078 - Experiments that Changed Fire Science pt. 2 - BRE Cardington with Tom Lennon

Wojciech Wegrzynski: 0:00

Hello, everybody. Welcome to the fire science show. Today we have a second experiment in the mini series, experiments that have changed the fire science. And oh boy, for sure. The today's experiment did that. Last time. We've talked about the round Robin part of Dalmarnock experimental program. If if you miss that. You're very welcome to catch up. And that was very impactful in how we treat modeling how we. Use modeling how we perceive modeling in fire science. And very impactful work. Today's work is something that actually lead to establishment of modeling as a useful tool. As a tool in structural fire engineering. We're going to talk. Cardington. Cardington is a town in UK. Where. BRE had it's uh, Testing facilities set up in the giant aircraft hangar. And in that they have carried multiple, multiple experiments that involve. Um, full buildings like full scale building size fire experiments. The only fire more than that, but fire is the part that interests us. Perhaps that's the first time when we've observed, when we've measured that. The response of a building to fire is, is lot more than just the response of each of its parts individually. And, the there are effects that we should include in our modeling. That has led to development of a massive library of results. That's are used till this day, like literally a month ago, I seen a paper with a new structural fire safety engineering model, that's based on Cardington and use Cardington as its validation case. Wow. What a legacy we're talking about research that has been carried from late eighties. through nineties to early two thousands. So, so suddenly yes, some time has passed, but still. It is making a daily impact on fire science. To talk this over. I've invited Dr. Tom Lennon from BRE Who has been involved with the multistory experiments and all the experiments that followed that. At Cardington so, uh, certainly. Some of the very knowledgeable about what happened there And the very nice person. I'm very happy that Tom has agreed to share. He's experienced from that time with us. So I guess that's enough. Uh, There's no point to prolong this anymore. Let's spin the intro and jump into the episode. Hello everybody. Welcome to the Fire Science Show. Today we have another episode on the experiments that changed the fire science, and in this case multiple, multiple experiments that were carried in Cardington, fire Research Station, BRE facility in Hangar. And I, I have Dr. Tom Lenon with me who has been heavily involved in many of them. Hello, Tom. Thanks for taking the in.

Tom Lennon: 3:21

Hello, Wojciech

Wojciech Wegrzynski: 3:22

I'm so excited. Cardington is a sacred name in fire science. When you enter the field, and especially if you are anywhere interested in structural fire engineering, so, let's, let's jump into that. the tests were carried over many, many years in, in the from starting in the eighties through, through the nineties. And, I wondered, first of all, how did you guys, found idea to, to do this super large scale experiments inside an aircraft? Hang. maybe you can tell me some stories from the, from the origins of the test program.

Tom Lennon: 3:54

Okay. Yeah, I think, the, the background to what became known as a large building test facility, so this Cardington itself, which was the hangar, which had been there for some time. So we had a very, very large space, which was a good start. but the background to what became the large building test facility was the discussions around whole building behavior, which. Why didn't just fire, contain things like, issues to do with ex blast resistance, dynamic response and was partly at least, a function of the disproportionate collapse of the tower block at Ronan Point in 1968. And that, I think had a big influence on some of the, Influential people within the BRE when I joined, and they, I think together with government were kind of pioneers in thinking this way. But I think the other area that shouldn't be underestimated is the influencer industry had because, and particularly at this stage, the steel in. I think the steel industry saw in Cardington and saw in this idea of whole building behavior, an opportunity for them to demonstrate. The inherent performance of the structure compared to the single elements. And this is where we maybe started to move away from standard fire testing towards a more sort of holistic, robust approach. but their motivations were. Commercial, they were looking to increase their market share and particularly in the office medium to high rise office, market, which was what the first building, still building inside carton looked like. Um, we had a different objective. We were looking to develop fundamental data to understand structural performance in fire. And I came from a structure side, not the fire side. And I think that was really quite significant cause the people on the fire side, Who had a background in fire dynamics, very clever people, but they didn't really have an understanding of structural engineering. And I think bringing together these two disciplines was one of the greatest achievements of Cardington and one which has had some, some legacy, I think.

Wojciech Wegrzynski: 5:58

it's quite funny. Did you say this? Movements into understanding the building behavior in fire and, using more advanced ways to demine the, the structural response to fire in, in general. When I had an interview with, with Professor Babrauskas some time ago, he told a very similar thing related to 1970s even, that they thought that the computer modeling will soon replace the standard testing. Then you positioned around mid nineties, had the same objective and I would say many of, fire research. Today still would have the same objective, like standard fire testing is, is is still here. It's not going anywhere. However, I the performance based, engineering and recognition of structural fire engineering has, has really changed over the course of years. Was there even structural fire engineering when you started this? Like would people optimize structure for fire?

Tom Lennon: 6:52

no, not really. I mean, it, it's quite hard to look back at that time and realize where we were because there's been so much progress made, then and now. Um, put our mindset back at that time, um, there wasn't really anybody talking about structural fire engineering. There were people who were materials experts. Steel in concrete, in timber. And there were people, certainly people who were fire experts in terms of fire development compartment, fire dynamics, et cetera. But there weren't really, I mean, some of the guys, some of the guys who were involved in the early stages who don't often get the recognition they deserve, um, some of the academics and in particular, we were working with, uh, university of Sheffield In the early stages and, um, Plank Ian Burgess at Sheffield, were really at the forefront of this, of, thinking, um, structural fire engineering. But think about it all you like, but what you need, if you're gonna develop design methods, you're gonna develop numerical tools, is validation for those design methods and those tools. And that's what we were in a very fortunate position to be able to provide data that could be used to discipline and to validate the tools that came as part of that discipline.

