Metrics; measurements with purpose. It’s a term I’d long left associated with those business managers that trade buzzwords with each other; inheriting, instead, the engineer’s standard unit- a deliverable. And deliverables are important; key performance indicators of beams designed per-hour or daily count of piles driven (OK, I’m being a bit facetious) are nothing compared to handing over a complete and functioning bit of infrastructure.

Last week I went to a talk from an enthusiastic young man from everyone’s favourite online takeaway service. The topic- Metric Driven Development. It’s fair to say that software developers have a real fascination with building and analyzing their processes; and in my short working life I’ve already seen the rise (and somewhat fall) of Test and Behaviour (Driven Development) approaches. But that’s what makes it so interesting…

So what is this metric driven development? Would it surprise you to learn that you’re already part of it? You click on the order button- was it always on the right? that took a moment or two to find- and stall for a bit at the checkout; unsure on whether you really need everything in your basket. But there’s that timer going; seems this deal is only for a short while. Best click through. Ahh, this site never remembers you payment details. The saving isn’t that great in any case- let it go. Have you seen that video with the hedgehog in the bath?

Every single step of that process has been measured (assuming this online store is using metrics). And someone is defining insights; goals. They know that 20% of people, like you, have dropped out at the last hurdle. And so they launch a few campaigns to inform a decision- 10% of visitors are now being offered PayPal as a checkout, and another 10% are being offered to save their card details. The monitoring continues- it turns out just offering to save the details only increases conversion by 5% (perhaps people resent all data entry?), but that PayPal link improves things by 10%. Slowly but surely all visitors are being invited to use PayPal…

There’s a lot of talk about in this example. Firstly let’s establish that their ultimate goal is to convert you from a browser into a sale. The metrics they collect are used to inform their design. They’ve targeted aspects that they think can inform decisions; not only watching your journey but also the speed at which you make it. In a previous incarnation people once gave up after spending too long considering their choice at the checkout- thanks to the timer, they no longer do this.

Although people slow down a bit finding the right buttons, the point where they lose the sale is when they ask for payment. So, following a development driven by metrics, it makes sense to target this aspect first. However it’s hard to know exactly how to solve this problem, so they prove their solution by doing something called A/B testing. They try both of the solutions they’ve considered, and see which one performs the best. Building an architecture to store payment data, is expensive so you want to be sure before you invest.

The last manifestation of the metric driven approach is more subtle. Despite PayPal being a clear way to improve conversions- they didn’t just roll it out in one day. Using an approach called feature toggling, they slowly switched it on for users. This allows them to use performance metrics to ensure they don’t bump into any problems; constantly verifying the health and load to inform decisions on how to scale it up from 10 to 100% of their customers.

I hope that the advantages of metric driven development are fairly clear. You get a very clear goal to inform every decision you make; I want to increase the measure of X, will Y do that? It follows a very scientific principle; hypothesise, experiment, evaluate, respond. Failures can be spotted faster, as can changes; by integrating instrumentation it’s easy to spot trends, and verify that what you put in to achieve something continues to do so.

One thing is for certain, civil engineering isn’t software engineering- however I don’t think that means that ideas are mutually exclusive. In my last post I talked about cost and consequences, and hinted at a need for instrumentation (that’s just the technical term for measurement equipment) as part of our infrastructure [Ed. There was even a comment about it.]. These days instrumentation is cheap, as is data processing.

There’s a few spaces where a metric driven approach might help construction. Starting at the most mundane, simply measuring how long it takes to achieve something and setting it as a metric to reduce can be surprisingly powerful. Sure- everyone in construction wants a fast turn around, but unless you make a formal statement of this you’ll just be using anecdotal balances and it’ll be hard to justify and discover exactly what you did that made it so fast/slow.

However, management theory aside, I think there’s some more exciting applications. Consider our infrastructure as one giant system. The goal is to get people from A to B as fast as possible. How do we evolve that system? Every new junction provides an opportunity for massive scale A/B testing– each with it’s own unique feature that either lives or dies based on the relative improvement. Measuring traffic flow is easy; it’s coordinating the results that will be the hard part.

