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Page 1: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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Page 2: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

Architect Architect --Eero SaarinenEero Saarinen

••Shape Shape --Inverted catenary curveInverted catenary curve

•• The Arch has no real structural The Arch has no real structural skeleton. The inner and outer skeleton. The inner and outer steel skins are joined to form steel skins are joined to form a composite structure. The a composite structure. The Outside skin is stainless steel Outside skin is stainless steel and the inner skin is carbon steel.and the inner skin is carbon steel.

•• DoubleDouble--walled, triangular section were placed one on top of walled, triangular section were placed one on top of another and then welded inside and out to build the legs of the another and then welded inside and out to build the legs of the Arch.Arch.

Page 3: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l DimensionsOuter Width: (Outside North Leg to Outer South Leg ) 630 ft (192m)

Maximum Height 630 ft (192m)

l Shape of Arch Section Equilateral Triangle

l Dimension of Arch at Base 54 ft (16.46m)

l Dimension of Arch at Top 17 ft (5.18m)

l Deflection of Arch 18" in 150 MPH wind (0.46 m in 240 km/h wind)

Page 4: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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Page 5: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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Method of Determining Deflection of Arch

l Calculations and Wind Tunnel Tests (240 km/h)

l Number of Sections in Arch 142

l Thickness of Plates for Outer Skin 1/4" (6.3mm)

l Type of Material Used in Arch Exterior Stainless Steel; #3 Finish Type 304

l Structural Capacity of Observation Area 100 lb/sq. ft (488 kg/m)

Page 6: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

����������������� ���l Stainless Steel Plate Exterior Skin: 886 Tons

(804 metric tons)

l Carbon Steel Plate Interior Skin 3/8" 2,157 Tons (1,957 metric tons)

l Steel Stiffeners: 1,408 Tons (1,277 metric tons)

l Interior Steel Members, Stairs, Trains, etc.: 300 Tons (272 metric tons)

l Total Steel Weight 5,199 Tons (4,644 metric tons)

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Page 7: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

�����������������l Between Skins to 300' (91 m) 12,127 Tons

(11,011 metric tons)

l In Foundation Below Ground 25,980 Tons (23,569 metric tons)

l Total Concrete Weight 38,107 Tons (34,570 metric tons)

l External Protection Six 1/2" x 20" (13 x 510 mm) Lightning Rods and One Aircraft Obstruction Light

l The bars, 1-3/4 in. in diameter, are made of alloy steel with an ultimate strength of 145,000 psi

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Page 8: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

l Reinforced concrete foundations are sunk 60 ft. into the ground and extend 30 ft. into bedrock – this contribute substantially to the structural strength of the Arch.

l Under a wind load of 55 psf (equivalent to a 150-mph wind), the Arch will deflect at the top only 18 in. in the east-west direction.

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Page 9: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l Each group of tensioning bars required careful positioning because the bars had to be inclined in two directions.

l To fit the curvature of the Arch, and the tapering cross-section of the legs.

l When the steel-work was in place, concrete followed. The bars were post-tensioned after the 5,000-psi concrete reached a strength of 4,000 psi--usually after 7 to 10 days.

Page 10: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l Massive foundations and filled walls are typical of a weighted catenary arch, structurally the soundest of all arches, for the thrust passes through the legs and is absorbed in the foundations.

Page 11: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l Each Arch leg is a double-walled equilateral triangle with a hollow core 40 ft. wide at the base. l The inner skin is of A-7 carbon steel, 3/8 in. thick, except at the corners where it is 1-3/4 in. thick to provide greater stiffness. l The outside surface is 900 tons of polished stainless steel in panels 14 in. thick, varying in size from 6 x18 ft. to 6 x 5 1/2 ft. l The outer and inner walls were fabricated in sections and bolted together.

Page 12: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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•For the Arch sections, at the top of the Arch, high-strength steel bolts were attached to the Z-bars.

•These bolts passed through holes in the inner skin of carbon steel and were held in place by nuts that applied a squeezing force to the concrete core of the wall "sandwich," creating a friction bond.

•To resist local bending, the outer and inner skins act as the top and bottom flanges of a beam, providing a stressed-skin action like an aircraft design.

Page 13: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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•From the top of the composite wall section to the crown of the Arch, all direct compressive loads are carried by the outer stainless steel skin and the inner carbon-steel skin.

•Vertical steel diaphragms, spaced 2 ft. on centers, connect the two skins and serve as stiffeners to prevent buckling of the inner skin.

• Steel angles spaced halfway between each diaphragm stiffen the outer skin. The stiffeners and diaphragms are interrupted at each field splice and do not contribute to Arch actions.

Page 14: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l The legs of the Arch acted as free-standing cantilevers before completion and were erected simultaneously without scaffolding.

l Crawler cranes where used for the first 72 feet.

l After 72 feet, two creeper derricks, each weighing 100 tons, were used in construction.

l The structure not only hadto support it’s self, it had to support the crepper derricks.

Page 15: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

�������� � * ���������������� � * ��������l The initial design for the Arch called for guy cables at about the 530-ft.

mark to stabilize the structure.

l First calculations showed that one 6-in. or two 3-in. cables on each leg would be needed for stabilization—this would increase the cost.

l Cost and other problems with the cables, the designers used a stabilizing strut or truss at the 530-ft. level.

l The bridge-like truss was shop fabricated of small wide-flange beams and tubular members made from high-strength alloy steel.

l It was connected to the Arch by a steel harness fitted around each leg, this allowed the increased loads and wind force on each leg to be transferred directly to the foundations.

Page 16: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

��� ������������� ��� �������������l The Arch, follows the form

of a catenary. The formula is shown on display inside the arch: (yellow line)�+�,-.-/!���01.12/3425

l This photo taken day the arch was topped-off and fitted the measurements of a catenary getting: (red line)�+�67/!���01.118/3425

l The red circles are the measurements, the red curve is the fit and the yellow curve is the published catenary.

Analysis by Alex Dzierba, Professor of Physics, Indiana University

Page 17: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l Here's a chain (upside-down picture) which hangs 20-in below a line connecting the two suspension points, also separated by 20 inches.

l The pix was digitized and fit to a catenary giving:

Y= 77*cosh[0.017*x-1]

Page 18: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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•A look at the mathematical equations used to create the catenary curve shape of the Arch.

Page 19: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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Page 20: ˘ ˇ ˆfaculty-legacy.arch.tamu.edu/anichols/index_files/courses/arch631/case/2002/gateway...Outside skin is stainless steel and the inner skin is carbon steel. ... flanges of a beam,

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l http://www.nps.gov/jeff/arch-ov.htm

l http://dustbunny.physics.indiana.edu/~dzierba/slarch/

l http://www.nps.gov/jeff/ar-facts.htm

l http://www.cr.nps.gov/history/online_books/harrison/harrison30.htm

l http://www.syncrolite.com.StLouisArch.html