Combatting Quakes with Seismic Retrofitting

August 24, 2021by Sheedy Crane0
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The San Francisco bay area is no stranger to seismic activity, thanks to the Hayward-Rodgers Creek fault system and the San Andreas fault system. The great earthquake of 1906 is still fresh in the memories of many San Fran citizens, and it still remains to be the deadliest earthquake in the history of the USA. It’s no wonder then that many buildings now utilize seismic retrofitting to ensure the safety of those in and around the building, as well as maintaining the integrity of the building. 

It seems that each year we’re reminded of the powerful nature of our planet, and the fact that it can very easily shake us off at any given moment. As an experienced provider of seismic retrofitting in the Bay Area, we know that natural conditions like quakes and wind can be costly to fix. That’s why we believe that seismic retrofitting is a must for any buildings which are expected to last longer than a decade in San Francisco.

Here is how seismic retrofitting can help keep your building/s upright.

How Do Earthquakes Cause Damage?

Before looking at how seismic retrofitting works, it can help to understand how an earthquake damages buildings in the first place. There are several different ways in which earthquakes can cause damage, which includes: ground shaking, surface rupture and ground displacement, liquefaction, landslides, tsunamis, and fires. 

Ground Shaking

Ground shaking is the most common cause of damage to buildings by earthquakes, as the movement goes against the rigid engineering which holds the structure up. It typically causes structural failure in most buildings, and can also lead to liquefaction and landslides which can lead to other issues.

Surface Rupture and Ground Displacement

While these don’t happen as often, they can cause monumental damage. Typically caused by horizontal or vertical movement on either side of a ruptured fault, surface rupture can cause ground displacement which can not only affect buildings, but roads, railways, and pipelines too. 

Liquefaction

Often caused by ground shaking, liquefaction is when soil begins to act like a liquid due to an earthquake. It usually only occurs when a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake. This can cause buildings and infrastructure to seemingly sink into the earth or dissolve, due to the lack of solid ground for the foundation to function properly. 

Landslides

While this may not be a concern to those who don’t live near mountains or cliffs, landslides can have devastating effects on buildings, typically flattening them and all else in their path. As with earthquakes, San Francisco is one of the most prone areas in the United States for landslides. Check out this document from the Association of Bay Area Governments to learn more about where they can occur.

Fires

Typically caused by damage to electrical systems in buildings and infrastructure, fires are a common problem during and after earthquakes. Although we’ve been fighting back against this problem for longer, more safety procedures and technology-oriented solutions are in place, and most buildings are already well-equipped to combat a fire.

How Does Seismic Retrofitting Help?

Now that we know all the different ways in which an earthquake can bring a building down, let’s look at what we can do to keep that building up. Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or liquefaction. These retrofit techniques have also proven to be effective in combating cyclones, tornadoes, and severe wind caused by thunderstorms. 

Seismic Retrofitting Strategies

The elements which make up seismic retrofitting work together to ensure that as many bases are covered as possible. These strategies include:

  • Strengthening the building to increase the global capacity by adding cross braces or new structural walls
  • The use of base isolation systems and supplementary damping to reduce the seismic demand
  • Increase the local capacity of individual structural components
  • Selective weakening retrofit
  • Allowing sliding connections to accommodate additional movement between seismically independent structures
  • Adding seismic friction dampers to add damping and a precise amount of additional stiffness

Bay Area Seismic Retrofitting

If the technical jargon in the last part of this article gave you a much-needed education on seismic retrofitting, then perhaps you’d benefit from working with our team at Sheedy Crane to explain and implement seismic retrofitting on your building. Not only are we a trusted provider of Bay Area seismic retrofitting, we’ve also provided retrofitted well-known buildings such as the Pasadena City Hall and the Martin Luther King Civic Centre.