Balfour Beatty VINCI announces appointment of new Managing Director for HS2 joint venture
Balfour Beatty VINCI, a long establis...
Balfour Beatty VINCI has announced the appointment of Mark Cutler as Managing Director for its HS2 Joint Venture.
Balfour Beatty VINCI, a long established joint venture between two global infrastructure leaders recognised for its portfolio of large scale projects, is currently shortlisted for four of the seven HS2 main civils works packages valued at over £4 billion in total.
Mark Cutler, Balfour Beatty VINCI Managing Director HS2, said: “I am delighted to lead the Balfour Beatty VINCI joint venture team for HS2. I believe our long-standing joint venture, an infrastructure powerhouse proven in innovative and collaborative delivery, with over 30 years of international major rail project experience, is a compelling proposition for the delivery of HS2.”
A Chartered Civil Engineer, Mark has extensive experience across the UK infrastructure market spanning a 26-year career. Mark re-joined Balfour Beatty last year as Director of Strategic Projects having previously led the Group’s UK regional construction and civil engineering businesses. Mark was previously CEO of Barhale and Managing Director of Morgan Est following his early career in Carillion, during which time he oversaw major projects on the West Coast upgrade and High Speed 1.
HS2, an iconic rail infrastructure project, will create significant opportunities for the UK construction industry by creating around 25,000 jobs and 2,000 apprenticeships, supply chain partnerships and local enterprises as well as boosting capacity on the existing rail network and improving journey times between London, the West Midlands and further north.
Balfour Beatty VINCI has bid four of the seven packages of main civils works including the Chiltern Tunnels and Colne Valley Viaduct, North Portal Chiltern Tunnels to Brackley, Long Itchington Wood Green tunnel to Delta Junction – Birmingham Spur, and the Delta Junction to West Coast main line tie-in.
Successful contractors for the main civils works will be announced in mid-2017 with mains work construction expected to commence in 2018.
Read the January 2017 issue of Construction Global here
Why engineers must always consider human-induced vibration
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.