RSS

Mighty Mac Comparison To Tacoma Narrows Bridge

A good comparison can be made between the engineering successes and failures witnessed in the construction of two bridges; Mackinac Straits Suspension Bridge (also known as the “Mighty Mac”), and the Tacoma Narrows Bridge (also known as “Galloping Gertie” or TNB).

At the time of its construction in 1940, TNB was the third longest suspension bridge in the world [1, pg xviii]. The construction of TNB was to alleviate the use of ferry fleet to cross the Puyallup River at the mouth of Pugent Sound. The bridge reduced the commute time to cross the river. The sound crossed by TNB often witnessed heavy winds, in some cases in the upper 70 mph range. Record temperatures range from 107ºF to -2ºF. On the day of its collapse, winds at Tacoma Narrows were recorded at 42 mph, [2, pg. 69]. The largest span between pillars on TNB is 2,800 feet.

The Mighty Mac spans a distance of five miles and uses only two support pillars. At the time of its construction, 1957, it was the largest of its kind in the world — nearly 60 years later it is still the largest in the Western hemisphere. When considering the enormity of this undertaking at Mackinac Straits, we must also be aware of the environment. In that area, record temperatures range from 115ºF to -35ºF, winds reach 78 mph, and as much as six feet of ice accumulates on the water beneath it. The two support pillars for the Mighty Mac are 3,800 feet apart. In the planning of he y Mac, engineers reviewed and took lessons-learned from similar construction, such as TNB, San Francisco-Oakland Bay bridge, and Golden Gate bridge.

The engineers’ attention to detail was a key factor in the success or failure of these grand projects. In the case of TNB, engineers witnessed unusual motion during construction. Quoting [Wake, pp. 46–47], “during the final stages of work, an unusual rhythmic vertical motion began to grip the main span in only moderate winds….” This torsional oscillation causing a positive feedback loop.

TNB construction placed stiffening girders to a shallower depth than its predecessors, only eight feet deep [2, pg. 69]. This reduced the dampening effect of its weight on aerodynamic lift. The reduced weight combined with the aerodynamic effects of the wind, setup an unexpected change. “… the extreme flexibility, slenderness, and lightness of the TNB allowed these oscillations to grow until they destroyed it. [3, pg 901].” [3] goes on to demonstrate mathematically how the resonance occurred and eventually collapsed TNB. In part, this was also attributed to the depth of the girders.

In contrast, construction of the Mighty Mac gave greater attention to natural forces including the rock underneath and the atmospheric effects. Steinman’s [4] explains how they investigated the geology beneath the piers. The rock in some areas of Mackinac strait is composed of Mackinac Breccia, a breccia formed by collapsed caverns [5, pg 246]. This potential for collapse necessitated thorough research of the rock. After diligent inspection and scientific work, including 51 borings and extensive data analysis [4, pp. 4-5], the geologists determined the rock had no caverns and significant enough strength to support the bridge in its environment. This exhaustive investigation ensured proper placement and depth of the foundations for the pillars.

Steinman also took into consideration aerodynamics. Prior to work on Mighty Mac, he had suggested “critical wind velocity” as a contributing factor that induced oscillations in TNB [6, 760]. The design of Mighty Mac allowed air to pass through a grate in the center two lanes. This eliminated the aerodynamic lift.

The final contrast is evident in human witness. Tacoma Narrows Bridge succumbed to natural forces after only four months. Mackinac Straits Bridge has withstood fifty-eight years of high-winds, subzero temperatures with ice flows pounding at its pillars, and, as of 2009, 150 million vehicles has crossed the Mighty Mac.

BIBLIOGRAPHY

[1] Scott, Richard. “In the Wake of Tacoma.” ASCE Press, Reston, VA, 2001.

[2] Steinman, David B. “Bridges” in Scientific American, vol. 191, no. 5, pp 60-71, Nov, 1954.

[3] Arioli, Gianni, and Filippo Gazzola. “Applied Mathematical Modelling: A New Mathematical Explanation of what Triggered the Catastrophic Torsional Mode of the Tacoma Narrows Bridge,” Elsevier, vol. 39, pp 901-915, Jan. 2015.

