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Tier 6 · Architectural Specification and Engineering

ASCE 7 wind load fundamentals

How a wind speed becomes a design pressure on roof-edge metal, which ASCE 7 edition sits behind which code, a worked zone-pressure example, and how ES-1 test ratings, field failures and the engineer of record fit together.

4 lessons · about 47 min · 13 diagrams · 0 videos

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  1. Lesson 1 · 12 min · 12 slides · 9 questions

    ASCE 7 wind load fundamentals: principles and terminology

    Why the roof edge is where wind loads concentrate, what ASCE 7 is and how the building code brings it in, the chain from wind speed to zone pressure, and who does what.

    You will be able to: Describe how a wind speed becomes a design pressure on edge metal, name the factors and categories that shape it, and say who decides each input.

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  2. Lesson 2 · 12 min · 11 slides · 10 questions

    ASCE 7 wind load fundamentals: materials, standards and design constraints

    Which ASCE 7 edition sits behind which code, what changed in ASCE 7-22, Kz and the roof zone coefficients, strength level versus allowable stress, the ES-1 test methods, and where published sources disagree.

    You will be able to: Match ASCE 7 editions to building codes, read the zone coefficients and enclosure and unit conventions, and place ES-1 test methods and the safety-factor disagreement.

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  3. Lesson 3 · 12 min · 11 slides · 10 questions

    ASCE 7 wind load fundamentals: methods and worked application

    A worked example from a trade seminar: velocity pressure, four roof zones, the zone width, conversion to allowable stress, a trap in the source, the square law, and a comparison that depends on the safety-factor convention.

    You will be able to: Build a zone pressure by hand from written-down inputs, convert between strength level and allowable stress, compare it with a published rating, and document every assumption.

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  4. Lesson 4 · 11 min · 11 slides · 9 questions

    ASCE 7 wind load fundamentals: defects, verification and case study

    Why roof perimeters fail first, what three hurricanes and an insurer study showed, common specification and installation defects, why an ES-1 rating covers only the assembly as tested, and a verification chain with its safety limits.

    You will be able to: Recognise how edge-metal wind failures start, read what field evidence shows, and follow a verification chain from the specification to the roof without claiming a rating that was not tested.

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Practical task

Build a wind-pressure job packet for the SPRI worked example (Chicago, Exposure C, 40 ft, enclosed, 119 mph), then repeat the method on a second, hypothetical set of inputs of your own, labelled as hypothetical. Show every step, write the level beside every pressure, and finish by stating what you are not deciding.

Hand in

  • A decision rationale: which ASCE 7 edition and building code you are working to, where the wind speed came from, and who decides each input
  • A marked-up roof sketch showing the perimeter and corner zones, the zone width a and where edge metal sits
  • An assumptions table with units: V and its source, risk category, exposure, mean roof height, Kz (table or formula), Kzt, Kd, Ke, enclosure class and the safety-factor convention
  • The calculation: q, the four zone pressures at strength level and at allowable-stress level, each tagged with its level
  • A quality checklist following the five verification stations, and a short defect analysis of one specification that says only "wind rated"

Rubric

CriterionMeets the standard when
Inputs recordedEvery input is on the page with units and a source, and the ASCE 7 edition is named.
Calculationq and the four zone pressures reproduce the worked example, with a level (strength or ASD) beside every pressure.
Zone widthThe zone width a is worked out from the rule as presented, and the rule is marked for checking in ASCE 7.
ComparisonAny comparison with a published rating shows more than one safety-factor convention and says the engineer of record decides.
Defect analysisThe defect names what the specification omits, such as the wind speed, the edition, the zone pressures or the tested assembly.
BoundariesThe packet states that it is not a design, sizes no edge, sets no fastener spacing and gives no wind speed for a real address.

Module quiz

10 questions drawn from a bank of 38; a new set each attempt. Pass mark 85%.

1. In SPRI's summary, which exposure category is flat terrain close to a large body of water?
2. In which hurricane did peeling edge flashing precede membrane blow-off at the Pensacola Naval Hospital?
3. How many roof zones does ASCE 7-22 use on gable and hip roofs, according to STRUCTURE magazine?
4. In the worked example, what is the velocity pressure at strength level?
5. In the chain from wind to a rating, which side produces a capacity rather than a demand?
6. What share of damaged roofs in post-hurricane studies were caused by perimeter failure, as IIBEC reports?
7. Which flat-roof coefficient does SPRI's deck give Zone 3 at 10 sq ft?
8. To get an ASD cladding pressure from an ASCE 7-16 result, what is the result multiplied by?
9. What value does the wind directionality factor Kd take for buildings?
10. If the wind speed used is ten percent too high, about how much too high is the pressure?