Meeting

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Summary

In this comprehensive meeting transcript, numerous aspects of fiber reinforced polymer (FRP) applications in civil engineering are explored. The speaker discusses the history and development of FRP materials, emphasizing their advantages such as lightweight and high strength, despite challenges like brittle failure and creep. Various application techniques such as strengthening columns, beams, slabs, and more are detailed, along with insights into FRP’s potential in marine and seismic settings. The transcript highlights ongoing research and future prospects in FRP technologies.

Highlights

FRP materials provide a lighter, corrosion-resistant alternative to steel in reinforced concrete applications 🦾.
Advancements in FRP technology are enabling faster, more economical strengthening of structures without altering their appearance 💡.
There are concerns about the brittle nature of FRP under certain stress conditions, but ongoing research is addressing this issue 📊.
FRP’s role in extreme condition applications, such as earthquake and marine environments, is being explored 🔍.
Potential future developments include using natural fibers to reduce environmental impact 🌿.

Key Takeaways

Fiber reinforced polymers (FRP) have been around for 15-20 years and have significant industrial applications in civil engineering 🏗️.
FRP materials are strong, lightweight, and resistant to corrosion, making them a great alternative to traditional steel reinforcement 🌍.
Ongoing research at Kingston and elsewhere focuses on expanding the applications of FRP, including in marine environments and seismic zones 🌊.
There are challenges like brittle failure and the need for more economic solutions, but new techniques like prestressing are helping to overcome these hurdles 🤔.
Future prospects include exploring natural fibers as an eco-friendly alternative to synthetic FRP materials 🌱.

Overview

Fiber reinforced polymers (FRP) have revolutionized the field of civil engineering over the past two decades. These materials boast impressive strength-to-weight ratios and offer excellent resistance to corrosion, positioning them as key alternatives to traditional steel reinforcements. The transcript highlights the substantial work done in research institutions, like Kingston, which are pioneering the shift towards adopting FRP in construction.

Despite its many advantages, FRP technology does not come without challenges. Unlike steel, FRP can be prone to brittle failure and can also creep over time, aspects that engineers are currently trying to mitigate through innovative techniques like prestressing. The conversation also dives into adaptive methodologies such as hybrid applications that lend more flexibility and reliability to FRP’s structural uses.

The transcript sets an optimistic outlook for the future of FRP in infrastructure. The potential to use FRP in marine and seismic zones is particularly promising, as is the exploration of eco-friendly natural fibers to replace synthetic variants. These avenues not only aim to improve environmental sustainability but also seek to advance the resilience of modern constructions.

Chapters

00:00 - 00:30: Introduction and Overview The chapter titled "Introduction and Overview" seems to revolve around a session or a lecture where the speaker discusses teaching structures and the collaboration within a team, highlighting the possibility of arranging a tour to view the laboratories. The main topic of discussion appears to be fiber reinforcement used in reinforced concrete, which the speaker admits to having limited knowledge about.
00:30 - 02:30: Introduction to Fiber Reinforcement The chapter titled 'Introduction to Fiber Reinforcement' begins with an introduction by the speaker, who then hands over to Ted, the main speaker for the session. The topic is the fascinating field of fiber reinforcement. The session appears to be part of research efforts at Kingston, aimed at advancing understanding and knowledge. David was mentioned as a key person who inquired about research opportunities when the speaker first showed interest in the subject. The chapter cuts off mid-sentence, indicating that there was likely more to be discussed about the specific research and advancements in fiber reinforcement.
02:30 - 10:00: Applications and Research at Kingston The chapter titled 'Applications and Research at Kingston' deals with the theme of polymers and modern materials. Despite the recognition of their relevance, it suggests that the focus on new developments or research in polymers isn't as prominent lately.
10:00 - 15:00: Characteristics and Behavior of FRP The chapter delves into the characteristics and behaviors of Fiber Reinforced Polymers (FRP), focusing on their evolution over the past 15 to 20 years. It highlights the historical aspect of FRP's development, noting that for a significant portion of this period, advancements and details about FRP materials and their applications were kept confidential, possibly for strategic purposes. Approximately 25 years ago, FRPs began to find their footing within industrial applications, particularly in the civil engineering sector.
15:00 - 18:00: Hybrid Applications and Challenges The chapter explores hybrid applications and the associated challenges, drawing on firsthand experiences from an engineering perspective. The narrative begins with the author's initial exposure to hybrid materials during a tenure at Atkins, a renowned engineering firm, approximately two decades ago. It highlights a specific case involving bridge assessment that revealed the use of hybrid materials that had been existent for around a decade, shedding light on their practical applications and challenges.
18:00 - 23:00: Durability and Extreme Loading The chapter discusses the durability of materials when subjected to extreme loading conditions. It highlights the importance of protecting materials, particularly the decking surface, from ultraviolet (UV) radiation to maintain their condition. In this context, when materials are well-protected from UV radiation, significant problems can be minimized.
23:00 - 26:00: Testing and Monitoring The chapter titled 'Testing and Monitoring' discusses the surprising durability of certain materials. It highlights the tension aspects and the combination of lightweight and strong properties of these materials. However, the chapter also acknowledges the negative properties that these materials may possess.
