Seismosoft | Earthquake Engineering Solutions

In previous version 6.5, it was possible to determine performance criteria specifically for concrete cover. This way it was possible to detect concrete spalling, if the predefined strain limit was reached. I assume the program would read strain levels at the cover area (outside the section core area) to check the aforementioned criterion. Core strain criteria were set independently.

In version 7, there is only one "concrete strain" related performance criterion. This means that detection of concrete spalling is not possible anymore?
Also, does this generic "concrete strain" criterion read strain levels exclusively inside the core area? If not, and just reads the sections' maximum strain (obviously taking place at the cover area), it won't be possible to determine critical strain levels of the confined area.

Dear grecer,

You may detect the concrete spalling by assigning the correct value in the concrete strain criterion type. You may find more information about this matter in SeismoStruct User Manual and Help System.

Dear Zoi,

The previous version had different criterion type to detect concrete strain at the core and the cover area. My understanding was that when the criterion was referring to the core, then seismostruct would read the strain values from the confined concrete area. On the other hand, when the criterion was referring to the concrete cover, then seismostruct would read the strains at the cover area, which are larger compared to the core area strains at the same instant.
For example, when the recommended cover spalling value of -0.002 is reached at the cover, the simultaneous core strain should have a lower value since the core is closer to the sections' centroid.

In version 7, this discrimination is no longer present. Therefore, it is not very clear where exactly seismostruct reads the strain values (at the cover area or the core area?) to check if a criterion is reached.
This information is exactly the same in the Help/Manual with the previous version, without clarifying the issue I am asking about.

Dear Greser,

SeismoStruct checks if the assigned value for concrete strain performance criterion is reached in all the concrete section's fibres. Hence, in order to check if you have cover spalling failure you should assign a value that corresponds to the ultimate crushing strain of unconfined concrete material. If you would like to check the crushing of the concrete core you should assign a value that corresponds to the ultimate crushing strain of confined concrete material.

If for example you are interested in checking the spalling of cover concrete you could assign a typical value of -0.002, as suggested in the User Manual. In this way, if this criterion is reached you would know that you have spalling of concrete cover for the examined element. The concrete core needs a greater value of strain in order to fail, but you may also insert a second performance criterion with the ultimate crushing strain value of confined concrete material assigned, to check if you have crushing of the concrete core.

Finally, if you would like to monitor specific sectional points, you could make use of the available stress points. For more information you may refer to the User Manual an Help System.

Hello Zoi,

Thank you very much for your help. I'm sorry i am consuming your time like this, perhaps I was not very clear previously.

Lets suppose that I want to set a criterion for concrete strain to check crushing of concrete core using the proposed value: -0.006.
When the concrete at the cover area reaches a value of -0.006, the strain at the concrete core should have a smaller value (e.g. -0.005) because it is closer to the neutral axis.
Naturally, Seismostruct should not flag it as a check-positive, since the core area in which I am interested did not reach the value of -0.006 yet. Nevertheless, this depends on the exact fiber of the section that Seismostruct reads the strain value.

So here is my question: Seismostruct treats the above case as crushing of core concrete or not? The correct should be no, but I am skeptical...

Dear Grecer,

Your point is valid, however note that the SeismoStruct performance criteria refer to all the fibres' strains of the section and not directly to the crushing of the concrete core. You may assign a larger value of the ultimate crushing strain value of confined concrete material in order to make sure that you have reached the crushing of the concrete core.

Thank you Zoi,

This was exactly my point. The previous version 6.5 had different criterion types for "Cover material strain" and "Core material strain", therefore I assume that each criterion referred to the strain of different fibre areas of the section.
That is why it seems strange to me to discard this option in version 7.
Thanks again for your valuable contribution.

Greser,

You are correct, the pre-v7 feature that you refer to could indeed prove useful for the cases that you mention, and I am sure that SeismoStruct's development team will try to come up with a way in which to reinstate it.

Btw, the disappearance of such analytical capability was not intentional, but rather the overlooked collateral effect of the (certainly positive) removal of the previous separation between core and cover concrete in the sections definition phase (which was something that many practicing engineers were finding somewhat unintuitive, quite rightly so).

Rui

Dear Rui,

I agree on both points. The use of different materials in the sections definition was not the best, since both the cover and core concrete were essentially the same material with different confinement level.
The discrimination of cover and core area in the criteria section though was useful, since those criteria were used to obtain a first quick glimpse of the structure's inelastic behavior. If it reappears in one of the next versions I believe it would be a positive move.
Thank you once more for your contribution in all issues I've commented so far.