Tuesday, August 17, 2010

Visualizing Structure

Structures and Design

An important component of my design ability comes from my understanding of structures. Not just understanding engineering but understanding how science and math can be used as a tool to inform design. This understanding first solidified in graduate school over a decade ago and this is how I remember it.

Frank Lloyd Wright's falling water, compliments of Google image search for cantilever. When I look at this cantilevered porch I can see the forces of sheer, bending, torsion and deflection and how they've been hidden away inside the structural parapet/railing. I also see how it informed his design and was carried through to other areas of the house to give the structure and architecture continuity.

Phil Gallegos of UCD (University of Colorado in Denver) taught a very practical class and one of my favorites -- structures. After years of engineering math, physics and chemistry, it all finally came together. A practical application of the knowledge learned to date.

Structures is a very math oriented technical class keeping many with interest in architecture from pursuing the study. This 'fear of math' was very apparent the first day of structures class at UCD, but Phil Gallegos saved the day in the last 5 minutes of class when he pulled out a crusty piece of yellow bed foam in the shape of a beam with black lines on it and bent it -- changing my life forever!

Remembering back, it may not have been beam shaped or with markings other than water stains, but when he bent the CFB (Crusty Foam Beam) and talked about the top being in compression and the bottom in tension, I immediately had a visual for the internal loads developed as a beam sustains transverse loading.
Diagram of simple cantilever

What the CFB did in an instant inside my head was to create a mind's eye visual image of Tension and Compression--two forces that drive structures.

And from here everything else we learned made sense. It was easy then to visualize a cantilevered beam as half of a simple loaded beam turned upside down. As long as I abided by the basic principals and concepts like equal and opposite forces, component reactions and outermost fibers, I could always rationalize my way through any structural problem to locate the critical stress and strain happening within.

Diagram of point loaded beam

We moved on to other forces like shear, bending moment, deflection, and torsion and then on to more advanced topics like catenary arches, trusses and balanced sections for systems with two or more different materials. It did get quite complicated but I loved it and if I ever had a problem I just referred back to the CFB. Sometimes visualizing it on end, upside down, being tugged in multiple directions or being twisted, the CFB continued to provide me with the correct answers through visualization.

Overturning due to lateral loads and no hold downs illustrated.

Many of the lessons of structures are simple but not so obvious. Take Lateral loads for instance. Why would a house with all it's mass ever need to be held down. I did see the wizard of Oz but some quick airfoil calculations make it more than apparent that even with 100 mph winds not enough uplift is generated for a house to fly!

But they can tip over, and Phil showed us how! By looking at the centroid of any object (it's center of mass), the lever arm acting on this centroid and the force being applied, it's easy to see why you need hold downs on a building even if it's heavy; because a rigid box with a lateral load has an overturning moment.

I enjoyed structures so much I brought in other designs to analyze; designs I knew we wouldn't get to in a year of structures but that I wanted to know about. Phil was always willing to share his knowledge of more advanced topics with me, staying late to discuss hypothetical structural situations after class.

Left-a cantilever chair. The advantage here is the longer length of the structural member allowing for more controlled deflection. In this case suspension to make the ride softer.

How structures changed my design

It is here, in these conversations, where my thinking of spaces and structure morphed into one thought process. When I realized that the components of a building not only needed to inform each other, I also realized that I needed to design in more dimensions. To design not just in plan and section, but in mechanical, structural, environmental and building code, and that details needed to be developed, building materials selected, construction process refined during the entire process of design. That consideration for all these elements needed to happen concurrently and that good design meant iterating the design to reflect these findings.

A classic ship illustrating Corbu's point
So it was at this point in my education, half way through my design studios and in my second semester of structures when engineering and architecture became one. Since then I have developed a distinct and identifiable style for my architecture focused on the integration of math and art.

A refinery. Beautiful considering zero design was applied to it's aesthetics.

Examples of math, art and design.

Corbu talked of the beauty of ships. Due to stresses, manufacturing, and economy the designs are honest to their materiality, yet have simple repeating elements and variations to the elements based on needs and conditions.

One of my favorite types of structures are cranes, because it's so easy to see the structure respond to the different forces and to trace the loads. Ever since the CFB (crusty foam beam) I've been able to not just look at a crane and understand deflection, overturning moment, bending and sheer but by tracing a fictitious loading condition in my head I'm able to take a very good forensic look at how failure may occur based on my imaginary loading.

Left-A large crane where you can almost see the tension in the cables and the compression in the trusses. The trusses get bigger in the middle to respond to buckling and have small removable pins at connections that transfer all the loads with sheer. And, if it picks up a large load now, the leg in the back will want to life up so all the forces going down are on the front two legs.

How I use this knowledge over a decade later.

