April 6, 2022

045 - Foundations of fire safety with Ruben van Coile and Danny Hopkin

045 - Foundations of fire safety with Ruben van Coile and Danny Hopkin

How does one decide when a building is fire safe? That is a real hell of a question to answer! Is it when no harm can occur? But such a condition can never be fulfilled... there is always a meteor waiting around the corner to fall into your building! So if some situations can occur for which we cannot prepare, when do we decide we are 'safe enough'? 

This is the tough question we try to decipher together with prof. Ruben van Coile and prof. Danny Hopkin. It is an inspiring journey, and you can trust me on this - at the end the episode gets even better!

Also, Danny was kind enough to curate this fantastic list of resources for you to read, if you would like to build a more complete idea on the concepts of risk and safety:

  1. D. Hopkin, R. Van Coile, and L. David, ‘Certain Uncertainty-Demonstrating safety in fire engineering design and the need for safety targets.’, SFPE Europe, 2017
  2. R. Van Coile, D. Hopkin, D. Lange, G. Jomaas, and L. Bisby, ‘The Need for Hierarchies of Acceptance Criteria for Probabilistic Risk Assessments in Fire Engineering’, Fire Technol, vol. 55, no. 4, pp. 1111–1146, Jul. 2019
  3. R. Van Coile, D. Hopkin, and D. Lange, Guest Editorial: Probabilistic Methods in Fire Safety Engineering. Springer US, 2019
  4. R. Van Coile, N. Elhami Khorasani, D. Lange, and D. Hopkin, ‘Uncertainty in Structural Fire Design’, in International Handbook of Structural Fire Engineering, K. LaMalva and D. Hopkin, Eds. Cham: Springer International Publishing, 2021, pp. 323–411
  5. D. Hopkin, I. Fu, and R. Van Coile, ‘Adequate fire safety for structural steel elements based upon life-time cost optimization’, Fire Safety Journal, p. 103095, May 2020
  6.  R. Van Coile, G. Jomaas, and L. Bisby, ‘Defining ALARP for fire safety engineering design via the Life Quality Index’, Fire Safety Journal, vol. 107, pp. 1–14, Jul. 2019
  7.  D. Hopkin, M. Spearpoint, and R. Van Coile, ‘The J-Value and Its Role in Evaluating Investments in Fire Safety Schemes’, Fire Technol, vol. 54, no. 6, pp. 1547–1564, Nov. 2018

Also, keep your eyes open for the next edition of SFPE Handbook where my guests are publishing a new chapter on "Economics and Decision Making in Fire Risk Analysis"



[00:00:00] Wojciech Wegrzynski: Hello, and welcome to the Magical Paint Podcast, your weekly source of knowledge and inspiration on how to give fire resistance to any material. with just a single layer of paint. No primer required. And today we're going to learn everything you need to know about how to give fire resistance to the underwater parts of pylons.

[00:00:21] Wojciech Wegrzynski: Oh, actually, I'm horrible at making jokes. Apologies. Uh, it was an attempt on April fool. But, it kind of doesn't work when your podcast does not air on April fool's day. It seems that the next opportunity is 2026 for that. And. Yeah, you better be ready. At work on the comedy skills. And for today. Well, if you hope for magical paint, I'm not going to have great information for you. But for everyone else today, we're going to talk about something. Very fundamental. And that is the safety per se or what is safety? Actually, we're going to talk about risk based concepts in fire safety engineering.

[00:00:59] Wojciech Wegrzynski: [00:01:00] But that conversation has drifted towards really, fundamental. And important aspects on what we are doing, how we're doing it. And what are the boundaries of, what should we do?

[00:01:13] Wojciech Wegrzynski: And I find the conversation great because of the great guests I had. And these are professor Ruben van Coile from Ghent university. And Professor Danny Hopkin from OFR and Sheffield university. And they're both worldwide known experts in structural fire engineering and performance-based structural fire engineering and risk methods in this field. So it was natural to ask them,

[00:01:38] Wojciech Wegrzynski: about how the risk-based concepts are intertwined with structural fire engineering, but, oh boy, we went quite far away from just that touching really, really interesting things. On how probabilistic methods can be applied, how risk methods can be applied, why should they be applied? And how can you benefit from that? [00:02:00]

[00:02:00] Wojciech Wegrzynski: And, if I may give you a hint, the episodes gets better and better till the end. With some really cool things being said in the very last part of it. So, uh, if you're not usually listening to the end of the episodes, this one you might actually want to,

[00:02:18] Wojciech Wegrzynski: okay, so let's not prolong this and let's give you a chance to join our conversation and risk. Based methods in fire engineering. So let's spin the intro and jump into the episode.

[00:02:52] Wojciech Wegrzynski: Hello, everybody. Welcome to Fire Science Show. I'm today with two professors. I admire first professor Ruben van [00:03:00] Coile from Ghent university. Hi Robin. Ruben to have you in the podcast.

[00:03:03] Ruben van Coile: Thanks for the invitation.

[00:03:04] Wojciech Wegrzynski: welcome and a much welcome comeback.

[00:03:08] Wojciech Wegrzynski: Number one star of the podcast, Danny Hopkin. Hi Danny

[00:03:11] Danny Hopkin: always check. Very good to be back.

[00:03:13] Wojciech Wegrzynski: Yeah, I hope you brought your click-bots again. That's a much welcomed.

[00:03:17] Danny Hopkin: Yeah. Yeah. I'm sure you'll get a, another 500 downloads from Northamptonshire. Yeah.

[00:03:23] Wojciech Wegrzynski: I must be a star a

[00:03:25] Danny Hopkin: So disproportionate number of people interested in this podcast in my home county yeah.

[00:03:29] Wojciech Wegrzynski: Yeah, I wonder if there's, as interested in structural fire engineering and risk, approaches in that as in timber. Well, we'll see. We'll see. So you probably wonder why I have brought you in here. Well, actually, you know, it's the risk methods, in fire safety engineering and actually a risk methods in in structural fire engineering, because I'm, I find it quite interesting that, many aspects of like risk acceptance, probably the approaches different ways on how to [00:04:00] design structures made it way to structural fire engineering and seem to be quite well developed in there.

[00:04:06] Wojciech Wegrzynski: To start with, In what way? This performance based approaches make its way into structural fire engineering. And for me as someone who's running a fire laboratory, it's usually very straightforward way to demonstrate safety. You know, I put things on the furnace. If they meet the criteria after 60 minutes of the experiment, they have the classification and we're not really exploring much alternative roads maybe because Poland is very prescribed country.

[00:04:39] Wojciech Wegrzynski: And, I wonder how do you see the use of, this advanced methods in structural engineering?