26:00 - 32:30: Advancements in Materials The chapter titled 'Advancements in Materials' introduces several ways to cope with emerging materials. The speaker is optimistic about the integration of these new materials in construction and engineering. However, it is noted that these advancements are not expected to replace traditional steel reinforcement in the near future.
32:30 - 41:00: Practical Applications and Projects The chapter 'Practical Applications and Projects' discusses the significant role of reinforcement in structures, particularly focusing on F glass fiber reinforcement. Reinforcement is emphasized as a crucial factor, taking up to 20-50% of importance in such projects. The chapter highlights the advantages of glass fiber reinforcement, one of which is the material's stability or non-growth in size under certain conditions.
41:00 - 45:00: Future Directions and Conclusion The chapter discusses the future directions and conclusions regarding reinforcement in concrete structures, emphasizing the importance of maintaining proper conditions to extend durability and properties of the concrete. An example project connected to this topic is briefly mentioned.

Meeting Transcription

00:00 - 00:30 teaches structures Wave your hand please Yeah Teaching structures You guys teach structures Um it's quite a nice team There's some nice laboratories um that maybe one day we'll arrange a tour of so you can see the work for yourself But um tonight he's going to be talking about fiber reinforced fiber reinforcement used in reinforced concrete It's a subject I know very little about
00:30 - 01:00 So without further ado I'm going to hand over to Ted to talk to us tonight about this particularly interesting subject and what's being done here at Kingston to further knowledge David was the first person that asked me when I came about researching in my interest what could be done which is I'm
01:00 - 01:30 not very thank you for this okay polymers some saying new modern materials probably not not so much lately u they're around They're around
01:30 - 02:00 probably 15 20 years considering that most of this time they have been kept secret maybe purposes and from about 25 years I would say that we can fight industrial applications in the area of civil and
02:00 - 02:30 engineering Uh my first uh case when I get knowledge about those materials was during the time when I worked for Atkins about 20 years ago and making assessment bridge it appear that has been already materials for I think about 10
02:30 - 03:00 years So what is the condition and very good it was on the cans upper surface of the decking and well protected from UV radiation which is one of the main problems with materials And in such cases it seems that there are no significant problems in the
03:00 - 03:30 durability which was a bit surprising for me It was even more surprising that there strong speaking about tension aspect and they excellent materials lightweight strong Of course they have negative uh properties as
03:30 - 04:00 well I'm going to to discuss few of them during the process of presentation Uh the good news is that there are ways to cope with those elements and perspectives from my point of view quite good I'm not expecting that they will soon replace steel reinforcement This is not something that probably
04:00 - 04:30 anybody is expecting to happen but taking significant part maybe 20 30 maybe 40 to 50% reinforcing structures it's such type of reinforcement say this is f glass fiber reinforced the best thing is that they don't grow the Think of such type of
04:30 - 05:00 reinforcement on the is almost limited durability If suppose the concrete is kept in proper conditions that past the properties that extend to the com The photo on the first slide is connected with one of the projects that I was involved in Atkins connected with
05:00 - 05:30 strengthening columns and typical case of application of FP as many layers as fabrics Many layers and performs in such cases because we are protecting them from impact loading of heavy vehicles It's
05:30 - 06:00 ke that it's used it and white color is coming actually from protect protective layer paint that it's that it's uh for protecting the the [Music] radiation radiation contribute to
06:00 - 06:30 this few words about so the presentation is about 99% about the work that we have done in Kingston for those 20 almost 20 years that I'm here I wouldn't say that I have started actually remember one of my colleagues who retired camera that already
06:30 - 07:00 um had some materials already in our labs Uh but I would say that more intensive work started to be developed after my U what we're doing we are using the first step was to use different FLP materials for strengthening
07:00 - 07:30 uh those ways of indicating C is for carbon so this is carbon fiber reinforced polymer G is for glass fiber polymer is for A is for So strength is actually the first area that such material started to use it very intensively years ago They are
07:30 - 08:00 significant number difficult to make exact exact destination about how many but I would say probably more than 10 maybe more than 20% of the structures in UK reinforce complete structures are strengthen it's easy fast economic way don't change the appearance don't create additional load and sufficiently durable I would This is that continues
08:00 - 08:30 to be developed Um [Music] we developed some additional research connected with so-called hybrid applications and I'll explain the mean we need hybrid applications say steel FP different types of FP u the main problem is the brittle failure when we have hybrid hybrid
08:30 - 09:00 application you're actually receiving the moment of destruction on different periods of time which is equivalent to so-called artificial yielding plot to be created this way Uh in addition to this we used to have quite uh intensive investification of research about extreme loading constructures blast impact
09:00 - 09:30 dynamical earthquakes I would say probably a little bit less intensive lately maybe because of additional health and safety requirements for our labs uh in aspect of fire and blast especially but uh we have some traditions and we we have some roles in this area Districtive testing is the other area that we tend to develop even we have
09:30 - 10:00 from this student here that it's working exactly in this dissertation and uh the the view is that we're going to increase our activities in this aspect especially looking for combination with innovative materials like andual health monitoring We have other colleague that colleagues that are interested in this and another
10:00 - 10:30 perspective for future development This very important area for keeping infrastructure type of projects appropriate level of development Uh a little bit about the external appearance of this So I already mentioned blush carbon army Another material that I haven't mentioned is Basel Actually it appears
10:30 - 11:00 that Basel is having very similar qualities as glass [Music] fiber I would say in some aspects probably even better especially in aspect of durability invented so effect which is one of the negative sides of of those
