May 16, 2020

Carillion and Balfour Beatty in Surprise Merger Talks

Balfour Beatty
Mergers and acquisitions
UK cons
2 min
The companies previously worked together on the East London Line Extension project
Carillionis in talks withBalfour Beatty over a merger that could create a £3bn-plus construction company to rival some of the worlds largest infra...

Carillion is in talks with Balfour Beatty over a merger that could create a £3bn-plus construction company to rival some of the world’s largest infrastructure players.

The two companies have a deadline of 5pm, 21 August, to announce either a firm intention to merge or state that the deal will not go ahead.

With Balfour Beatty currently lacking a Chief Executive after a troubled 18 months that saw Andrew McNaughton leave the company following a series of profit warnings, Carillion CEO Richard Howson is likely to take the job at the joint business if a deal is concluded successfully. However, the companies said no structure decisions have been made at this time.

Carillion, one of Britain’s leading support services companies, has enjoyed a far more positive year and a half, growing from £1.3bn to £1.5bn on the back of lucrative contract wins at home and in the Middle East. Balfour’s value, by contrast, fell from £2bn to £1.6bn in the same period.

In a joint statement, the two companies’ board’s said: “The Boards of Carillion and Balfour Beatty can confirm that, following an approach from Carillion to Balfour Beatty, they are engaged in preliminary discussions in relation to a possible merger of Carillion and Balfour Beatty.

“(We) believe that the merger of the two groups has the potential to create a market leading services, investments, and construction business of considerable depth and scale.”
Both companies added that they must be satisfied that a merger create “significant value creation for the benefit of both sets of shareholders.”

Balfour said the sale process for its US-based consulting and engineering group, Parsons Brinckerhoff, would continue regardless of Carillion talks. Several private equity firms and trade buyers are said to be interested in buying the company.

Balfour Beatty is currently in the midst of an 18-month programme to turn around its construction business.

Shares in Balfour Beatty climbed 10 percent, (24p), to 256p while Carillion’s rose 12 percent to 380.4p on Friday morning. The combined value of the firms rose to about £3.4billion. 

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Jun 17, 2021

Why engineers must always consider human-induced vibration

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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