“Divide et impera”, popular ancient Rome motto later attributted to the Roman emperor Julius Caesar. “Divide and dominate” or better known as “Divide and rule”, was the strategic foundation on which the Roman Empire was built (27 bC – 476 ac). Almost nothing. In line with the political and military relevance of this slogan, in the mathematical field, it gave its name to one of the eight classic heuristic strategies of problem solving, together with codification, organisation, experimentation, analogy, introduction of auxiliary elements, search for regularities and assumption of the solved problem.The others are proper notation, solution drawing, systematic experimentation, analogy, introduction of auxiliary elements, problem reformulation and way back.
The solution strategy we are talking about is based on breaking a problem into a set of smaller sub-problems, solving these sub-problems, and combining the solutions. This methodology is widely used in various scientific fields and that under different names, theorems, or methos, such as the method of integration by parts (integral calculus) or the principle of virtual jobs (strength of materials), has promoted the resolution of complex problems by converting them into multiple “easily” solvable problems.
If there is one thing that characterises the world of engineering, it is precisely this eagerness to transform problems. We have all heard the joke about how an engineer calculates the volume of a cow and how, compared to the functions of approximation to a surface and its subsequent integration that a mathematician would carry out or the performance of a physicist using Archimedes’ principle and putting the cow in a swimming pool, the engineer would give his solution by approximating the cow to a sphere.
In the field of structural engineering, the branch in charge of the design and calculation of structural elements and systems to ensure in advance an optimal structural response (safe, resistant and functional) applies the mechanics of continuous media, a super nice calculation model in the “academic” world whose application in real life is very “chunky”. That´s why we resor to the finite element method, another “divide and conquer” engineering glorification, where the strategy is to convert the continuous medium into a finite number of parts, “elements”, whose behaviour is specified by a finite number of parameters at certain characteristic points or “nodes”. This is commonly called “simulation”, although it should at least be called numerical.
Professionally, I work in this area to design “things” optimally. But when these things are sets of configurable elements or product catalogues, and we want to cover all the options to offer the best, we could talk about the need to develop dimensioning applications or system and product calculation configurators.
Well, after years working on these developments for different sectors, I can say, without fear, that dismembering a project among the different knowledge teams will be the iceberg that leaves us frozen. It seems logical to think that if we are talking about the development of a robust validation application of a configurable product, we need someone who knows the product perfectly, with all its variants and possibilities, its terminology, its meaning, its cost and even its soul, if I may say so. In the same way that we need, at this level of knowledge, someone capable of calculating and validating the product in resistant and functional terms and who knows how to transform, transcribe or visualise this numerical validation in a user-friendly platform. NO, prepare the lifeboats. A dose of reality difficult to digest for an engineer and staunch defender of multidisciplinary projects like me and of breaking down problems. NOT EXACTYL, get lifeboats ready. A dose of reality difficult to admit for an engineer staunch defender of multidisciplinary projects.
Professional experience, with blood, sweat and tears included, has improved our conception of strategy, avoiding sectorial strategies that push the global objective, and ultimately the product, to the background. And to understand this, there is nothing better than the well known expression “cobbler to your shoes”. Do you know what I’m talking about, not yet?
However the presence of different team members’ roles in this kind of work, make it impossible to detect errors or incoherencies derived from lack of conception and lack of understanding cooperation between professionals. It is unavoidable. Architects and engineers do not speak on the same scale, for example. In addition sectoral strategies relegate the functions of the “expert of the product” to setting the norms, rules or ranges of consideration. Which seems quite illogical since the expert is separated from the course of the project. The question is how do we detect failures? and when? it may be even more important. Everything points to final report. So we work such as Titanic’s valiant musicians and we’ll see how the ocean of corrections treats us. I’m talking about that ocean like a succession of final versions succession in which we will be submerged by unforeseen failures and with the corresponding increasing final workload. Now we do know what we’re talking about, don’t we?
All this, without going into responsibilities which it have also been diluted. To blame are those who…If the person or persons responsible had bid me do so, I might have…
In this sense it is impossible to offer a service aimed to set up validation of configurable products application development if it is not a completely calculation project. So Turnkey project or I hope you are good swimmers.
However, trainings should also be conducted by people that are knowledgeable about the subject matter or the product, better even than costumer who can have been in the business for more than 30 years. We must become experts and think. It’s the only way to cope successfully such a service and that under a holistic approach where each part must be considered as one. So we avoid misinterpretations, unreasonable casuistic, excessive computing (no scale-resolving simulations) and cannot effectively communicate (the customer never knows what he wants until you show it to them). I want to stand out with it the necessity of acting “in” the moment and “for” the future.
For those interested in these possibilities… where are we going to find someone who wants to learn? To find someone who wants to ask questions? To find someone who can improve the product and performance for your company, and have the ability to do so. I am talking about to use experimental or scientific techniques, with computational capacity and that you can also implement it on a platform so that its usability improves, for example, the competitiveness of the different technical and sales departments of other companies? Can you imagine pressing a button to get the weekly job of a technician?
Computer-aided engineering tools (CAE) are more pervasive nowadays, and finite element analysis is having more impact than at any other time. In the past, CAE abilities have been used in specific fields with highly trained engineer teams and large computing facilities. For example, in the aeronautical industry the objective is, among others, to design more efficient airliners and the automotive industry must produce safer cars in case of accident.
Currently there are not field of science or engineering that has not been affected, and in some cases transformed, by computer simulation. Almost most manufacturing companies, regardless of the industry, can take advance of CAE abilities to simulate their process and improve their performance.