11:00 - 11:30 materials Um so gener significant percentage of it is consisting of fibers uh and those fibers are not nanom materials that they're more like micro scale not you know uh mill scale but still very very small fibrosis
11:30 - 12:00 diameter and uh by themselves they are not sufficient to have sufficient capacities but when those fibers are connected with corresponding matrix in most of the cases we're speaking about epoxy but there are other variations one is getting popular they're having significant strength I can't even uh colleagues from
12:00 - 12:30 industry that they they used to say that they're giving awards for people that are able to break something like this This this is carbon fiber polymer for strength and so forth plates such material Uh and speaking about this we could care plates we could care fabrics uh we could have bars when we speaking especially for uh new elements not for not so much
12:30 - 13:00 existing ones all of them very successfully applied We have already sufficient amount of duties and information about how how to do it it's not in general of something that it's completely unknown from one side from other uh side we have to keep in mind that there's quite a lot of failures and I'm going to mention such ones that the
13:00 - 13:30 the design approaches are in process of development and here you could see application of C2 laminates such type of material for straight of bridge deck especially parts This is the reason to the top of the decking Uh and having in mind that usually we have some material that it's covering laminates This is one of the very
13:30 - 14:00 successful very comfortable I would say way of applying ST those materials some general information about characteristics Uh so you could imagine that this line here that is getting horizontally it's a bit longer probably than they supposed to be but it's representing the steelless behavior So
14:00 - 14:30 we have close to linear development initial stage and then yielding to generally this is the point where we have lucky for us who still not brittle type of failure So we have good yielding relatively gradual process of destruction Uh FRP materials we have one positive element So this is CFP and this is and this is GFP as
14:30 - 15:00 materials with different models Uh so the stiffness that ging and the inclination of those lines is different They could be much much stronger in general they're stronger than steel You can see that the stairs that we achieved is quite high from one side from the other side This is one of the good points When we reach this point
15:00 - 15:30 the the next step is vertical line downward We don't have the restriction The capacity of those elements depends on the material Uh so this is the reason that usually is accepted that We calculating structural elements with such type of enforcement We have capacity somewhere to use some somewhere around 50% of the real capacity of such
15:30 - 16:00 type of structural materials to be far away from the dangerous z about the level of inclination that I mentioned This is Another tricky tricky point for those materials uh generally they're quite deformable is significantly lower than steel and we danger if we use say the
16:00 - 16:30 same amount of reinforcement as cross-sectional area say the same number of parts with the same diameter we definitely the ultimate capacity of such elements could be significantly higher than posterior reinforcement But they will be for more and actually to cope with this excessive information we need to probably two times more material I have colleagues that have
16:30 - 17:00 made quite intensive research in University of Girona about this and this makes the things more expensive and actually doesn't make a lot of sense to use much more material when we don't need it [Music] speaking but there is way to cope with this problem as well and lately especially even for strength in but especially for new reinforcement to
17:00 - 17:30 sustain applications we looking more and more to restressing we have ability about resting that we're working meet with colleagues from FIP and uh I would say that the interest about this approach is more and more intensive because the problem with the
17:30 - 18:00 mobility as a result of relatively modest leveling uh could be solved quite successfully Uh this is one example how useful to be FRP as material for strengthening One of the bridges that I had the pleasure to deal with with some requests for strengthening of the can parts of the decking Actually this is
18:00 - 18:30 the part that needed strengthening Uh and one of possible options was to remove the services uh to be attached to the steel part of the structure Those are paper on builders and to cast additional concrete on place where services used to be and it's not very good solution because it's a lot of work Additional
18:30 - 19:00 uh movements of the This is creating not so pleasant appears and generally slower and more expensive approach using FRP actually we could keep the same situation we could keep the services here put laminates that they as you see about 1 2 mm thick so we don't have any dramatic change in the appearance and they are able to to do
19:00 - 19:30 the same The strength of those materials is very very high about strengthening of existing such I generally divided the the whole presentation two parts First part is strenging which is popular from longer time and reasonably well developed but still areas that need improvement
19:30 - 20:00 Um we have mainly two types of applications EV is for externally bonded type of laminates like like this one that are glued with special types of epoxy glues to the post concrete surface and that ensuring reasonably good connection with this way of gluing and very fast and easy way for PL than steel plates that
20:00 - 20:30 need to be drilled and to have holes that are going inside the concrete etc Of course uh all positive elements are having negative aspect as well with glowing we always at a little bit of risk to haveation but as long as the level of loading is not exceeding comfortable zone the risk for such is not very dramatic The other possible
20:30 - 21:00 application is NSM which is near surface mounted reinforce usually slots on the surface of the concrete element in the area concrete cover not damaging the existing reinforcement And then different options but one of the options is to to have bars that are placed in those slots and again which correspond to blue etc The benefit of
21:00 - 21:30 this approach is that the the connection between deficit is much much stronger and the danger for the rumination is we we were able to see this from our experiments is much much many many times smaller than the other one Of course NSM is quite easy to be applied when we speaking about the surface If you need to make slots in the concrete on the
21:30 - 22:00 sand from below the the slab it's terrible and construction companies that are making suspected are not happy with such approach So certain limitations about such application Uh this element is from we we had some contacts with colleagues from Japan So
