The 5 features of earthquake-proof buildings

earthquake-proof-buildings

I know what you’re thinking, who needs to know how an earthquake-proof building is built in Australia? We don’t get earthquakes! Aside from the fact that there are areas in Australia, namely Newcastle, that do get earthquakes, many of the techniques used to earthquake-proof a building can be applied to cyclone-proof a building. Now surely we all know a few places in Australia that get cyclones and tropical storms, Broome, Cairns and Darwin just to name a few.

Earthquake-proofing a building is all about putting extra measures in place to ensure a building avoids as much damage as possible. Technically, ‘proof’ isn’t the word to describe these measures, earthquake-resistant should be used instead as most buildings still come away from an earthquake or cyclone with minor damage. However, the difference in an earthquake-proof building and a building that is not protected lies in the potential damage to the core of the structure, which in turn can risk the safety of everyone in the building.

The 5 key features of any earthquake-proof building across the globe are:

  1. Stiffness
  2. Multiple safety strategies
  3. Foundations
  4. Cross braces
  5. Materials

Earthquake-proofing is a common part of designing buildings in countries, states and regions where they are regular occurrences, such as California, South East Asia and Chile. Because of this, the research on the subject is thorough and well tested over the past century. Some of the tallest buildings in the world are designed to withstand earthquakes of up to 8.0 on the Richter scale. Below we’ll go through the five key features of earthquake-proof buildings.

1. The stiffness of the earthquake-proof buildings

While it may seem counterproductive to build a rigid building in an area where the ground moves, this is actually a very popular way of stabilising a building and keeping it together. The main thing that is missed during this process though it is ensuring lateral stiffness. It’s easy enough to build a vertically stiff building, but ensuring the building moves equally side to side during an earthquake is harder.

A key characteristic of an earthquake-proof building is its regularity. This is directly linked to the lateral stiffness of a building. If a building has equal lateral stiffness across the floorplan when it is rocked from side to side in an earthquake the energy will be able to dissipate without placing too much pressure on one area. This is the first step in building an earthquake-proof building and no matter what other features you put in place a building won’t be secure without this.

2. The multiple safety strategies built into earthquake-proof buildings

A truly earthquake-proof building has multiple safety strategies in place to ensure it doesn’t collapse. This adds to the cost of building an earthquake-proof building but instantly proves its worth when you are hit with an earthquake or cyclone. Essentially, earthquake-proof buildings will have more than one of the features on this list. Generally, it is the use of equally distributed strength, laterally and vertically, as well as foundations, cross braces and materials.

cross-brace-earthquake-proof-buildings                  Cross Braces and trusses used to secure a building.

3. The foundations of earthquake-proof buildings

Ensuring your foundations will support your building is key in designing an earthquake-proof building. It is the same as with any building, you need to ensure that where you are building has a secure foundation to provide a stable building base. However, when you are building in earthquake or cyclone-prone areas you often need to reinforce the structure. Areas that are prone to these natural disasters also often have softer ground material which can move and cave during heavy rain or vibrations.

There are a number of different ways the foundations of an earthquake-proof building can be secured to the earth. Piles are commonly used to drill down into the bedrock, securing the building beyond the soft topsoil. Beyond piles, other foundation techniques used to stabilise a building during an earthquake or cyclone include damping and trusses.

Damping comes in a range of forms but essentially describes the action of removing as much energy as possible. In other terms, damping is used in foundations so that when an earthquake hits, instead of the vibrations hitting the building head-on, the dampers reduce vibrations as much as possible.

Trusses are also used in the foundations of earthquake-proof buildings thanks to their ability to spread the weight of the building evenly across the foundation and reduce the force of an earthquake’s vibrations. Trusses are also very popular in cyclone-proof buildings as their webbed design ensures a building holds together even under extreme weather.

4. The use of cross braces in earthquake-proof buildings

Cross braces are used throughout earthquake-proof buildings across the world thanks to their simplistic design and ease of installation. Cross braces are similar to trusses except are built into the walls and floors to provide the necessary stiffness. The cross braces provide the necessary distribution of force to enable a building to safely move with vibrations. Cross braces also send vibrations back down the building, often softening the force of the movement. Without cross braces, buildings have a high chance of collapsing in on themselves or sustaining dangerous structural damage.

materials-earthquake-proof-buildings                  The Transamerica building in San Francisco using trusses to protect it from earthquakes.

5. The materials used in earthquake-proof buildings

The materials used in an earthquake-proof building can make or break the structure’s stability. Some materials, while creating a strong and stable building, are not built to handle the movement of earthquakes. Bricks, in particular, are extremely susceptible to the vibrations of an earthquake. Materials often used in earthquake-proof buildings are:

  • Structural steel
  • Wood
  • Bamboo
  • Reinforced concrete

Structural steel has been used for years in earthquake-proof buildings. This is because it is able to undergo massive amounts of stress and movement, which is necessary for a building to withstand an earthquake or cyclone. Structural steel is known for its ductility, the ability to undergo significant deformation before rupture, and so is extremely popular in skyscrapers and earthquake-proof buildings, allowing them to move with the vibrations. Wood and bamboo are also exceedingly ductile and commonly used in smaller, low-lying structures such as houses, sheds and small civic buildings.

Reinforced concrete is concrete with reinforcing steel bars (rebar) included. This turns a low ductile material, concrete, into a higher ductile material. While it is common-place now for almost every concrete pour to include the use of rebar it wasn’t always the way. Reinforced concrete is used in conjunction with structural steel to create earthquake and cyclone-proof buildings. Without steel reinforcement concrete is prone to cracking and structural failure in buildings that are put under stress from high winds or ground vibrations.

Considering Earthquake or Cyclone-Proofing a building?

While it is always recommended to go through an engineer to ensure that the building designs are safe and will work in the case of an earthquake or cyclone, once the structural designs have been approved you’re going to need materials. On iSeekplant, we have suppliers across Australia providing a range of services. From concrete supply and pumping to structural steel and rebar supply to demolition services and mobile crane operators we have everything and everyone you need to get your building cyclone and earthquake-proof.

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