Wojciech Wegrzynski: 8:08

uh, Let, let's build the timeline of, of this experiments. I know the first experiments that happened in 1980s, were related to the behavior of unprotected steel elements, I guess that, that predates your involvement in, in, in the Cardington program,

Tom Lennon: 8:23

Yes.

Wojciech Wegrzynski: 8:23

or were you, you see.

Tom Lennon: 8:25

when I first arrived, those experiments, the natural fires in large scale compartments, which was a British steel technical and FRS collaborative program that was actually taking place when I arrived at Cardington, but I didn't have any direct involvement. I was aware because I was involved in the structural ER codes, I was aware of this work and it was largely to do with validation for the time equivalent and the early parametric approach, which eventually ended up in Eurocode. so that was going on, but by the time we started with a steel building, which was the first building that went up inside Cardington, Those experiments were complete and, yeah, we, we moved on looking at structural behavior rather than what was going on there, which was effectively heat transfer validation,

Wojciech Wegrzynski: 9:12

Mm-hmm. So, so then you moved into this, uh, multi-story building, uh, behavior, as I understand correctly. And, this is the main thing I wanted to talk about today. So to, to give context. You've build, multi-story. How, how build, how big was it? Eight stories. Uh,

Tom Lennon: 9:30

It was eight stories. It was a modern composite construction, so it was steel frame with, uh, composite decking. and at that, at that point in time, that was the most common. Sort of office building type that was being constructed in the city of London and elsewhere. And it was designed and built as a real building. It wasn't an experimental building, it was designed by, designers, uh, who were practicing engineers. It was built by contractors who were doing this day in, day out, and there was nothing special about it. So it wasn't a, it wasn't a building designed for a specific purpose in terms of the experiments. It was designed to be a typical office building built in composite construction, and, We were, like I say, we were fortunate enough to get the opportunity to work on that and to cause all sorts of damage on the building. but uh, it did manage to survive everything we threw at it one way or the other.

Wojciech Wegrzynski: 10:25

how did you decide, how big will it be? Like, so someone came, let's, let's build eight stories and everyone was okay, or, or was there a bigger brainstorming behind the size and the dimensions?

Tom Lennon: 10:35

no, there was a brief, there was a design brief. which was based around, a city center development in Bedford, which is the closest town to Cardington. But, the, the whole purpose of the large building test facility was to move. Towards as close as you could towards reality. And that was reality in terms of what you were dealing with structurally. But it was also reality in terms of a fire and everything that went around it, including when we did the first, large natural fire experiments, including things like double lazed, windows, and fittings. And so, you know, everything has an impact and. If you can realistically model what is actually there, rather than just a single element, then you've got a better chance of predicting what's likely to happen in a real fire event. So that's, we were learning all the time. Um, I think, uh, I think that the process was one, to start from the very small and to work our way up and at each stage in the process we were learning and improving our knowledge. Structures in fire, in this case still in fire, but we, I shouldn't neglect to mention, we also had a seven story concrete building and a six story timber building within the same facility. And there were also, uh, experimental programs on fire carried out on those, on those buildings.

Wojciech Wegrzynski: 11:59

Like at the same time,

Tom Lennon: 12:01

almost sequentially. I mean, we've, we completed the main program, collaborative program with British Steel and some partners from Europe on the steel building. And then we moved straight onto the uh, European Concrete Building Project, and I think. Almost straight away. After that, we moved onto the, uh, timber frame, which was a residential, building meant to be a block of flats. and yeah, it was really active period. there was also the work, the work on the euro codes going on at the same time as well. So, yeah,

Wojciech Wegrzynski: 12:30

this. the timber one would be very, very popular research if you carried it today

Tom Lennon: 12:34

It was quite groundbreaking at the time, to be honest with you. you know, there were, there are difficulties in all these projects. You can't get these things built and you can't carry out work on this scale without the cooperation of industry. And so we're working very closely with the steel industry on the steel building, the concrete industry on the concrete building, and the timber industry. On the timber building. But the trick for an organization like b E is to maintain independence and impartiality, and you can work closely with them to get things achieved, but you can't work too closely and you need to make sure that that is set out from the beginning and that you have different objective. And that those objectives are made clear. So I think we managed to tread that line quite well, to be honest.

Wojciech Wegrzynski: 13:20

I, I guess that that is especially important when you start getting negative results. Like something goes other way than than someone expected it to be.

Tom Lennon: 13:27

Absolutely. Yes. Yeah.

Wojciech Wegrzynski: 13:29

I, mean, I'm working in the research institute as well, and, we share the same issue.

Tom Lennon: 13:33

Well, I know, I know we're talking about carton, but we are still treading that line now and, we, we are still involved in large scale compartment tests, even though we don't have carton and the same issues are still there and the same concerns are still there.

Wojciech Wegrzynski: 13:48

Exactly.

Tom Lennon: 13:49

In my view for the industry, even if you get a negative impact from some of the work we are doing, it's better to find that out now than in a real incident in a real fire.