22:00 - 22:30 them making experiments here with strength columns on similar way that I mentioned on the first slide In this case the columns are rectangular section This makes the things a bit more complicated Usually we looking for rounding the corners with such rectangular columns to have a little bit less dramatic area point of view good connection between net and the
22:30 - 23:00 surface In this case the our Japanese colleagues haven't done it but but they're using relatively narrow strips which probably it's much easier to be applied even when we have that kind of shape and the stanking on the top is about stanking against printing shear and this is another quite popular and important application and we're working for quite
23:00 - 23:30 a few years one of our PhD students he is going to to continue our work in this uh but uh I would say one of the problems that is not completely solved So if we have some information how we could solve it we could apply such type of stamping but uh we are not sure how exactly how how it could be more economical with this
23:30 - 24:00 because the the main problem is coming from putting the laminates to the concrete and this is usually outside the zone working laminate And uh we tend to be uh a bit pessimistic and to to ensure non significant outcomes because we're not 100% sure how things are going to behave and this is
24:00 - 24:30 something that we already making steps to investigate Otherwise speaking about anchorage those are uh some samples that we have modeled strengthened slap with the same thickness but just taking one linear element of this relatively narrow element from the sling which is definitely laminate You can see the
24:30 - 25:00 last sample here and we developed few options for additional eyeing that is improving that the connection and actually especially these the poses one appear that it's giving 20 30% of increase in the capacity just because of those additional one which is considered as Good result good
25:00 - 25:30 achievement I would say that our paper has been already cited many many times about this this approach use it uh strenging of beams and stops uh with laminates One of the first
25:30 - 26:00 investigations that we have made is behavior of elevated temperatures because there's always question mark okay what's happening when we have f and of course the first thought it's okay this is f type of plastics that means that it's god uh which is not exactly the case actually and I have seen quite a lot of publications that are and quotes as well that are stating okay if we reaching glass transition temperature then we couldn't count anymore on on
26:00 - 26:30 this strengthening not that it's very big deal I mean after the fire if the element is still intact let's say existing we could just remove previous and install new ones but it appears that it's not so simple because last transition temperature is usually below 100° So it's quite low We speaking about blast transition
26:30 - 27:00 temperature because this this is the weakest point of this combination And it appear that we according to our research that actually quite significant amount of strength and capacity is kept above above You could see here uh say levels of loading 20 20° in this graph is this the
27:00 - 27:30 tallest bar chart which allows this is without any negative influence from heating and up to 150° we still have uh somewhere around 70 75% of the capacity remaining with such level of heating Uh so our research this was DO that have made her dissitation in this
27:30 - 28:00 area showed that the things are not so bad uh and their spare capacity that in some cases could be quite useful In addition to this of course we always when we speaking about buildings danger to getting high temperatures due to fire the building Outside probably there is more risk for very high temperatures but when it's inside building closet space we could have quite fast increase of the
28:00 - 28:30 temperature you're familiar probably soal standard curves etc Um so for such type of elements it's very natural to use type of paints that are giving additional protection against So very fast heating of such elements Continuing about the same area
28:30 - 29:00 elevated temperatures and could see some samples that actually have been prepared This is the control sample without heating and the other sample heating I believe yeah 300° was was the highest and uh apart from some changes to the color of code that there's corresponding change about capacity
29:00 - 29:30 uh we learned that they weren't available literature sources at this time what type of changes happening and actually what we use it we use it the good opportunities in Kingston University we have very good electronic equipment microscopes on microscope electron
29:30 - 30:00 microscope and we were able to monitor what's happening the three components that it's defining the behavior of such type of stylements the three components are the concrete itself the haz and the and as I've mentioned already that has it is see that it's wicked wicked element but again we could we were able to to make
30:00 - 30:30 investigation on changes to the materials and make connection between those changes changing mechanical properties The the good news is that those changes are happening gradually So it's not like working okay up to 80° and 90° only So we have gradual development and this makes the the application less tricky and few examples of strening to
30:30 - 31:00 different types of elements One of them was full scale testing of masonry was for perpendicular to the plane of the wall One of the first students that we had working this way was doing those experiments The best option appear that it's the the
31:00 - 31:30 third one here from the schemes I'll call it hybrid actually type of reinforcement because it consisted of basled fiber bars placed horizontally in the gaps between different rows of bricks and carbon fiber laminates in vertical direction So this is the last significant increase
31:30 - 32:00 of ultimate load to the such approach We had several other options You could see these two of them here Uh they they have some positive result but but not so significant as the last option Uh and again about me is actually very good thing about researching me
32:00 - 32:30 structures in general Um is another testing small scale this time for loading on on plane type of loading loading that it's parallel to the plane of the measurement So this yellowish part is actually part that is consistently small bricks by 50 by 25 mm
32:30 - 33:00 uh produced by cutting to standard bricks and we using diamond type of testing equipment that have been developed from some other project to mention about it later Actually in this specific case it was final year students who had dissitation project that have made such testing and
33:00 - 33:30 uh the testing was uh without any additional strenging of such type of so you're speaking about wall but low in inclined position So the rows of bricks are 45° in one direction between bricks in the other direction So the the way that appears on this photo section without strening can be investigated what's happening if we
