"Welds: How to Spot Problems and Improve Weld Details" by Erik Nelson Annual Steel Design Conference Worcester Polytechnic Institute June 5, 2015 | 8:30 am - 3:30 pm
Structures Workshop just completed the structural design of the Hitchcock Center in Amherst, MA meeting the Living Building Challenge. The project (DesignLab Architects) is aiming to be net zero energy, water independent, using all non-toxic materials (all locally sourced wood construction - black spruce gluelam beams, spruce decking, exterior northern cedar frames, eastern white pine, etc). This is one of just a few LBC projects on the East Coast. Below is our Revit model which helped us complete the CDs...
In addition, Structures Workshop (Swansan Builders) was the structural engineer for the first Passive House in Rhode Island. This will lead to energy consumption reduction of 60-80 percent (we designed double wood walls and roof frames for continuous unbroken insulation).
Structures Workshop has moved! We purchased a boiler room building in a former knife factory in the Jewelry District of Providence for our new home. This will allow us to grow from 4 to 5 (or 6) as well as provides enough space for a small workshop in the back for testing materials/joints, building stuff, creating steel/wood/glass connections, not sure what. Also, we will finally have our own sink! Come visit us... 18 Imperial Place, Courtyard Building - Providence.
The stairs were actually designed with thin saw tooth vertical plates hidden within the thickness, here is an FEM screen shot...
The stair was not governed by strength (only about 11ksi) but by live load deflection (1/4") and vibration. We wanted to keep the vertical frequency above about 8Hz without adding to the steel weight. This was set to limit affect of exciting the second harmonic when descending stairs quickly. We did this by trimming down the thickness of the tread and risers, and increasing the fin plates thickness. Also, we reduced the landing hangers from 6 to 4 and cantilevered the corners of the 3" platform over 4 ft.
Published "Philosophy of Engineering What It Is and Why It Matters" in the Journal of Professional Issues in Engineering Education and Practice... http://ascelibrary.org/doi/abs/10.1061/(ASCE)EI.1943-5541.0000205 Here is an early DRAFT.... (with permission from ASCE)
Please join SEARI for an educational presentation on torsion in concrete by Erik Nelson, PE, SE of Structures Workshop, Inc. Erik will introduce the basics of designing for torsion using ACI 318-11. He will describe best practices for evaluating various components of concrete structures for torsion, including stiffness assumptions in modeling spandrel beams. Please note that the event will take place at the Department of Administration, One Capitol Hill, Providence in Conference Room B on Tuesday, May 20, 2014.
We were the engineers for this huge wood sculpture called "the latern", hanging within a large atrium space at UMass Lowell. We collaborated with the Architects who created the lantern, Perkins+Will, and visited the project this week. It is nearing completion... We designed the two feature staircases as well in this space, and the wood wall hangs and folds around them.
I while ago, my friend and I wrote about the analytical challenge of a peculiar type of framing orientation that we called the Infinite Load Path, which can occur in projects - but we didn't have a built example at the time. Now we do. It looks something like this in plan, and can occur around openings (not a great example, but illustrative)...
There are two associated problems with this framing layout, one of analysis and the other of construction. To erect this framing layout would require temporary shoring of at least one of the inside corner connections. In practice, therefore, we should make every attempt in avoiding this condition, although the completed system is perfectly stable (and is easily solved by most structural analysis programs). Recently, we designed one on a project. It required the edge of two finished openings to be lined up (so we could not do a continuous beam).
We know this system is stable from statics, but it seems to have a dynamic or iterative quality (point loads seems to move in circles). If we think about a uniform load applied to all four beams, how do we solve for equilibrium? And second, how and when does the system actually reach equilibrium? See that article for suggestions.
“Infinite Load Path” beam systems can be shown to work for larger scale structures too. We built a small dome at RISD a few years back that could be scaled much larger...