Or one step further. A structure built of metrics. A bridge wired with sensors. Using the responses from the sensors to evolve the design– sending across the first car, measuring the response and strengthening accordingly. Slowly rolling out to more and more traffic and making the adjustments as discovered- entertaining new prospects through the A/B pattern; toggling structural aspects to manage their effect. Sure, a more modular construction approach would be needed, but I wouldn’t be surprised if you ended up with a more efficient structure that was easier to build (as it had to be built as we went along). And, of course, you’d learn a lot.

It’s clear from my most extreme example that the approach is more of a science than a traditional engineering one. Alone it’s much more of a fool doing for a pound than a precision penny; lots of guesswork and learning through feedback. However the role of the engineer in this scenario is to interpret the metrics and suggest appropriate responses. Something, you might argue, that your average civil engineer already does!

Of course, in our current system this is a bit of a pipe dream, however as a thought experiment it’s an interesting one.

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My better half and I have just bought a house (which explains why my “weekly” posts, have not [Ed. it’s a backlog I’m working through- please bear with me…]). And like most couples, it seems, decided to test our relationship by spending seven hours in those circles of hell known as IKEA. As this is a blog about engineering, I won’t dwell on the truly amazing techniques the Swedish veneered timber export giant uses to trick the unsuspecting into spending inordinate amounts of time looking at home furnishings, but instead talk about something they do even better: prefabrication and modular design.

This isn’t the first engineering lesson IKEA has taught me; but as I spent a second day assembling flat packed furniture I began to marvel at just how well engineered their products are for assembly (no- I’m still not on commission). The fact is, IKEA has managed to achieve what civil engineering has been striving for since it’s inception- kit that can be constructed cheaply, quickly and safely by an unskilled workforce.

As it slowly became clear that my weekend would be a crash-course in IKEA assembly, I decided to see if I could learn some lessons of my own. It seems fair, considering my last article on their products, to start with the good, but it’s not all tales of wonder- after the 48 hour assembly marathon I had formed some strong opinions of where IKEA’s system is lacking; and by extension formulated some key principles to improve prefab and assembly construction.

The Good

By far IKEA’s greatest achievement is that they manage to create instructions that require no text. If you want a measure of how easy your design is to explain; consider- could you do it in a short picture manual (à la Lego), or do you need a library of 300 page documents (à la most civil engineering designs…). Unlike our B&Q fence (which came with zero instruction, pictorially or no) every step can also be completed exclusively with dry-work handtools; reducing the skill level to “following instructions”- which even an engineer can do (eventually).

For reasons of our own we ended up buying six identical shelving units. This was where IKEA really came into its own. While the first was easy enough to assemble, but by the sixth we were a well oiled machine. Because IKEA is a system, it is easy to learn, and consequently improve and predict. For simple processes this means that reliability dramatically increases in a short time and familiarity makes a smarter and more efficient workforce; let alone a safer one- if you know exactly what you’ve got to do, you can keep prepared and create a safer working environment.

Of course- the pedantic among you might argue that IKEA has an advantage- an IKEA shelving pack builds a shelf and not much else (excepting maybe a flimsy table or a fire when you get frustrated). However the observant will probably notice that IKEA reuse a lot of the base components across multiple products; much like our own modular systems- making the odd hole redundant for some configurations, but inventively reducing the number of part-lines they have to maintain (and hopefully extending the availability of spares).

Room for Improvement

As someone who’s dipped a toe in the terrifying pool of temporary works, it irked me that the construction methods often resulted in unstable temporary conditions. It should not be a requirement to use your leg as a prop when assembling furniture. By extension the temporary conditions should ‘fit’ into a space similar to the installed site; no one appreciates having to relocate their bed as ‘enabling works’ for a wardrobe. And if you can’t eliminate this issue, then you should at least inform people up front: “You will require a screwdriver, six square feet of space and an unused DVD box-set to use as a prop.”

Considering my healthy distrust of instruction manuals; it is to IKEA’s credit that there was only one time when I had to disassemble and restart; I had discovered that IKEA has performed the unforgivable sin of providing two different types of fixings distinguishable only by the subtle fact that one was 7/8ths the size of the other. But there are a lot of instances of hole-counting with the kits to choose which almost identical piece of coloured chipboard you’ll need. For reliable construction your pieces need to be free of ambiguity, but more than that- they need to be communicable. If you’ve ever had to explain across the room which flat piece of wood you need, you’ll know what I mean. For this, I suggest a colour/letter system- you’ll need the Red-A, or the Yellow-B.