33:30 - 34:00 have strening along the diagonals of of this diamond shape with a type of CF laminates and uh with two different widths 25 mm width of the laminate and 50 mm uh type of loading was uh quite typical for upgrade loading with alternative movements of the
34:00 - 34:30 testing run in the other direction and the other increasing intervals and amplitude of movements and it appeared that actually the result is those are his very helpful for estimation of the And this is happening It appear that uh
34:30 - 35:00 it's yes uh changing the order Uh we have so uh light blue line is unstrengthening support uh red one is is tanking with 25 mm laminates and the dark one is with 50 mm laminates and see obvious increasing of the capacity such flows generally the the idea is to investigate what's
35:00 - 35:30 happening and how helpful that contribute significantly to increasing capacity of the walls situation Uh this diamond type of rig was developed in connection with project that it's connected with investigating
35:30 - 36:00 connections between steel frame structure and thin wall infield plates The type of she was that we investigated already for quite few years and uh such type of connections have been actually tested with imagine that this is the sheer wall Those are the parts of the steel frame and this is blade that in our case 0.8
36:00 - 36:30 in little thickness but giving significant capacity The bracing actually bracing instead of bracing we have thin wall t this type of structures are quite well known for some period of time but we made it quite traditional quite important traditional investigation about the development I'll come later to this and we focus in this specific case about using this equipment for uh including
36:30 - 37:00 the connections between them And coming back again to this type of shear walls and you could see one example of investigating sheer walls with openings in this case a little bit artificially circular opening of course it's similar situations for situation for windows or doors or suspected
37:00 - 37:30 openings and uh this interesting thing is we we try different ways case of stiffening in case of openings to reduce the negative effect of creating an opening And you could see on this graph that actually with great is [Music] uh with with blue W1 is without opening before before having opening the way of behaving with red
37:30 - 38:00 after having open caring she and green one is with opening and with adding layers of effort materials on both sides of the in so we speaking about couple of millmters material that is glued to the surface on both sides and those couple of millmters actually is increasing the
38:00 - 38:30 capac capacity I would say significantly above the level before making properly in suspects So this was actually one of the first cases that we have applied different materials to suspect stual elements Since then at the moment we have already third person that is working in further development and we reached significant
38:30 - 39:00 increase of the capacity as summary the effect is around 40% increasing of the capacity still loss into place and adding of material to them and it's not only increasing the capacity actually one of the key points is the effect of materials to energy dissipation because
39:00 - 39:30 we energy dissipation resisting structures and it appears that that is strange enough because many of the authors are expecting if the material is linear elastic behavior will be zero couldn't contribute to developing a significant discation It appears that the combination of the enforced concrete and the way
39:30 - 40:00 that concrete could be restricted gradually and relatively let's say small speed of destruction allows to have significant energy stretches One other approach for strengthening is about punching shear strengthening And you could see that we have quite detailed investigation for
40:00 - 40:30 several different types of structural elements Small scale samples on the left And actually the main experiments were medium scale size So about one one and a half meters side of the post complete slab that we subjecting to punching sheet and monitoring the process of development and as expected
40:30 - 41:00 actually increasing the amount of FMP and especially applying additional like sample we have very good results above certain level actually for this last sample the is not so significant So we still in process of investigating what various this and how to estimate probably the angles that
41:00 - 41:30 it's working in progress So this is about uh the same she walls with thin infield plates And as I mentioned the second series of investigations gave excellent results compared to pure steel infiltrated habit in steam And uh we have another PS that was
41:30 - 42:00 focused on connection between different plates and the the plane And now we have four PhD student that working on combination of knowledge in those areas to get the maximum beneficial effect and we're looking for potential development
42:00 - 42:30 design approaches and using type of innovative structural systems One interesting element connected with uh strengthening still of structures So if you look on the photo here on the top there's one black rectangle which is s type of s material to the concrete and uh we have
42:30 - 43:00 artificially introduced damages of the connection between them uh placing material that is not actually equivalent to to the facet that we we are using You could see such elements This is glass fiber So we could see the damages that are on purpose
43:00 - 43:30 created So for glass we could see through to through the layer of glass to the layer of effort it's completely not transparent So we couldn't see we don't know what's happening and if we have such problems this could compromise the connection between and this make the whole exercise not not useful Of course there are other ways for investigating say
43:30 - 44:00 knocking on the surface of the laminate here about potential gaps in the haz and it could be injected on this place Actually we made from point of view of investigating say 100 m long bridge that it's with such lamin it's all over the length of the bridge and knocking on the surface one or two or three laminates is fine day after day
44:00 - 44:30 to go to apply the same approach it's not very reasonable approach so what we have tried is to use infrared theography for investigating and the result was excellent We could see actually the infrared photo and with red we have the exact position not only the positioning we have diameter of the dime that we have wrong
44:30 - 45:00 places and how it works uh very very simple approach actually uh if you have proper layer of adhesive without any gaps the conductivity on this place is approximately the same This is this yellow area is such such type of thing But if you have air at certities changing and when we heat the laminate and make
