May 16, 2020

Recycling waste from construction projects

Recycling waste from construction projects
Catherine Sturman
2 min
Recycling waste from construction projects
With the increased need for the construction of sustainable buildings alongside the rise of smart cities and sophisticated technologies, the constructio...

With the increased need for the construction of sustainable buildings alongside the rise of smart cities and sophisticated technologies, the construction industry has become increasingly focused on recycling waste products from construction projects more effectively, in order to provide builds which have long-term advantages, and can provide increased energy efficiency.

We take a look at how construction companies can recycle and reduce waste from construction projects more efficiently, therefore reducing CO2 emissions and cost within their works.

1. Deconstruct buildings instead of demolishing them

Recycling old brick is limited when buildings are demolished, at which utilising current brickwork becomes increasingly accessible through deconstruction.

However, when buildings are demolished there is increased accessibility to recycled glass, which can then be crushed to provide further materials for building work, such as insulation.

2. Implement recycled materials into new builds

Materials, such as brick can be utilised for concrete and aggregate materials; in addition to rubble and wood which can be implemented in new builds. Appliances and fixtures can be taken out of old builds and recycled. Wood can be used for energy, sawdust or chipping, whilst metals can be used for various products.

This increased use of recycled materials will reduce the cost of new materials and transport for further materials to be provided.

3. Reduce waste by building to standard measurements when possible

Building to standard size measurements and not over-ordering products will increase the chances for materials to be reused in further projects, minimising the level of waste.

4. Provide suitable storage areas for recycled materials

Ensuring there is a specified area for recycled materials to be stored separately which is also weather proofed will reduce potential contamination and damage to materials.

5. Ensure all hazardous waste is sent to a facility that can handle such products

it is imperative that companies are aware of how to discard of materials safely, with products such as plasterboard releasing toxic fumes through demolition, or electrical products.

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Jun 17, 2021

Why engineers must always consider human-induced vibration

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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