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The New CISC Architecturally Exposed Structural Steel Documents

Presentation given at Construct Canada, November 29, 2012.

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The New CISC Architecturally Exposed Structural Steel Documents

  1. 1. The New CISC Architecturally Exposed Structural Steel Documents
  2. 2. Presenter: Terri Meyer Boake, B.E.S. B.Arch. M.Arch. LEED AP Associate Professor School of Architecture, University of Waterloo, Canada
  3. 3. What is AESS?• Architecturally Exposed Structural Steel is steel that has been purposefully left exposed• It must fulfill structural functions• It is normally part of the Architectural aesthetic of the space• It usually requires detailing, finish and handling that requires more attention and care than regular structural steel• It adds to the cost of the contract
  4. 4. High Tech Architecture Hollow sections were only “invented” in the 1970s and their adoption truly changed steel design and detailing. Foster, Sainsbury Centre, 1977
  5. 5. Contemporary AESS Chicago O’Hare United Airlines Terminal by Murphy/Jahn was the first AESS Airport – finished in 1987
  6. 6. How good is “Good Enough”? • AESS was being used on very high profile projects • AESS was also being specified for mid to lower end projects • Not all projects had/have the budget to pay for the sort of detailing of “A Calatrava” • There was no agreed language or specification that could assist in the communication of expectations between the Architect, Engineer and Fabricator Wisconsin Art Museum, Calatrava
  7. 7. Problems Specifying AESS• Miscellaneous Metals spec does not address the structural requirements of AESS• AESS can be priced out of sight on projects if excessive requirements are added “out of ignorance”The Bottom Line is that:• All AESS does NOT need to be equally crafted…• Not to say that it should not be properly crafted, but not all situations or projects either need or can afford the same level of detailing
  8. 8. “God is in the details”What are they doing?
  9. 9. They are grinding the surfaces …
  10. 10. ... for a structure that willbe visible close-up, but forpassengers that are juststanding by, waiting for anairport taxi.
  11. 11. The welded connections on thistubular truss are basic weldedconnections, not particularlyrefined.
  12. 12. Why?Because it doesn’t matter,given the thickness of thecoating …
  13. 13. … and the distance.
  14. 14. Purpose of the new AESS Documents To find common ground And clarify communication
  15. 15. Architectarchitect engineer fabricator I want nice connections!
  16. 16. AESS Custody Battle! Exposed steel is “owned” by the Architect, the Engineer and by the Fabricator! Success requires cooperation.
  17. 17. Not all AESS need be created equal. Conference Center Sculpture Arena University Building
  18. 18. Exquisite/expensive detailingNeeds to be closeenough to be seen,and even touched, tobe warranted
  19. 19. Distance should play a factor Can anyone really see this?
  20. 20. Distance should play a factor MUST this be filled? MUST this be realigned?City Hall Atrium
  21. 21. Distance should play a factor (360o)9 Storey Atrium
  22. 22. Coating, protection systems should be a factor Galvanized Hi-gloss Thicker intumescent Thick intumescent Medium gloss
  23. 23. Connection types are important differentiators
  24. 24. Bolts vs WeldsThe choice is there…. And the AESS is very different…
  25. 25. AESS: Primary Factors of influence• Distance. Visibility. • Interior or exterior• Connections mostly setting bolted or welded • Paint finish, corrosion• Tolerances required at resistance, fire fabrication and erection protection• Access to detail to perform required finish• Degree of expression• Size and shape of structural elements
  26. 26. AESS: Primary Factors of influence• Distance. Visibility. • Interior or exterior• Connections mostly setting FINISH bolted or welded • Paint finish, corrosion• Tolerances required at resistance, fire fabrication and erection protection FIT• Access to detail to perform required finish• Degree of expression FORM• Size and shape of structural elements
  27. 27. New AESS Documents Subdivision of Specification for Structural Steel Fabricator’s document Visual Guide for specifying AESS Category Matrix
  28. 28. AESS: Factors of influence• Distance. Visibility. • Interior or exterior• Connections mostly SPEC setting GUIDE bolted or welded • Paint finish, corrosion +• Tolerances required at resistance, fire CODE fabrication and erection protection• Access to detail to perform required finish• Degree of expression• Size and shape of MATRIX GUIDE structural elements
  29. 29. Approximating Cost Premiums• Discussions/roundtables made it apparent that Architects and Engineers wanted cost premiums provided• Cost premiums could begin to differentiate the AESS Categories• A “range” of extra cost has been included• The range is very wide and should only be used as a starting point for contractual discussions between the Architect, Engineer, Fabricator and Client
  30. 30. Categories go from lowest at the right tohighest at the left.
