May 16, 2020

BAM Launches Cost-reduction Programme after £59.6m Project Losses

BAM
Nico de Vries
uk construction
European Construction
Admin
2 min
BAM Launches Cost-reduction programme after £59.6m project losses
BAM is launching a new annual £80m cost-cutting drive across its business following a series of unexpected losses on projects totalling £59...

BAM is launching a new annual £80m cost-cutting drive across its business following a series of unexpected losses on projects totalling £59.6 million.

The savings are expected to be delivered by the end of 2015 and will derive in part from a streamlining of the structure of the operating companies, with a focus on market segments and value creation.

BAM said this measure would enhance the ability of its businesses to capture synergies and efficiencies, and capitalise on their strengths.

The substantial losses stem from two projects: firstly the deterioration of a large civil engineering project in Germany, one of a handful of loss-making projects reported last year. The problems are due to adverse weather conditions; BAM has implemented technical solutions to keep the project on schedule but they are proving more costly than expected.

The second problem project is a mid-sized UK civil engineering project which was bid for in 2012, due to a combination of adverse ground conditions and bad weather.

BAM said it would maintain its current structure based on two operational sectors – Construction and M&E services and Civil Engineering.

Nico de Vries, Chairman of the Executive Board said: “I am extremely disappointed to have to announce these negative developments. Our underlying strategy is the right one, but our delivery has not been good enough. It is fully clear to the Executive Board that BAM must act urgently and decisively to get all parts of the Group to contribute positively to our results. That is why we are taking the actions being announced today.”

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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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