[00:04:44] Ruben van Coile: it's, funny the way you, you mentioned actually you say I can, uh, if I go that correctly demonstrate safety. So my question would be, is that what you are doing when you do classification test [00:05:00] from the pony it links with, earlier discussions you had on podcast regarding timber structures and so on

[00:05:04] Wojciech Wegrzynski: yeah, I'll answer it. It's what the architect thinks I'm doing. And that's what my stakeholders think I'm doing. That's that what the society thinks I am doing. And, yeah, it calls me on guard that this is not what I'm doing, , but that's a very, very good point. You should start the podcast.

[00:05:22] Ruben van Coile: But then you what you're saying is, is already potentially a major problem, right? So,

[00:05:27] Wojciech Wegrzynski: Yeah.

[00:05:28] Ruben van Coile: if your stakeholders think you are doing something delivering safety, you know that you are maybe not really doing that because it's classification

[00:05:38] Wojciech Wegrzynski: Mm

[00:05:39] Ruben van Coile: the prescriptive guidance. Then we have a completely different discussion about what's a, should you actually

[00:05:45] Wojciech Wegrzynski: Hmm.

[00:05:46] Ruben van Coile: But to answer the question

[00:05:47] Wojciech Wegrzynski: Yeah.

[00:05:47] Ruben van Coile: probabilistic, uh, structural fire safety. So yet then if you would look into the uncertainties you have on fire loads, factor, your your structure, [00:06:00] which is changing during fire, take into account uncertainties, then maybe together with your model uncertainties, get up to a point where you say, well, okay, now I understand the performance and this isn't necessarily in probabilistic terms, just because every fire is different and so on.

[00:06:16] Ruben van Coile: And when you know your performance in public terms, then we can talk about safety.

[00:06:21] Wojciech Wegrzynski: Nice. This is good. Danny will add something

[00:06:24] Danny Hopkin: Yeah, I can give

[00:06:25] Wojciech Wegrzynski: you want to stab me as

[00:06:26] Danny Hopkin: no, no, I I've. I'll save that. Ruben can be back up. I'll be here. so my first foray into this area and, you know, from the previous podcast that my, my doctorate was in mass timber, and I feel like my, uh, my postdoc, if you like, is in reliability, under Rubens tutoring, it's kind of how the relationship works.

[00:06:48] Danny Hopkin: Uh, as a consultant, we're often faced with this kind of conundrum where we were, we were doing fire engineering calculations, and one of the most common things, structure fire engineers with that, the sort of the time equivalent [00:07:00] calculation, where you're trying to determine from first principles of the fire resistance period for a building based upon the fire intensity.

[00:07:05] Danny Hopkin: And, when doing that calculation, you, as the user, you have so many decisions that you have to make about parameters that you use that really influence the outcome of that calculation you. and so you have to make a decision about what is reasonable in the circumstances for that building, whether it's the size of the opening, whether it's the percentile of the fire load you use, um, my experience prior to coming to any of this, with any real knowledge of what was happening was you entered into some very subjective debates with.

[00:07:38] Danny Hopkin: or authorities having jurisdiction about what values you should use, why and what level of conservatism is fit for purpose in the given application. And, and there was, there was never really a good answer or an objective answer as to why one outcome of that process was more or correct than another [00:08:00] one.

[00:08:00] Danny Hopkin: and so got quite interested in how we quantify safety and how we decide is enough and under what circumstances, that level of safety we try and achieve as, it varies from one building to the next. and so for me this whole topic became a very objective way of deciding what level of safety we want to achieve for a given building based upon it is given circumstances.

[00:08:28] Danny Hopkin: and. how have we got to this point where it's developing to maturity instructor fringing? I think part of that is because it is already very mature as a concept in structural engineering. and I was never taught this whilst I studied structure engineering, but actually when you're designing an ambient temperature, you are designing in a semi probabilistic framework where your safety factors, whether they're on your loads, whether they're on your materials have been calibrated to deliver some [00:09:00] predetermined outcome in terms of the sort of maximum failure probability of that element.

[00:09:06] Danny Hopkin: then they're all sort of grouped into different consequence classes. So it felt quite logical for me. When I came into this area of working with Ruben, that you're kind of just extending a concept that you're doing anyway, ambient temp. And then taking it into structural fire design. And so actually you're just being relatively consistent in how you're designing your structure just for a different hazard.

[00:09:30] Wojciech Wegrzynski: it makes sense. He strictly, because this concept was already proven. That's the way you design structures And you extend this beyond the ambient. You go into fire temperatures and pretty much use the similar framework to build on, on, whatever is, uh, acceptable safety for you, which will we will reach.

[00:09:48] Wojciech Wegrzynski: But I wanted to ask now, okay. But why did I think, I'm proving safety in my fire resistance. That that's actually quite a good question. Why it is so how to [00:10:00] say juxtaposed to the concept of safety that you get this class you're safe, you don't have this class you're not safe.

[00:10:06] Wojciech Wegrzynski: Is it some sort of, I don't know, collective experience gathered to the ages? Is it, a matter of ease because let's face it. Fire is a complex problem and fire resistance is a fairly simple thing. They put something on the furthest, you get the. Or why it's so a welded to do our understanding of safety, this concept, and maybe why, how could we benefit by un-welding

[00:10:33] Wojciech Wegrzynski: it's from it,

[00:10:34] Ruben van Coile: Okay. So first of all, the background fire resistance classification. a book episode about it. so I mean, all kinds of historical background, I'm the expert in it, but, and it's a system which apparently has worked reasonably well, would say indeed, that based on experience we've a society, right?

[00:10:59] Wojciech Wegrzynski: Um, [00:11:00]

[00:11:00] Ruben van Coile: guidance codes, which for normal and common buildings actually has decent, fire resistance requirements and other requirements. and the issue then is when you start pushing your design by introducing new materials, by going beyond aspects where you have lots of experience about, at that point, your old fire resistance classes, they, or at least your requirements on those fires school classes, they don't really apply. And I think we need to them on the second point, make a bit of a distinction between the fire resistance classification and certain safety level in the building. from that perspective, I would say it's probably not an I, not a perfect methods to a specification, but it's principle. You could say, well, you can still use it.

[00:11:53] Ruben van Coile: It's very convenient. European markets, international markets, you buy a policy in one country, go to another country and so on. So it's [00:12:00] great. and then just depending on the building you have, and maybe depending on the material in the building, would have a different fire resistance class requirements as in different material will have a different safety level and sort of different requirements that way.

[00:12:13] Wojciech Wegrzynski: when they wrote, uh, sorry. When they read your papers. I don't remember in which it was the first shown, but you've shown the safety, safety design triangles, and the distinction between these two approaches where one was based on experience. Second was based on evidence and while experienced good work for known hazards, known buildings, known problems, like you said, known from the past we have as a humanity, we have a collective experience in providing, let's say fire safe.

[00:12:45] Wojciech Wegrzynski: Buildings in many occupations, but then you build something new, something with a completely new materials, some exceptional design that has never been accomplished. And this experience is, is too short. You then [00:13:00] need to show evidence that it works, or I don't know if you need, but I assume that's, probably a way if you want to achieve an optimal structure without exceptional margins of safety that you would put on top of that, if you only wanted to project experience, or can you even project experience like let's, uh, let's put, uh, sides, the advanced methods, and then all the probably sticks.