Wojciech Wegrzynski: 13:59

of course. Absolutely. That. So, you, you have built a eight story tall building in your facility. I guess the first thing you do is not, setting the biggest fire you can get on the bottom floor and see if it collapses, but you probably want to play with, with the structure a bit. So how, how does one, uh, design. Such an intensive research program on such a big structure with mind it would be nice for it to not collapse. I mean, it didn't collapse eventually,

Tom Lennon: 14:27

No, I didn't. No, we did try quite hard, but, um, no matter how hard we tried, it stood up. you're quite right and in the, in the early stages, the first. First tests I was involved in, on the building were using, gasified furnaces at different locations within the building. So some of them were external, some of them were internal, looking at the columns, heating up the columns and looking at the stiffness elsewhere and restraint to firm expansion and what that was doing. And we were doing it at different levels, of the building. So ground floor, third floor, and seventh floor, internal and external. Uh, and we were doing it at different stages in the construction. So we went there first when it was just a steel frame and a composite deck before the floors were cast, and then we could evaluate the additional stiffness that was provided once the floors were cast. but we obviously didn't wanna heat it up so much that we caused permanent damage even before the building was built. So we had to plan every stage of the experiments, bearing in mind what was coming in the. So in the first test, we limited the temperature of the columns to 500 degrees, to look at the issues of thermal expansion and restraint to thermal expansion. But then as we learned more, we got, uh, effectively a little bit braver each time. And the scale of the fires increased. So the first natural fire I was involved in was a compartment, which was nine by six meters in area. Uh, the last one was 350 square meters. which was half a floor area. So in each case we were, like I say, learning as we went along.

Wojciech Wegrzynski: 16:01

so, so this first test on, on building elements that, that was actually like, what you would do in lab with a little difference that the restrain of the elements is like in real building, not artificial on the furnace.

Tom Lennon: 16:12

Yeah, that's exactly it. We're basically, instead of bringing the element to the furnace, we're bringing the furnace to the building. And therefore you don't have to have idealized end conditions. You've got real end conditions. and some of the work that was done by British Steel, the original, uh, restrained beam test. They did, was very much that case of, uh, looking at the effect of restrained thermal expansion and contraction in the cooling phase as well, and how that affected connection behavior particularly. so yeah, it was very much a case of, build it up gradually. but yeah, that idea of keeping the structure real and then using the standard fire. Was one of the first examples, before we went on to look at real fire and natural fire behavior.

Wojciech Wegrzynski: 16:57

Have you seen a different behavior? I mean, that's an interesting, I would love to see such an experiments nowadays.

Tom Lennon: 17:03

Me, me too.

Wojciech Wegrzynski: 17:05

like today, okay, today we, we have this fancy modeling tools much, uh, due to the fact that you've provided validation data for them to be developed. but the then 20 some years ago you didn't have this fancy, finite element to method for fire, uh, softwares That must have been one of the first fully restrained building elements in in, they were loaded, right?

Tom Lennon: 17:29

Yeah, yeah. The, the building was loaded, um, on all floors. we, using sandbags, we had these one time sandbags that we moved around on pallet trucks. so yeah, there were realistic loads and they were fire limit state loads that we used. That were in place. So it was, the building was as, as realistic as, as it certainly for the steel flame building was as realistic as it could possibly be.

Wojciech Wegrzynski: 17:53

how hard was it to bring the furnace, uh, to the building? Because, you know, we were just talking, oh yeah. We brought the furnace to the building. We we're talking about seven or eight story building in a hangar in the middle of, not a research facility. And the equipment you, you've used. I would say like, based on my experience with equipment, I have much respect for the amount of equipment installed there. So it's not your everyday fire, fire test.

Tom Lennon: 18:18

I mean, the first thing we did was ship lots and lots of equipment from our headquarters down in, uh, in Gaston, up to Bedford. and then, one of the things we found when we got the furnaces up where we got the control equipment, the satellite panels, all the cabling, miles and miles of cabling, got everything up there and we realized we didn't have any guess. So that was a little bit of an issue. Um, so one of the first things we had to do was put in a gas line and run it all the way. To the bottom of the hangar, which was where the steel building was. And then we didn't have sufficient pressure to, uh, generate the gas pressures we needed at the furnace. So we had to put a booster in and get that up. but looking back, that was a challenge, but it wasn't as much of a challenge as getting the furnace up on the edge column on the seventh. so we had very large cranes, mobile cranes in there. Um, but we didn't at that time. I don't think I could be retrospectively arrested by the health and safety executive, but, um, at that time we didn't have any scaffolding in place and we didn't use mobile platforms. So in the first phase of testing, which was when we didn't have any concrete on the building, just the metal decks, it was very easy to trip over as well. The columns came hinged and you basically brought them in around the column, closed them up, and then did the bolts up the side. And, the only way we could get the bolts up was by one of my colleagues who's very strong, thankfully, uh, holding my ankles while I was draped over the side with a spanner and tightened, tightened them up. That's seven stories up on the floor. so yeah, I mean, I, I certainly wouldn't do anything like that now, but that was, Issues we face, we were faced with because none, none of us, to be honest. And no, nobody else had done it. But no, none of us had been involved in work on that scale in terms of fire testing. so it was, it was new to all of us. Um, the second phase, we bought a big, um, mobile platform with us and it was much easier, But, um, you live and learn.

Wojciech Wegrzynski: 20:11

I, I have similar stories, but I'm much more liable than, than you for, for 1990. So I will choose to not, not shed them in gear. . Yeah. But, uh, that seems to be a shared mentality between a fire scientists who really love what they're doing. Uh, how many people was involved in that, dozens, hundreds.