  31. 31. Viewing distance is noted as thedifferentiating factor between the high andlow end AESS Categories. Grinding No permitted $$ Grinding!!
  32. 32. Characteristics are listed from the mostcommon/least expensive at the top to themore specialized at the bottom.
  33. 33. Estimated cost premiums over StandardStructural Steel are noted at the bottom.
  34. 34. AESS 1 Roof trusses for arenas, retail warehouses, canopies Cost premium: Low (20-60%)
  35. 35. AESS 1 – Basic Elements Arena Library
  36. 36. AESS 1 1.1 Surface preparation to SSPC-SP 6 SP 3 : Power Tool Cleaning SP 6 : Commercial Blast Cleaning SP 15 SSPC-SP 6 for complete removal of visible oil, mill scale, rust, Dry-Tec website -
  37. 37. AESS 11.1 Surface preparation to SSPC-SP 6 Shot blast cleaning with the use of abrasives
  38. 38. AESS 1 1.2 Sharp edges ground smoothphoto: AISC AESS Guide
  39. 39. AESS 11.3 Continuous weld appearance
  40. 40. AESS 11.4 Standardstructural boltsHex bolts by defaultThe side on which the boltheads should appear can be TC Boltsspecified …. not the rotation!
  41. 41. AESS 11.4 Standardstructural boltsor TC (tension control) bolts TC Bolts
  42. 42. AESS 1 1.4 Standard structural bolts or TC (tension control) bolts TC BoltsIt is a VERY simple request,but makes a HUGE aestheticdifference!
  43. 43. AESS 11.4 Standardstructuralbolts TC Bolts
  44. 44. AESS 11.5 Removeweld spatterWeld spatter preventsa quality/smooth finishas the imperfectionswill translate through Bolts TCthe coatings.
  45. 45. AESS 2 Retail and architectural bldgs viewed at a distance Cost premium: Low to Moderate (40-100%)
  46. 46. AESS 2 – Feature Elements (>6m)
  47. 47. AESS 2 2.1 Visual Samples (optional)1. 3-D rendering;2. Physical sample of surface preparation and welds;3. First off inspection; First element fabricated for use in finished structure4. Mockups; Scaled or full-scale. Mockups are to demonstrate aesthetic effects as well as qualities of materials and execution: a. May have finished surface b. Architect’s approval of mockups required; c. Retained until project is completed; d. Approved full-scale mockups may be part of work.
  48. 48. Option 1: 3-D renderingThis standard 3D image, taken fromthe Fabricators’ detailing software,combined with built examples ofprevious work was enough to agreeon the requirements.
  49. 49. Option 3: First off inspection Element is included in the final structure. Subsequent elements may have minor modifications.
  50. 50. Option 3: Approved first off inspection assemblyOne of the“wishbones” is thefull scale first offinspected assembly.Can you tell whichone?
  51. 51. When a Mockup is required …Remember that the shopconditions are different than thefinal conditions, with respect to:- Distance- Position- Lighting
  52. 52. When a Mockup is required …
  53. 53. When a Mockup is required …
  54. 54. AESS 22.2 One-half standard fabrication tolerances
  55. 55. AESS 2 2.3 Fabrication marks not apparentphoto: AISC AESS Guide
  56. 56. AESS 22.4 Welds uniform and smooth
  57. 57. 2.4 Welds uniform and smooth 3 very different welded conditions, yet all are appropriate to the project
  58. 58. AESS 3 Airports, shopping centres, hospitals, lobbies Cost premium: Moderate (60-150%)
  59. 59. AESS 3 – Feature Elements (≤6m)
  60. 60. AESS 3 3.1 Mill marks removed Grinding first appears in AESS 3!photo: AISC AESS Guide
  61. 61. AESS 3 3.1 Mill marks removedExample of mill mark show through.