[00:13:25] Wojciech Wegrzynski: Can you reasonably project experience by applying safety factors or these approaches deemed to fail at some point

[00:13:34] Ruben van Coile: Okay, difficult. The first time we published something about the safe triangle was actually on the, in the FP magazine

[00:13:43] Wojciech Wegrzynski: Yeah.

[00:13:45] Ruben van Coile: which Danny lead and D the concept of our

[00:13:48] Ruben van Coile: guidance documents, and so on are generally based on experience. It's nothing fundamentally new. you have a bum paper. I like a lot by Spinardi of, on the sociological issues and fire safety.

[00:13:58] Ruben van Coile: and then there's a part which talks about that [00:14:00] in more detail. , Crucial thing I would say is that you have to realize that when you are doing a design based on prescriptive guidance or when you are doing performance based design, based on a single credible, worst case evaluation or a set of caterpillar breast case evaluations, you are making decisions about risk in the end,

[00:14:20] Ruben van Coile: you design does this, and you have, has a risk profile mean probabilities consequences, combinations of the two. So fundamentally there is no difference if you go from. Risk bottom up instead of just immediately picking something, It's both, whatever you build, it always has the risk profile. And then you say, oh, can you just use safety factors and so on?

[00:14:44] Ruben van Coile: Well, we're not really there yet. As in, in the work we're doing with, with Danny, with Thomas Gernay uh, with Negar Elhami-Khorasani and many other collaborators, we are generally still working full probabilistic. We've been trying to have [00:15:00] some kind of safety factors, like a global safety factor here, or there may be trying to find a way to go forward, but the probabilities and fire are generally not.

[00:15:09] Ruben van Coile: So let's say, well, behaving that we can easily define the safety factor, which applies to.

[00:15:15] Wojciech Wegrzynski: you mean, I think you meant like explicit safety factors. What I manage is if, if a tall building has two hours walls let's make a super global end cap for our walls. Just in case, this type of, anecdotical safety factors then do you think we can project safety from experience on unknown structures?

[00:15:34] Wojciech Wegrzynski: Is it even, because our governments do that, man. It's like, if we want to stop them less, but to explain them, why not?

[00:15:41] Danny Hopkin: no, I, I think in our publications, we argue quite robustly in favor of not doing that quite explicitly because, foreign engineering generally is Rubens explained. This is predominantly deterministic. We, we

[00:15:54] Wojciech Wegrzynski: yeah.

[00:15:55] Danny Hopkin: maybe a single scenario. We have two or three scenarios. And you, as the engineer, you make [00:16:00] decisions about, the outcome you're trying to achieve and the, and the inputs you put into that process.

[00:16:04] Danny Hopkin: And, it's almost through trial and error that, we apply this deterministic approach, that leads to a building that gets built. And then we get to observe whether that approach ultimately led to some outcomes that we didn't consider, unacceptable, or if there was an unacceptable outcome and effectively we recalibrate ourselves.

[00:16:24] Danny Hopkin: and that might inform the magnitude of the inputs or the conservatism in the performance criteria that we apply. And so you're inherently limited, to cases that you get to experience two, to kind of guide you as to what level of conservatism you need to apply in, in that process. And so if you're extrapolating.

[00:16:45] Danny Hopkin: Uh, for a variety of different reasons, you, you are extrapolating to a case that you're very likely to experience. So you, you have no, preread sort of knowledge of what level, sort of rough magnitude of safety factor

[00:16:59] Wojciech Wegrzynski: Hm.

[00:16:59] Danny Hopkin: [00:17:00] apply. and so this is where we argue in favor of it in this safe design triangle.

[00:17:04] Danny Hopkin: That actually there must be this explicit evaluation of the safety level because, um, you don't have that anchor is by sort of definitely there's an exceptional case that you're up against.

[00:17:16] Wojciech Wegrzynski: And how does one obtain this explicits evidence of safety?

[00:17:22] Danny Hopkin: so conceptually at least it's it's, we've introduced, there's a few different ways and we do

[00:17:28] Wojciech Wegrzynski: Yeah.

[00:17:29] Danny Hopkin: through acceptance concepts, as we refer to them, where, uh, one extreme. You have, what is it effectively a comparative assessment. So you made sure that the safety level of your building is in keeping with something that could be built following a recognized code and has therefore been kind of massaged or calibrated to meet society's expectations for the safety levels that they want to achieve

[00:17:54] Wojciech Wegrzynski: Sorry, but could you like, let's say I, have building A have building B that is slightly different.

[00:17:59] Danny Hopkin: yeah.

[00:17:59] Wojciech Wegrzynski: So I [00:18:00] say is almost the same as a, might be safe by comparison, but then it's the building C then is building D at some point, we, it does the chain need to connect to this building a, in which the safety was proven or what can we like extrapolate

[00:18:15] Danny Hopkin: No, no,

[00:18:16] Wojciech Wegrzynski: tiny

[00:18:16] Wojciech Wegrzynski: steps?

[00:18:17] Danny Hopkin: certainly can't extrapolate. and so we, this is where we introduce what our kind of implicit or explicit tests on

[00:18:24] Wojciech Wegrzynski: Yeah.

[00:18:24] Danny Hopkin: It's the terminology we use. and so you, as you, as the designer have always got to make sure that your reference design is kind of with a range of outcomes.

[00:18:34] Danny Hopkin: You, you might expect to witness in, whatever your proposed design is. And so you can't reference the Burj Khalifa against a two story house or that kind of extreme comparison. And for those kinds of cases, what we actually kind of encourage people towards this, this kind of fully quantified risk assessment process, where you, you evaluate the, uh, sort of [00:19:00] risk profile, the residual risks associated with the design and you benchmark them against some kind of acceptance criteria.

[00:19:07] Danny Hopkin: and I think That's kind of the tricky thing at the moment is conceptually, we can quantify risk, the probability of a hundred fatalities or, or the FN curve as it is commonly known what we're lacking. it's not really within our gift necessarily as designers to establish is that acceptance criteria or that tolerability limit in terms of what normal societal stakeholders expect buildings to do.

[00:19:33] Danny Hopkin: And that's kind of the job of the regulator, really, I think, , to set those criteria, which we do in the UK for different hazards, for nuclear, with the health and safety executive, for example. but for safety, we've never, um, we never seemingly approached the problem from this fully quantified and explicit level of risk that we're willing to accommodate that.

[00:19:55] Wojciech Wegrzynski: When I was reading your papers, there were many names used to refer [00:20:00] to accept this criteria, acceptable, adequate tolerable, and they all have this flavors. And it seems there's a, quite a big difference between worlds adequate and what's tolerable. So, uh, what would be the goal?

