A mast section was being lowered behind a building. In free air, the wind conditions were manageable. But London’s built-up streets and the wind blowing around the capital’s high-rise tower blocks meant the crane’s load was caught up in unexpected airflow. It ended up crashing into a nearby building, causing huge damage.
“That local built environment, it set up an unpredictable reaction in the load,” says Craig Hook, head of lifting solutions at Sir Robert McAlpine. The incident is an example of an issue crane engineers are having to think about much more carefully: wind is not one load, coming from one direction at one speed. When wrapped around tall buildings, it can accelerate, funnel, reverse and form vortices.
These kinds of incidents are exacerbated by our changing climate. The UN’s Intergovernmental Panel on Climate Change says the global proportion of category three to five tropical cyclones has likely increased, while the average peak wind speeds of tropical cyclones are projected to rise as the world warms. Yet the picture is not as simple as everywhere becoming steadily windier; evidence for past changes in the maximum winds of extratropical cyclones, which are more likely to affect Britain, is yet to be fully found.
But for a subsection of crane engineers who rely on absolutes to plan out and keep safe their practices, any uncertainty is itself a design problem.
Revised approach
Hook sits on the European standards committee responsible for EN 14439, the tower cranes safety standard. A series of incidents across Europe in the early and mid-2010s showed cranes could be damaged by winds – and by different load cases – that had not been adequately allowed for, he says. The result was a revised standard, BS EN 14439:2025 in the UK, which replaced the previous 2006 standard last year.
The revised approach includes five load cases intended to give a more realistic picture of what a crane can experience, says Hook. And as a consequence, the physical capabilities of cranes may well have to change.
“A crane that used to stand to a certain height now will have to be reduced slightly for its freestanding height, or they will need to have slightly stronger mast sections,” he says. The maximum loads available within the foundation are also increasing, requiring changes in the ground engineering at the crane’s base.
That poses a challenge for those in the sector – can they rework the existing fleet, much of which may no longer be up to spec? While new cranes can be designed from first principles to meet the newer requirements, existing ones can’t and might be out of spec but still used.
To respond to this, manufacturers are producing retrospective load information so older cranes can be assessed to an equivalent safety level, rather than allowing the safer standard to become a commercial disadvantage for companies buying newer equipment.
Another route that can help avert potential disaster is to try to foresee where things can go wrong and take action before they do.
Computational fluid dynamics (CFD) is being used by engineers to model airflow around both buildings and cranes, and to account for the shielding and acceleration caused by nearby structures.
Winds of change
In laboratories, researchers have already combined wind fields they have modelled from CFD with crane models to calculate the impact of wind loads and vibration. And Sir Robert McAlpine is doing something similar with tech initially invented to analyse the aerodynamics of motor racing vehicles to model how air moves around their sites.
Any construction engineer worth their salt knows that site-specific wind calculations are already used to account for the quirks of local terrain and nearby tall structures. But what’s needed, Hook reckons, is to make that thinking part of crane planning from the outset, rather than post hoc.
How to deal with cranes when a site is not active also needs to change, reckons Hook. Repeated gusts of wind when workers are off site can push a crane into what Hook calls “autorotation”, spinning the crane again and again. “The power cable will just start to wind up like an elastic band under constant rotation and then it will sever the power cable,” he says.
Simple solutions
Two comparatively simple solutions to that are slip rings that allow electrical connections across rotating sections, or braking systems able to slow a crane from entering autorotation in the first place.
“It’s not just about the design of the crane,” Hook says. “It’s about the management of the activities on site.”
IMechE Crane Safety 2026 takes place on 11 November at The Lowry Hotel in Manchester. Now in its 10th year, the conference will cover new safety technologies, regulation and standards, and inspection tools including drones and sensors. The event is co-located with Nuclear Lifting 2026. Find out more and book.
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