Tom Lennon: 20:32

No, no, I, I worked with a very small group, but a, a very, accomplished group of guys. So I had a couple of guys working, for me who were basically involved in cutting and drilling and, fixing and lifting and shifting. I had one guy who worked with me for years who was, um, in charge of the instrumentation and he was absolutely fantastic cuz it's difficult to appreciate in this building. Say we were testing one column, then we were instrumenting that column on every floor. and a column one bay away in each direction on every floor with strain gauges, top and bottom, high temperature strain gauges in the area. We were heating normal strain gauges, outside displacement transducers, and that was without any temperature measurement. So, um, and rotation transducers as well. So the, the actual logistical issues were enormous and we were very small, but very, Very efficient, group working together. And we worked there for about 10 years, to be honest. So, um, we were quite good at it by the end.

Wojciech Wegrzynski: 21:36

I guess even data management would, would be a hell I, I see it be a trouble if I, if I was to design this today. I would struggle with, data management, data logging, even with bottom computers and fancy little data loggers that you take,

Tom Lennon: 21:50

Yeah,

Wojciech Wegrzynski: 21:51

to your pocket and, and, go

Tom Lennon: 21:52

our ones were heavy. They were, uh, quite big. But we used, uh, we used a series so you could slave different, Additions to the main log up. And we had, but we had typically around about a thousand channels of data, uh, for each test we did. And, all that data had to be analyzed afterwards, and needed to be, secure, and identified so we could identify the position of every single instrument. And yeah, it was, it was quite an achievement, particularly back in, at that time.

Wojciech Wegrzynski: 22:21

any video recordings of these fires or, or, was it not popular back then?

Tom Lennon: 22:25

Uh, yes, they were, we had professional video recording done at the time, but uh, that was all done on vhs. so I dunno what happened to it. I mean, we worked alongside British Steel and I think they, probably made more effort than we did, uh, to actually capture uh, the video images because, you know, afterwards there was the idea of selling what you've done effectively and taking this out on the road. Um, I used to go, I remember going to one meeting in, I think it's Dub near Manchester Airport, and had to travel with a television and a vcr. Um, so I needed like a massive car just to get the, the tele in the video record doing. But I don't, I dunno what's happened. I've, I've still got some, uh, video tape, but, I dunno what's happened to the.

Wojciech Wegrzynski: 23:06

in my office I have a video cassette from BRE with a compartment fire test. And I was like, I've shared that image on Twitter some time ago, and people were like, oh my God, this is the holy grail of of teaching fire. So, yeah, you can, you can get a lot of Vs. all videos and, and today we learned, uh, when doing our large scale experiments in modern times, we, we really appreciate the knowledge you get by just observing and recording multiple angles. You, you can really learn a lot from just this, uh, video image.

Tom Lennon: 23:38

I think structurally it's the most important thing actually, to be honest. I mean, we've just finished, this is slightly off kilter, but we've just finished, uh, fire experiment we did last month. And in terms of the evaluation, the insulation, we need, the temperature measurements for, but really everything else you can, uh, do through visual observation. So,

Wojciech Wegrzynski: 23:56

it's so, so powerful. I'm great that you did record. I haven't really seen much recordings from Coton, so I wondered, but it is good to know that they are there. Maybe we should send some Indiana Jones to the British Steel Archives and then dig them out and,

Tom Lennon: 24:09

Indeed. Yeah. Yeah. I mean, we used to, at Brv we used to have our own, AV department, and they were, they were professionals, you know what I mean? So, um, they, they, the quality of it would've been very good.

Wojciech Wegrzynski: 24:20

Nice. Okay. so let's move from the furnace test into natural fires. So, so tell me what was the reason you wanted to see natural fires in this multistory buildings and how did you plan out the, the experiment on its own?

Tom Lennon: 24:35

I mean, I think that side of it is, quite clear. I kind of mentioned in the early days we were working alongside our colleagues at British Steel and there was also a partnership with, um, European Common Steel community. I think it's, uh, RFCs now. but there was a European project involved. Their motivation was mainly commercial, to sell more steel, to make the steel industry more competitive. Our main objective was to understand structural behavior in fire. And to do that We had quite a good understanding of structural behavior cuz that was our background, but we needed to understand fire. And, this was something for compartment fire dynamics. It was reasonably well understood, but the impact on the structure wasn't. but from our side on the structural side, at b e, we didn't have much experience of dealing with fire, looking at design fire parameters. And I learned quite a lot from some colleagues at FRS at the time Fire research station. But what we were trying to do was look at, effectively realistic fires. And most fires, don't actually develop, post flashover. Most of our fires are. dealt with in the early stages and we had, we had one situation where we, we built this realistic compartment for the first corner fire test, which was a nine nine by six meter compartment with, plasterboard linings and double lazed windows. um, so we lit the fire. Um, we had a, I think an opening, but a very small opening and surprise, surprise. Basically the fire went out and, um, we didn't have sufficient oxygen. because we'd had discussions with colleagues, we were aware that this was potentially going to happen, and we'd spoken to the fire brigade who were on, on hand at the time and said, okay, if we get to this stage, what you're gonna do is break the windows. And I dunno if you've ever tried to break a double lazed window with a, a fireman ladder free story up in, uh, in the air, it's Not. that. easy. So I was sitting there thinking, watching this ladder bounce off a window, bang, bang, bang, thinking, oh my God, I've just wasted quarter of a million pound or whatever it is, and we're gonna get nothing out. But thankfully they did manage to break a pain. And then we had, the fire developed itself. It was sufficient oxygen, it was preheated. We had a rapid flashover, and then we had a full scale fire test. But that was my first experience of, uh, natural fires. And now I always make sure that, there's plenty of ventilation and that we don't end up in that situation, uh, a second time.