[00:20:13] Wojciech Wegrzynski: Would it be an acceptable risk or safety of tolerable safety? Because, I'll drop a punch as well in, I loved it in, SFPE in Rotterdam and Brian's Mitchem talk. There was a guy who said that current cheapest available technology, not involving persecution. and he was so spot on, on what would be the preferred level for the, industry who's building the buildings, not necessarily the owners or users.

[00:20:42] Wojciech Wegrzynski: So I feel like the challenge is even defining like, should we find the cheapest, the best, the most reasonable, the most adequate

[00:20:50] Ruben van Coile: Well, there you are. for my interpretation referred to different perspectives, in the risk evaluation also in the cost evaluation. So yes, [00:21:00] the costs of fire safety are different, depending on which perspective you take. So on a project, on the one hand side, you would have general societal cost and benefits of having a fire safe design, where let's say society has limited how much they can invest in fire safety makes in a way, or it should make perfect sense.

[00:21:21] Ruben van Coile: And you keep on investing in fire safety. At some point, you should have spent that money on something else. Maybe it's education, maybe it's health care, but your benefits or your marginal benefits is reducing and then you have private stakeholder who might. I think that the fire safety, issue is not their problem. and they just want to get the building built in which case the private stakeholder should adopt to country's requirements. So they can be legal requirements can be guidance with times or maybe specific case. The stakeholder wants a higher safety level because it's a warehouse. And if the warehouse burns down completely, but as compartmentation, [00:22:00] without suppression systems, the companies.

[00:22:04] Ruben van Coile: And maybe this is which is not acceptable with this private stakeholder. Well, to country society can say, well, this is not a problem. and then, so this is one private stakeholder, but of course you have many. So then indeed, when you

[00:22:16] Wojciech Wegrzynski: Yeah,

[00:22:17] Ruben van Coile: a project, maybe a contractor is maybe definitely contracted a stem to substitute a product.

[00:22:23] Ruben van Coile: If on paper they have the same performance and one is considerably cheaper than the other one. So, I guess communication is a very key issue there make it clear.

[00:22:33] Wojciech Wegrzynski: I really wonder who is have the final say in that is it's the. Society, is it the investor? Is it the contractor? Because as you said, they will have a completely different objectives like society. I think for, for societal level, it would be the, let's say the, having the statistics low enough that they don't cause the social unrest.

[00:22:58] Wojciech Wegrzynski: Maybe I defined it horribly, but [00:23:00] from a societal level, the goal would be completely different than from the subcontractor level who, if he saves some money, if they save money, they earn money actually, because there, the savings may be their profit. So, you have completely different, set of, objectives there at each level of construction of the same building and the investor.

[00:23:20] Wojciech Wegrzynski: You said the investor may be one kind that wants to have. Just meet the law requirements as they are, and be done with it, the cheapest cost possible, or you can have investor who knows that they're going to store some important materials in the building that are critical for their company. And they would like to have a double or triple the safety normal because it is so important for them.

[00:23:45] Wojciech Wegrzynski: And they would be willing to overpay for that. So that's a whole set of competing objectives. and I don't even see how you could fit that within a low framework, actually.

[00:23:57] Ruben van Coile: It's not

[00:23:57] Ruben van Coile: in a law framework structure. [00:24:00] We get very, very strict in a sense you have the societal requirements and then

[00:24:06] Wojciech Wegrzynski: Yeah.

[00:24:06] Ruben van Coile: the question, how do you get those societal requirements into a legal framework? Okay. But you have to societal requirements and that is the minimum and it should be. And then the yes, yes.

[00:24:21] Ruben van Coile: And then, private stakeholders have the freedom to go beyond that. then what beyond that means. And so on, maybe we can discuss about that a lot, but fundamentally for my personal opinion, maybe in the way, but there is, it's very clear societal minimum requirements and then private stakeholders can go beyond.

[00:24:41] Ruben van Coile: So it's up to the fire engineer up to the architects. And so on to, to open that conversation, on, bigger projects that would say, and make sure that different private stakeholders are aware about what they're actually getting. returning to the beginning of this podcast, you can indicate it's that [00:25:00] people probably think they're getting safety or thing.

[00:25:02] Ruben van Coile: They're getting something. And maybe they're not, as in certain fire resistance, if my building has a fire resistance, which is required by the legislation, think, and I'm

[00:25:12] Wojciech Wegrzynski: I think.

[00:25:13] Ruben van Coile: that my building will survive burnout. As the fire engineer who might be aware that this is not necessarily the case at which point should have the discussion with the architect, the business stakeholder and so on.

[00:25:25] Ruben van Coile: Although once say like, by the way, we want to look into this more instead of just going for the R 60 or whatever it is that we need.

[00:25:33] Danny Hopkin: Yeah. I think what Ruben's explained is, is entirely compatible with the kind of the legislative format. In most countries, your, your building regulations are there to re present predominantly the interests of the societal stakeholders and set that minimum boundary condition on, on what's acceptable.

[00:25:52] Danny Hopkin: and then anything you want to do in that it's beyond that, whether it's business continuity or property protection, that decision is left at their private [00:26:00] stakeholder level to make that investment.

[00:26:01] Wojciech Wegrzynski: Sorry, but I have to drop a bomb on you, but what if my law is stupid? What if my law is nowhere? Like you assumed that the law would give the minimum and in the perfect world, it would, but for my. It's nowhere close, minimum at points. It's ridiculous at points it's over exceeding something I would call reasonable.

[00:26:25] Wojciech Wegrzynski: am I doomed? Or I guess this concept could also help me find a new reasonable minimum if my minimum is stupid.

[00:26:34] Ruben van Coile: Yes. So definitely if the cited requirements are too high, you could do through calculations, for example, evaluations and show like fire resistance requirements you have here is a big over-investment. This doesn't make sense. Let's

[00:26:50] Wojciech Wegrzynski: Yeah.

[00:26:51] Ruben van Coile: in that case, yeah. You have an argument there, depending on the legal framework you have to ask for deviation can be an argument.

[00:26:57] Ruben van Coile: And also it's very, it's really [00:27:00] is inputs or should be input in developing new goals, codes, and guidance. The other case

[00:27:05] Wojciech Wegrzynski: Hmm.

[00:27:05] Ruben van Coile: very interesting situation where the. Legal requirements. then again, through the guidance may be depending on the country, too low.

[00:27:13] Ruben van Coile: And then this is, I think, very important for four, five engineers and for architects and swarm, just following those guidance, things doesn't mean that you are free from your full liability.

[00:27:25] Ruben van Coile: And so if you are as a fire engineer, aware of that, this doesn't really make sense. You are involved and you just hide behind the guidance or the legal documents. Something happens if it turns bad, that your liability question is not that clear. people might think.

[00:27:43] Wojciech Wegrzynski: And Danny, does objective minimum exists. Is there like objective baseline to which I could refer regardless of my country where I am or is it's like, because if you ask a politician, okay, let's agree on how many fatalities per year [00:28:00] can occur. And then start with that. You will never get an answer. No one will ever answer.