[4] D. B. Steinman, “Mackinac Bridge Final Geological Report,” St. Ignace, MI, Geology Report, Apr, 1956.

[5] J. Monroe, and R. Wicander, (2014). “Engineering and Geology,” in The Changing Earth: Exploring Geology and Evolution, 7th ed. Stanford: Cengage, 2014, ch 10,  sec. 10.1, pp 246-247.

[6] Robert C. Post, “The Bridge At Mackinac Straits: Another Fiftieth Anniversary”. Technology and Culture, vol. 49, no. 3, July, 2008, pp. 752-763.

 
Leave a comment

Posted by on February 12, 2015 in Class Writing, Critical Inquiry

 

Tags: , , ,

Becoming a Critic Of Your Thinking

Even being aware of my morality, I still violate some of these simple rules from this article. Becoming a Critic Of Your Thinking.

Extract:

A How-To List for Dysfunctional Living

Most people have no notion of what it means to take charge of their lives. They don’t realize that the quality of their lives depends on the quality of their thinking. We all engage in numerous dysfunctional practices to avoid facing problems in our thinking. Consider the following and ask yourself how many of these dysfunctional ways of thinking you engage in:

  1. Surround yourself with people who think like you. Then no one will criticize you. 
  2. Don’t question your relationships. You then can avoid dealing with problems within them.

  3. If critiqued by a friend or lover, look sad and dejected and say, “I thought you were my friend!” or “I thought you loved me!” 
  4. When you do something unreasonable, always be ready with an excuse. Then you won’t have to take responsibility. If you can’t think of an excuse, look sorry and say, “I can’t help how I am!” 
  5. Focus on the negative side of life. Then you can make yourself miserable and blame it on others.

  6. Blame others for your mistakes. Then you won’t have to feel responsible for your mistakes. Nor will you have to do anything about them. 
  7. Verbally attack those who criticize you. Then you don’t have to bother listening to what they say. 
  8. Go along with the groups you are in. Then you won’t have to figure out anything for yourself. 
  9. Act out when you don’t get what you want. If questioned, look indignant and say, “I’m just an emotional person. At least I don’t keep my feelings bottled up!” 
  10. Focus on getting what you want. If questioned, say, “If I don’t look out for number one, who will?”
 
2 Comments

Posted by on January 19, 2015 in Repost

 

Father’s Achievement

I watched some emotional videos the other day; and they made me think, what can I do to make my life more meaningful, influential, … memorable? I considered what I have done and what I could do to make my effect on those around me more valuable. And, maybe more importantly, how that effect can be measured or recognized; how can I determine if I did lead my life in the greatest way possible? I began to perceive what I want from my life. I recognized criteria that will reveal the effectiveness my life or anyone’s life.

I came to this conclusion: My life’s accomplishment will be the greatest I could possibly want, if after I am gone, I am missed. That’s it; being missed. After I’m gone, if those that I love notice I am not here, then I have done good. At that moment, my legacy will be realized. I began reflecting on events and interactions in my life. I wondered if those moments would be remembered as I remembered them. I wondered if each of those “learn from me” instances would be valuable. I wondered if my presence would be missed by the ones I love.

In that reflection on who I am, in who I have become, in my achievements, in my transgressions, in my reached and missed goals, in all the life I enjoyed, in all the love I have shared, in the lessons I learned and taught; it was observing those moments that I realized how meaningful, influential, memorable, and great my Dad’s life was.

Dad, you are missed.

 
Leave a comment

Posted by on October 26, 2014 in Memories, Writing

 

The Secret Casualties of Iraq’s Abandoned Chemical Weapons

This is a long article, eight parts. I am sharing this public, because it is important that it gets shared. Our government, for the past 15 years or more, has placed our soldiers in harms way, and has ignored their needs. This article describes the chemical weapons our servicemen are exposed to, and then how our government ignored them. These chemical weapons are now controlled by the “Islamic State”.