Which leads nicely onto my next improvement- in-line instructions. This might seem lazy- but if IKEA assembly instructions are so easy that they can be conveyed pictorially; why can’t they be on the products themselves? This has a more important ramification I noticed when moving- no one in their right mind catalogues and retains IKEA manuals; and thus, when it came to disassembling an old favourite there was a lot of improvisation– had the instructions been on the product, I would have known exactly what to do. CDM people, CDM.

One of the more bewildering parts of IKEA’s philosophy is that everyone has a hammer and screwdriver (both flathead and Philips) but doesn’t own any Allen keys. This regularly leads them to enclose sub-standard tools with their products whose only purpose is apparently to lacerate hands and fill the toolbox. This odd skill grading comes to a head when you are just expected to know the ins and outs of wall mounting fixings. If you’ve targeted the illiterate screwdriver wielding masses then you can’t simply leave them with a “now attach to the wall- no tools, instruction or fittings included.”

When it comes to prefabrication and on-site assembly IKEA have dominated the market so insidiously that if they’d included secret microphones on their products they could have given the NSA a run for their money. If a civil engineering firm could come up with the same simplicity for the built environment; well- we wouldn’t be able to move for sites filled with people despairing at instruction 15/71 because they’ve realised they need to go back and traverse the shakily propped “thing with the holes on the left” to get a Stanley #1. – and what a world that would be.

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Last year I got an email from an engineer called David. After seeing my embarrassment of a video about loving civil engineering, he wrote to tell me that he, too, loved civil engineering. But what he also did, was tell me about a project he’s been working on to share his career in the profession: an online engineering portfolio.

As someone who is forever saying we should do more to share our work with the public; I was a little embarrassed to realise that the idea of a portfolio had never crossed my mind. It’s a simple thing; and so much of our work is visual (sketches, analysis plots, drawings, site photographs) that it really lends itself to the format.

David started his online portfolio as a way of helping civil engineers working in the building and design of bridges. At last count there are 43 projects featured; charting his time with Kier, May Gurney, Alfred McAlpine, Carillion, Birse, Balfour Beaty, Network Rail- with a massive amount of information and photographs. It’s really satisfying to see his photos tracing projects from breaking ground to black-top; in fact, by the time I finished, I was fairly envious of his career!

Being able to browse through 15 years of someone else’s experience in the industry is pretty fascinating in itself; but it also does a lot to promote and celebrate good, honest, civil engineering. Too often, I think, engineering campaigns get tied up in attempting to force the glitz and glamour of “saving the world” and building architectural mega-structures, and forget the actual civil works behind it.

Maybe it’s time we all started a portfolio? But until then:

Check Out DBM Bridges

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Did you know that most important Brunel (of Being Brunel fame) bridge in Bristol lays abandoned; rotting away along the side of a dock? Although he wasn’t born there- the city owes a lot to his engineering efforts, and is arguably the home most celebrated for his achievements. The only abandoned Brunel structure in Bristol, this Grade 2* bridge is now listed as being at extreme risk on the English Heritage Buildings at Risk Register.

Before you run off to check the papers for news of the Clifton Suspension Bridge’s collapse, let me clarify- I’m talking about Brunel’s other bridge; the Howard’s Lock Swivel Bridge. Unlike its more celebrated cousin, which was largely a posthumous achievement completed by William Barlow and Sir John Hawkshaw; the Swivel bridge was completed 15 years earlier- under the direct supervision of the man himself (although let’s not neglect to mention Brereton– who was probably responsible for most of the detailed design- Brunel was very much a Blue Sky thinker…)

The Swivel Bridge

Before I continue, I should mention that there’s an exhibition on this structure at the Bristol Central Library from the 5th of January to the 15th of February; which will be much more comprehensive than my attempt!

