Nick Carne
US engineers are taking a novel approach to storm surge readiness, attempting to incorporate both aesthetics and adaptability.
A team from Princeton University has created the preliminary design for what it calls dual-purpose kinetic umbrellas.
Made from concrete and certainly a little oversized, they’d provide shelter from the sun on a nice day but could be tilted in advance of a storm to form a flood barrier. They’d be more attractive and less restrictive than permanent seawalls.
“It’s the first time that anyone has really tried to integrate architecture as an inherent component to a coastal countermeasure,” says Shengzhe Wang, lead author of a paper in the Journal of Structural Engineering.
Nevertheless, engineering is at the heart of the project.
The proposed umbrellas are shells of reinforced concrete about 10 centimetres thick, built in the shape of a hyperbolic paraboloid (hypar) – a saddle-like structure that curves inward along one axis and outward along the other.
According to co-author Maria Garlock, the structure takes inspiration from the work of the Spanish-born architect Félix Candela, who designed hundreds of buildings with thin-shelled hypar roofs in Mexico in the 1950s and 1960s.
Garlock is a Candela fan and had received funding (appropriately from a source that supports the pursuit of unconventional ideas) to study the potential of hypar umbrellas as smart structures to capture energy and rainwater.
Then she came up with the idea of adding sensors that could make the conversion to a seawall, and Wang took on the task of working out whether that would work.
With colleagues he used simulations to test parameters and functionality, then modelled a storm surge using data about hurricanes along the US East Coast between 1899 and 2012.
This showed, they say, that the umbrellas would remain stable when faced with a wall of water about 75% of their deployed height.
They have now built 15-centimetre models of the umbrellas and are testing their response to the dynamic forces of turbulent flows inside a three-metre water channel. Wind forces characteristics of landfalling hurricanes are created via wind tunnel testing.
“In reality, you’re not going to just have a pile of static water,” Wang says. “You’re going to have waves; you’re going to have wind that generates those waves.”
It’s a work in progress and, he adds, a complex task. Most previous studies have evaluated the ability of vertical walls or slanted barriers to withstand storms, but the hypar’s complex geometry requires “a whole new set of rules that govern how the structure will perform”.
Of course, getting it to work may be easier than getting councils to approve it.