They can become domes only because if stacked they form curvature based on the tangent of the thickness of the material to the length. But they can be flat as well. Lamellas (and tensegrities, for that matter) are special cases of these types of framed structures (where member sizes is repeated, or Platonic/Archimedes solids used as starting points for geometry).
For this steel project, it was economical and efficient (even though erector had to shore the first member to build the next three). But again, these types of structures should only be used when simpler framing is not possible. Here is the house during final days of construction...
Beauty, Truth, or Goodness? In a previous article I wrote called 'Twilight of the Idols', we learned (from Nietzsche) that truth is not a useful concept to designers and structural engineers. Let science (or religion, for that matter), have ownership of truth. We can do 'truth' in our spare time. We also have learned (from manifesto on goals being useless), that beauty is a by-product of our work, not something we need to consciously drive towards. What is left? Goodness. Quality. We should focus in this arena of Plato's Trinity, not the other two.
We design buildings, bridges and other structures, but how do we do this well or how do we improve over time? Does our conception of the structure to be built change with experience and improve? Yes, we learn what is feasible and what is practical with experience but what about Quality? When we develop options for consideration or make a decision based on a certain amount of information, how do we choose the best option and make the best decision?
The entries in the Manifesto blog herein, are some attempts at improving design, and many others have written on the subject for structural engineers. For example, David Billington in The Tower and the Bridge, described how the best designers of the past made engineering decisions based on a balance of efficiency, economy and elegance. We can add to those considerations such as durability, constructability along with resilience and sustainability. Also, when thinking about quality, we can do this in two ways, the end (the structure itself), and the process (the design process). We can say to ourselves “I want quality in the form of the structure and the assemblage of materials” or “I want to design well, I want to be good at engineering decision making”. These may overlap. For example, how does the description or idea of the final artifact as “quality”, create a path for working towards it? After all, we are typically designing new and novel things (i.e.. not pancakes that we can taste, recook and/or adjust ingredients easily).
In may be worth investigating what the Philosophers of antiquity thought on the subject of quality, beauty, and art. I found that a terrific anthology to get a good background on this subject is Hofstadter’s Philosophies of Art and Beauty: Selected Readings in Aesthetics from Plato to Heidegger. In it we find the beginnings of our conception of quality. For example, we find that Aristotle, in his Parts of Animals Book I believes that one has to have a clear picture of the structure first (the end), and simply work towards that.
He starts by forming for himself a definite picture, in the one case perceptible to the mind, in the other sense of his end – the builder of a house – and this he holds forward as the reason and explanation of each subsequent step he takes. Art indeed consists in the conception of the result to be produced before its realization in material... The plan of the house has this or that form; and because it has this or that form, the construction is carried out in this or that manner. For the process of evolution is for the sake of the thing finally evolved, and not this for the sake of the process. (Aristotle, Parts of Animals Book I, 640).
But how does one conceive of an end first? How does one know ahead of time that something will be good, correct and well proportioned or efficient and economical? Here we learn from Aristotle, that good design is done by those who can take a complex task and split it up into smaller and simpler problems. One step at a time. Engineers are pretty skilled at this. It may also be that when a good engineer has a vision, or an end to be aimed at, he/she has a command of measure (what we now may think of as proportion). The engineer, according to Plato, must know the nature of measure for the proper portioning of structures (artistic as well as scientific). Measure for Plato, is essential to quality and is the fundamental principle that defines quality. A column should be this size, not that, for many reasons.
Basic to any art, is the art of measure without which there can be no art at all. For to know the proper size of a column, proportion of a window, the proper organization of language in a poem, is to command the art of measurement.... There are accomplished men, Socrates, who say…the art of measurement is universal, and has to do with all things.” (Plato, Statesman 285b)
So if we think we succeeded in the proper form by creating something well proportioned, how do we know we are right? How do we judge quality?
Every art does its work well – by looking to the intermediate and judging its work by this standard. (Aristotle, Nicomachean Ethics Book II 1106)
He agrees that the science may have a hand in the judgment of art.