But splitting hairs about the level of IK’s involvement isn’t what makes this bridge so very important; it’s an early example of a wrought iron plate girder bridge, and his first tubular flanged bridge. In the swivel bridge, to the initiated eye, we can see Brunel’s engineering development of plated girders and and tubular flanges that were echoed throughout his later career in the likes of the Royal Albert Bridge, or the Chepstow Railway Bridge.

Commissioned in 1844 the 33.7m long (23m nose) 68 tonne bridge was designed and built by Brunel and his staff in 1849 to carry traffic over the new south entrance lock (also by Brunel) to the Cumberland Basin. Originally rotated through a hand turned crank (like ye-olde train turntables), the swivel was replaced with a hydraulic mechanism in 1901. Perhaps most interestingly, the bridge was shortened and relocated to it’s current location at the north entrance in 1872-3, and then in 1875-6 a replica (differentiated only by it’s more modern section sizes) was built in the original position; presumably just to confuse future historians. Until the M5 was built it remained on a primary route; but in 1968, after the construction of the Plimsoll Bridge, it was decommissioned, and rotated one final time to be laid to rest under the new bridge.

Brunel’s Other Bridge

Fantastically, however, a group (aptly named Brunel’s Other Bridge) have been working to save this monumental structure. The history of the bridge’s restoration has been an interesting one; it was almost saved by the Sustrans scheme in 2008, however the council were reluctant to restore the bridge (repairing and maintaining old infrastructure is a substantial risk). After a failed lottery funding attempt by Bristol’s Cycling City Team, however, the Clifton & Hotwells Improvement Society, Bristol Industrial Archaeological Society and Avon Industrial Building Trust decided to move forward, on the 12th of April 2013, and repair the bridge themselves, independent (but with agreement from) the council.

Since 2013 They have been raising funds and carrying out work to repair the structure using volunteers. This year they’ll be doing everything from paint analysis to jacking up the bridge! You can see the sorts of stuff they’ve been up to in their photos… Of course, none of this is cheap; and the easiest way you can help save our engineering heritage is by making a donation.

The best bit, to me at least, is that if you fancy chipping in; you can- no experience needed. Personally the chance to get my hands dirty and ground my life of analytical design with some honest labour is good enough; but the opportunity to say I’ve worked on one of Brunel’s structures… well, that’s impossible to turn down. So I’ll be offering to give up a weekend sometime this year (expect a chuffed article to come), and, if you want to move off of the theory and start doing the practical (surely this counts as C1-5), here are the provisional dates for 2015:

• February 21-22
• March 21-22
• April 18-19
• May 16-17
• June 20-21
• July 18-19
• September 19-20
• October 17-18

Click Here To Help Save Brunel’s Other Bridge!

This article owes an awful lot to Grace’s Guide, which is an amazing resource for industrial structures.

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As part of the small minority of people that actually takes an interest in the NCE Graduate of the Year Award (read: previous winners, and the parents of this year’s batch) I’ve been finding it hard to ignore a certain pattern that persists between the years: The consultant always wins (especially if he works for Arup). However whilst the male/female divide over the last ten years of victors has been largely representative of the slow-balancing equality across the industry, the consultant, contractor and (dare I mention,) client distribution has left a lot to be desired.

In fact, Harry Potter would have had enough to time to find out he was a wizard, kill that guy from In Bruges and complete a masters in Horse Psychology since the last Contractor won the NCE’s Graduate of the Year Award. (That’s a year short of a decade, for those of you without the knowledge of some-what popular culture). In my year, in fact, we didn’t even have a contractor in the final six…

As a direct statement the trend reads: Graduates in consulting enjoy more notable achievements than their contracting contemporaries- or to put it more succinctly:

Actually, from my own observations it seems that contracting graduates win less awards entirely. Falling back on stereotypes, the guess is that consultants tend towards the academic while contractors have a habit of being more practical. I suspect that this means the entry form is in the favour of a consultant, with half the challenge focusing on a essay of the hypothetical.

Anecdotally one of the excuses I’ve had suggested by friends who are contractors is that they just don’t have the time. I know that in the year I entered, only 19% of the entrants were contractors. In fact, the contractors appear under represented all round; noting that, even being charitable with the designation of more specialist firms, the number of sponsoring (and therefore judging) companies that are consultants outnumber the contractors two to one.

