What wind load must the shelter actually resist — and who decides the number?

The buyer decides the number, not the supplier. A shelter must resist the peak wind pressure at your specific site: wind speed squared, converted through dynamic pressure (q = ½ρv²). A 40 m/s gust produces roughly 1.0 kPa of dynamic pressure; after gust, height, and shape factors, the resulting design pressure on a shelter structure typically falls between 0.8 and 2.5 kPa — and rises materially in typhoon and cyclone belts (indicative global ranges; confirm against your local code).

This distinction has a direct procurement consequence. If the tender does not state the design basis, each bidder assumes its own — and the cheapest bid is usually the one that assumed the calmest site. The governing frameworks are:

• EN 1991-1-4 (Eurocode 1, Wind Actions) — used across Europe, much of Asia, the Middle East and Africa. The buyer states the basic wind speed v_b from the National Annex, the terrain category, and the return period (50 years for permanent structures is standard practice).

• ASCE 7 (ASCE/SEI 7-22) — used in the United States and US territories such as Guam, and as a reference in much of the Caribbean and Pacific. Basic wind speeds are 3-second gusts, running from roughly 47 m/s (105 mph) inland to about 67 m/s (150 mph) on hurricane-exposed coastlines, with a Risk Category assigned by the owner (indicative — confirm the governing edition and local amendments).

Write the following sentence into every shelter tender: "The structural design shall resist the wind actions for [basic wind speed / Risk Category] at the site, calculated to [EN 1991-1-4 / ASCE 7-22] with the applicable National Annex, and shall be demonstrated by a calculation report signed by a licensed structural engineer." Without it, you have no contractual basis to reject a structure that folds at 90 km/h.

What must be fixed before you go to tender?

Eight site and loading decisions must be locked before bids are invited, because every one of them changes the structural design and therefore the price. Fixing them also prevents the classic post-award dispute where the supplier claims the foundations "were not in the original scope".

Items 1–3 are pure buyer inputs — no supplier can decide them for you. Items 4–7 come from your own reference design or the supplier's proposal, but must be frozen at the drawing pre-approval stage before fabrication starts.

Which documents prove the structure will stand?

Four document groups prove wind-load compliance. Treat the first two as pass/fail gates — a bid without them is not a bid — and score the rest.

Ask for the calculation report before contract award, not with the delivery dossier. A supplier who resists releasing calculations pre-award is telling you the calculations do not yet exist — which means fabrication would start from a catalogue guess and your project would be paying to discover the answer on site.

How should you score suppliers on wind-load compliance?

Score wind-load capability out of 100 inside your technical evaluation, with 70 as the pass gate. Weighting evidence of engineering process over marketing claims is what separates a fabricator from an engineer.

YEROO's own project history is weighted exactly this way by buyers in exposed regions: the wind-resistant Guam shelter programme was specified against Pacific cyclone loading, and the wind-protected stainless steel shelter with P4 LED advertising in Iceland combined North Atlantic gale exposure with a large digital sign face — the combination that produces the highest structural demand. Ask every shortlisted supplier for two references of the same character, not just the same product.

What acceptance checks go into the delivery record?

Acceptance is where wind-load compliance becomes enforceable. Write these four checks into the delivery and acceptance section of the contract, and hold retention against them:

1. Document check against the approved drawings. Member sections, bolt grades and anchor types on site must match the calculation report — photograph and file every plate stamp.

1. Anchor pull tests on post-installed anchors to BS 8539 practice: test a sample (typically 5–10% of anchors, indicative) to 1.5× design load. Failures here are cheap to fix on day one and catastrophic to discover in a storm.

1. Torque and grout verification on base plates, recorded on the sign-off sheet per unit.

1. Deflection spot-check on the first installed unit of each model, measured against the tender's stated limit (e.g. L/150 at canopy tip).

Conditional rules that map your project situation to the required tender clauses:

• If the site lies within 500 m of open coastline and inside a typhoon/cyclone belt → then require design pressure demonstration for cyclonic loading, cyclic-fatigue-rated connections, and anchorage sized for uplift — standard inland spec is not acceptable (indicative rule; confirm locally).