The chief forms of beauty are order and symmetry and definiteness, which the mathematical sciences demonstrate in a special degree. (Aristotle, Metaphysics Book XIII 1078)
So we can learn a bit about what Aristotle and Plato thought about how to conceive and judge quality structures, but we have learned less about the individual engineering designer. It is the engineer's personal ability that contributes to great work. The engineer that seeks personal excellence will see that transcend themselves and into the built world. It may be obvious that all designers aim for quality structures as Aristotle suggests in his opening to Nicomachean Ethics.
Every art and every inquiry, and similarly every action and pursuit, is thought to aim at some good; and for this reason the good has rightly been declared to be that which all things aim. (Aristotle, Nicomachean Ethics Book I 1094).
And to which all engineers should aim - but not aim towards goodness, it is not a goal, it is a way. Here we are back to the process of design, how the individual designer takes action and aims at some good, or quality (and being good is integral to this, but not going there). It a process that requires constant reflection and the way to create safe, economical and efficient structures and do it better and better over time.
We know that the design of structures combines the objective science (material mechanics) with more complex subjective decision making requiring sound judgment (heuristics). Problems encountered by the structural engineer are complex and nuanced and require experience and judgment to better sift through the multiple design ideas. If you have been reading this blog, one recurring theme is that idea that engineering is more of an art than a science. Not art as beauty or aesthetic vision, not at all. Again, that is useless. In the forward to Nervi’s book Structures, Mario Salvadori says it best when describing one of the greatest structural engineers of the 20th century:
Nervi’s results are not achieved by consciously trying to meet aesthetic demands, but by tackling the fundamental structural problems from the outset, and giving them an obvious and clearly articulated solution. Beauty, says Nervi, is an unavoidable by-product of this search for satisfactory structural solutions. [Salvadori 1956: vi]
So no answers or short cuts to quality, just more questions. The original of my poem on Nervi called "The Structure That Sings" (later published in STRUCTURE) has a similar conclusion (beauty as an end and not sought after)...
There is something called "design science" (bio-mimicry, form finding, geodesic geometry, etc) which has mathematical, scientific, and objective procedures to create form. So "truth in form" is okay - but again, it is very rare that good design is driven by scientific methods. It can be, but more often not. So, if I could re-write this, I would replace "truth in form as a means", with "quality as the means". Quality, is by definition, process. As Pirsig would say, quality is "the knife edge of experience", and living in it and with it, beauty just becomes.
2013 was a terrific year with a new record 149 projects along with 20 new and great clients! This allowed us to reinvest in new technology including 3 new and powerful computers, 6 large monitors, new/updated licenses of Revit, SAP, ETABs, SAFE, Tedds, and BlueBeam. We continue to have amongst the best computer/software infrastructure in the industry, as much as the largest firms, to tackle all types of projects. In addition, we have hired our 4th engineer at the beginning of 2014 (see previous blog entry). Check back with blog/website for completed 2013 projects which have not been included yet. More to come!
In order to grow, we need to understand who we are. A popular but limited definition of structural engineering is "the art of molding materials we do not wholly understand into shapes we cannot precisely analyze, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." This is clever and fun but only addresses uncertainty of forces and materials. What a limited understanding of what we do! Yes, we are experts in the ability to make decisions under great amounts of uncertainty, but that is only one aspect of our work. Stress and strain are necessary calculations but represent only a small fraction of all that we do; otherwise, we could be completely replaced by computers. Those of us who do genuine engineering are never concerned about this.
Another flawed definition comes from the British Institution of Structural Engineers: "Structural engineering is the science and art of designing and making, with economy and elegance, buildings, bridges, frameworks and other similar structures so that they can safely resist the forces to which they may be subjected." This sounds pretty good, right? Unfortunately, it fails completely in describing how one goes about designing. Like most other definitions, it puts too great an emphasis on force resistance. Yes, we proportion members based largely on forces, but that is only one of many design considerations - we also have to take construction practices, architectural constraints, client needs, and many other factors into account. As Hardy Cross famously put it, "Strength is essential, but otherwise unimportant."