The Secret Casualties of Iraq’s Abandoned Chemical Weapons

 
1 Comment

Posted by on October 15, 2014 in Politics

 

Sustainability Brief Overview of Solar Utilization Network

Integrative Graduate Education and Research Traineeship: Solar Utilization Network (IGERT-SUN)

The IGERT-SUN program is funded by a grant from the National Science Foundation. The faculty includes: Willem (Wim) Vermaas, DSc, Program Director; Cesar I. Torres, PhD; Jenefer Husman, PhD; David Guston, PhD; and, Ana Moore, PhD. A key goal of the program is to enlist PhD students from a wide range of disciplines to examine how to advance solar energy science and usage, focusing on three approaches: photovoltaics, solar thermal, and photosynthesis driven bioenergy. IGERT-SUN is designed to seek transitioning our current fossil-fuel based economy to these various forms of solar energy. The variety of participants includes students pursuing doctorates in Engineering, Biochemistry, Environmental Engineering, and Sustainability Engineering; one member is identified as “Human and Social Dimensions of Science and Technology” doctoral student.

The IGERT-SUN project highlights video on Vimeo demonstrates the faculty’s and the students’ vigor in pursuit of advancing these alternate energy resources. Miles Brungage, a student in the program, described how he appreciates the opportunity to work with colleagues of different studies but working a similar goal, sustainability. And Joseph Laureanti highlighted how this program offers him the opportunity to connect with people within alternative energies fields, and glean from them real purpose in the program. In some abstracts, I read a program focus on attracting “underrepresented groups, particularly Hispanics and Native American” candidates to the program. Although an admirable goal, if carried to excess, the achievement of that goal may result in reducing the diversity of the participants, or even narrowing the breadth of knowledge the program sought to nurture.

 
Leave a comment

Posted by on October 5, 2014 in Class Writing, Sustainability

 

Tags: , ,

Sustainability Essay

In our Introduction to Sustainability coursework, I have identified four areas for me to change: water usage, fossil fuel usage, red-meat consumption, and pesticide usage.

Last year, I purchased a new home with low-flow shower heads, low-flow toilets, new water-efficient appliances, xeriscaped yard, and no pool. My previous home used approximately 10,000 to 15,000 gallons of water per month. My new home reduced water usage to less than 4,000 gallons per month. I plan to continue to pursue reductions in my water use with methods described in Infographic 17.7 (Karr, p. 308).

From the new home, my commute increased from 40 miles to 80 miles round-trip. As described in our textbook, the “extra carbon causes problems such as global climate change, acidification of oceans, and alternations of communities worldwide” (Karr, p. 121). To reduce my impact, I telecommute one day per week. I did consider an electric vehicle. However, Mitchell Ng points out “alternative energy vehicles are cost-inefficient when compared to fossil-fuel based ones” (Ng, p. 56). Instead, on restricted income, I am pursuing the purchase of an Elio; it will triple my fuel economy from 18 MPG to an estimated 65 MPG (Resource Week, p. 159).

Graham Hill also pointed out “eating a mere hamburger a day can increase my risk of dying by a third” (Hill, 0:40). In our textbook, Karr explained, “Replacing some red meat with fish, poultry, or non-meat sources of protein decreased risk [of dying] by 7%–19%” (Karr, p. 368). I am very health, but by reducing my red meat intake and increasing the vegetables and fruits, my good health can be extended even further.

My home has frequent visits from desert wildlife and insects. Rather than using chemical pesticides, I believe I can use some organic pesticides to remove or restrict them, but with less environmental impact than chemicals. Using Karr’s recommended resource, SafeLawns.org (Karr, p. 327), I can help reduce impact on our water supply and deter those creatures from entering my home.

Works Cited:

Karr, Susan, et al. (2014) Scientific American Environmental Science for a Changing World Extended. 1st Ed. New York, NY: W. H. Freeman.

Ng, Mitchel. (2011). Short and long-term cost efficiency analysis of fossil fuel versus alternative energy vehicles. Journal of Business Studies Quarterly, 3(2), 45-56. Retrieved from http://jbsq.org/wp-content/uploads/2011/12/Dec_2011_4.pdf.

Hill, Graham. (2010, February). Graham Hill: Why I’m a weekday vegetarian [Video file]. Retrieved from: http://www.ted.com/talks/graham_hill_weekday_vegetarian/.