For years now, because of two semesters of Structures, two good books and one dedicated and knowledgeable Phil Gallegos, I've done the preliminary engineering on all my projects. I'll diagram the loading, figure my volumes and weights, trace the loads, solve beam reactions, calculate footing areas, point loads, size beams and check them for deflection, horizontal shear and bearing. And the I will go through and adjust my design accordingly.

Right-diagrams for a simply loaded beam. a)Loading diagram b)Shear diagram c)Moment diagram d)slope diagram e)deflection f)Phil never tough me what this one is!!

For as long as I can remember, I've been using Wendell Reed of Reed and Associates for my engineering. Even though I'm not an engineer and don't know the latest engineering codities (code + oddities), the fundamentals Phil left me with have allowed me to save thousands on engineering by doing this preliminary work. With these savings, I allocate more time to iterating and improving the design.

The Challenge When the CFB and the engineer don't see eye to eye!

But I do have a question for Phil Gallegos of University of Colorado and PE.

Left- On the structure being framed, there is debate between Wendell and I over the stresses driving the sizing of the steel poles which are perpendicular to the roof.

In the picture of the building being constructed, Wendell and I have had numerous discussions on which forces drive the design of the angled steel poles (photo of building under construction) Wendell insists that the steel pipe supports are driven by bending moment because the poles do not point towards the center of the earth (straight down). I contest that because there are metal hangers/connectors at the ridge end of the rafters and because this ridge is attached to a shear box, that they can't drop on this end but in fact they're hinged. If they're hinged, then they want to rotate and by having the steel posts perpendicular to the roof they are in pure compression and will fail by buckling, having no bending moment.

Another example of what I consider to be a hinged roof. The rafters are firmly attached with nails and plywood to an existing structure. The attachment at the house can't move up, down or out- if it weren't for the poles, it would rotate. So putting poles perpendicular to this rotation puts them in pure compression.

Thursday, August 5, 2010

A truly 'Green' Gate

Cheryl's Living gate.

Designed and built by Brad Hankins, the green guy.

dbBrad is Mr. Greenguy.
Almost 5' wide and 5' tall, this gate weighs about 400 lbs. And it's filled entirely with natural materials (forest duff) and moss harvested from my dad's property in Snoqualmie, WA. This moss comes with a layer of bark for nutrition and is wonderfully embedded with licorice fern. Because it's old, its dense with decaying layers under healthy moss and its able to absorb an incredible amount of water. My guess is the gate can hold about 50-100 lbs of water. This is about 5-10 gallons.

Jimmy had some massive hinges left over from a project that worked perfectly for stealth mounting and are plenty strong. Pleasantly, the gate swings freely and has a nifty Inertial Latch I designed.

Using Newton's First Law (also known as the Law of Inertia)  that awhichstates that an object at rest tends to stay at rest and applying the knowledge of momentum, which is equal to mass times velocity, I was able to design a prototype inertial latch that seems to work like a charm.  It's actually no latch because the resistance of the hinges and the mass of the gate ensure that where you leave it is where it is. Thus, the Inertial latch is a fancy name for no latch.  Simple is always better!

And it comes apart, just by removing four bolts, two of which are pictured above. The tricky thing here was that in order to access the center, the ring had to come apart too.

From Below to Bottom-
The removable washer allowing the mesh to be installed and supported by the flange of the ring.
The components
Brad artfully fits the gate with forest duff, moss and salvaged plants
Side view showing innards of the living gate.
The top mesh is placed and the removable ring installed
The gate, mostly assembled and stood on edge, ready for the top (edge) piece. Cheryl through the center.
Josh demonstrates skill trimming a portion of the panels for assembly with a grinder and shielding the cedar from sparks at the same time.
The gate on edge showing the massive scale relative to josh.
Tightening the bolts on the removable edge.
The hinges

Because I wanted a 2x2 grid (the ideal spacing to hold material but allow plants to grow through) but didn't have a budget for fancy woven steel materials, I took 4x4 mesh and welded two sheets together. As a result, there is a depth to the material lacking in the standard 2x2 grid. Next time I'll take 3 sheets of 6x6 to accomplish the same but with even more complexity and depth.

The components are simple. A rectangular frame and hinges strong enough to hold the weight. Two panels, one for each side. And the ring.

The finished product a bit more complicated since it is all designed to come apart to be redone, though I anticipate with watering, the plants have enough organic material to survive for at least a decade.

Once all the pieces were designed, priced, iterated and completed, they still needed to be assembled. In my 25 years of building, ideas that seem great in theory sometimes don't work out so well in reality. Needless to say, I was very pleased when everything fit together as planned and the gate was planted, assembled and hung in less than 4 hours.

Because I used forest duff, I had log pieces that I placed around the edges to help hold the other material during assembly. We filled any voids left over with wood chips and covered it all with a thick layer of moss.