[00:28:05] Wojciech Wegrzynski: No politician will ever answer this. No one, like I have this feeling. It is super difficult to when you start quantifying safety, it starts to be horribly hard to agree on what is this acceptable minimum. I think it's more easy to agree on some artificial thing. Like R30, 30 minute fire resistance for this building is.

[00:28:33] Wojciech Wegrzynski: Rather than accept on. Okay. If we have a fatality every 10 minus six, like you have to minus six probability, you die in this building. You're okay. I have the feeling that even the first one is very artificial, very misguiding, very abstract, but agreeable, the second is very precise, sharp well-defined but somehow difficult to get a [00:29:00] consensus between the stakeholders.

[00:29:01] Wojciech Wegrzynski: Do you have this impression as

[00:29:03] Wojciech Wegrzynski: well?

[00:29:04] Danny Hopkin: it's interesting. You use the word acceptable because, ultimately society judge, jury and executioner on, on what is acceptable, right? And unfortunately we don't get to go out and quiz 60 million people,

[00:29:19] Wojciech Wegrzynski: Okay,

[00:29:20] Danny Hopkin: for their

[00:29:21] Wojciech Wegrzynski: good point.

[00:29:22] Danny Hopkin: of return of a fatality is, is, would be tolerable to them.

[00:29:25] Danny Hopkin: so we've, dealt with this historically through, um, And kind of these concepts have revealed and stated preferences, in particular and, and , we've placed values on, on lives, out of that process. And ultimately we've tried to seek to balance the cost and benefits, which, is an objective way of looking at the problem, but it doesn't take into account, necessarily, or difficult to gauge society's view on what would actually be acceptable to them until they've experienced it.

[00:29:59] Danny Hopkin: So you're, [00:30:00] you're right. It's very tricky. And actually the way the structure engineering gets around this is to deal with everything in a, in a quite straightforward risk. What was arguably a

[00:30:10] Wojciech Wegrzynski: Hm.

[00:30:11] Danny Hopkin: way, which is simply let's, let's look at the lifetime cost of our building and let's, minimize it.

[00:30:21] Danny Hopkin: It's lifetime. And that is the acceptable safety level, the failure probability corresponding to that minimum investment over the lifetime of that building. and they do that by factoring in that, that your safety investment in a building is upfront. you put your protection in, you put your systems in that has a cost.

[00:30:40] Danny Hopkin: Those systems might not be called upon through the lifetime of the building, or they are called upon at some low probability. And in that event, that those systems failure, you, you have some fatalities, you have some damage. you have some indirect costs, all of which you can evaluate. And so you're, you're constantly trying to embark to balance how much you're [00:31:00] investing upfront in a building against future unknown costs.

[00:31:05] Danny Hopkin: and so instructor engineering, they've kind of come up with these effectively model situations where they look at this lifetime cost for a series of model buildings, they are determined these minimize in terms of the cost and that corresponds with, a safety target per annum, whether it's a failure probability of one times 10 to the minus five, one times 10 to minus six, one times 10 to the minus seven a, and so it's a very cold in many respects, balancing or optimizing of costs and benefits.

[00:31:34] Wojciech Wegrzynski: do implement that in fire safety, maybe even instructionally that requires you to put value on life, which is probably a hell of a discussion. The second thing I think my life is valued more than my neighbors and we come into societal versus individual risk acceptance in a way I can accept pretty high societal risk, but when it's due myself, I would prefer not, [00:32:00] you know?

[00:32:01] Wojciech Wegrzynski: so this is in a way very, I find this discussion very difficult in fire engineering. Did in structural engineering could also involve the calculation of like say fatalities and probably, yeah, probably these to,

[00:32:15] Ruben van Coile: Innovate. Although it seems to be often not the dominant factor, which makes it maybe in

[00:32:23] Wojciech Wegrzynski: uh huh.

[00:32:23] Ruben van Coile: a bit easier the cost of the building and so on is so high. but in the end, it is when we talk about societal requirements, we're talking always about at least conceptually ALARP requirements.

[00:32:40] Ruben van Coile: So reducing the risk as low as reasonably practicable, if I may say a concept, so whether or not your local legal system is, is different, that doesn't really fundamentally matter. The concept is we're trying to reduce the risk as much as it's reasonable and what is reasonable, but lot depends how much society can pay for it.[00:33:00]

[00:33:00] Ruben van Coile: And how much can society pay for it? Well, I also reasonably depends on how rich the society is because you want to spend money in society for

[00:33:09] Ruben van Coile: pleasure and private things, but for education, for those hospitals, for all kinds of stuff. So the devaluation of risk to human life, there are different approaches to it.

[00:33:21] Ruben van Coile: Yeah, you can, you can ask people, you can look at how much people have paid in, in their jobs. personally, I'm very reluctant about those kinds of studies, very weird things come out of that. So as you can probably imagine, right? So while, so the approach that we in the papers of. Use and also, which is by the way, adopted the ISO standards, 2394 which is for structural really the the life quality index.

[00:33:55] Ruben van Coile: So it's, includes a balancing it takes into account GDP. It takes into account life [00:34:00] expectancy, those two together. It finds how much society is capable of paying average, across all kinds of risks for reducing.

[00:34:12] Wojciech Wegrzynski: I can imagine where the studies go, because if you start following this new will also reflect all the inequalities of the world in this index. And, you can come to conclusions which cannot be published in mainstream.

[00:34:23] Ruben van Coile: very interesting. So teaching exactly this kind of topic, couple of weeks ago,

[00:34:29] Wojciech Wegrzynski: Yeah.

[00:34:30] Ruben van Coile: risk management. I wanted to choose what the students from, from Pakistan. And maybe it's an uncomfortable thing to, to mention, in a lecture as in, well, actually, depending on GDP, life expectancy, we take into account, there's a valuation of and say, well, but it's fundamental.

[00:34:47] Ruben van Coile: Because if a country would burst to adopt a standards and American standards, European standards, which is too expensive, this country is [00:35:00] over investing in whatever that is, structural safety, fire safety, and losing welfare that way. this particular student that raised his hands and they applied example, on fire safety in Pakistan, apparently they adopted, a standard and it, as far as I understood it, turned into, uh, something had to change because also most practical, not practicable, too expensive to.

[00:35:26] Wojciech Wegrzynski: Um, Danny you've mentioned the, the ways to demonstrate safety, to the routes of PD.

[00:35:31] Wojciech Wegrzynski: And you've, you've mentioned this comparison. I know another way is to find this minimum, like diminimous, level of safety and just go with that if that's acceptable, but there was also like three pathways, that allow you to actually demonstrate safety, whatever the safety is. Maybe, maybe you would like to go into these pathways because I found them very interesting in terms of what tools and what challenges are related to.

[00:35:57] Danny Hopkin: you mean the acceptance concepts?