  62. 62. AESS 3 3.2 Butt and plug welds ground smooth and filled Right side shows groove weld ground AISC AESS Guide
  63. 63. AESS 33.3 HSS weld seam oriented for reduced visibility
  64. 64. AESS 3 3.4 Cross sectional abutting surface aligned 3.5 Joint gap tolerances minimizedphoto: AISC AESS Guide
  65. 65. 3.5 Joint gap tolerances minimized Required to accommodate complexity and alignment
  66. 66. AESS 33.5 Joint gap tolerances minimised Regan International Airport, Washington, DC Required to accommodate complexity and alignmentPritzker Pavilion, Chicago
  67. 67. AESS 33.6 All welded connections (optional) Field weld Shop weld Requires skilled field welder.
  68. 68. AESS 33.6 All welded connections (optional) Discreet bolts can be proposed as unobtrusive.
  69. 69. Unobtrusive connections Even where design governs, there are alternates to field welding
  70. 70. Hidden connections or splicesWhere site weldingmight beproblematic, makeparties aware thatbolted connectionsmay be effectively“hidden”
  71. 71. Hidden connections or splicesThis hiddenconnection mustalso beweatherproof
  72. 72. A boltedconnection canbe used for asplice. Asimple sleeveis fitted overthe connectionto providecontinuity ofappearance.
  73. 73. AESS 4 Showcase or dominant elements, sculptures Cost premium: High (150-250%)
  74. 74. AESS 4 - Showcase or dominant elements Custom platework + sharp edges Custom unusual Large castings curvedmembers
  75. 75. AESS 44.1 HSS seam not apparent
  76. 76. AESS 4 4.2 Welds contoured and blendedphoto: AISC AESS Guide Very expensive
  77. 77. AESS 44.2 Welds contoured and blended
  78. 78. AESS 44.3 Surfaces filled and sanded
  79. 79. AESS 4 4.4 Weld show-through minimizedphoto: AISC AESS Guide
  80. 80. AESS C This section is for those who have unusual requirements or are confident enough to create their own set of requirements
  81. 81. Re-used / Sustainable Steel• An increasing number of projects are making use of re-used steel to be sustainable• Some of these projects choose to leave the steel exposed to “celebrate” its re-use• A Custom spec will be required for such projects as the demounting, transportation, re-erection of the steel will be unique and vary by project
  82. 82. Adaptive Re-use • Project used an old steam locomotive shed • Repurposed for offices and a grocery store • Most of the steel was left in its original condition to show off the reuse • Other was “cleaned up and repainted, leaving the original rivets exposed.
  83. 83. Highlight Re-used Elements Steel beams saved from demolition were reused to support the roof.
  84. 84. Rivets
  85. 85. The core idea! FORM, FIT & FINISHTwo “TREES” – both AESS – each quite different from the other – sowhy would the AESS Specification be even remotely the same????
  86. 86. Access for cleaning (and re-painting)
  87. 87. Added Topics in the AESS Guide The AESS Guide for the Architects includes all of the technical issues addressed in the Spec and Code
  88. 88. Additional Topics …with more information and image references on: • Maintenance & design •Coatings & finishes • Connections • Member types • Curves & Cuts • Erection issues • Steel with glass • Steel with timber
  89. 89. Coatings & Finishes • The protection type and finish MUST be known at the beginning of design. • The level of gloss will either mask or reveal minute imperfections.
  90. 90. EXTERIOR VS INTERIOR FINISHES• Water, snow and weathering areobvious issues here. Steel must bedetailed so that moisture does not gettrapped inside, causing the structureto rust out.• Some details create ledges that willtrap snow and meltwater.• Some arrangements will also collectdirt and provide roosts for pigeons.
  91. 91. Primers & PaintingSHOP VS SITE PAINTING• Quality is better with shop painting• Shop painting is less costly• Shop painted steel requires better care and handlingduring transportation, site staging and erection• Anticipate that some touch up work will be requiredPRIMERS• A BIG caution note here!• Each type of final finish requires a DIFFERENT primer• Incompatible primers must be removed• Especially important with intumescent fire protection.• Some steel does not need a primer – cost and environmental savings!
