Why Buildings Respond Differently to Earthquakes

[ralf-nz]

Engineers pass inspections (using the current building code) with the knowledge that approving a WOF means the building should withstand any future major quake. That is the purpose of the inspections.

I cannot agree. No building can withstand "any future major quake". That is just impossible. No one knows what future earthquakes might be like.

How do you explain the damage? Either the engineer did not follow the building code or the engineer followed the code but the code needs to have higher standards.

I don't all the names of our colleagues who did these inspections. However I am convinced that they undertook them responsibly in accordance with our Code of Ethics; http://www.ipenz.org.nz/ipenz/who_we_are/ethics_inc.cfm!

It is not a need but an option. E.g. we as a society could agree on safer cars but we don't. We take deliberately a certain amount of fatalities into account.

[ricktee]

I cannot agree. No building can withstand "any future major quake". That is just impossible. No one knows what future earthquakes might be like.



I don't all the names of our colleagues who did these inspections. However I am convinced that they undertook them responsibly in accordance with our Code of Ethics; http://www.ipenz.org.nz/ipenz/who_we_are/ethics_inc.cfm!

It is not a need but an option. E.g. we as a society could agree on safer cars but we don't. We take deliberately a certain amount of fatalities into account.

Sorry. You are right no building can withstand any future major quake. What I wanted to say was:"

Engineers pass inspections (using the current building code) with the knowledge that approving a WOF means the building should withstand any future major quake of at least equal to the magnitude of past quakes (7.1 on Sep '10). "


I believe we need to change the code to a higher standard. Tall buildings should be able to withstand at least a 7.1 magnitude quake. We need to learn from history. Guess it is up to the government to decide.

[ricktee]

"The big difference" needs to take into account other differences: The location of the epicentre, and its depth, and the specific ground conditions.
Also, did the design follow just the building code or has there been done voluntarily more?


I don't agree that it "proves" it. It is an indicator to rethink our risk assessment as a society.
The technical evaluation is not finished yet. Currently no one can tell. How our findings will be evaluated again is also a question.
As I wrote earlier: "Finally it will be up to the government - as the society's representatives to decide further action, if required. "The Government may also consider whether the design levels expressed in the Building Code represent the risk appetite of the New Zealand public and balance that against building and occupancy cost.""

Christchurch had 2 major quakes of at least 7.1 in magnitude. There have been significant damages on a lot of buildings. Some buildings have collapsed. In my opinion, buildings should be made to withstand quakes of similar magnitudes in the future.

You're right, The technical evaluation is not finished yet. The explanation of the damage could be because of other factors and not because of an inadequate code.

My opinion: Engineers used the same codes in approving the safety of buildings before the 2 major quakes. It is my own conclusion the reason for the damages is because the current code needs to have a higher standard (maybe like Japan). For me, that already proves the code is inadequate. Others might disagree, I respect that.

[ralf-nz]

Okay

Engineers pass inspections (using the current building code) with the knowledge that approving a WOF means the building should withstand any future major quake of at least equal to the magnitude of past quakes (7.1 on Sep '10).

I just think that you are concentrating too much on the magnitude. The magnitude is only one way describing and measuring an earthquake. This has now been mentioned by others and me in several posts.
As the consequences of an earthquake relate to several contributing factors you need to consider all of them and not just one.

[Super_BQ]

My opinion: Engineers used the same codes in approving the safety of buildings before the 2 major quakes. It is my own conclusion the reason for the damages is because the current code needs to have a higher standard (maybe like Japan). For me, that already proves the code is inadequate. Others might disagree, I respect that.

Well, the current code appears to be pretty good IMO. I mean, how many lives were lost in a building built under current code? If it shows that many lives were lost in a newly built building, then yes, there should be an upgrade. But you have to consider that downtown Christchurch had many old heritage like buildings and by efforts, most of them didn't meet the 67% current standard. Let me reiterate, taking old buildings and upgrade strengthening them to 67% of the current standard. So right off the start, you could have 80% of the buildings not meeting the current standard and you suggest to increase the standard again? What future would this have for old buildings that can't even make 67% today? We may end up with a lot of empty parking lots downtown if things get too tough.

[ralf-nz]

Christchurch had 2 major quakes of at least 7.1 in magnitude. There have been significant damages on a lot of buildings. Some buildings have collapsed. In my opinion, buildings should be made to withstand quakes of similar magnitudes in the future.

You're right, The technical evaluation is not finished yet. The explanation of the damage could be because of other factors and not because of an inadequate code.

My opinion: Engineers used the same codes in approving the safety of buildings before the 2 major quakes. It is my own conclusion the reason for the damages is because the current code needs to have a higher standard (maybe like Japan). For me, that already proves the code is inadequate. Others might disagree, I respect that.

There was only one earthquake with such a magnitude of 7.1. The second one was of less magnitude but more damaging. This is evidence that magnitude is not all there is.

BTW our code not only uses the hazard factor "Z" as mentioned in an earlier post but there are more factors e.g. for "site subsoil class", being "near [a] fault", "importance of a structure".


As also written earlier there is currently no evidence from the latest major earthquakes that the Japanese building code is indeed of a "higher standard" than our NZ one!

[Duncan74]

Well, the current code appears to be pretty good IMO. I mean, how many lives were lost in a building built under current code? If it shows that many lives were lost in a newly built building, then yes, there should be an upgrade. But you have to consider that downtown Christchurch had many old heritage like buildings and by efforts, most of them didn't meet the 67% current standard. Let me reiterate, taking old buildings and upgrade strengthening them to 67% of the current standard. So right off the start, you could have 80% of the buildings not meeting the current standard and you suggest to increase the standard again? What future would this have for old buildings that can't even make 67% today? We may end up with a lot of empty parking lots downtown if things get too tough.

Oh carp, I agree with a SBQ post. Did someone spike my drink?

[ralf-nz]

Oh carp, I agree with a SBQ post. Did someone spike my drink?

[ralf-nz]

What future would this have for old buildings that can't even make 67% today?

The threshold for existing building to be upgraded is generally 33%.

E.g. you want to alter an existing building; change its use etc. This building needs to be evaluated re seismic resistance. If it qualifies for 1/3 of the current code it does not need to be strengthened. Is it less than it needs to be strengthened for 2/3s.

So there are - how many? - old buildings that don't make 33% today.

[Mamee & Co]

The threshold for existing building to be upgraded is generally 33%.

E.g. you want to alter an existing building; change its use etc. This building needs to be evaluated re seismic resistance. If it qualifies for 1/3 of the current code it does not need to be strengthened. Is it less than it needs to be strengthened for 2/3s.

So there are - how many? - old buildings that don't make 33% today.

In Christchurch now...probably not very many