China Collaborates with UK to Meet Green Building Targets
The UK construction organisation, Building Research Establishment (BRE), has signed an agreement with the Shenzhen Municipal Government to set up a training and R&D centre in the growing city.
The new centre will deliver training on a national scale to other cities and promote its services including certifying buildings to green construction standards.
The deal marked the beginning of a trade mission led to China by British Business Secretary Vince Cable, which aims to secure contracts for UK firms worth millions of pounds. He is accompanied by more than 30 SMEs from several British towns and cities.
Rapidly growing Shenzhen, which has a population of 10 million, has been selected by the Chinese government to be a showcase city for a several new radical sustainability policies and reforms.
While the Chinese green building market is in its infancy, the Chinese Government has set the target of green buildings accounting for 30 percent of new construction projects by 2020.
BRE China aims to certify over 1,000 buildings across China to its standards, which will generate £10 million income and potentially as much as £200 million of work for UK supply chain companies, according to government body UK Trade and Investment (UKTI).
Director of BRE China Jaya Skandamoorthy, said: “We are excited by the collaboration with the Shenzhen Government and supporting them to achieve their goal to be the greenest city in China. We hope our international standards, research and training programme will provide a platform for leading companies, British and Chinese, to collaborate on green products, technologies and buildings.”
Cable added: “The UK has a strong competitive edge in building modern and environmentally friendly cities, through our world-class expertise in architecture, consultancy, design, IT and engineering.
“The green construction market offers a wealth of opportunities for ambitious British firms and the companies in their supply chains wishing to export. I am in China to open doors for those companies and help to lay the groundwork for deals to be signed.”
During the seven-day visit, the Business Secretary and his accompaniment will visit Guangzhou, Beijing, Qingdao and Chonging.
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.