Understanding tests and engineering of a metal roof systems


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Drexel Metals has announced receiving approval for its third AIA CES accredited course - Course # 731 - Understanding Metal Roofing Engineering and Test Requirements. The new seminar focuses on metal roofing design and engineering and was written by Drexel Metals’ technical and engineering team.

The seminar takes an in-depth look at the laundry list of testing requirements a metal roof manufacturer must go through in order to ensure products perform in their intended environment and application. The architect will learn each test definition, specific test agency and their required tests, how these tests are relative to the building code and how to differentiate between what's marketing and what is real world fact.

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Understanding tests and engineering of a metal roof systems

  1. 1. Understanding Metal Roofing Engineering and Testing
  2. 2. Who are they? • UL – Underwriters Laboratories • ASTM – American Society for Testing and Materials • FM – Factory Mutual
  3. 3. United Laboratories • UL certifies, validates, tests, inspects, audits, and advises a wide variety of products to ensure that the products used either directly or indirectly by the general public is safe as specified by various guidelines. • Drexel Metal Inc products fall under the category of Roof Deck Construction (TGKX) in accordance with UL.
  4. 4. ASTM • Now known as ASTM International, is similar to UL in that it is used around the world to improve quality and enhance safety of products.
  5. 5. Factory Mutual Global • FM Global provides comprehensive global commercial and industrial property insurance, engineering-driven underwriting and risk management solutions, groundbreaking property loss prevention research and prompt, professional claims handling.
  6. 6. Wind Up - Lift Test
  7. 7. UL580 What is it? • UL 580 (a.k.a. uplift test) is a test that applies both positive (pressure) and negative (suction) loads on the roof deck assembly. These loads are both static and oscillating for a specific time. • It not only tests the panel but it test the roof deck (solid) assembly the panels are attached to. Including ALL the components!! • Real world application would be the wind uplift loads acting on the roof system. • Evaluates multiple layers. What’s it look like?
  8. 8. UL 90 What is it? • The Class 90 (UL 90) is the rating given to an roof deck assembly test in accordance to UL 580. • This means that the roof deck assembly has achieved a Nominal (Average) Static uplift pressure of 66 - 90 psf for a duration of 60 minutes, but it must also sustain a combined pressure of -105 psf for 1 minute at the end of 60 minute cycling.
  9. 9. UL1897 What is it? • The UL 1897 test is an extension to the UL 580 test. • The purpose of this test is to provide uplift resistance data regarding the securement of the roofing system to the roof deck. • The biggest difference between the two test is that UL 580 is oscillating & static and UL 1897 is static only.
  10. 10. TAS 125 What is it? • TAS 125 is a combined test of the UL 580 and 1987 Wind Uplift, which requires three (3) tests, (2) field tests and (1) corner test. • This test represents an ultimate uplift pressure for a sustained time of 1 minute without failure, per UL 1897. • This gives Drexel the allowable design uplift pressure for the panel installed over a particular assembly.
  11. 11. ASTM E-1592 What is it? • This test method (a.k.a “Bag Test”) is an evaluation of the structural performance of sheet metal panels under static air pressure applied to the underside of the roof or wall assembly. • ASTM 1592 is tested over open framing. • Focuses on single layer construction. • Real world application would be uplift pressures acting roof panel due to wind. What’s it look like?
  12. 12. Similarities and Differences of UL 580 & ASTM 1592 Similar • Both evaluate the roof under wind up-lift conditions. • Both evaluate the roof panel configuration as well as the accessories. • Both measure the deflection of the panel, which would be a factor in serviceability and design. • Both are timed. Different • UL test can be tested over a solid roof deck assembly i.e., OSB, plywood, metal deck, etc. • ASTM test is tested over open framing. • ASTM is static • UL is cyclical and static • ASTM requires the panel to return to the original shape.
