May 16, 2020

Trade association agreement to boost growth

trade association
DHI
GAI
Lucy Dixon
2 min
Trade association agreement to boost growth
The worlds two largest trade bodies in the architectural ironmongery and door hardware industry are entering into a major knowledge-sharing collaboratio...

The world’s two largest trade bodies in the architectural ironmongery and door hardware industry are entering into a major knowledge-sharing collaboration agreement to boost the continued growth of the sector in the UK and USA.

The Guild of Architectural Ironmongers (GAI), the only trade body in the UK that represents the interests of the whole architectural ironmongery industry, has signed a Memorandum of Understanding (MoU) with the Door and Hardware Institute (DHI), which represents the non-residential, door and hardware industry in North America.

Maria Powell, President of the GAI, said: “Our aim is to build a strong, long-term relationship between our organisations based on reciprocity and mutual benefit to support and further the growth of the architectural ironmongery and door hardware market and its many customers throughout the world.

“We share many common goals and interests. We’re both committed to innovation and technical development, as well as education and training, developments in accreditation, certification and the conduct of the industry.

“These key elements will inform and drive the relationship forward alongside an exploration of the commercial advantages that can be achieved.”

Bob Maas, President of the DHI, added: “The MoU provides an excellent opportunity to leverage the synergies that unite us, as we concentrate on introducing new ways of working together on complementary initiatives, especially education, that can support the aims of both our organisations.

“By pooling our resources in this way, I’m confident that we will achieve even higher levels of value for all of our members.”

Under the terms of the MoU, the two organisations will consider collaboration opportunities between the UK and USA in areas such as advocacy, the improved specification of hardware, innovation and best practice. 

They will also share and promote new ideas on education and qualifications, while supporting each other’s accreditation and certification activities and code of conduct.

The two organisations will also collaborate on communications opportunities, sharing publications of interest to each other’s memberships and discussing event ideas, topics and meeting agendas.

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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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