Wojciech Wegrzynski: 27:07

I would like to, to scout now, what was the, background at the time? In the documents about the, design of these experiments. I've read that the test was very influenced, by Broad Gate fire, which was, uh, building fire in which the building did not, did not collapse. But then again, some years ago there was this famous collapse, and I, I think there were other buildings that, that like progressively collapse in. So I guess it, it was not obvious if a building can or cannot collapse in fire as a, just an effort of a

Tom Lennon: 27:39

Yeah.

Wojciech Wegrzynski: 27:40

the Broadgate survived.

Tom Lennon: 27:41

I think Board Gate was, as far as British Steel were concerned, and, and the European steel industry, I guess was the, uh, the critical issue. The board gate fire I think was in 1990. so that was just predated what we were doing, uh, here at Cardington. But if you relied on standard fire resistance, Test data, then you would've predicted a collapse of Broadgate and the issue. Cause Broadgate, I'm sure, many of your listeners will know, but, uh, it was a fire that happened during construction and before the fire protection was installed. So you had unprotected. beams and columns, unprotected connections. and although you did have significant defamation, you had no collapse, and the idea was that the inherent resistance of the structure was different to the inherent resistance of a single element. And I think there was some. some people with a lot of foresight at British Steel at the time was a chap called Jeff Robinson, who was, uh, fundamental in developing the program, from the British Steel side. And I think they saw Broadgate as a, an opportunity to demonstrate this whole building behavior, which I mean, there's two sides to hold. Building behavior. I think it's very important to recognize this. You've got the, the be. Aspect of restraint. you've got alternative load carrying mechanisms such as tenile membrane action, but it's not the only one. but you've also got alternative failure mechanisms, which maybe could be things like connection failure because we don't test connections in standard fire testing. So, so you've got to look for both. I think you have to look for the beneficial effects, but you've also got bear in. That if you look at a real situation, there are detrimental aspects to whole building behavior as well. And like I say, we, we were, we were literally learning as we went along because we were starting from a very, very low base in terms of understanding. But the kind of, speed with which we learn, because of this work was, was really something quite incredible. I think. So by the end of the process, by the time they closed, Cardington, I think we developed to be, uh, effectively have a very good idea of how real buildings behave in real fires.

Wojciech Wegrzynski: 29:51

and, how many experiments in the multistory you've burnt

Tom Lennon: 29:55

Oh, well, I mean in, in the, on the steel building, there were, I think in the original, scope, there were like six large experiments, four of which were natural fires. But then we came back later, uh, in 2003 and we did another one, which was, um, with, uh, university of Prague and, some guys from Portugal as a collaborative program. but then if you were to include. uh, the natural fire safety concept test, which weren't on the steel building, but were on the same floor area. there were another eight full skull tests there. Um, we also tested two large, houses, steel frame houses on the same area. And we tested, uh, some ho core, uh, floor slabs in the same area. And then we went to the concrete building and we did, uh, large scale testing on the concrete. And then we went to the timber building and we did large scale testing on the timber building. So, and we did additional work on, on, uh, modular systems. Um, so it went on and on to be honest,

Wojciech Wegrzynski: 30:52

It sounds like a lot of hard work, but I'm kind jealous to, to hear, uh, someone who's given the, the opportunity work with so many

Tom Lennon: 30:59

I feel, I feel very fortunate Wojciech, uh, to have been there at that time with those people who gave me the opportunity and gave me the responsibility to, be involved in that work. I feel very, very fortunate, place at the right time.

Wojciech Wegrzynski: 31:15

Okay. So moving from the furnaces to natural fires, how, how did you define the natural, what was the, the source of the natural fire? I, I see cribs on pictures, so, so I guess that was it.

Tom Lennon: 31:25

uh, generally timber, cribs, cause they're quite, the behavior's quite predictable and we know what we're gonna get. I mean, it's a way of getting, as far as we are concerned, it's a way of getting the temperatures you want into the structural members. That's all it is. It's a means of loading. That's how we saw it, and that was the difference between us and the fire scientists who proceeded us to us. We considered the fire as a form of loading. And then how does the structure actually react to that load? So we were looking to provide a realistic, but also predictable, thermal input to the structure. And we kind of relied on the, the design methods for. Compartment time, temperature response that were available at the time. and we actually, I think we actually helped to refine those methods as we, proceeded with the experimental work. But the natural fire test was, something which was. Realistic in that it was not a standard fire exposure, it had a cooling phase, it had a, um, a growth phase, a very rapid growth phase generally, and it had a steady burning phase. So yeah, the idea was to have something that was much more realistic than the standard fire exposure.

