Feature Working at height

HIGH RISK STRATEGY

When working at extreme height, weather conditions can be more severe than on the ground. Stephen Cousins reports on how new Met Office technology is helping contractors including the JV building the new Forth crossing

Above: Construction of city skyscrapers, such as London’s 230m

Heron Tower, can face disruption through

weather-related issues

LONDON IS ON THE BRINK of what has been referred to as a “tsunami of towers”, with an updated survey commissioned by New London Architecture discovering that there are 263 buildings over 20 storeys either in construction, with planning permission or awaiting decisions. Among these are 25 at 50 storeys or above. But building higher means entering a

realm of more extreme and hard to predict meteorological conditions, which threaten

to disrupt construction work, add to cost and programme, and potentially put workers’ lives in danger. The trend for building tall also puts extra demands on rope access workers, highly trained specialists who can take their skills to other sectors (see interview, page 40: “Oil and gas is really, really safe, and that’s why I moved”). The term skyscraper is commonly applied to buildings above 150m, and any

construction professional who’s worked on one will know that wind is the most obvious weather factor to consider above 100m. Although a range of factors are likely to affect the speed of wind, as a rule of thumb, meteorologists estimate that at a height of 100m on an average day, sustained wind speed is about one and a third times its speed at a ground level of up to 10m. And at 200m, it rises to roughly double that on the ground.

> CONSTRUCTION MANAGER | APRIL 2015 | 35

IMAGE: AMBERNECTAR