said:

Part 3 is for existing building. Does it applicable in my case where we are designing a completely new structure? or it is a good practices to take into account of the provision of Part 3?
Also, I get confused as following:-
No collapse is 475year while near collapse is 2475years seem confusing as no collapse should require a more critical case but 475 years of return period sound required lesser support than return period of 2,475years?

Click to expand...

-It is true that Part 3 is for existing buildings but you can use the same rules to see the performance level of an existing design.
- No collapse requirement should cover operational levels . If the performance is at life safety level , my interpretation is , could be assumed reasonable for very rare event only ( 475 yrs).
- Near collapse level is severe damage . Repair generally not possible. But still collapse is not allowed. ( 2475 yrs)

EC 8 considers setting the 475 year event as the “minimum” for new designs . However If the region has low seismic activity ( your case ) , specifying engineer / owner respresentative may decide that the hazard could be under-predicted by the 475 year event and revise the minimum considered ground motion definition to a 2 % probability of exceedance in 50 years, or a recurrence interval of about 2500 years.

I hope my respond answers to your question and make sense.

HTURKAK said:

-It is true that Part 3 is for existing buildings but you can use the same rules to see the performance level of an existing design.
- No collapse requirement should cover operational levels . If the performance is at life safety level , my interpretation is , could be assumed reasonable for very rare event only ( 475 yrs).
- Near collapse level is severe damage . Repair generally not possible. But still collapse is not allowed. ( 2475 yrs)

EC 8 considers setting the 475 year event as the “minimum” for new designs . However If the region has low seismic activity ( your case ) , specifying engineer / owner respresentative may decide that the hazard could be under-predicted by the 475 year event and revise the minimum considered ground motion definition to a 2 % probability of exceedance in 50 years, or a recurrence interval of about 2500 years.

I hope my respond answers to your question and make sense.

Click to expand...

Hi

Yes and I would like to apologise, I just reread and found that I have misinterpreted the wording near collapse which should be more critical.

And yes your answer is definitely the exact answer to my question.

While I am waiting for my client to confirm if the return period of 2,475years requirement is referring to no collapse or near collapse, I would like to ask if he is referring to no collapse, any references on how we modify the ground motion acceleration? is it referring to 3.2.1(3) will do?
I have not yet going thru the reference you share in the previous post but I will read it in this weekend.

Edit as bold above

Hi all,

I would like to made a follow-up question.

A) Regularity of plan/elevation
The building has 3 floor, L1, L2 and Roof
All are identically in term of layout and size(about 140m x 62m) , However, because the floor height is very high at 7.0m, a small part of the floor has an intermediate floor, forming L1A and L2A (20m x 40m)
Is the building is still considered as having regularity in plan?


B) Lateral load
The clients has clarify and instruct us based on the following assumption:-
1) The lateral stiffness of shear wall is >85% of total lateral stiffness in the building
2) The building should be designed as siesmic-resistant shear wall system, NOT a moment frame system.

From our understanding, Based on EN1998; 4.2.2(4);
1) All beams and columns are now secondary seismic member that follows design and detailing is EC1 and EC2
2) Only shear wall to be designed based on EC1, EC2 and EC8.

Here come the tricky part, how do we analysis the building?
I am thinking that we can analysis the whole building as gravity only + Wind +EHF is any, and superimposed the seismic action into the shear wall. for this purpose, the seismic action will be calculated by manual calculation and distribute to each shear wall based on the stiffness.

Anyone can advise me that appropriate method for this purpose?

Your latest post should be new thread.
I will suggest you , delete your latest answer and prepare new thread with new title.

HTURKAK said:

Your latest post should be new thread.
I will suggest you , delete your latest answer and prepare new thread with new title.

Click to expand...

Hi, I have done it.
You may find the post here