Wojciech Wegrzynski: 32:37

And, and did you ignite like one crib and then allow it to naturally spread, through the room or,

Tom Lennon: 32:42

What we did, I mean, the biggest one was the 350 square meter one. Uh, what we did was we connected all the cribs using, uh, channels, which the channels fiber strips, which were soaked in powerin, and then we'd light the powerin strips because we had quite a number of cribs in there. I've actually seen some of the videos from a large compartment fire test, and it's a little bit frightening when you see the video. I was in there with a colleague and we were walking together down the line, just lighting strips as we went along, and then eventually we walk out the door and the door sealed. But when you see, which I wasn't aware of at the time when you see the flames coming over your head, because it's a very rapid fire development and, uh, yeah, if I'd known what was happening, I would've moved a bit quicker. But, um, but yeah, we, we, we, we are always, even nowadays, we are looking to, cut short the growth phase. So, the early stages of fire are massively important for people who study life safety. Massively important. but for people who are interested in structural response, the early stages are not so important. What matters is when you get to temperatures that are gonna have an impact on the structure. So we are trying to accelerate that growth phase to an almost instantaneous flashover.

Wojciech Wegrzynski: 33:54

I would actually challenge that with the modern approach, the traveling fires and stuff like that, where we see, exposing part of the structure to a preheating conditions where a part of the structure might be exposed to 200, 300 degrees for a prolonged amount of time, especially if protected with, with, um, typical means under this fire situation where, where, when the fire eventually comes to that, to that point. So I, obviously the traveling fires is something that had happened in, let's say last 10 or 12 years.

Tom Lennon: 34:24

Well, no, I mean, I, traveling fires either happen or they don't happen. They weren't invented in the last 10 or 12 weeks. it's, either a phenomena or, or it's not. I mean, I, I, I have certain views myself. I think what we were looking to do was to provide. A fire that was realistic. Now, that realistic fire will change if you change the geometry of the compartment. So if you have something like the natural fires in large scale compartments work, which you uh mentioned earlier, where you've got a very long effectively corridor with a ventilation condition only at one end, then I have absolutely no doubt that you'll have a traveling fire. But that's a function of the ventilation condition and the geometry and possibly the, uh, ignition source. it's not necessarily something which is going to happen in all cases, uh, where it's not gonna happen in all cases. We know that. and I think we are not sure at all about where the transition is. so for me, if you were looking to. Evaluate a response of a building, which was a very long, narrow corridor. Then you put in a fire that is like that and, and you set light to it and what you get is what you get. If you get a traveling fire, fine. If you get a, a wand D post flashover compartment, it's fine. Uh, but I, don't know enough to know where that transition is, and I'm not sure who does.

Wojciech Wegrzynski: 35:42

of course, I don't think anyone knows exactly where, where the transition is. Uh, I, that's the reason why we have ongoing research on so many places around the globe. But at the moment, what I wanted to point out is, is that well, There's an evolution, you know, of, of our knowledge. And, your piece was an important part. In the middle of it, we, we we're still evolving and maybe someone in 30 years in holographic podcast will say, oh, these guys did very primitive, you know, methods. and now we have, so now we finally understand the structure of behavior, right? you've, uh, started with. Standard fire. So natural fire is a, a major, major improvement. How did you control the ventilation? Because I know a lot of effort was, I think it was the later tests in which you were assessing the natural fires in terms of, how they rank

Tom Lennon: 36:30

Yeah, I mean, it, it depended on, effectively, it depends on the job. So the early ones, we didn't really control, the ventilation at all because we were looking to get something which was realistic. However, when British Steel did their natural fire, or the first one, they actually had a, um, a screen which was movable so they could alter the ventilation condition. So they had one ventilation condition. For ignition. And then once you'd actually developed the fire, they changed that ventilation condition to follow a specific curve because they had a slightly different objective to us and they were looking to generate particular temperatures in the steel. I think for the work we did for a validation of the parametric approach the Eurocode, We had ventilation condition was something, we was one of the parameters we were looking to investigate. So we had different ventilation conditions within fixing all the other parameters, to try and ascertain what that was. So in that case, obviously we are manipulating the ventilation for a specific reason.

Wojciech Wegrzynski: 37:37

but in the first national test, you would just like open the window to have oxygen inside to ignite it, and then they would fall out. Or you started with a completely open wall.

Tom Lennon: 37:46

I dunno if I've mentioned this one already on the discussion, but we did have the, uh, issue with our first, compartment test where it was double glazed window and had to end up with the fire brigade breaking that window. We were aware that that was, um, a potential issue cause we. Spoken to colleagues in FRS who were more, at that time, more expert in, in fire development. And they probably said, well, you need some ventilation. And, uh, say, yeah, yeah, yeah, but we wanna do this cause this is how it is. And there were two kind of conflicting, uh, aims. So we started with one way, but we said to the fire brigade, if this happens, can you break the window? And they said, yes, we can. And that's what happened.

Wojciech Wegrzynski: 38:21

But then the rest of the windows would be damaged by the fire.

Tom Lennon: 38:24

Yeah, once you had that initial, cuz you had a preheated compartment effectively, once you had a fairly small influx of, uh, incoming air, it quickly took off and the whole lot came out and they were aluminum windows, uh, frame. So they just melted and the whole frame came out. But yeah, I mean, other situations we've had the large compartment tests. We had I think a third of each, elevation that was un glazed, and then two thirds that was glazed on either side, to represent an opening condition. But we know, the behavior of fire of glass in fire is. Unpredictable, to be honest. And, it can vary during the course of a fire.

Wojciech Wegrzynski: 39:01

and were you looking also to the external effects of the fire? I don't know the, the extent of, of external flaming or the damage to the bi forat or related to that or not.