45:00 - 45:30 photo see where exactly is the place where we have problems So uh and we continue Yes So do you actually ation It's more like artificially introduced problem So it's not loaded and not the elimination starting but but we something like bubble wrap that we placing instead of the but has it on this place but yes we we seeing exactly where we have put them because we know
45:30 - 46:00 where we put them So those three zones are actually three defects The red ones and the red is indicating that the temperature there is a bit higher than the other usually like one of the degree or something like this but this is sufficient to be able to see that But this is as a result of applying alone No this is the result of heating on the surface with something like hair D
46:00 - 46:30 uh and making photo with infrared car The other possible approach is to have hitting some other places like blankets and removing the blanket and making with camera to get the same effect It's not delimination due to loading It's you could see it's in static position [Music]
46:30 - 47:00 small Let's say a similar situation if we have to estimate what is the condition of strenging the existing bridge state after certain period many years and you could do the heating and immediate to make recording the We haven't done this practical point of view but not
47:00 - 47:30 uh and we're moving to the second area about FP materials using FP for internal reinforcement like again this type of parts replacing steel reinforcement with FMP parts Why we need to do this quite often uh we have say bridges in marine environment or or just bridges with the ice and salts that
47:30 - 48:00 are quite often creating a lot of problems You could see the corrosion of steel reinforcement and this is I would say the main problem actually for reinforced concrete structures in aspect of durability effort reinforcement is generally not very cheap but it appears that with latest developments at least my information from industry that the cost of FMP bars so this type say last time polymers but
48:00 - 48:30 there don't have problems with them it's somewhere between stainless steel and usual so it's actually more economical from my point of view probably we haven't done investigation about probably more applicable from the point of view that stainless steel and concrete the connection between them is not so good as as usual steel and concrete and FRP materials the efforts
48:30 - 49:00 that have been made to have good connection with the concrete by treating the surface of in this aspect probably it's better so uh more and more we are speaking about new elements not taking of existing class but new elements reinforce it with effort reinforcement Canadians and Americans are having already a lot of bridges with reinforcement but from my point of view
49:00 - 49:30 actually the huge development in this area is still coming because with global warming and increasing the sea levels etc we will be forced to make more and more offshore structures uh and in in seawater environment probably is the best option Uh still there is some I would say slightly
49:30 - 50:00 pessimistic approach that not not everything is clear and especially for very big projects uh they prefer to look for some ways of protecting enforcement and monitoring etc I think that we will have to use them intensively about such type of structures and again I'm speaking now about new structures not strengthening existing
50:00 - 50:30 ones and uh positive aspects corrosion and durability definitely much better than usual steel strength limitations uh We have excellent behavior We have to keep in mind that we have kind of mobility to create models from one side from other side There is additional effect that is
50:30 - 51:00 good to be kept in mind as well And this is so creepy and creepy is very unpleasant It it generally says that if we have spiritual element with different feeling forcement inside and it's loaded to significantly high level say 50 60 70% of the ultimate
51:00 - 51:30 capacity this element could stay say many years and then boom to the point you have without warning you get broken and became collapsing So very dangerous phenomenon Americans are solving this problem for the moment with a little bit of I would say okay it's not good to use primitive
51:30 - 52:00 but simplified Let's say simplified approach They're saying for example pre-stress ints allowed up to 30% of capacity because it's considered that with 30% or lesser level of loading the danger of such rupture is almost zero uh from my point of view there is need
52:00 - 52:30 of additional investigations about this because in some cases it might be 30% indeed but in some cases say we had resting and I'll come back to this later we had testing with 70% and according to some specialists in the area that are having a lot of experience but it depends of what kind of material specific issues they said that few hours it will collapse into but actually such levels of
52:30 - 53:00 distressing with baselmers we monitor it for many many days weeks I would say without any case of having such type of problem u few other elements that have kept in mind electromagnetic effects A steel reinforcement is not very good for laboratories where we have electronic
53:00 - 53:30 equipment Not very good for hospitals where the electromagnetic properties of the steel reinforcement is interfering with the equipment in those hospitals So another area for using steel and it appears that more detailed investigations about the effect on CO2 emissions etc uh FRP appears that it's at the end carrying in mind the
53:30 - 54:00 life cycle effects and all possible considerations is giving lesser amount of superition that production of steel So from this point of view and from point of view of durability it could be considered as healthy material from point of view of saving the environment mitigated let's
54:00 - 54:30 say so uh some practical aspects about such application one of them still in process of completion manufacturing experiments for the post complete frames with reinforcement Uh even so interesting that we have colleagues from Japan that have been very interested about the results Uh again there was a few some time ago
54:30 - 55:00 that effort reinforcement must be used for frames not for columns as well And it appeared actually if you see the graph here this is comparison between steel reinforced frame and effort reinforces frame with the same diameter the same position at the bottom The type of loading those hysteric curves obtained
55:00 - 55:30 by so-called standard earthquake loading with gradual pushing and pulling with corresponding number of cycles and gradually increasing the amplitude especially the type that is applicable for in post concrete elements according to ACI u we we using similar standard for testing steel elements that I mentioned a bit earlier about the them
55:30 - 56:00 again so called standard earthquake volume it's not earthquake volume like shaking table but but actually gives good information on how the things could develop with increasing the earth so um and we estimating not only multiple capacity with such type of loading but dissipation as well as And the results are quite positive You would see that ultimate capacity say
