What if The Colosseum was Built on Helical Piles in Philadelphia?

By Steve Gencorelli

“While stands the Colosseum, Rome shall stand;
when falls the Colosseum, Rome shall fall;
and when Rome falls – the world.” 
– Lord Byron

Recently, I had the glorious pleasure of visiting the massive and impressive Colosseum!  This would be the meeting place of 50,000 Romans screaming for the fierce gladiators to emerge victorious. The gigantic structural stadium covered 6 acres and stood 12 stories into the clouds. Metal, Travertine Stone, Cement, Bricks, Tiles and Tuff were the construction components of the Flavian Amphitheatre that weighed approximately 400,000 TONS!!

Suppose we liked the roar of gladiators in battle versus watching the Philadelphia Phillies…

So I decided to build the Colosseum instead of Citizens Bank Ball Park.

How many Helical Piles would we need to support the gravity weight of the building and the roaring 50,000 fans?

Please note that this brief analysis excludes building design considerations.

LOADS:

• Metal, Travertine Stone, Cement, Bricks, Tiles and Tuff = 800,000 KIPS (400,000 TONS)
• 50,000 Screaming Fans @ Roman average weight of 145 lbs = 7,250 KIPS
• Approx. Total Weight = 810,000 KIPS

Original Foundation: 

• Approximate Area = 615′ x 510′ = 314,000 SQFT

Assumptions:

• Boring was taken from site during the construction of the ball park.
• Ground water table was approximately 30 FEET from the ground surface.
• Large mat pile cap to support the structure.
• Helical Piles spaced at 7′ x 7′ on center = 1 Helical Pile for every 49 SQFT
• Factor of Safety = 2.0

Helical Pulldown Micropile Foundation Design:

• Number of Helical Pulldown Micropiles = 314,000 / 49 ~~ 6,400 piles
• Design Compression Load per Helical Pile = 810,000 KIPS / 6400 Piles = 127 KIPS
• Ultimate Compression Capacity per Helical Pile = 254 KIPS
  
  • Helical Pulldown Micropile with a 7″ uncased grout column
  • SS225 with 8-10-12-14-14 helix configuration
  • Approximate Depth of pile = 40-45 FEET
  • Required Installation Torque = 22,000 FT-LBS (This includes friction from grout column)

Conclusion:

• 6400 Helical Pulldown Micropiles to support the Colosseum!

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Steve Gencorelli, P.E. is Danbro Distributors’ resident Structural Engineer.  He has designed buildings in over fifteen states on the east coast in the past twelve years.  He enjoys European culture so much that he married a British woman last year!

For technical information and assistance please contact Steve at steve@danbro.com.