Tom Lennon: 39:11

No, at this stage and for some years after we'd finished at Cardington, I don't think there was much effort expended at all to look at the, impact of external fires in terms of cladding fires. There were issues to do with, external flame spread away from a building. And we were measuring in some of the experiments, we were measuring heat, flu, away from a compartment. So that was a factor that was considered, but I think it wasn't, um, unfortunately it wasn't until many years later that there was a, a proper, attempt to bring together fire engineers and structural engineers on external fire.

Wojciech Wegrzynski: 39:47

there were a lot of research questions anyway, so I guess you had your hands, uh, full of work anyway.

Tom Lennon: 39:53

yes. I mean, we were starting from scratch basically. And, and it seems strange cause it, it's, it's a long time ago, but it's not that long ago. but the actual state of knowledge in terms of structural fire engineering, not, not fire dynamics and not structural engineering, but bringing the two together, um, it was kind of evolutionary to be honest.

Wojciech Wegrzynski: 40:12

Okay. And between the tests, let's say I, I see this hugely displaced beams and slabs actually massively displaced but they are still there. Uh, were you trying to fix the structure between the experiments or you just move the fire to another location in the building? How, how did you approach the, the, structural damage

Tom Lennon: 40:29

Yeah, I mean, uh, I think I mentioned before there was an incremental thing, so we're gradually getting more serious. We're gradually getting larger. So, um, we didn't start off with the biggest fire cause we might have been in a problem, but we did also move around on the steel building. We did move around different locations and that was kind of planned originally. when we came to do the final test in 2003, which we ended up with the biggest defamations, actually I think a meter deflection on the floor slab, that's a meter deflection and a slab that's spanning nine, nine meters. So, you know, that's, that's you, you're going downhill like, like this, you know? Um, yeah. And, and when it came to doing that one, there weren't too many areas left that were unaffected. So, um, we weren't exactly spoke for choice about where we.

Wojciech Wegrzynski: 41:17

and the building was still standing. Beautiful. Uh,

Tom Lennon: 41:20

yeah, it still was Uh, when, when we left

Wojciech Wegrzynski: 41:22

okay. let's talk a bit about the effect this, uh, research had because you have done it not, not only for fun. As you've mentioned multiple times, you contrary to the industry. You wanted to understand the, the behavior of the building in, in, in real fires, natural fires. First of all, which gap you wanted to feel and, and you think in your opinion you have successfully filled the best with with these tests?

Tom Lennon: 41:49

Yeah, I mean, I, I was aware of what the, uh, the original objectives were of, The programs I was involved in and the European programs. and a lot of that I mean, it wasn't, it wasn't for a start. We didn't set out to determine a new design method. we were out there to understand what was happening, but we were specifically looking to provide validation for numerical. And I think on side, we achieved the objectives and I think, we probably superseded our objectives in terms of what actually came out in terms of the understanding, in terms of the new design methods, particularly for, uh, Uh, composite construction and, and tensile membrane action. And also it's, again, it's hard to go back. When I was involved in the first natural fire expo, we had some of our colleagues in Europe did some, uh, modeling to predict the fire behavior. And, they came out with peak temperatures of, uh, 600 degrees in the compartment. And, uh, now you probably, yourself, you think, well, that's ludicrous. You know, it's, it's gonna be somewhere around a thousand, maybe above, whatever. But, um, we didn't have anything to judge that by at the time. Um, and. By the end, we'd produce sufficient data for, not just for structural models, but also for thermal models. And the work we did, I think on the validation for, the parametric approach in newer code one, was also something which confirmed some of the problems that had been in the past and the importance of things like, uh, lining material. on fire development and, the importance of maybe different types of fuels and how they're, plastics and, and timber combination of timber and plastics, how they're evolved. So we were doing both on the structural side and on the fire development side. I think we made some really. great achievements, to be honest. And it was a, you know, it's a collaborative effort. There were lots of people involved in this. nothing like this happens, you know, unless there's, a lot of people involved and a lot of people contributing. And, uh, I, I worked with some fantastic people over the, the period I was working at Cardington and.

Wojciech Wegrzynski: 44:00

for the parametric model, you've not only validated it, but you've, considerably, expanded the limits of its use because, uh, you could apply it to 500 square meters. you've changed the installation, you changed the opening factors for which the model was validated for.

Tom Lennon: 44:17

Yeah, I mean, I, I you are based in Poland, I presume? Wojciech I mean, uh, we have in the UK we have our own national annex as well, and there are still some areas where we have, Some differences of opinion between those in Europe and those in the uk and I think it's important to have, maintain that expertise within the individual countries so we can have some choice, uh, in these areas. I think where we think we maybe have a slightly better way of doing it.