56:00 - 56:30 this is the dot is a little bit less than ultimate capacity for steel again we speaking the same diameter for um basis for comparison but actually it's not dramatic difference and from other side we have much longer gradual development of reflections which actually indication the Below those curves is indication
56:30 - 57:00 about energy dissipation So we have strangely better dissipation for planes with steel reinforcement Uh and we made additional investigations connected with different levels of confinement and what is the behavior So I'm not going into detail because still not completed the PhD but next few
57:00 - 57:30 months it will be completed we have already publications connected with it another structure element this type let's say usual sheer walls within concrete type of shear walls but the steel reinforcement replace it with and we have very similar results for them to the results from the plane So again similar capacity gradual
57:30 - 58:00 destruction bigger energy dissipation is prec I already mentioned that again the relatively low models say around 50 gigap pascals uh in capacity with steel Speaking about glass fiber carbon fiber is much better
58:00 - 58:30 and and all companies that are producing such products actually are aiming to improve the end problem So we have recent developments about this but still uh way that we could solve the problem of this stage of development is testing because this reduces the mobility and the role of relative lower it's not going to be so significant
58:30 - 59:00 Um so we are solving the probability We have another problem that we need to solve brittle failure and we are working in this direction with using different levels of prestressing different partial pre-stressing as approach Uh we still don't have very categorical result but that this brittle to suspect we have a lot of
59:00 - 59:30 strength with traing in most of the cases we're speaking about mics strips that could be actually practically u so it works it works uh about mass production of uh pre-cast elements say we approaching this stage not really already reaching it but I agree that it
59:30 - 60:00 will be in not far away future uh I already mentioned this problem as long as we not overload them close to ultimate limit state capacity that is I would say eliminated again a bit conservative from my point of view say 30% is no problem for glass fiber for
60:00 - 60:30 basel fiber for any type for carbon the risk is relative But carbon is relative is expensive So we more like think more of glass than the cheapest ones and very good ones Diagnostics is another very interesting element because nobody have been really interested in this We're just starting to apply say
60:30 - 61:00 elements internal reinforcement We don't have strictly speaking well developed testing methods uh for for this we have another PhD student here M that is going to develop this in near future hopefully we have already some positive results I imagine that it will not take too long time to have some methods for uh detecting
61:00 - 61:30 positioning time in existing spiritual elements trying to be ahead of demands that are going to appear from industry because we have a lot of demand for necessity steel type structures Uh another interesting actually element uh FP material and uh
61:30 - 62:00 uh it it's very strange because uh um say this is pre-stressed being with pre-stressed reinforcement and we are loading and you could see significant deformationations and significant cracking almost reaching the top level concrete
62:00 - 62:30 section and strangely enough if you remove the load this the whole element is going to horizontal position like spring this is due to linear elastic behavior of this material so we don't have we We have caused some minor losses due to damages of the connection between the the testing reinforcement and the
62:30 - 63:00 concrete but it's still very very elastic So which is additional benefit say we have this type of elements even if if they're over at point probably the cracks will be almost completely closed if they're in if this excessive amount of water is removed And on the other side you
63:00 - 63:30 probably noticed that we have here something like supports below the element because the final stage is when we have destruction the destruction is very similar It's going down If you have any equipment below it we know that the people that are working to stay sufficiently far away but if you have any equipment we had such cases is broken So actually those additional supports
63:30 - 64:00 are preventing them for real stretches is is more I would say less dangerous situation because we usually not having simple supporting but some level of fixity at the end even if the precast elements So uh probably a little bit less dangerous but but still something that we have to keep in mind
64:00 - 64:30 uh about pre-stressing of internal reinforcement We started many years ago with one of the PhD students actually with post tensioning having ducts inside the casted concrete and after that placing the reinforcement and apply tension and it ends U this is the type of elements that I mentioned that we have 70% of ultimate load
64:30 - 65:00 applied as pre dressing without any problem for beers for many weeks Uh I'm not saying that this is the right way to do it but the statement that this is extremely dangerous and going to a bit I would say a bit too conservative still something that needs
65:00 - 65:30 to be investigated process investigating what's happened different um and again similar situation about way of developing restriction You will see with blue the steel reinforced element almost the same load bearing capacity as ultimate load but host elements we have much more gradual restriction and any much better
65:30 - 66:00 So again point of view and especially consider molding etc [Music] It it gives quite reasonable results and pre-stressing with pre-tensioning and this is actually good point where we could see what is the level of precessing and with 40% promoted low level of stressing we have actually higher
66:00 - 66:30 stiffness element still actually 40% dising is approximately equivalent to 20% specific steel So u it works very well and you could compare with non prestress So we have several times more mobility and this 40% prestressing can for 30% prestressing
66:30 - 67:00 actually we could say that we have approximately the same moabilities for usual non prestressive type of elements would still reinforce Okay Uh another interesting investigation that we have made very recently about year and a half ago completed postponing is to investigating losses of distance and
67:00 - 67:30 this is extremely important because uh without knowing what will be our losses of distance we are not able to design such type of elements So uh there are many things around the world that are working on this problem I would say that some sort of competition with with them but we have good initial development