[00:35:59] Wojciech Wegrzynski: [00:36:00] yeah.

[00:36:01] Danny Hopkin: Yeah. So, kind of three core ways of doing it. And then there was variations on a theme within those acceptance concepts. So you we've touched on the first one, which is this, this sort of comparative assessment. Where basically you're, you're assessing, the, the residual risk profile of, that building, as a reference point, and then you're designing your building to make sure that your residual risk or failure property, however you want to think of it is consistent with that reference building.

[00:36:27] Danny Hopkin: And, and at no point, are you assessing if the range of consequences in your building and their likelihood, explicitly tolerable to society, you're kind of assuming that the.

[00:36:40] Wojciech Wegrzynski: If it was in the previous building.

[00:36:41] Danny Hopkin: than it is for yours. And therefore you're kind of, you're making an assumption that , the range of consequences and their likelihood in your building are broadly similar to what you have in your reference building.

[00:36:54] Danny Hopkin: And then we extend that concept of slightly way you have that comparative analysis, but you have, what [00:37:00] is this sort of explicit assessment of the consequences and they're like here, so you actually have an explicit check on this tolerability threshold. but they're kind of the comparative parts.

[00:37:11] Danny Hopkin: other one we postulate, which is. I think it's a really nice idea. It's actually very difficult to achieve in practice is, is explicit safety target Ida, which is what we have in structural engineering under, under ambient conditions. So if you look in E N 1990, annex B, there are consequence classes or reliability classes for structures, one, two, and three, and, and they are basically a gradation of the number of fatalities and material damage that you would expect.

[00:37:41] Danny Hopkin: so three being a high number of fatalities and a high amount of damage. And, and as you move through those five, those, um, structurally structural failure induced consequences there, the failure probability you accept or is optimal I guess, I suppose the right term So you go [00:38:00] from sort of one times 10 to the minus five to one times 10 to minus six to one times 10 to minus seven.

[00:38:05] Danny Hopkin: and so. We kind of hypothesized that you could develop such a thing for fire safety engineering, where you have a series of safety targets. So if you were designing, I don't know, a 10 story residential building, then the probability of a fatality should be some

[00:38:20] Wojciech Wegrzynski: Um,

[00:38:21] Danny Hopkin: And if you demonstrate that you meet that threshold, then it is implicitly a lot.

[00:38:26] Danny Hopkin: It's it's um, it's satisfied that condition.

[00:38:29] Wojciech Wegrzynski: it's a very, like how well tunnels are being designed

[00:38:31] Wojciech Wegrzynski: in many European countries, especially Alpine, where you have FN curve that says, okay, at this point, you're okay. At this point you have to, admission, safety, uh, solutions. If they're practical, we'll above that. You're not loaded at all.

[00:38:46] Wojciech Wegrzynski: yeah, that, that.

[00:38:47] Danny Hopkin: involved in arriving at what those targets should be, and it could be. I don't know, a regulator gets around the table and just arbitrarily decides what those numbers are, or it could be something more involved like [00:39:00] the structure engineering process. Series of kind of reference buildings and determining those Optima.

[00:39:07] Danny Hopkin: and then the final approach is this kind of full blown, quantitative risk assessment process, where for your building, you're calculating the consequences you're calculating all of their likely hurts. Your you're plotting effectively the FN curve for your, building design. You're comparing it against some societal acceptance criteria, societal risk threshold.

[00:39:29] Danny Hopkin: So that is determining that the design is tolerable. So in principle, you can build it there wasn't a fire event in it, and it had that profile of consequences and likelihood, there would unlikely be societal unrest. you are then obliged to go beyond that point and make sure that any further investment in the safety measures would be disproportionate to the benefits.

[00:39:52] Danny Hopkin: And this is this ALARP condition. albeit we propose that actually that, If you're satisfying this tolerability [00:40:00] criteria, which is already has some level of disproportionality in it, because you, you, you have a difference between society's point of view on a hundred fatalities versus one, that actually your cost benefit analysis, your lap demonstration simply resolves to, is it more expensive or other the cost more than the benefit?

[00:40:17] Danny Hopkin: And at that point you effectively stop investing.

[00:40:21] Wojciech Wegrzynski: So essentially your trial design would not end when you just satisfied the criteria, but you go on checking. If it can be reasonably improved. Yeah.

[00:40:30] Danny Hopkin: exactly. and, another way of looking at any one of these problems is, is when you test your failure, probability of your residual risk profile, and you find yourself in what we call the de minimis region. So that's the consequences in their likelihood or a such a low profile that you kind of accept it By, uh, observation almost. It's

[00:40:50] Wojciech Wegrzynski: Hmm.

[00:40:51] Danny Hopkin: the risk profile of the building is a couple of orders of magnitude below what's it's tolerable and

[00:40:55] Wojciech Wegrzynski: Uh, you, you have no flammable materials inside too.

[00:40:58] Wojciech Wegrzynski: It's hard to expect the fire. [00:41:00]

[00:41:00] Danny Hopkin: Yeah.

[00:41:00] Wojciech Wegrzynski: Yeah.

[00:41:00] Danny Hopkin: do you not bother with that cost benefit alarm assessment, because you are already kind of at the floor in terms of what you're going to reach the, for the risk profile of your building?

[00:41:09] Wojciech Wegrzynski: And you mentioned residual is the residual risk. Sorry, how you find

[00:41:13] Wojciech Wegrzynski: one?

[00:41:14] Danny Hopkin: I use, I use that terminology very specifically and we do in most of our publications because. I think maybe we should have started the discussion is in anything you design in, anything that you build, ultimately the, risk is not zero,

[00:41:29] Wojciech Wegrzynski: Um,

[00:41:29] Danny Hopkin: some likelihood of some adverse event happening.

[00:41:33] Danny Hopkin: And you, as the designer are trying to get that residual risk down to a level, which is adequate, is the term we use. and so it's just acknowledging that you have never driven out all of that risk. There is a residual component to it, you're trying to manage that residual component to a level, which is, is adequate in the circumstances, whether that's because it's de-minimis whether that's because it satisfies the alarm condition, [00:42:00] whether it's proven to be equal to a reference design.

[00:42:02] Wojciech Wegrzynski: when I do go into discussion with stakeholders about risk, I like to set up the discussion field with some ridiculous example, like, okay, if a meteorite hits the building, are we okay with that? Or should we design against that? And there is usually yeah. We're with you. Okay. With, with meteorites. Okay.

[00:42:24] Wojciech Wegrzynski: So you have agreed that there is a level of residual risk you're willing to accept. Let's move into fires. If a thousand megawatts fire happens in this building, which is very unlikely. Let's say you have a sports arena, someone parked seven oil tankers, this is impossible to happen. So you're okay with such whisky as we are, then let's try to find this most, unreasonable scenario at which you are still okay.