All things being equal, if one fifth of the entrants were contractors there should have been at least one finalist in my year, and the gap between site-based victors somewhat shorter. This is a statement that begs a question; and indeed it might well be worth answering: Why do Arup dominate the NCE Graduate of the Year Award?

Arup, as a consultancy, focus on prestige and are large enough to support a broad range of esoteric disciplines and intrigues. Graduates at Arup, it seems, are typically exposed to either high-profile projects, or smaller intricate designs of obvious technical merit. Next to that a railway siding and some off-the-cuff hardstanding design is unlikely to hold much sway. Moreover, winning consultants typically get some interesting contracting experience in a philanthropic way.

My suspicion is that the risks involved for contracting firms on high-profile projects make it hard to delegate the same degree of technical responsibility to their graduate than a consultancy, and that the length of the projects contractors are exposed to are typically longer than that of the average designer. This means that, on paper at least, the achievements of a consulting graduate will tend to look better.

Personally, however, I’m a little dubious about whether contracting really is less interesting than consulting. Although I’ve spent most of my career, thus far, on the technicalities of design- I’ve done enough time on site to get my boots dirty, and from what I’ve seen it’s not as dull as all that…

I’d like to finish by saying a big congratulations to this year’s winners, but next year I really want to see a Contractor on the top spot!

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It is surprisingly easy, sitting in the office, to forget that the bunch of design calculations and drawings you’ve been pondering over all morning will one day have to be built by someone. Consideration of constructibility is a CDM requirement nowadays, and the dream of designing something that doesn’t cause a contractor to baulk is not yet dead.

So here are five, of the many, deadly sins that consultants often commit, which cause contractors to die a little inside (so I’m told)…

Rebar for Superman

Although no longer health and safety cannon the ’25 kg’ rule is still a good way of gauging what an individual can lift. This means that using 40 mm bars should be avoided, unless you’re planning to employ a gang of weight-lifters to build it.

Avoiding the largest rebar is only the start, however. The following table gives the weight of the maximum 12m length bar, and the length of a 25 kg bar for each diameter. Note that you need a small camel to lift a full H40 length.

Amazon Wish Lists

Not everything on a civils project can be designed using the fundamental elements of concrete and steel. Eventually you’re going to need some proprietary assistance, and the time comes to start specifying products. Often this selection will have some influence on the design and, if you’re lucky, you’ll be able to ask the contractor for a preference. More often than not, though, you’ll have to make the first guess.

In these situations, I have found, its better to consider product selections as assumptions. To be competitive contractors have to be able to shop around, and (unlike a lot of architects) suppliers don’t pay commission to designers. The problem is that the contractor cannot safely just pick anything. For example, the breaking load of steel parapets vary wildly between manufacturers; the wrong product could cause the structure to fail.

Whatever product is selected needs to meet both the specifications of, and the assumptions behind, the design. The following almighty three words, however, are our saviour of compromise: ‘Or Similar Approved‘. Tagging this note onto any named product gives the contractor scope to find the best deals (as most suppliers can provide similar products to their competitors) while still ensuring the consultant gets a chance to check it against the design.

Digging to the Centre of the Earth

A few years ago the rules for excavations were fairly simple, and trenches shallower than 1.25m didn’t need support. Now it’s much more complicated, and digs require support if they pose a risk. Regardless of this, many engineers still start with a 1.25m is safe attitude; and then work from there.

Digging, especially around buried services, is a difficult and laborious task. It follows that with almost every drainage or services design I’ve been involved with, the contractor has always asked ‘can we make it shallower?’.

There’s no ‘one-size-fits-all’ solution here, but with trench like excavations you can consider using oversized pipes to lessen long gradients- or use engineered, rather than nominal, cover requirements to bring buried aspects of the design back up to ground level.

Equal Opportunity Design

On the surface, the existence of the term ‘Contractor Designed Detail’ is a little bewildering. This is especially true when you consider that the basic definition of a engineering consultant is someone who designs. Of course there are times when you simply cannot design something until the contractor is involved. Typically this is when the project requires specific construction methods, or employs specialist techniques that require input from sub-contractors.