The American Society of Civil Engineers unfortunately defines civil engineering thus: "The profession in which a knowledge of the mathematical and physical sciences gained by study, experience, and practice is applied with judgment to develop ways to utilize economically, the materials and forces of nature for the progressive well-being of humanity in creating, improving and protecting the environment, in providing facilities for community living, industry and transportation, and in providing structures for the use of humankind." How could a definition of engineering omit the most important word - design! This one is lengthy and dull, and fails to describe what we do, instead focusing on the end product, what we make. Saying that a cook makes cake does not describe cooking very well.
Here is more of the same from the National Society of Professional Engineers (NSPE): "Engineering is the creative application of scientific principles used to plan, build, direct, guide, manage, or work on systems to maintain and improve our daily lives." This suggests that our creativity is not employed for artistry, self-expression, costs, or constructability, but solely for science. That is just plain weird - and wrong. The applied science portion of what we do is actually the easiest and most straightforward. It is objective and has its own linear, step-wise methodology. That is why young engineers are doing the calculations and the modeling, while more experienced engineers are doing less. Yes, it needs to be right, so there is a lot of responsibility in this phase; but that does not necessarily make it difficult. The experienced ones are doing the other 90% of what we do, the more difficult tasks that require much more than calculations. Design is the other 90% of engineering that is only achieved after one graduates from being a mere applied scientist (or technician) to being a genuine engineer!
It is a widespread misconception that engineers are applied scientists. Scientists are applied scientists. Most of our engineering educators are applied scientists. Scientists make sense of what exists in nature. They test and examine nature. Scientists discover. Engineers take nature and make what exists outside of it. Engineers invent and create. Engineers are makers. Engineers are designers. Alan Harris put it succinctly: "Engineering is no more applied science, than painting is applied chemistry."
Here is my own definition:
Structural Engineering is the design of BIG things.
The know-how required to do this is immense and is only obtained via lifelong learning. Engineers are 1% to 10% of each of the following:
- Computer Scientists
- Information Seekers (State of the Art)
- Specialists in Systems
- Experts in Construction
- Citizens of a Locality of Construction Practices and Material Availability
- Cost Estimators or Experts on Best Practices to Reduce Cost
- Experts on Local Fabrication and Construction Technologies
- Experts on Building Codes, Specifications, Standards, Guides, and Regulations
- Risk Evaluators and Code Interpreters
- Experts in Calculations
- Experts in Three-Dimensional Representation in the Mind
- Experts in Synthesizing Complex/Unsolvable Things into Simple/Solvable things.
- Experts in Analysis Modeling Using Software
- Skeptics of Engineering Software
- Debaters of Efficiency, Economy, and Elegance
- Artists, Philosophers, Poets, and Dreamers with Unconstrained Self-Expression
- Drafters and/or BIM Specialists
- Collaborators Working Within Design Teams
- Listeners of the Vision and Needs of the Project/Client/Architect
- Users of Rules of Thumb (Heuristics)
- Experts in the Ability to Make Decisions Under Great Amounts of Uncertainty
Civil (Structural) Engineering is the design of big things. You might ask, well Architects design big things too don’t they? This is correct, but they are not hired precisely because the thing is big. We are. "Big" does not mean good - I use it here to clarify what we do (we do not design spoons).
This definition may contribute to a positive re branding of the profession and I believe it will improve “career appeal” if we simply and succinctly told the truth. Why is the retention rate in engineering schools around 50%? That is a real problem but I think it is a marketing problem. Our educators are not good engineering mentors and they likely mislead our students into believing we engineers merely complete calculation procedures. Engineering is so much greater than that!