Sport industry show off this fact, for example, SPEEDO produced swimsuits including compressing effects for changing, in certain way, the shape of the swimmer’s body. Using this idea, SPEDOO designed suit able to achieve drag reductions in more than 15 per cent. In the JJ.OO. of Beijing, 94% of the medals were won by swimmers dressed with SPEDOO swimsuits (Michael Phelps, Mireia Belmonte …) and 23 out of 25 Olympic records where beaten using this technology (according to data from FINA).
For an airliner or for an Olympic swimmer the engineering problem is essentially the same. There is a shape moving through a fluid and the drag must be minimized. That is, advanced engineering aerodynamic concepts also works in the textile industry. This example clearly defines the current situation of CAE abilities, where high technology is used to solve what we could define as trifling problems.
According to Lesa Roe, NASA Langley Research Center director, “Modeling and simulation is older than NASA”. Since the first models of digital calculators, computing machines evolved step by step and around year 2000 some experts believed that engineering simulation programmes had reached its peak due to the big improvement in abilities for the limited supply of high-level engineers.
However, the more powerful computers and the friendly integrated analysis environments have allowed companies to take advantage of the enormous potential of simulation programmes to make accurate predictions about natural phenomena, providing compelling evidence that we are really gaining in our understanding of how the products, processes and services can be optimized. Therefore, the almost endless engineering simulation techniques provide big growth opportunities, based on the current needs and the challenges that this poses.
As the saying goes, “Necessity is the mother of invention” CARTIFbelieves and works in endless possibilities to help customers develop better products and processes. I would like to stress in a particular application: the estimation of the static and buckling behaviour of very thin walled containers for food packaging.
Through simulation programmes we are able to detect weak points and design failures prior to manufacture, with consequent savings in time, material and money. Note that the containers are manufactured by plastic injection machines using expensive cast moulds. During the analysis are taken into account parameters such as constitutive material properties (PET, HDPS, aluminium …), thickness, type of liquid or granular product to be content, etc. that define the containers and allows us to predict its performance, resulting in deformation curves under load, loads of collapse, tensions and stretching under certain loads which it may be subjected to circumstances of the production process, storage and transport conditions, including temperature, pressure and impact effects among others.
Beside theses services, being aware that “data is the new currency”, CARTIF is also working on structural health monitoring in civil structures. The aim of this work is predict when maintenance will be needed or what the expected behaviour of structure should be if the real system begins to deviate from the digital models’ behaviour. This idea can be reviewed in my previous post ‘When structures age’.
How to reduce structural conservation task expenses by implementing monitoring systems?
The structures are not everlasting. They are projected to play a role for a certain number of years. Thus, a wind turbine mast lifespan is about 20 years while in the case of a bridge it depends on the type and the material used. According to Guy Grattesat, metal bridge will have a lifespan of 40 years, 100 years for a reinforced concrete, between 15 and 20 years for those made of wood and about 200 years for masonry. Nevertheless, exceeding the life expectancy does not necessarily mean dismantling the structure. Generally, what we do is a more comprehensive monitoring effort and implementing conservation works if necessary.
Wire and accelerations sensor installation process inside the handrail
The European bridge stock is catching its lifespan and it is showing signs of fatigue. According to Eva Lantsoght, Professor of engineering at the University of San Francisco de Quito, “European bridges are old, but their replacement involves a great investment. Only in the Netherlands, there are about 3,000 bridges that could cause problems, being their refurbishment cost around one million euros each”. To mention another example, the first wind turbine parks (1984), whose technological emergence came in 2002 (according to the GWEC, Global Wind Statistics), have great needs for maintenance and the increase of these needs will have the same exponential curve, I can imagine, that its development has had in the past.
18 triaxial MENS accelerometers (sensors developed by CARTIF) installed equidistant along the span inside the handrail.
Having this background in mind, I would like to highlight the importance of implementing new maintenance strategies to reduce structural conservation task expenses. State-of-the-art monitoring systems, developed in recent years at increasingly low costs can be the solution. Usually in this type of structures, the procedure consists on the installation of a network of accelerometers to record the ambient vibration response of the structure. Using identification techniques, the modal characteristics can be estimated and be used to evaluate the structural integrity.
The idea is to know the structural behavior in operation conditions and to determine the valid rangeby controlling only a few parameters (frequency, mode and damping), being these parameters easy to evaluate and to record their trends along the time. Although the meaning of the word ‘monitoring’ refers to the capacity of the acquisition system to record certain values, it is also important to add the ability to process the data and to generate alarm codes, if it would be necessary.
In this aim, researchers require a deep understanding of the technical matter involved as well as a big experience in experimental techniques and data processing. OMA (Operational Modal Analysis) identification techniques are based just on the acceleration records but if some loading signal applied on the structure could be also record, additional information can be obtained using EMA (Experimental Modal Analysis “EMA”). Both approaches should gradually replace, or at least complement, the traditional visual inspections and static loading tests. Monitoring systems could be an emergent business for technology-based companies in cooperation with new maintenance standards or strategies by the infrastructure’s authorities.
In this regard, I can mention the success of low-cost monitoring system of Pedro Gómez Bosque footbridge (built in Valladolid) operated by CARTIF team since 2012. This stress-ribbon structure undergoes no linear effects. The collected data has been useful so far to understand the behavior under dense pedestrian loading, at different met conditions (summer or winter, strong wind…), etc. Analyzing this information, we know what it is normal and what is not, so we can establish an optimal operational range and determine when anomalies appear and why. In these terms, the structure is an ideal benchmark not only for structural monitoring but also for understanding mechanical problems, pedestrian loading and other engineering issues.