  13. 13. Air and Water
  14. 14. TAS 100 What is it? • TAS 100 is a Wind Driven Rain test. • Test the resistance of water infiltration of a discontinued roof system including perimeter flashing details. • Applicable to slopes of 2 on 12 or greater. • Tested over plywood substrate. • Real world application would be how wind driven rain acts on a roof assembly. What it look like?
  15. 15. Air Infiltration - ASTM E 1680 What is it? • This test method is a procedure to determine air leakage under specific air pressure differences. • This test method is exclusively for metal roof panel systems conducted over open framing. • This test is performed with and without seam sealant in the female leg of the panel. What’s it look like?
  16. 16. Water Infiltration - ASTM E1646 What is it? • This test method is a standard procedure for determining the resistance to water penetration under uniform pressure on the sidelaps (field area) of the panels only. • This test method is exclusively for metal roof panel systems conducted over open framing. • Uses the same test bed as ASTM E 1680. • Real world application would be how wind driven rain acts on a roof assembly.
  17. 17. Air Infiltration - ASTM E283 • This test method is a standard procedure for determining the air leakage characteristics under specified air pressures. • This test method is for exterior windows, curtain walls and doors. • This test is ran in conjunction with ASTM E 331. • Real world application would be how wind would act on a wall assembly.
  18. 18. Water Resistance – ASTM E331 What is it? • This test method is a standard procedure for determining resistance to water penetration under uniform static air pressure. The exterior pressure is higher than the interior pressure. • This test method is for exterior windows, curtain walls, skylights, and doors. • This test is ran in conjunction with ASTM E 283. • Real world application would be how wind would act on a wall assembly.
  19. 19. ASTM – E 2140 What is it? • • • This test method is a standard procedure for determining water leakage through metal roof panel system sideseams, endlaps, and roof plane penetrations when the roof system is subjected to a specified static water pressure head. A.k.a “Hydrostatic Water” test. Real world application would be in regions where drifting snow exists on a roof would melt due to thermal transfer from attic and metal roof causing standing water between the roof panel and snow drift. What’s it look like?
  20. 20. Debris and Hail
  21. 21. ASTM 1886-03 What is it? • • • This test method was designed to test the performance of windows, curtain walls, and doors once their integrity has been compromised by wind blown debris. Also known as the “Missile Test”, are similar to E 330; however, 1886 test the impact of windborne debris. Real world application would be how debris from a structure’s surrounding affects the performance of a building during a windstorm. Basically once the building envelope becomes compromised the structure is no longer considered a closed structure. For design purposes the design pressure could potentially be increased by 30%.
  22. 22. ASTM E330 What is it? • This test method test the structural performance of windows, doors, skylights, and curtain walls under static air pressure. • This would be comparable to the ASTM E 1592 except it is for walls specifically. • Real world application would be how wind load acts on a wall system.
  23. 23. Hail Impact UL 2218 What is it? • This test method test the resistance of an entire roof covering to the impact of a steel ball, which is a simulation of a hail stone.
  24. 24. Fire Resistance
  25. 25. UL 263 – Fire Resistance What is it? • The scope of this test method is to determine the ability of composite materials of an assembly to retain it’s structural integrity and/or resistance to heat during a period of time exposed to interior heat or flame. • This test is not to be confused with fire ratings Class A, B, or C. The National Fire Protection Association NFPA is responsible for assigning the classifications of ratings. • The rating that UL provides is given in a time frame ½ hour, 1 hour, etc.
  26. 26. UL 790 What is it? • The scope of this test method is to test the resistance performance of an exterior roof covering material from a fire outside a building. • This test provides the roofing covering with either a Class A, B, or C rating. • The substructure can be either combustible or non combustible material. • This test is similar to ASTM E-108.
  27. 27. Concentrated Loads
  28. 28. FM 4471 – Foot Traffic What is it? • Is a test to check the ability of a panel roof assembly to resist foot traffic. There shall be no puncture of the panel roof and no separation or disengagement of the or end laps. • The purpose of this test is to evaluate the structural performance of the metal panel when a concentrated load is placed on the panel at mid span. • The only panel that we have in our inventory that has undergone this test is our DMC 200 X 16” X 24 ga. • Test is conducted over open framing.