[00:42:51] Wojciech Wegrzynski: Because the service so unreasonable. And then we suddenly start, you know, narrowing down to where is this boundary at [00:43:00] which the, low probability Evans would still be, accepted. And that gives you one boundary to the question. The second is like, super, like high probability, very low consequence events.

[00:43:11] Wojciech Wegrzynski: Like, If there is a fire off of the trash bin, should I design against that nerve? It's obvious it's the consequences will not be, not be severe. So we're again in high probability, very low consequence region and narrowing between these two, probably at some point leads to acceptable, adequate deliverable risk, whatever that risk is.

[00:43:33] Wojciech Wegrzynski: am I following a good path there?

[00:43:35] Ruben van Coile: Well, first of all, um, Danny you put that very nicely. So was great. , and then what you're saying now, Wojciech it's to me, it sounds like you're talking about the tolerability of your design. So yes, you have tolerability very frequent, low consequence. At some point, it doesn't get, it's not tolerable anymore, probably as in, if you have daily, a fire, something as wrong and.

[00:43:59] Wojciech Wegrzynski: And then you have to [00:44:00] design against that from my perspective.

[00:44:01] Ruben van Coile: this is the frequency limit. On the other hand side, you probably have indeed or at least I like the concept of having a consequence limit. You say, well, everything, which, but a low probability high consequence there, like the last thing, the first thing you said, the probability solo that's okay.

[00:44:17] Ruben van Coile: I'm now not

[00:44:18] Wojciech Wegrzynski: yeah.

[00:44:19] Ruben van Coile: this anymore. However, crucially, the talking about tolerability does not by itself gives you safety. adequate safety is always conceptually ALARP and which it doesn't always mean that you have to do a cost and benefit evaluation. You could do that, but we have these other routes, right?

[00:44:40] Ruben van Coile: safety, comparative safety potentially, and also a cell. So very important point if you say, ah, yeah, but still , this is not realistic. What you're saying. Yeah. It can also be quality. As in, within the F few on residual risk, as Danny pointed out, you can, as a designer, make a qualitative assessment of [00:45:00] your risks.

[00:45:01] Ruben van Coile: And maybe you before doing any calculation, you already come to the conclusion that your risk is de minimis it's conceptually possible. So it definitely not saying that you have to do all kinds of calculations for every design.

[00:45:13] Wojciech Wegrzynski: Okay. And to close up the, episode, let's try and clean out what all of this means, to fire safety engineer. we've started with, buildings that are exceptional designs with new applications, new materials. is this the place where you would go all the way in, in this, uh, analysis?

[00:45:34] Wojciech Wegrzynski: Would you go there if you were only to demonstrate you can build the building cheaper, or maybe you would go there to demonstrate that the low limits are unreasonable, because I find many applications of what we are discussing in here. Like we're not, or you guys who are researchers, I don't think you're trying to find these answers just for the point of finding answers and having [00:46:00] papers, but it's supposed to be practically useful, to engineers and, I wonder, is there a boundary where one switches.

[00:46:09] Wojciech Wegrzynski: Prescriptive to this type of performance approach, when it becomes really useful. So people start considering it's worth for them or if they should actually consider switching,

[00:46:22] Danny Hopkin: so when, when we write that first paper, that Certain Uncertainty one, I think that was very much a pitch to. To dealing with those exceptional cases where safety can not be assumed to be achieved through or adequate safety, our collective experience because we've no longer got that guiding light of a massive building stock that experiences fires to allow it to kind of inform us on our design fire scenarios and our performance criteria.

[00:46:51] Danny Hopkin: So that where we, we initially made the appeal that it's in those uncommon building situations I suppose, is [00:47:00] the term. but as a consultant, these kinds of tools have become. Kind of commonplace in what we do at OFR in particular. So, just a few ideas on, on how we apply structural reliability in

[00:47:13] Wojciech Wegrzynski: Yup.

[00:47:13] Danny Hopkin: we do.

[00:47:14] Danny Hopkin: Um, it's a, it's a very powerful tool for appraising existing buildings, in particular. So, so if you're faced with an existing building and there's some uncertainty about the level of performance you're achieving and, and actually it would be unreasonable to that existing building to satisfy a contemporary standard or guidance document, we will quite often use a reliability based method to appraise that structure, to determine its failure likelihood, and to compare that against some kind of acceptability criteria.

[00:47:46] Danny Hopkin: and so it becomes a demonstration of, uh, of an existing building having an adequate level of safety and therefore it might not need a massive amount of remediation that's because. When we go through that probabilistic [00:48:00] process, we're able to weed out and quantify what can be an awful lot of conservatism's in what a deterministic approaches for structural design.

[00:48:08] Danny Hopkin: So we can take into account the fact that, the characteristic strength is actually a very low percentile. In reality, we have probably more strength than we expect. We can take into account the fact that load on any given day, when we have a fire event is probably a lot lower than codes. Be just to believe we have the ignition frequency that we can take into account.

[00:48:31] Danny Hopkin: So, it just becomes quite a powerful tool in demonstrating that actually remediating something might not be ALARP. might already be there virtue of just having a lot of extra meeting. And in your structure that you perhaps didn't contemplate.

[00:48:48] Wojciech Wegrzynski: But by taking three influence, All the

[00:48:50] Danny Hopkin: All the uncertain.

[00:48:51] Wojciech Wegrzynski: getting, maybe not even getting greed, acknowledging where the safety factors

[00:48:56] Wojciech Wegrzynski: were,

[00:48:57] Danny Hopkin: Yeah,

[00:48:57] Wojciech Wegrzynski: especially the unintended safety factors that [00:49:00] you just assume the worst case scenario If you had no idea of the distribution of the, of

[00:49:04] Wojciech Wegrzynski: the scenario, say.

[00:49:05] Danny Hopkin: a bit like, so as a structure engineer, you're told when you've got C 30 concrete, that means it's got a 30 MPa a strength. Well, no, actually it's it, most of the time, it's much, much higher than that. And that just happens to be the characteristic strength for the purposes of code calibration.

[00:49:20] Danny Hopkin: and so you can start to bring some of those extra distributions into play. and actually, Luke Bisby gave a good talk about this a few years ago. what we like to think in guidance documents around fire resistance in particular, in the U K K in England, we have this quite weird where we have.

[00:49:40] Danny Hopkin: Uh, fire resistant recommendation of five meters. We now have one at 11 meters. We have one at 18 meters. We have one at 30 meters, and then we have nothing flight. If it's 30 meters, plus just give it two hours. And so it feels unbounded. when you look at our structural design regulations, we actually have a boundary condition for [00:50:00] disproportionate collapse, which says for a consequence class rebuilding, which be a 15 story office or a 15 story block of flats, you have to do a systematic risk assessment for disproportionate collapse taking into account all reasonable hazards of which fire is a reasonable houses for you to consider.

[00:50:17] Danny Hopkin: So, uh, if we're dealing with a tall building, we will use some kind of probabilistic assessment of what the fire resistance period is and how the structure performs as part of that risk assessment process to support the structural engineer and disproportionate collapse so, a little sales pitch, and I think we've mentioned it before we have.