The first glimpse of the finished project with Cheryl in the background. This was one of those projects that was so satisfying to see come together that there was quite a bit of 'stand back and looks so cool' going on!

Once the panel was slid into the 3 sided channel frame, we had to trim a few pieces of the mesh to get the top (side) on. And then we had to stand back and look some more!

Finally fitted, the side bolts are tightened and the gate is ready to be installed.

The hinges were drilled and tapped so that 7" x 5/8" bolts come from the backside of the post. This was done to grab more wood, to hide the fasteners and dock washers and because on a butt hinge the screws have to be flush which isn't so easy to do with big bolts. We trimmed the bolts flush after torquing with a grinder.

All steel fabrication, much design credit and special thanks to Jimmy and his two sons, Jack and Aiden Cussen, the Irish Welders.

All steel from Skagit River Steel and recycling except for the custom hog wire, by dbBrad and Skagit Farm Supply.
Steel plates and Cedar from Pete @ Two Dog Timber works
Steel chain and special thanks to Dave at Island Recycling, not located in cyberspace but still just north of Freeland on Hwy 525.

E/L Ponds a success in healthy habitat

Just under 2 months after being completed and christened with Koi and plants from Moore haven, we have another announcement about the success of the ponds.

Of coarse flooding, the original drive behind the ponds and wetland has longs since been controlled, the enjoyment of the spaced created is just beginning.

And we have news!

Not only are there polliwogs (tadpoles) galore, but yesterday when we were there, putting the final touches in the beaches along the variable edge, but there are baby fish.  And there are only 4 koi in the big pond.

 Above-The lower pond just a few months ago.  
Below-Brad on his favorite rock marveling over the successful habitat, where breading has brought fish and frogs both.

Though a few goldfish inhabited the big pond earlier, it is unlikely that any eggs they had laid made it through the final stage of the ponds (E/L week 4).

This leaves two possibilities.  That these little fish, less than an inch long and almost translucent floated the rapids of the E/L Middle fork, or these are baby Koi.  It may be wishful thinking, but when viewed underwater with a mask, they seem to have an assortment of variations of skin pigmentation.

What really blew me away today was the 50 + frogs we found today along the pond edge.  These, some with tails, are positively baby frogs from the tadpoles.

Above-Frog at E/L lower pond edge, born and raised same spot.
Below/Right-Baby Koi, compliments of Google image search.

They appear to be of the spotted frog type and not our native tree frogs but  today they were so small and so brilliant green, it was hard to say.

Two Bellow-There are tadpoles in the pond that are bigger than this newly amphibious frog.  I suspect there from the large toad  (bottom).

Interesting that some of the tadpoles in the pond are larger than fully operational frogs.  I'm wondering if the big toad has a batch of young coming too?

Computers and Architecture

During my graduate architecture study at the UCD (University of Colorado in Denver), I took a computer modeling class.  Though I still truly believe no computer design software can hold a candle to a thick pencil on a good piece of paper, I learned two very valuable concepts from the instructor, Robert Flanagan.

Robert had a background working with CAD (Computer Aided Drafting).  He had been responsible for all the computers and files in an architecture firm if I recollect correctly. He also had a very intuitive process for design.

The first thing Flanagan taught me was that computers are the next millenniums tool for information  management.  This was still true as I took the class my Second year around 1998.  This gave me a new vision  of  how to truly use a computer.

After his class, I have always thought of computers in the following way.  They can't do anything for you but store and retrieve data.  If you cant organize your information, you cant find it and therefore it's of no value.  This has helped me maintain a hierarchical folder system I still use today to find a singe item out of tens of thousands of files.  Very valuable information to get so early in my architecture career.

The 5 elements in my version of Frank Lloyd Wrights 'Price Tower'.  I've always loved the ambiguity of top vs. bottom, it's defiance of any scale, and how the buildings structure, environmental systems and function seamlessly collide.

The other and really the most important, is the development of 'an element'.  In a later design studio, Kieth Loftin was able to provide an academic process and an architectural description for what this element might be, the notion that element is developed, adapted and then iterated, but Flanagan first inspired me to consider repeatable elements as a very important architectural tool.

We actually designed a building with a a series of elements.  Some people used one or two and others like myself 5 or 6, but through scaling, mirroring, rotating and arraying, we created all kinds of things.

I at the time was interested in skyscrapers and the repeatable elements of 'floors', but enjoyed taking it to the smaller level-a repeatable section which could be pre-fabbed.

Always trying to tie the studies of one class to another, I gathered my thoughts from studying this tower in precedents, engineered the overall system and the cantilever floors, and then rendered it with minimal pieces for a second version of Flanagan's process.  And loved every minute of it.

So thank you for teaching me these two things which fully integrated into my own process of design.  Concepts which even a decade later, I take as fact;

Computers can only store information.  But they can also reproduce and alter this information to create elements, and from this you can create architecture.