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Could line dancing bring down Thwing?

Steven Mazurek

Issue date: 12/5/08 Section: News
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But if the collapse in Jerusalem was caused by the owners' negligence and bad construction, why are students not permitted to line dance in Thwing?

The answer comes in the form of a letter from Stephen F. Ebersole, of Ebersole Structural Engineers Ltd. The company had been contacted by David Davison, vice president of operations for Technical Assurance Inc., which had been hired to investigate by Bondra. Davison and Ebersole's offices inspected the structure of the building from the underside of the Thwing ballroom.

The firms concluded from a visual inspection that there was no evidence of loading weakness in the ballroom. In other words, the ballroom should have no problems with the weight of a capacity sized crowd. The letter notes that the "floor structure of wood deck supported by wood floor joist spanning to steel girders appeared in very good condition." The structure in question is old, but solid.

"They found it's a pretty sound building; it was built back in the early 1900s so they did a pretty good job and the beams are in good shape," said Medley.

After the visual inspection, Arthur Huckelbridge Jr., professor in the civil engineering department at Case, was employed to perform a vibration analysis of the structure. The analysis was necessary because even if the structure is strong enough to carry a static (stationary) load, it may be susceptible to dynamic (moving) loads.

A prime example of the danger of dynamic loading is the Angers Bridge collapse. Four hundred and seventy-eight French soldiers in Angers, France marching in unison over the suspension bridge caused it to buckle in 1850. The reason that structures can be particularly vulnerable to this kind of motion arises from oscillation. In the case of the Angers Bridge, the soldiers marching in unison would cause the bridge to deflect with each footfall. Each time their feet came down, the bridge would deform by a small amount. The bridge would then compensate and swing in the other direction. Normally these minor vibrations can be absorbed by the structure, which resists being deformed. But when the vibrations are large enough and happen with a regular cadence, or frequency, the dynamic loads can work against the bridge's natural restoring forces. The soldiers might stomp each time the structure swings in one direction, and lift each time it swings the other way. The result is that they reinforce and strengthen the oscillations of the bridge. If this continues, the bridge will deflect more and more, until the most vulnerable structural supports snap. In the case of the Angers Bridge, the corroded wire anchor cables broke, and the bridge collapsed.
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In This Issue

News

  • Black History Month luncheon
  • Empowered by credit cards
  • Have you heard about: Engineers Without Borders?
  • Integrity Week to kick off
  • Robert Petit lecture elucidates Cambodia's "killing fields"
  • Student State of the University Address looks for improvement
  • Survey results provide new details of SAGES progress
  • Tuition increase scaled back amid tough times

Sports

  • A strong finish, finally
  • Browns fans should rethink rivalry
  • Dukes, Gardella place at Wheaton Invitational
  • Hockey: Against Pitt-Greensburg, third period and power play problems
  • Spartan Spotlight: Bryan Erce
  • Swimmers get wins in last meet before conferences
  • Throwback Weekend: Old-school jerseys are a growing trend
  • Track: Case, Mellon go head-to-head in first dual
  • Women's Basketball: Henry's last-second layup lifts Spartans

Fun Page

  • Crossword Answers
  • Jumble Answers
  • Sudoku Answers

Opinion

  • Editorial: Modest tuition hike shows consideration
  • Engineering solutions to climate change not ideal, but worth studying
  • Letter to the editor: Putting life on hold for inauguration is over the top
  • You don't have to hate Valentine's Day: expand your options

Focus

  • Alternative girl band makes its Cleveland debut
  • Case Men's Glee Club sings their hearts out for another year
  • Fantasies come true
  • Film based on self-help book falls flat, despite star-studded cast
  • Listen Up
  • Local band makes name for itself, even across the Atlantic
  • Rocker teaches how to make a band work in new book
  • The Buzz
  • The Secret Ingredient: Popcorn Paradise
  • The Spartan guide to style: Preparing to spring forward
  • The Worst Case Scenario: Saving the economy
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