Canada Green Building Council to deliver green training
Canada’s Green Building Council (CaGBC) will be delivering training in key areas of sustainability in partnership with Urban Green Council, which is part of the US Green Building Council.
Aimed at trade professionals, Green Professional Building Skills Training (GPRO) consists of a series of courses and certificate exams developed by Urban Green Council that aim to close the gap between conventional and sustainable construction practices.
Thomas Mueller, President and CEO of the CaGBC, said: “It is clear that Canada’s building industry is embracing greener, higher performing buildings as best practice. We are introducing GPRO to meet the demand for trained construction professionals which are knowledgeable and skilled to deliver top quality buildings in the growing green building industry.”
Canada is a global leader in green building with the highest number of LEED buildings per capita in the world. A recent CaGBC report titled Green Buildings in Canada: Assessing the Market Impacts and Opportunities further confirmed this, projecting that LEED projects (those that have certified between 2005 and end of 2015) will generate approximately $62.3 billion in total GDP and create over 701,000 direct jobs over their lifetime.
Builders and operators are already using GPRO certified trained professionals to bring LEED into their projects across the United States and in the Greater Toronto Area. Offering GPRO training nationally means bringing a much-needed set of green skills training to Canada’s construction industry, and in turn supporting Canada’s economic and societal push toward actionable solutions to climate change.
The Toronto Chapter of the Canada Green Building Council has been offering GPRO education in the GTA since 2015. The CaGBC is currently preparing course material and will roll-out the first round of national training in the fall of 2016. Certified trained professionals will earn AIA and GBCI credits while completing the training.
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.