Tuesday, December 1, 2015

The Code

http://www.bbc.co.uk/programmes/b01bd49x

Recently, I watched the Code.  I was studying projectile motion and potential and kinetic energy.  Potential energy exists in an object at a certain height.  The higher the object, the greater the potential energy.  mgh.  The mass of the ball as it falls gathers momentum because of the gravitational forces pulling the object down ward, acceleration.  We know that potential energy because kinetic energy as it is falling.  mgh = 1/2 m V^2.  The mass cancels out.  This is why a feather falls the same as a metal ball.  Mass is inconsequential.  The feather and metal ball fall at different rate because of air friction and drag.  The body falls through air which is a fluid.  So fluid dynamic elements such as surface, buoyancy, viscosity etc. come into play to cause the falling at different rates.  We can also think about height in dimensions of time.  A higher ball will take longer to reach the ground then a lower ball.  This is because acceleration in gravity is measurement of distance over time squared.  Because it has the element of time, it also has the element of relativity.  Einstein extends Newton's notion of mass mechanic into time mechanic.

The laws of potential and kinetic, being equal, allows Marcus to predict the velocity (v = (2gh) ^ 1/2 ) of the ball and put it into the projectile motion.  Math can help us predict where the ball will lands as Marcus du Sautoy sits just a few meters from where the heavy metal ball lands.  
       

Friday, May 22, 2015

Modeling Sap2000


Ctrl r replicates is similar to offset in CAD
Extrude is like location.

Sunday, April 5, 2015

Highway Bridge 30





The location of this span is near the Oregon Convention center.  The spa’s function is a highway to carry traffic towards Interstate 5 towards North to Seattle.  It is highway 30.  
The superstructure is steel girder with varying depth to span ratios.  The smallest span crosses a two lane road and pedestrian sidewalk.  It is approximately 30’.  The Steel girder for this section of the span is smaller than the previous span.  Thus it has a smaller depth girder.  The smaller girder sits on the bent cap next to the larger depth girder.  There are two different thicknesses for the bent cap.  The bent cap rises to meet the smaller girder to create a level transition. 
The superstructure depth to span ratio is bulky.  The proportion is not ideal.  The span of 30’ has nearly the same girder depth as the previous girder which seems to span 90 or more feet.  This might be because the much smaller girder would require another bent cap.  Further study is needed to find the right depth to span the 30’.  It does however match the next girder’s depth.  Perhaps the designer decided to match at least one girder to create a smoother transition and to make the bent cap seat the same for the right bent cap.  One option is to make the girder the same size as the previous girder.  However, the need for clearance might have motivated the designer to narrow the depth of the girder as much as can be done.  Most like the depth at this section was to match the next girder and to make ease of construction and detailing a priority instead of structurally expressing the span to depth ratio of the girder.  The designer could have celebrated this section of span as a gateway to the city with a smaller girder and creating haunches to express the gateway towards the city.  As is, the column land haphazardly on the pedestrian sidewalk and the other one extending to another level below.              
The bent cap is connected to circular columns.  The bent cap cantilevers beyond the circular column on both ends.  The cantilever part of the bent cap could have been drop to express the structural proportions.  The deck protrudes beyond the steel girders creating shadows to differentiate the different levels.  The effect is to reduce the mass of the structure and expresses each part of the bridge structure.  Underneath the girder there appears to be diagonal cross bracings which look to be approximately the same depth as the girder but flush with the bottom of the girder.  The railing is concrete which makes the bridge look bulky.  An option is to use metal lattice railing.  But the thin concrete railing is much smaller than the steel girder that one hardly notices it.  Perhaps the concrete railing provides more of a visual stability for the automobiles which could crash into the railing and fall onto the highway below it.  Some of the support is shew because there is no room for the column to land due to serval lanes coming together at various angles which intersect.   
Overall the design is not well thought out and the transitions clumsy.  As is typical of most highway bridges, the way it is designed, priority is given to practicality and utilitarianism.  There were opportunities to express the structural proportions in the depth to span ratio and create a unique gate way for the traffic heading toward the city center.              

Friday, April 3, 2015

Building Better Bridges



In ‘Building Better Bridges’ Paul Giroux wanted to highlight some of the unique challenges and issues we all face in the signature bridge market. 
Society has love affair with landmark bridge:  The challenge of any design problem is to find the right balance of aesthetics (form) and performance (function).  There are a lot of frustration with the politics, selection process, time, inaccurate budget estimates, constructability and durability.  Paul used the Minnesota Bridge as an example of unclear bidding process.  Even with these frustrations, society want more then just function, they want form and project their fantasies onto the bridge hoping that a bridge will beautify their surroundings.  There is a demand for major bridges to be more than just spans.  Bridge also wants to be monuments.  Paul used the San Francisco Oakland Bay Bridge (SFOBB) as an example of the politician’s desire for a landmark.  They didn’t want a “freeway on stilts”.  The Dallas City Council hops to transform and improve the Dallas landscape with their new bridge across the Trinity River designed by Spanish architect Santiago Calatrava.  The politicians in western New York want to emulate the success of the Golden Gate as a new gateway, a defining moment of entry.     
Form vs. Function.  Paul spoke about form follows function idea in design.  If we put function as a priority then form follows its function.  Conversely, when a bridge is designed with aesthetics as a priority, its function follows its form.  There is a spectrum between form and function.  A successful bridge would be a balance of the two.  A bridge by function could be defined as a structure to span a gap and to provide passage.  A bridge by form could be defined as work of art, to span time and provide an icon for the dreams and vision of a society.  Between those two poles a tug of war goes on as we endeavor to make our bridges all things to all people. 
Historically, Function has dominated much of bridge design.  The new Signature bridges are replacing the old ones.  In the process of selecting a bridge, the economic involve is difficult to sort through because the design is still in a schematic phase and cost has not been finalized.  The modern post-tensioned technology and improved concrete mixes have allowed reinforced concrete bridge to be push ever higher levels of performance, longer spans and increased durability.  We are replacing the broken bridges with new signature bridges.  Paul is concerned that our selection process places too much emphasis on aesthetic considerations.  This needs to change.  He lists the following categories of changes:
·         Depoliticize the Process
·         Training and Education
·         Learning from our Past
·         Realistic Conductible Details
·         Inform bridge selection:  Form and Function
·         Maintain what we build.