67:30 - 68:00 So uh the level of time that we have investigated the characteristics of such type those are pre-ressed beams with control ones with steel reinforcement and the others with different levels of precessing u and tested in about 90 days continuation and we monitor it and not only we other teams are monitoring the same the process of losses of stress is
68:00 - 68:30 almost stopped even to this level in a short period of time Let me check Yes you could see actually the ground developing process of this test and I would say that actually the the only element that is still in process investigations losses due to relaxation
68:30 - 69:00 So the process of relaxation is not the same as by itself is quite complicated We already have made some research We continue to investigate [Music] this and of course consideration of pre is very important because according to some
69:00 - 69:30 investigations say you could keep horizontal for 5 10 20 years and then we have some significant failure But again we we have ways to make this more gradual either combining different levels of precessing or combining different type of materials till the moment we more investigating combination of FP material but this is not very good
69:30 - 70:00 approach why because we count reinforcement to have corrosion if you put steel reinforcement there it's going to so this positive effect will be lost but we could use different types of FL with different different levels of distancing and this could solve the problem with the brittle failure and silver failure potential here and again the the view
70:00 - 70:30 very experienced teams and investigators is that up to 30% level of testing for the moment it might increase as as limit but for the moment up to 30% doesn't It's not connected with danger And another element if you ask me a little bit like uh the Golden Gate Bridge you know that this is used to be
70:30 - 71:00 called the bridge that will not be able to be built and yeah it's built it still stay there So similar view for frames and for columns effort reinforcement is not appropriate for elements sold to compression they're not working well and we have made investigations this is in our lab and actually again the
71:00 - 71:30 capacity is not here but I I have the glass if anybody that would send them the capacity is approxim the same as steel reinforcement a little bit lower but not not dramatically lower Um I'm not saying that that the way that reinforcement is behaving is syntactic the way that steel reinforcement is behaving for but still we had very reasonable behavior and I don't see reasons to
71:30 - 72:00 ignore completment for such type of elements uh one of the tricky points is uh this one here I don't know if you're able to see but this longitudinal FL bar last time polymer is actually broken here completely So the the two parts of the bar like like such position So we still haven't investigated this is
72:00 - 72:30 happening at final stages not not stages and reaching the ultimate go already there was some doubts that actually reaching ultimate load is this because specific cover loading for the bar that is appearing after crushing of the concrete So the and and in this aspect actually effort is a little bit better probably because steel is usually
72:30 - 73:00 bending yielding the falling significantly and significant part of the skeleton is still staying even when you would see that the concrete is completely gone in this crack here But uh one of possible factors that we need to investigate is what is the role of the links because our type of description we monitor exactly where we have links So maybe there's some
73:00 - 73:30 influence between them and bus uh we want to clarify this and potentially to look for way of solving to avoid such otherwise the focus was on confinement We used links with different distances 7500 and 530 m and we had very
73:30 - 74:00 interesting results both in aspect of motor destruction and in aspect of capacity [Music] So let's say the motor destruction 430 is a bit less brittle on one side but with lesser ultimate capacity in capacity small distances So still something that needs more investigation but at the moment we have
74:00 - 74:30 the experimental results We make political modeling to clarify how we could present and how we could explain some specific aspects and a little bit as final few words long uh about future developments This is the way the times look at not only me Okay
74:30 - 75:00 I'm saying quite often I but actually here group of researchers in Kingston University that are working together say four members that are that full-time members and corresponding approximately same number of PhD students that we have and then we get same job So in the future u codes
75:00 - 75:30 and standards they in process of active development Let's say that Euro is falling a little bit behind the Americans ACI in the sense that we have draft version of code two that is having about enforcement and it will be official version soon but it's not actually within the main body of the is some additional part which is
75:30 - 76:00 probably doesn't matter so much but Americans are having their own version about reinforcement um widening of applications for bridges offshore seaside structures this is the area that I believe it useful the moment we don't have alternative type of reinforcement that do the job we will probably have to follow this
76:00 - 76:30 but The other question that it's appearing more and more often is okay in uh it's synthetic material not exactly friendly from point of view of the environment not strictly speaking very damaging but but we're looking for natural fibers and there are quite a lot of investigations about this for the moment the capacity that we getting with natural fibers is not very high but
76:30 - 77:00 maybe You don't need very high strength in many cases and maybe we could find type of natural material that work properly This would be excellent space applications This is another interesting story as long as I know I might be just rumors but this is what I've heard that actually say
77:00 - 77:30 have been developed initially from Russians and I tend to agree with this because I had guests from United States and they were interested in Basel and actually were looking for buying basel fibers from companies in UK that were imported from Russia and China is producing such material But what what is the idea the
77:30 - 78:00 idea is that they had planned to make base on the moon and they needed building material to to make sufficiently strong I mean precious sufficiently strong base and then their solutions have been they don't have other materials but using say basel using su maybe su based concrete could be
78:00 - 78:30 If you're looking for using the traditional methods for building there of course so space applications space we're probably going to use this one list of references and this is photo with microscope it's not gold this is something material between carbon fiber
78:30 - 79:00 So thank thank you very much for your attention Oh thanks very much I have to admit that early on in your presentation when