  29. 29. Anatomy of a Florida Product Approval • Product Approval Program Oversight Committee is a group of individuals who oversee that the products (see below) used for construction has undergone testing from a independent testing lap approved by the State of Florida. • The products: Panel walls, exterior doors, roofing products, skylights, windows, shutters, structural components, and new and innovative building envelope products. • The products listed above must undergo a standardized test, or comparative or rational analysis based on the Florida Building Code as a guideline, which is a derived from the International Building Code. • Not to be confused with Miami Dade Notice of Acceptance. • http://www.floridabuilding.org/fbc/committees/product_approval/ product_approval_powerpoint_031604.pdf
  30. 30. Anatomy of a Dade County Approval? • Miami-Dade County Approval is a derivative of Florida Product Approval, that is adapted for high velocity hurricane zone (HVHZ). • Similar to Florida Product Approval it is governed by a oversight committee, which ensures that the products submitted for approval have undergone testing, or evaluative analysis under the guidelines specific to Miami – Dade County . • Section 8-40 PRODUCT APPROVALS. Any person desiring to use – materials/products used for protection of the envelope of the structure, limited to windows, exterior glazing, wall cladding, roofing, exterior doors, skylights, glass block, siding and shutters shall obtain a high wind velocity zone approval from the Florida Building Commission or shall obtain a local approval from the Building Code Compliance Office.
  31. 31. Anatomy of a TDI approval • Texas Department of Insurance (TDI) is a regulator of all Texas-based insurance companies and ensures that Texas consumers have access to competitive and fair insurance products.
  32. 32. Engineering
  33. 33. Codes • Two of the major entities that play a major part in providing guidelines for design loads on various structures are the International Building Code (IBC) and American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and Other Structures. • All fifty states have adopted or adapted their own state code, based on the design methods that these two organizations have developed.
  34. 34. Wind speed versus design pressure? • Wind speed along with a number of other variables are converted into a Velocity Pressure. • These other variables relative to the design pressure include: Exposure Factor, Importance Factor, Topographic Factor, roof slope, roof design, mean roof height. • Important to understand that knowing these factors will provide the best possible roof system to withstand the theoretical design pressures acting on the roof and wall system. • It is also OUR responsibility!!!!!
  35. 35. Positive Loading v. Negative Loading • Positive Load – forces acting toward the roof or wall system (snow load, wind load, dead, and live loads). • Negative – forces acting away from the roof or wall system (wind up-lift loads). • Deflection – is the deformation of the roof or wall panel over a specific linear dimension l/180 is the standard deflection limit applicable to metal roof panels.
  36. 36. Failure Team 4: Steep Slope Hurricane Charley Clip Spacing • Failure of a roof can come from irregular spacing of clips either in the field of the roof or in the edge and corner zones. 4-29-6. Older wood roof that lost shingles in the field and at hip sections. 4-31-3. Standing-seam panels lifted from irregularly placed clip attachment.
  37. 37. Failure otte County EMS station. Pre6-11-2. Charlotte County EMS station. View rance. Design for Edge and Corner Zone of failed center roof and corner damage (arrows). • It is important to understand that when designing for wind loads on, any roof system, that there are specific areas to be considered when attaching the metal roof panel to the substructure. otte County EMS station. Roof truss or straps failed in tension. 6-11-4. Charlotte County EMS station. Standing seams failed at all four corners.
  38. 38. Sample Given • Roof Type = Gable • Slope = 6 on 12 • Eave Ht. = 20’ • Exposure Factor = “C” (default) • Wind Speed = 120 mph • Risk Category = III Wind Speed Map
  39. 39. Sample Design Pressure • Using the variables from the previous slide the design pressure would be the following for each of the zones illustrated on the right. • Zone 1 = -35.1 psf • Zone 2 = -61.1 psf • Zone 3 = -90.3 psf