May 16, 2020

Bilfinger secures a €1.2 billion deal with Swedish equity firm EQT

Bilfinger
EQT
Mergers and acquisitions
Pinder Singh Hujan
Admin
2 min
Bilfinger secures a €1.2 billion deal with Swedish equity firm EQT
Engineering Group Bilfinger has procured a deal with Swedish equity firm EQT in the selling of their building and faculty section for €1.2 billion...

Engineering Group Bilfinger has procured a deal with Swedish equity firm EQT in the selling of their building and faculty section for €1.2 billion. Bilfinger will be entitled to 49 percent of any re-sale from EQT in the near future. The deal will increase opportunities for future business developments and bolster technological advances.

Pinder Singh Hujan, Executive Chairman of Bilfinger Europa, told FM-World: “With this new investment buy-out confirmed, this opens the opportunity for the building, facility and real estate division to pioneer new developments across the businesses. This is an exciting opportunity for Bilfinger Europa and our subsidiary companies and we look forward to driving this new chapter.”

EQT invests in companies whilst providing a strategy geared towards growth and development, with over €16 billion having been invested in over 140 companies, with revenue of approximately €15 billion. EQT has offices in 15 countries and 100,000 employees within EQT portfolio companies.

Bilfinger’s Chief Financial Officer Axel Salzmann added: “The sale of the segment generates the greatest value for Bilfinger and opens up new perspectives. With additional liquidity, we will expand our position as market leader for industrial services in the process industry through targeted acquisitions and investments in the future. In this regard, we are focusing on our technology and service competences, which are greatly appreciated by our customers.”

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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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