Dear Researcher,

Please find attached links and files for info. 

Thanks and regards,

https://www.youtube.com/watch?v=k3ua-oe6SMY

Thank you for the answer but i didn't ask for a general information about shotcrete. The purpose of my question is to obtain information about the application of shotcrete specially in existing masonry infilled RC frames (concerning either technical or simulation/modeling issues) that takes place in order to upgrade the seismic performance of the whole structure.

Some issues, for instance are: the proper application of the anchorage of shotcrete at the surrounding RC frame, the influence of the wall's existing plaster and any kind of simulation issues (either "practical" or shophisticated..) but also even any kind of apllication issues.

Thank you.     

Thank you for the answer.

Can you explain why is this technique "absolutely" not recommended ? (actually, the use of this specific word makes me ask you..).

In such cases, the strengthening of infill walls (of course, always together with the surrounding RC frame and not just shotcreting the infill walls) under certain conditions, can alter the behavior of them and act as shear walls (in conjuction with the surrounding RC frame). Probably, it won't be rational to make such an attempt in all the infilled bays of the structure but, perhaps, at the first (lower) stories.    

Infill walls (even if they are completely unreinforced) definitely play a crucial role in the behaviour of the whole structure (positively or negatively). So, for a realistic assessment of the seismic performance of a structure, the most times, infills cannot (it is wrong) to be ignored anyway. In this context, if an effort is given for strengthening infills, it could be beneficial for the overall structure’s behavior.

The question is in which way this can be done in a reliable manner by taking into account various issues that may affect the efficiency of this method (and of course, to prevent adverse/negative results that may be introduced). It is a fact that when infills are very strong and stiff (comparing to the surrounding RC frame), then they may cause negative results such as the local effects at the surrounding RC frame can make, or/and by introducing overall irregularities in the morphology of the structure, so they have to be treated carefully if they are going to be strengthened. For this reason, if such a technique is selected for the structure’s overall upgrade, infills have to be properly connected with the surrounding RC frame in order to behave in a combined manner.

That what you said is a completely different aproach (acceptable but just different)... Generally, there are many kind of approaches in seismic retrofitting. Furthermore, the term that you used "non-supporting walls" concerns only their behavior under gravity loads (so that's why they are usually called as "non-structural eleements" but in fact they usually are, partially, "structural elements"..). Under lateral loads they play a crucial role anyway (even if they are just there, without trying to strengthen them). Of course, all cases of existring structures are not the same so such an approach some times may not be very rational indeed (if for instance infills are already very weak, or they are designed and built poorly, etc). 

Researchers have given much effort in strengthening masonry infill walls by using FRP's and i am just asking about using another way of strengthening them.

Thank you Mr. Borjan for your thoughts anyway.

It depends on ... situation. See attachment.

Just a comment Borjan: If you try to "dis-correlate" infill walls with the surrounding RC frame, in order to "reduce the stiffness contribution", there is another major issue that you have to take care of: to ensure the safety of infill walls against the out of plane failure. And this is not an easy issue anyway...

Thank you Jacek for the attached paper, it is quite interesting. However, the techinique of strengthening infill masonry walls should be treated as a seperate case comparing with the case of strengthening pure masonry buildings. 

This is an interesting paper, thank you.

This kind of material (that is a non-conventional one) would probably be more efficient and proper for the upgrading technique that i am talking about, indeed. But, as you said, the cost of its application will probably be also too high so it won't be much "efficient" from this point of view...

When talking about “conventional” methods, using shotcrete on infill walls of a structure (in selected bays), it might be a sufficient technique concerning both aspects (either technically or economically). Furthermore, as concerns the cost-effectiveness issue, when comparing the above mentioned method with another also “conventional” method for structure’s seismic upgrading, as it is by applying concrete -shotcrete- jacketing to structural elements (columns, beams) in order to increase their capacity or/and their ductility, it may be a better choice because in the latter case you have to break down infills in order to “jacket” columns or beams all around them (perimetrically) and then rebuilt them, while if you shotcrete infills together with the surrounding RC frame there is no need to demolish them..). When a RC frame is flexible by default (in absence of shear walls), then the addition of RC shear walls is usually needed in order the structural system to obtain an adequate stiffness and strength anyway, so in such cases maybe by shotcreting infills (in selected bays) together with the surrounding RC frame (in such way that it will act as an “equivalent” shear wall) will be a sufficient method concerning all kind of aspects.

Of course, this may not be the solution for any case but I think that it should be one of the methods that may be considered in order to obtain the most appropriate solution to a seismic-upgrading topic.

After all, this technique is already a part of some codes (as it is for instance in the Greek Code for Interventions -KAN.EPE-).

Well, i suppose you are right...(shotcrete is generally a bit "messy"..). But unfortunatelly, most rehabilitation techniques causes such kind of "inconvenience" (and perhaps it is not the first priority to try to avoid it, at least not always). 

Regards.

Hi Anastasios,

The attached may be of interest.

Good luck with your work!

Luiza

Thank you for your interest Luiza.

Could you make the attachment please?

Hi Anastasios,

please see attached.

Best regards.

Luiza

Hi Luiza,

Even if i was initially asking information about using shotcrete and not any other material for strengthening URM walls, nevertheless it's an interesting paper.

Thank you any way.