May 16, 2020

Safra Group buys iconic London skyscraper, the Gherkin

The Gherkin
London Infrastructure
European Construction
S
Admin
2 min
One of Brazil’s wealthiest businessmen is buying London’s Gherkin skyscraper.
One of Brazils wealthiest businessmen is buying Londons Gherkin skyscraper. Joseph Safra – owner of Safra Group - agreed to acquire the iconic bui...

One of Brazil’s wealthiest businessmen is buying London’s Gherkin skyscraper. Joseph Safra – owner of Safra Group - agreed to acquire the iconic building after its previous owners fell behind with mounting debt.

Safra Group is believed to be paying in the region of £726 million ($1.2 billion), according to reports.

Safra is not the only overseas investor with his sights set on the English capital – other companies including Qatar Investment Authority, Brookfield Property Partners LP and Singapore’s GIC Pte Ltd. are pursuing London office space on expectations rents will climb in the next decade.

According to reports, office rent in the City of London financial district, where the Gherkin is located, is projected to climb 5.3 percent a year for the next five years.

Brookfield and Qatar last week approached Songbird Estates Plc, the owner of London’s Canary Wharf financial district, about a possible takeover. The owner of £6.28 billion pounds of real estate rejected the proposed bid as too low.

The Gherkin

The Gherkin has become one of London’s most iconic landmarks since it opened a decade ago and was one of the first skyscrapers in the city to earn a nickname.

According to Bloomberg Billionaires Index, Joseph Safra has an estimated net worth of $12.2 billion. Last month, Safra Group and Brazil’s Cutrale Group agreed to buy banana producer Chiquita Brands International Inc. for about $681 million.

“While only ten years old, this building is already a London icon that is distinguished from others in the market, with excellent value growth potential,” Safra Group said in the statement.

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Jun 17, 2021

Why engineers must always consider human-induced vibration

Vibrations
Engineering
design
Structuralintegrity
Dominic Ellis
3 min
Human-induced vibration can lead to a number of effects upon the structure and its users

Human induced vibration, or more accurately vibrations caused by human footfall, often conjures images of Millennium Bridge-style swaying or collapsing buildings.

But in reality, the ‘damage’ caused by human-induced vibrations is less likely to ruin a structure and more likely to cause discomfort in people. Though not as dramatic as a structural failure, any good engineer wants to make sure the people using their structures, be it bridges or buildings or anything in between, can do so safely and comfortably. This is why human-induced vibration must be considered within the design process.

Resonance v Impulse

There are two ways that human-induced vibrations affect structures: resonant, and impulse or transient response. Put simply, resonance occurs when Object A vibrates at the same natural frequency as Object B.

Object B resonates and begins to vibrate too. Think singing to break a wine glass! Although the person singing isn’t touching the glass, the vibrations of their voice are resonating with the glass’s natural frequency, causing this vibration to get stronger and stronger and eventually, break the glass. In the case of a structure, resonance occurs when the pedestrian’s feet land in time with the vibration.

On the other hand, impulse or transient vibration responses can be a problem on structures where its natural frequencies are too high for resonance to occur, such as where the structure is light or stiff. Here the discomfort is caused by the initial “bounce” of the structure caused by the footstep and is a concern on light or stiff structures.

Engineers must, of course, design to reduce the vibration effects caused by either impulse or resonance.

Potential impacts from human induced vibration

Human induced vibration can lead to a number of effects upon the structure and its users. These include:

  • Interfering with sensitive equipment Depending on the building’s purpose, what it houses can be affected by the vibrations of people using the building. Universities and laboratories, for example, may have sensitive equipment whose accuracy and performance could be damaged by vibrations. Even in ordinary offices the footfall vibration can wobble computer screens, upsetting the workers.
     
  • Swaying bridges One of the most famous examples of human-induced resonance impacting a structure occurred with the Millennium Bridge. As people walked across the bridge, the footsteps caused the bridge to sway, and everybody had to walk in time with the sway because it was difficult not to. Thankfully, this feedback can only occur with horizontal vibrations so building floors are safe from it, but footbridges need careful checking to prevent it.
     
  • Human discomfort According to research, vibrations in buildings and structures can cause depression and even motion sickness in inhabitants. Tall buildings sway in the wind and footsteps can be felt, even subconsciously by the occupants. It has been argued that modern efficient designs featuring thinner floor slabs and wider spacing in column design mean that these new builds are not as effective at dampening vibrations as older buildings are.
     
  • Jeopardising structural integrity The build-up of constant vibrations on a structure can, eventually, lead to structural integrity being compromised. A worse-case scenario would be the complete collapse of the structure and is the reason some bridges insist that marching troops break step before crossing. Crowds jumping in time to music or in response to a goal in a stadium are also dynamic loads that might damage an under-designed structure.

How to avoid it

As mentioned, modern designs that favour thinner slabs and wider column spacing are particularly susceptible to all forms of vibration, human-induced or otherwise, but short spans can also suffer due to their low mass. Using sophisticated structural engineering software is an effective method for engineers to test for and mitigate footfall and other vibrations at the design stage.

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