May 16, 2020

Arup has already hit several milestones this month

Arup
Toronto-York Spadina subway extension
One Central Park Australia
Garden Bridge London
Catherine Sturman
2 min
Arup has already hit several milestones this month
Arup is one of the biggest players within the construction, design and engineering world, with over a thousand workers in the US alone. Famous for its p...

Arup is one of the biggest players within the construction, design and engineering world, with over a thousand workers in the US alone. Famous for its projects, such as One Central Park in Australia,  Garden Bridge in London and the Toronto-York Spadina subway extension, the company aim to drive the construction world through sustainable initiatives and innovative solutions.

Arup has been officially named as the number one global technical advisor in Infrastructure Journal Annual League Table and has also partnered with seven Dutch design, to provide key solutions within construction and design in a collaboration titled ‘Innovation Area Development Partnership’ (IADP). Sander den Blanken, Group Leader of Arup in the Netherlands has commented: "Innovation is necessary in order to develop this type of demanding environments, as traditional solutions are not sufficient anymore. Our partnership offers an exquisite platform for innovation and co-creation."

The company is always open to joint ventures in order to achieve long-term goals or promote and develop new or existing infrastructures, at which Arup is currently working alongside AECOM in a joint partnership. The collaboration will enable the development and expansion of New York’s new subway line, improving existing transport infrastructures and providing long-term advantages for the growing city.

AECOM and Arup have recently completed the first phase of the $4.451 billion project, constructing four new underground stations and appropriate tunnel ventilation, utilising sophisticated technologies to provide key results and ensure minimum disruption.  The project will increase the quality of life for residents and the 20,000 commuters which utilise the subway every day, therefore reducing potential delays.

Also within the US, Arup has recently appointed Katherine Aguilar Perez-Estolano to their LA offices as Cities Leader for Southern California. The role incorporates the company’s long-term vision to expand their operations within the region and strengthen current infrastructures through the delivery of sustainable and first-class initiatives.

The role will also incorporate Arup's Americas Cities Strategy, strengthen relationships with communities, partners and stakeholders and uphold collaboration with C40 Cities.

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Read the January 2017 issue of Construction Global here

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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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