Wojciech Wegrzynski: 44:46

And for the foundation of these structural modeling software, I guess you guys were delivering the data and experiments and with other groups. Can you tell us about, uh, who was doing that and, and

Tom Lennon: 44:56

I mean, at the time I think we were working with, uh, TNO and ct CTICM um, and certainly, uh, what was our bed or now, And all those guys were involved in numerical modeling, some of them using Diana, I think, British Steel. And, uh, when the University of Edinburgh came on board in the latter stages, I think they were involved using Abacus. but we were also, the formulation behind your code was also done by the same guys who were involved in developing Sathi. So, Like I say, it was, it was both on the structural end and the thermal side that I think we were providing validation across the board. And this, you know, one way or another, all this, all this data was made available. Um, I think British Steel puts some big efforts into, uh, making sure that this. data was made public, um, so anybody could use it. And so even if you weren't, directly involved with somebody with uh, a model, then somebody with a model could use our data,

Wojciech Wegrzynski: 45:58

I will link, uh, in the description to that because it's, I, I find it actually astounding that 20 some years after this happened, it still is, uh, shared. It still is available. The data is, It's in a pristine form. It's very, clingy. You don't wonder where this transducer was a, there's a lot, lot of effort in labeling everything. I, I really appreciate that as someone who's doing, uh, fire experiments because That's the annoying part of the job. You know, watching a fire burn down the building is is the fun part of the job. Prob probably the most stressful in the end, but the fun part. But, uh, labeling, uh,

Tom Lennon: 46:33

well, I, I had one guy working for me, chap called Nick Petty, who was my sort of chief instrumentation guy, and he loved it. So, uh, ,that was his, his

Wojciech Wegrzynski: 46:42

you you want the jackpot Then

Tom Lennon: 46:45

yes, absolutely.

Wojciech Wegrzynski: 46:46

that makes, works so much so much easier. okay. Tom, we are, we are heading till of the, of the podcast. So maybe I would love to like ask How did the program change you as, as a fire engineer? You're still practicing fire engineer, I guess you, you still come back to the experiences from, from carton and, still use them in, in, in your ongoing efforts, right?

Tom Lennon: 47:08

yes. I was, I was quite young. I just, I hadn't, I'd come outta university, but I was a little bit older cause Bre paid for me to go to university. I was already working. I'd just come outta university when I first. Took over on the, uh, structural fire side and then very shortly afterwards I ended up at Cardington. And it has had a major impact, not just on my career, but on the way I, I do things, the way I work. and I mean, I do lots of other things now. So we do site inspections, we do assessments, we do all sorts of things, but we still do large scale testing and I. What it's given me is, and anybody who's been involved in this area will know, an ability to organize cuz that's what you need to do. The, the, the thing I brought to it was getting things done. There were people much more clever than me at the beginning who were saying, Tom, go and do this. And, but I was able to get. That done deal with the contractors, do all the project management, all that side of things that needs to be done. And I think anybody who works in large scale fire testing, knows how difficult that is to actually get from a drawing board onto the fire and get the result you want in the end and have all the information available. So I think it's had a major impact on the way I work. I would say a lasting.

Wojciech Wegrzynski: 48:26

Having all this experience, would you do it again given a.

Tom Lennon: 48:29

Oh, a drop of a. hat. Yeah, I would, uh, it was, I mean, it was, in terms of work wise, I mean I'm very happy with what we are doing now. It's, it's a very good and a very, uh, productive period for me and the guys who work with us. But, I think that probably was the best time of my life, in terms of being able to do that and being so fortunate to be in the right place at the right.

Wojciech Wegrzynski: 48:50

I just took a quick look on the Google Scholar and, uh, the book from, uh, the multi-story, experiments has been cited 276 times. like, even this year, it already has been used as validation for new models. So the ongoing impact is, is tremendous. And, and thank you. And, and Buri and British Steel and everyone involved for that. This is, uh, certainly one of the experiments that changed the fire science.

Tom Lennon: 49:15

Yes, indeed. I, I believe so,

Wojciech Wegrzynski: 49:17

Okay, Tom, thank you so much for, for this episode and this, this insightful journey to the carding. And I hope to, to see around maybe to talk a little more on, on structural side of engineering.

Tom Lennon: 49:28

Of course. Thank you very much for the, uh, invite and, I hope uh, you get on well. And, um, I've actually, uh, instigated now within our team. Every time we have a team meeting, we're gonna watch one of your episodes

wojciech_wegrzynski: 49:40

Oh,

Tom Lennon: 49:42

internal training. So,

Wojciech Wegrzynski: 49:43

great, great, great, great policy. you so much.

Tom Lennon: 49:46

my first choice was Danny's one, so um, that's the next one we're gonna look at.

Wojciech Wegrzynski: 49:50

Good. He'll, he'll be very happy to, to know that. Thank you so much. And thats it, boy what a legacy at Cardington amazing research program and. even took me a significant amount of time to understand the timeline of what was happening there because these guys have done so many groundbreaking experiments. Like saying you are talking about Cardington is not saying enough because there have been so many. Experiments. That changed the fire science. You have to be more specific than, than that. I guess that's the lesson I learned after this episode, but I'm very happy to talk with Tom about the timeline and all the history of discovery that happened at I guess the next step for you is to jump into some reading and I've linked. some resources from Cardington happily, there's lots of stuff available. There's a lot of data preserved at different sources. So very easy to get very clear and very useful. And that would be it for today's experiments that changed fire science and I hope you've enjoyed this interview and you enjoy the mini series. I have more of these coming. If you have in your head, an idea about what was an experiment that has changed. fire science. Let me know, I would love to talk about it on the show. So, yeah. Thanks for being here. And I invite you back on. Friday, I think where we're going to post the question and answers episode a. Bonus episode four, November is going to be published in December though. Uh, one in which I will answer the listener's questions that I got. I hope that will be interesting. To you and back to normal cadence on Wednesday Where you will a. I learn more on fire science, actually structural fire engineering again. And we're That always excites everyone. Thanks for listening. See. See you. Bye.