• If canopy cantilever exceeds 6 m or the shelter is fully enclosed (AC shelter, enclosed hub) → then require independent third-party structural review as a payment condition.

• If the supplier did not produce the calculation report before award → then withhold the progress payment tied to fabrication start until the report is approved at the drawing pre-approval stage.

• If foundations land on an existing slab of unknown strength → then require core testing and post-installed anchors with an ETA, designed to EN 1992-4 and installed per BS 8539.

• If a digital screen or large sign face is mounted on the shelter → then require the calculation to include the sign drag area explicitly — sign faces are frequently "forgotten" in catalogue structures.

• If the funder is a development bank or public authority → then require calculations, weld records and as-built drawings in English, signed, as a condition of final payment — the same evidence discipline used across YEROO's internationally funded deliveries.

What does getting wind load wrong cost?

Wind-load failures are rarely gradual. The structure stands for three years, then one storm rewrites the budget.

Every row above is preventable with the four-document evidence set and the four acceptance checks — which cost a fraction of one storm season.

FAQ

What wind speed should a bus shelter be designed for?Design for the basic wind speed at your site, taken from the governing map — EN 1991-1-4 National Annexes in Eurocode countries, or the ASCE 7 map in US-influenced jurisdictions. Converted to design pressure, most shelter sites fall between 0.8 and 2.5 kPa, with cyclone-belt coastal sites higher. The buyer states the number in the tender; the supplier demonstrates it.

Do bus shelters need structural calculations, or is a catalogue spec enough?A catalogue spec is only valid if the catalogue was calculated for your wind zone. For any public procurement, require a site-specific calculation report signed by a licensed engineer, covering the frame, connections and foundations. Catalogue data can support the bid, but it cannot replace the signed site-specific calculation.

What is the difference between EN 1991-1-4 and ASCE 7 for shelter projects?EN 1991-1-4 uses mean wind speeds with National Annex adjustments and is standard across Europe, much of Asia, Africa and the Middle East; ASCE 7 uses 3-second gust speeds and a Risk Category system, governing the US and its territories. They are different frameworks, not interchangeable numbers — state which one governs, and never let a bid mix them.

How is wind-load compliance actually tested on a shelter?Through documents and site tests rather than a full-scale wind tunnel in most projects: a signed calculation report for the design, EN 1090-2 execution and weld records for fabrication, and anchor pull tests plus a deflection spot-check on site for installation. Wind-tunnel or type-test evidence is added for unusual geometry such as large cantilevers or enclosed structures.

Who is liable if a bus shelter fails in a storm?Liability follows the design responsibility written into the contract. If the tender assigned full structural design to the supplier and you hold its signed calculations, execution records and acceptance tests, liability sits with the supplier and its insurer. If the tender was silent on design responsibility, the dispute lands on the buyer — which is why that single clause must never be left open.

What wind-load spec do coastal and typhoon-region projects need?Specify design for cyclonic loading explicitly: higher design pressure, uplift-resistant anchorage, fatigue-rated connections, and debris impact consideration for glazing. Reference projects in comparable climates — such as YEROO's Guam storm-resilient shelter programme — are the most reliable evidence a supplier can genuinely build for cyclone belts.

Conclusion: get the number in the tender, then make the supplier prove it

Wind-load procurement succeeds or fails in two documents: the tender clause that states the design basis, and the calculation report that proves compliance before award. Fix the eight pre-tender inputs, gate the bids on the four evidence documents, score with the 100-point matrix, and hold retention against the four acceptance checks. Do that, and the storm you cannot control becomes a cost you already paid to prevent.

YEROO has delivered wind-resistant and cyclone-exposed shelter programmes from Guam to Iceland, and provides tender-ready structural documentation — calculation reports, EN 1090-2 execution records and itemised anchor schedules — with every quotation. [YEROO DATA NEEDED: standard structural documentation set included per quotation]. Send your site wind speed and reference design through the YEROO contact page and request a wind-load-specific quotation with the full structural evidence pack, or browse the YEROO bus shelter range for the base models behind these programmes. For the wider document set that surrounds this topic, see the bus shelter specifications checklist for procurement officers and the factory verification buyer's checklist.