May 16, 2020

British Safety Council supports Healthy Workplaces for All Ages campaign

workforce
construction
industry
Business
Admin
2 min
British Safety Council supports Healthy Workplaces for All Ages campaign
The European workforce is ageing fast, and it's affecting the construction industry. By 2030, employees aged over 55 are expected to make up 30 perc...

The European workforce is ageing fast, and it's affecting the construction industry. By 2030, employees aged over 55 are expected to make up 30 percent or more of the total workforce in a lot of EU countries. In the UK, 30 percent or more of the total workforce is already over 50, while 60+ employees constitute 23 percent. This figure is set to rise to 30.7 percent by 2020.

This demographic trend creates significant challenges and opportunities for both employers and their workforces. Thus, the European Agency for Safety and Health at Work (EU-OSHA) has launched the Healthy Workplaces for All Ages campaign this month. It is set to alert European employers to the urgency of the situation and the need to respond in a positive way.

The aims of the 2016-2017 Healthy Workplaces for All Ages campaign are:

  • promotion of sustainable work and healthy ageing and the importance of risk prevention throughout working life;

  • assisting employers and workers of all ages by providing information and tools for managing occupational safety and health (OSH) in the context of an ageing workforce, and

  • facilitation of information and good practice exchange in this area.

Mike Robinson, Chief Executive of the British Safety Council, said: “The official retirement age in EU Member States is increasing. In the next two decades, a large proportion of employees over 50 will leave work for ever, taking their market expertise, professional experience and skills with them. Meanwhile the demographic data suggests that there is unlikely to be a sufficient supply of younger people in Britain who would replace retiring workers. These facts cannot be ignored by any employer.

“Retaining older workers will become not only an economic but also a social imperative. The companies that would be prepared to retain older employees will remain more competitive and diverse, with a greater pool of skills and talent. However, longer working lives would mean greater exposure to a variety of health-related risks. The management of issues such as disability prevention, rehabilitation and return to work will increase in importance. Older workers are also more vulnerable to certain hazards, particularly in an industrial work environment. Therefore, the introduction of specific measures to ensure work safety and the efficiency of older employees, as well as age-sensitive risk assessments, would have to become a key part of occupational health and safety policies.”

 

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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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