A bridge stretched across a river, Heidegger argues, provides such a sense of space. Out of numerous possibilities along the river, the construction of a bridge was the site in which a place was constituted. For Heidegger the bridge in not just a functional object, nor is it a dual signifier of referential object and symbolic meaning. For Heidegger, a bridge is a manifestation of the fourfold which is at the base of all dwelling. A bridge collects and unites all aspects of the fourfold, earth, sky, mortals and divinities into a "thing". Such things are distinguishes from one another by the manner in which the manifest the unity of the fourfold. A bridge, in other words, allows for dwelling on account of its predetermined unification of the fourfold.

Monday, March 23, 2015

Materials and Dematerialization


Making the Modern World: Materials and Dematerialization

This book is a second book about material that piqued my interest.  The first book is 'Stuff Matters'.  Vaclav Smil's book seems more serious compare to 'Stuff Matters' written by a scientist and engineer.  The Strength of material class  got me interested in looking at material.   In our Structural Systems class we had a speaker from the Architecture department gave a talk about material in construction.  He compared parking garages and the concrete material versus steel.  He looked at which material is more sustainable then the other one.   Concrete has some problems with it.  A fact Bill alerted me to is that China used more cement in the last three years than the U.S. used in the entire 20th century. 

Before other building material ,  I was interested in paper as a material for journal writing, structural models and origami.  I had not thought about structural system or selection nor the material production of concrete and steel.   We were taught to design but I don't recall having a deeper understanding of material selection or production cost and the environment.       
Bill Gate's Review has some interesting thoughts on paper because he is pushing towards a paperless office.  As a mortgage processor I know that we have decrease the amount of paper file we keep.  Most of the documents can now be electronically signed.  Most of our papers are handed in to an electronic drop box in the form of PDFs.  Smil suggests that paper will still be with us for a very long time. 
Smil's idea of dematerialization states that as a given product becomes more efficient to produce, prices go down and consumption goes up.  An example, someone  makes a cell phone with less metal, which makes them cheaper, which makes them more widespread.  "Less,"  Smil states, "has thus been an enabling agent of more." 
There are some great infographics on Mr. Gate's review.  Check it out.       

Tuesday, January 6, 2015

Datong Art Museum



Assignment:  Write a memo on the design of a specific gravity structural system.  Indicate significant features the system was trying to solve and the methods used to address the issue. 
The Datong Art Museum has a pyramidal space truss roof.

The Datong Art Museum has a pyramidal space truss roof.  The space truss roof can span very large spans and space.  The 40m high roof composed of four interconnected pyramids supported on a series of inclined, two-layer steel space trusses.  The spans range from 75 to 130 m.  The art museum program calls for large open space so the museum can display large-scale works of contemporary art.  This dedicated space is called the Grand Gallery, the museum’s center piece.   The Grand Gallery is a large, column free exhibition space that will be 37 m tall and features a clear span of about 90m.  Architect Norm Foster led the design.    Wang Chun Guang and Yang Jie were the structural engineers for the project.  Most of the building is underground to a depth of 12m.  .  The pyramidal space truss erupts from the ground. 

The tilting planes in the roof achieve a simpler structural concept than a conventional beam and column solution.  Each space truss will consist of two planar trusses from hollow circular steel sections; the main chord member is 400 mm in diameter.  The truss depth ranges from 7 to 16 m.  Yang describes the four pyramidal structures as a fusion of each individual pyramid, forming an integrated enclosure.  The engineers noted the long-span trusses providing the vertical loading support system and “the so-called spatially penetrated joint connections in the trusses bearing the axial loads and transferring the lateral forces”.          

The bracing element will be added to the roof ridge and the main roof edge connections, enabling the trusses to work as a loop beam, the engineers explained.  This technique will stabilized and strengthen the roof structure.  The reinforced-concrete shear walls varying in height from 7 to 13 m and from 300 to 500 mm thick act as the plinth for the roof truss structure.  Their location is permanent so these shear walls crate the circulation channels within the museum galleries.  The foundation system is made of piles.  The piles are 800 to 1,000 mm in diameter.  The pile depth ranges from 10 to 15 m.  Because most of the building is underground, the building needs to be protected against groundwater intrusion.  The design features a water cavity, waterproof concrete, and other waterproofing materials.    

References:

Reid, Robert L. (2012, December). Datong Art Museum Will Feature Pyramidal Space Truss Roof. Civil Engineering, 82(12), 24-27.