But with great power comes great responsibility, and abuse of this note will win you no friends.

The Ikea Instruction Manual

Every designer should aim to create economical engineering solutions, working with high utilisations and no wasted parts. There comes a point, however, where the finish product becomes too meticulous to be reasonably built.

Creating connections, for example, made out of seven different bolt sizes for maximum efficiency is, at best, likely to come back with a plea for rationalisation or, at worst, result in some serious construction mistakes.

Providing a single, worst case, pile design and repeating it for hundreds of piles will also, however, rub your contractor up the wrong way; contemplating all the money lost on a truly uneconomical design.

The art is to aim for enough division to provide the perfect balance between economy and buildability; which is about as close as Civil Engineering gets to Zen Philosophy.

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This week I have been spending most of my evenings musing on buried services. This is not part of a new and desperate technique for getting to sleep, but the result of some interesting night shifts. In my short experience as an engineer I think that few things change as much between design and as-built as the route of new buried services across existing.

As a designer your first hint of what is underground is given through a C2 or C3 survey. Essentially this just means writing to every conceivable statutory utility supplier in the area and asking them to provide information about any buried services across the site. Aside from highlighting that there may be something there, this information is no where near as helpful as it sounds, or perhaps should, be. There will be no indication of depth, the location shown is indicative at best, and apparently fabricated at worst. More over it is entirely possible that some of the services shown won’t be there, or worse; services not shown will.

In attempt to manage this considerable risk further CAT and GPR scans are carried out. Effectively sonar for the street, these provide are more refined view of what is going on. Locating services, however, is a bit of a black art- and although we now put identifying tape down, the majority of services are unmarked and don’t appear clearly enough. This is especially the case when one line runs under another.

Eventually, however, you’ve got to come to some conclusions and provide a drawing that shows the route this new buried service will take crossing the road. This means taking into consideration the guidance off all third parties and ensuring that there is adequate cover to protect the new pipe. Finally a route will become apparent, and a contractor will send out a team to install the new buried service. This is where it all becomes more interesting.

In an ideal world you’ll want to dig a full length trench, exposing all the services in their as-built location. This would give you the opportunity to plot an optimised route through all the intersecting existing buried services; matching the specifications of all involved. The nature of our infrastructure means, however, that the majority of this work is undertaken in limited (~6 hour) night shifts, and such a luxury cannot be afforded. The best you’re likely to get is the trench being dug in 1-2m advanced lengths.

Considering that the surrounding live services necessitates hand digging: The guys actually doing the work will, of course, want to keep the trench as shallow as possible- both to get the job done quickly and limit the need for temporary support to the excavation. This ideal minimum needs to at least provide adequate cover, which is normally stipulated at 750mm. Additionally it needs to keep without the influence of other foundations (normally assumed to spread at 45 degrees), which is easier for shallow excavations.

As a designer you want to protect the pipes as much as possible. Although many ducts and pipe forms are designed for buried loading, few can sustain the knife-edge loads associated with traffic. The aim is therefore to ensure that the surrounding provides enough distribution to prevent this. A sure fire way of doing this is to specify concrete, but that means waiting for it to cure. Using a dry mix can help to address this, and allow more immediate compaction. A good depth of quality fill will also go some way to providing a similar distribution- especially in conjunction with a solid bitumen road repair.

Typically gas mains want 150mm of sand between them and any hard spots created by the new services. Similarly electric cables, etc. specify 300mm. This is covered by adding a specification to instruct minimum covers in the likely case of unexpected services or locations. In the scope of digging a trench by hand accommodating this is quite a significant ask, with the nominal depth easily falling to 1-1.5m.

It is not, however, unthinkable that two services will be found; positioned such that these blanket specifications simply simply can’t be accommodated within the minimum bend, and the need to dig in short lengths means that ducking under will require significant back dig. Diversion is always an option, but that involves a lot of risk- what are you diverting in to, and how are you going to get back?

For example, dropping the cover to 600mm can be justified if the backfill will provide enough distribution. Similarly getting closer to existing services might be considered allowable if the surround is lost and a finer material, such as sand, is used to bed the difference.

Ultimately, like a lot of engineering, it will all come down to experience.

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