Resource Week. (2014, March 23). Elio Motors Inc. Displays Enclosed 3-Wheeled Vehicle At Valley of the Sun Clean Cities Coalition Legislative Breakfast. 159.

 
1 Comment

Posted by on September 23, 2014 in Class Writing, Sustainability

 

Fatherhood Moment

Our family took a long road trip to Michigan from Arizona for a family reunion. On our road-trip vacation, I got the chance to see the results of being a father. Our travels took us first from Phoenix, Arizona, to Shamrock, Texas, then Lake of the Ozarks, Missouri, then a layover in Chenoa, Illinois, and finally to West Branch, Michigan. The second leg of the journey took us from Shamrock, Texas, toward Chenoa, Illinois, with a to-be-determined waypoint in Missouri. Somehow, coming out of Oklahoma City, Oklahoma, I had made a wrong turn and we were traveling north. We had to take an alternate route east toward Tulsa. We ended up on a two-lane road through rural parts of Oklahoma. The road weaves across hills and dales through rural farming areas. The sides of the roads are defined by wide gravel shoulders and shallow ditches. The ditch lines are broken by infrequent gravel driveways that access farm homes set back from the road.

Along our path, I saw a car on the opposite side of the road with its trunk open. It was oddly situated at the edge of a driveway but just off the road. Initially, I continued past the vehicle, but in my rearview mirror I noticed an older male retrieving something out of the trunk. I also noticed the passenger-side rear tire was flat. At first, I continued on my way, but my principles forced me to turn around and return to see if the gentleman needed assistance.

When we reached the disabled car, it was situated to not allow me to easily park behind it. To avoid completely blocking the nearby driveway, I parked in front of that car. When I got out of the car and approached the gentleman, he seemed put aback by my offering assistance. The stranded motorist was alone. He was a grey-haired, older man, appearing to be in his mid to late-70’s. He was not a feeble man; he stood about 5’ 8” to 5’ 10”, and likely weighed 180 to 190 lbs. The presence of perspiration on his brow disclosed some distress. He first declined and seemed to be annoyed at the offer. But, after a brief pause he griped about the modern automobiles complex storage of simple items like a car jack. I moved to the trunk of his car and insistently, but respectfully, offered to find the parts for the jack before I left.

As I was locating the pieces in his trunk, Dom and Aric approached from our car. I handed the jack to the gentleman. He attempted to locate where to place the jack based on the vehicle owner’s manual, but pointed out it was difficult to identify. He suggested the manual identified the corner of the wheel well and the body as the jack point and placed the jack as if he were going to use it there. I interceded and located the proper location for the jack, about 8 to 10 inches toward the front of the car. At this point, Dom pointed out the wheel lugs needed to be broken loose before lifting it off the ground, and he offered to do that. I handed the lug wrench to him. The gentleman stepped back and let Dom, Aric and I continue working on changing the tire. He did not intervene or suggest he was offended. Dom finished starting the lugs, and I jacked the rear tire off the ground.

After the vehicle was off the ground, I stepped back and began to chat with the gentleman. Aric joined Dom with finishing changing the tire. The gentleman and I exchanged introductions, and I shared our story of taking a road trip to Michigan. He expressed his appreciation for the assistance. And then he explained his circumstances. He was on his way home from Tulsa from the hospital. He had been there for three days tending to his wife. She had been hit on top of her head. The impact ended up fracturing her skull, forcing her to go to the hospital. As he shared his tale, tears formed in the corners of his eyes, but he fought off any significant tears or sobbing. Because of the swelling around her brain, the doctors had to place her into a coma, and extract fluid from around her brain. He was on his way home to pick up some clothing and other items for the both of them. He didn’t offer any prognosis.

The gentleman complimented Dominic and Aric’s chivalry. When the boys finished changing the tire, the gentleman thank them and me. We wished him well and offered our prayers for his wife.

My sons’ actions fill me with pride. They continue to show they have grown to be good young men. My sons are young, they make some foolish mistakes. That’s normal, but they also demonstrate mature and honorable actions. I hope they continue this path.

 

 
1 Comment

Posted by on July 8, 2014 in Memories, Vacation