Short-Term vs 50-Year Strength Worksheet

The crush figure on a crate datasheet is a short-term value. This worksheet walks the reduction chain that turns it into a long-term design strength, then checks it against the load your build-up actually delivers. Enter your supplier’s numbers — not ours.

Short-term strength from the datasheet (kN/m²)

The EN 17150 value, or whatever headline number the supplier prints.

Creep reduction factor (RF_CR)

From the supplier’s own EN 17151 50-year data. If they cannot give you one, you are guessing — and this worksheet will say so.

Installation damage factor (RF_ID)

Handling, backfill and compaction damage during installation.

Durability factor (RF_D)

Chemical and environmental degradation over the design life.

Partial safety factor (γ_M, CIRIA C737)

Applied by your designer, per the design code.

Factored design load at the crate (kN/m²)

From your structural calculation: overburden plus traffic, spread to the tank at your cover depth.

Do you hold the supplier’s EN 17151 report?

Step 1 — Datasheet headline

EN 17150 short-term ultimate strength

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Step 2 — After creep

÷ RF_CR (50-year creep, EN 17151)

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Step 3 — After installation damage & durability

÷ RF_ID ÷ RF_D

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Step 4 — Allowable long-term design strength

÷ γ_M (partial safety factor)

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Enter your figures to compare the allowable strength against your design load.

What this shows, and what it does not

Every factor above divides the headline number. That is why an allowable long-term design strength is routinely a fraction of the crush figure a supplier prints — and why comparing datasheet headlines between suppliers compares nothing useful.

The chain follows the same logic a US government geotechnical manual applies to buried polymers: long-term design strength is the ultimate strength divided by reduction factors for creep, installation damage and durability, before the design code’s own safety factor.

The creep factor is product-specific. It must come from that product’s own EN 17151 test at a 95% confidence lower bound. Independent academic review found very few published compression tests on geocellular units and almost no creep-rupture study, so there is no defensible “typical” value to borrow. If a supplier cannot produce their report, the number in the box above is an assumption someone must sign for.

Ask Storm Manage for the test reports behind our numbers

A teaching worksheet, not a structural calculation. Factor values are entered by you and must come from your supplier’s test data and your designer’s application of CIRIA C737 / CEN TS 17152-4. Storm Manage holds short-term compression data (Intertek 190702149GZU-001: vertical did not fail at 600 kN/m², a sensor-limited run-out; lateral 186 kN/m²) and does not hold an EN 17151 long-term creep report.