  92. 92. Intumescent coatings• Acrylic Commercial/architectural applications, mostly interior, field applied – water based • longer to dry, more fragile, but “greener”, for interior – solvant based • faster, most common use, robust, mostly interior setting but also exterior• Epoxy Industrial applications, ext. or int., shop applied • very fast to dry, very resistant (also anti-corrosion)
  93. 93. Intumescent coatings have become a widely used way of expanding the application of exposed steel, but have major ramifications when specifying the level of fit and form on a project!Solvent basedintumescent being siteapplied.
  94. 94. Intumescent Issues • The finish is not the same as paint – it has an orange peel like texture • Intumescent coatings will NOT provide a precise colour match to adjacent paint • Must be top coated against damage • Should be detailed to allow for routine repair and refinishing
  95. 95. When you need corrosion protection … • Galvanizing • Hot Metal Spray (metalizing) • Paint systems • Intumescent coatings (epoxy) • Weathering steel • Stainless steel
  96. 96. Corrosion + Fire Protection Support legs covered with a shop applied epoxy intumescent coating. Requires additional care during erection to protect (and repair) the surfaces.
  97. 97. THE ENGINEER AND FABRICATOR SAY ABOUTGALVANIZED STEEL:It was NEVER meant to be a “FINISH”!It is a corrosion protection system!THE ARCHITECT SAYS:But it looks so cool! I want it as a FINISH – can you make it look consistent please??
  98. 98. What impacts the final look of galvanized steel?• Impurities, presence of certain chemicals, especially silicon• Steel origin from several different heats• Thickness of material: too thin, too different• Access to all surfaces being dipped• Size of pieces of steel
  99. 99. Differences between heats of steel!In the galvanizing process the zinc layer bonds to the steel.
  100. 100. Galvanizing Applications
  101. 101. Weathering SteelHow do we detail for a material that changes its colour andfinish hue over its life; can bleed onto the concrete below.
  102. 102. Most common application: BRIDGESWeathering steel contains copper andnickel, is less porous than carbonsteels, and creates a protective patinaafter about 2 years
  103. 103. • Weathering steel will stain,mostly in the first two years• It “needs” wet/dry cycles todevelop the patina • No residues should remain on the steel • Not advisable for a roof • Colour is not completely predictable but almost always beautiful!
  104. 104. Interior Weathering Steel Issues If weathering steel is used on an interior, it must be pre- weathered as the wet/dry cycles will be absent.
  105. 105. Connection Design SELECTING A CONNECTION TYPE • A huge impact on detailing! • Impacts fabrication costs • Impacts erection and constructability • Impacts timing of the project • Impacts transportation • How big are the pieces • How much can be assembled in the shop? • BOLTS VS. WELDS • SHAPES VS. TUBES
  106. 106. Also included! Sections on: Erection & Challenges • Best Practices • Transportation Issues • Care in Handling • Erection Issues • Staging and Site Area Requirements • Steel and Wood • Steel and Glass • Curved Steel
  107. 107. Wayne Baigent SAMPLE AESS SPEC FOR STRUCTURAL STEEL Santiago Engineer Calatrava Architect FabricatorGUIDE FOR CODE OFSPECIFYING PRACTICEAESS
  108. 108. Design process implications• Architects and engineers have to talk to decide on AESS Categories.• AESS Categories need to appear on all contract documents as per Spec.• We typically expect that there will be 2 Categories specified per structure – ex. AESS 2 upper portion of atrium, AESS 3 for the lower portion; 1 and 2; 2 and 3; 3 and 4…• Fabricators to bid on Engineering documents and the Categories specified.
  109. 109. Fabrication and Erection Implications• Architects need to fully appreciate and include AESS considerations in their designs and negotiate with the Fabricator for more appropriate details• Categories specified infer sequencing, cost and constructability issues.• Higher level of care as provided for in the Code for Fabricators.• AESS Categories to appear on all Shop and Erection drawings.
  110. 110. New AESS Documents• Available for purchase and download: – CISC Guide for Specifying Architecturally Exposed Structural Steel• Available for download at – Sample Specification – Code of Practice for Fabricators – Matrix
  111. 111. Understanding Steel Design For more detailed information on the various uses of steel in architecture! by Terri Meyer Boake Birkhauser 2011
  112. 112. Terri Meyer Boake Sylvie Boulanger Terri Meyer Boake: Credit for material development and input to Sylvie Boulanger: Thank you!