Roof Load Ash Collapse Risk Checker

Audit independently measured wet ash loads against caller remaining zone capacities and sum physical ash mass; capacities must account for other loads and this is not a collapse forecast or structural/access-safety certificate.

Description

Ash mass produces roof pressure through gravity.

Ash mass produces roof pressure through gravity. Remaining structural capacity must account for loads already present.^[1]

When to use Roof Load Ash Collapse Risk Checker

Use this tool to audit independently measured wet ash loads against caller remaining zone capacities and sum physical ash mass; capacities must account for other loads and this is not a collapse forecast or structural/access-safety certificate.

Gather the relevant observations and fitted model parameters. Use the stated units and time basis; keep paired observations aligned.

How to use Roof Load Ash Collapse Risk Checker and understand its results

Gather the relevant observations and fitted model parameters. Use the stated units and time basis; keep paired observations aligned.
Enter wetAshMassLoadingsKgPerM2, roofZoneAreasM2, callerRemainingUniformCapacitiesPa, gravityMPerSecondSquared using the field table and calculation rules, then run the tool.
Read ashWeightLoadingsPa, callerCapacityMarginsPa, aboveCallerCapacityFlags, totalAshMassKg. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
wetAshMassLoadingsKgPerM2	Wet ash mass loadings kg per m2	list of number	Required
roofZoneAreasM2	Roof zone areas m2	list of number	Required
callerRemainingUniformCapacitiesPa	Caller remaining uniform capacities Pa	list of number	Required
gravityMPerSecondSquared	Gravity m per second squared	number	Required

Align positive zone areas, nonnegative wet loadings and remaining capacities. Report pressure, signed margins, flags only for negative margins, and total mass as the sum of loading times area. Equality does not flag exceedance.^[2]

Paired lists must be nonempty and have equal lengths.

pressure = wet ash kg/m² × gravity; margin = remaining capacity − pressure

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
ashWeightLoadingsPa	Ash weight loadings Pa	list of number
callerCapacityMarginsPa	Caller capacity margins Pa	list of number
aboveCallerCapacityFlags	Above caller capacity flags	list of number
totalAshMassKg	Total ash mass kg	number

json

{
  "input": {
    "wetAshMassLoadingsKgPerM2": [
      10,
      20
    ],
    "roofZoneAreasM2": [
      2,
      3
    ],
    "callerRemainingUniformCapacitiesPa": [
      200,
      100
    ],
    "gravityMPerSecondSquared": 10
  },
  "output": {
    "ashWeightLoadingsPa": [
      100,
      200
    ],
    "callerCapacityMarginsPa": [
      100,
      -100
    ],
    "aboveCallerCapacityFlags": [
      0,
      1
    ],
    "totalAshMassKg": 80
  }
}

Limitations and assumptions

Caller capacities and measured wet loads are required; this arithmetic does not certify roof stability.

Numbers and computed results must be finite; overflow produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Ashfall Load Thickness Conversion: Convert distinct dry ash layers and independently retained water into surface mass/weight load; dry bulk density includes pores, and structural capacity or collapse is not assessed. For a complementary task, use Isomass Loading GM2 Contour Tool: Locate a target isomass contour by log loading versus square-root enclosed area; supplied areas require no coordinates, circular radius is an equivalent proxy, not a mapped boundary.

Further background: Volcanic ash loading on roofs.

References

Volcanic ash loading on roofs — USGS
Roof Load Ash Collapse Risk Checker — tool.io

Similar or alternative tools

Ashfall Load Thickness Conversion
Convert distinct dry ash layers and independently retained water into surface mass/weight load; dry bulk density includes pores, and structural capacity or collapse is not assessed.
Isomass Loading GM2 Contour Tool
Locate a target isomass contour by log loading versus square-root enclosed area; supplied areas require no coordinates, circular radius is an equivalent proxy, not a mapped boundary.