[00:50:36] Danny Hopkin: This great tool that my colleague Ian Fu developed to recall a SFE PRA, which is our kind of Python Monte-Carlo library, which is this reliability based calculation of fire resistance periods for buildings. And so that is that we use almost on a day-to-day basis to inform what fire resistance we should be giving buildings, taking into account their specific risk profiles, their [00:51:00] specific hazards, and the specific consequences of that.

[00:51:02] Wojciech Wegrzynski: Ruben, why do you teach all of this to your students besides torturing them with, difficult concepts and need to think.

[00:51:11] Ruben van Coile: ' cause it's the basics really? it's extremely fundamental. as Danny said earlier, as in every design has a residual. So thing we definitely should mug do is assume that if you follow codes and guidance, that it has always been fine and it will always be fine in the future.

[00:51:28] Ruben van Coile: That's definitely not the way to go. and there are two, or at least to, to, to use these kinds of methods. One is to okay, to use advanced methods to guidance documents. this is definitely something which we should do. not just from academic perspective, I think, but also as society, this is very cost-efficient or it can be very cost-efficient.

[00:51:48] Ruben van Coile: So you spend some money, you do some investigation, you have yourself a guidance and you can follow that guidance is great because that's the risk of you. I talk about this. This sounds no, you have to [00:52:00] throw away your guidance. Definitely not saying that guidance is great. Very cost efficient for designing buildings.

[00:52:05] Ruben van Coile: But that's on making guidance documents, then you have specific projects now, then he gave a couple of just now. and I would basically old, I often say, or try to get, to the students as well. Is that on project you have to, acknowledge what you don't know.

[00:52:23] Ruben van Coile: So having an open mind, looking at the project, talk with the client about what you actually want to achieve. this discussion can be very short in the sense that, well, we just want to get the building built, but you have to have the. Kind of starting point you defined, this is what I want to achieve for this building.

[00:52:42] Ruben van Coile: We own the same page. And then often guidance can be enough, sometimes it will not be guidance and sometimes take some stunning gates. You will have an exceptional structure and then you don't really have a choice.

[00:52:54] Wojciech Wegrzynski: I like positioning it as fundamental safety safety. So [00:53:00] let's not assume we have one. Let's quantify one. I like this.

[00:53:05] Danny Hopkin: I think the, one of the appeals we commonly make is to this sort of concept of a consistency of crudeness. Now, I think that's the terminology we've used Andy Buchanan , in the first paper that we wrote and what we seem to be doing as a community. We spend an awful lot of time developing really complicated tools to solve complicated problems.

[00:53:25] Danny Hopkin: but actually if you take them into the real world and try to apply them the first, the biggest uncertainty, I think we have when we're designing buildings ultimately what we're trying to achieve. And how we know we've achieved it in terms of the level of safety that, that we think we're getting the level of safety that we want.

[00:53:44] Danny Hopkin: And so throw all the finite element models and all the CFD model as you want at the problem. if you have these massive aerobars on what an adequate level of safety is and how you've quantified it, then the precision of those instruments is irrelevant because [00:54:00] you cannot place them in the context of what's acceptable in the circumstances, or was adequate in the circumstances.

[00:54:05] Danny Hopkin: and so. This is why these tools are so fundamental because they are part of the engineering decision-making that allows you to decide whether your design is achieving the goals that you think it's achieving not. and our appeal to the community has really been, invest more time and on this discussion, because actually the incremental improvements you're making in finite element models or material, understanding of, load induced, transient, thermal creep, or whatever it might be, those gains are so marginal compared to what level of safety are we trying to achieve and how do we know whether we've achieved it?

[00:54:38] Danny Hopkin: and yeah, so, so we make that plea and I think we still continue to make that play here some five years later.

[00:54:43] Wojciech Wegrzynski: So it seems you want to apply acceptance concept five to two to add the discussion in the academic world and engineering world. Yeah. let's measure it. let's measure the return of our investments in science I like that a lot. I liked it. that's a third level of [00:55:00] inception in, in this episode.

[00:55:02] Wojciech Wegrzynski: I hope a lot of people made it to the end because the end was , really strong game. Might actually need to advertise it with the final words because it's definitely worth it. Okay, guys. Highly appreciate your time. I'm really happy. After seven months of ranging this, we finally met in the studio to talk it over, I'm really thankful for this discussion. And, that's lots of things to think about. That's a lot of food or for tough. So I hope many people enjoy it as much. Thank you so much guys. Yeah, she is

[00:55:36] Wojciech Wegrzynski: And that's it. Thank you for staying at the very end. I hope it was worth it.

[00:55:41] Wojciech Wegrzynski: And I hope you're not disappointed with the lack of magical pain content in this episode. Regardless. I think it was quite an powerful discussion on what the risk methods are, how you can use. Them to find acceptance criteria to find your tolerability limits, to [00:56:00] find your. True safe solutions and, um,

[00:56:03] Wojciech Wegrzynski: I really liked the practical spin that Danny gave in the end. With how these can be really, really used well for existing buildings in assessing their true level of safety. This is something I did not really considered before, but it makes so much sense that instead of blindly applying.

[00:56:22] Wojciech Wegrzynski: Any more than the solutions required by the codes like magic. And you get go into full risk assessment and actually determine what is the residual level of safety of the existing building? And if that needs to be changed based on the modern guidance. I think that that's really powerful because we are entering an era where.

[00:56:44] Wojciech Wegrzynski: Buildings will change. The existing buildings will change. Renovation is way more efficient than building new buildings. So we, we need to use what we have to the best we can. And I [00:57:00] foresee that this kind of work. We'll be more and more important in the future. So definitely a great skill to acquire. And I also really liked the idea of using the Life Quality Index. In assessing the benefits of safety solutions. It's a hard choice. When you have to calculate how much money you save, how much lives you save, how much life is worth. Very very difficult things to do. And as Ruben said in different countries,

[00:57:30] Wojciech Wegrzynski: This will be different. There will be different. The amount of money, people are willing to pay to save one's life. And. Unfortunately, that is a brutal reality in which we live in. And yeah, you need to cutter these requirements cutter these solutions. To the place where they are used. So you serve the people that are best.

[00:57:53] Wojciech Wegrzynski: And the use of life quality index seems like a quite biased. Way to measure that quite a [00:58:00] good escape from this. A hundred, we have with estimating the value of life or the value of investment in safety. So that was also a good, takeaway for me. I hope you've enjoyed the whole episode. I think it was very worthwhile to spend this hour with us.

[00:58:17] Wojciech Wegrzynski: And the discussion was really good. I'm certainly going back through it after some time, because I need to digest it and maybe implement some of what has been said here in my own work. And, uh, and anyway, thank you very much for being here and as usual. Next Wednesday. Next episode. See you there. Cheers.