Seismic retrofit facts for kids
Seismic retrofitting is a way to make old buildings stronger. It means changing buildings that already exist so they can better handle earthquakes. Think of it like giving a building a superhero upgrade! This helps keep people safe and buildings standing.
Engineers also use these methods for other natural disasters. They can make buildings safer from powerful tornadoes or very strong winds from thunderstorms.
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Why We Make Buildings Stronger
When engineers retrofit a building, they have important goals in mind. These goals help decide how much work needs to be done.
Protecting People and Buildings
The most important goal is always to keep people safe.
- Saving Lives: The main reason to retrofit is to protect people inside. It helps make sure the building doesn't collapse during an earthquake.
- Stopping Collapse: Retrofitting aims to prevent the building from falling apart completely. Even if it gets damaged, it should stay standing.
Keeping Buildings Useful
Sometimes, the goal is more than just safety.
- Staying Open: For important buildings like hospitals or fire stations, it's vital they can still work after an earthquake. Retrofitting helps them keep their power and services.
- No Damage: In some cases, engineers want the building to be almost untouched by an earthquake. This is for very special or expensive structures.
How Buildings Get Stronger
There are many ways to make a building more resistant to earthquakes. Engineers look at how the building was built and what materials were used. Then they decide the best way to strengthen it.
Adding New Support
One common method is to add new parts to the building.
- Braces and Trusses: Imagine adding strong metal X-shapes or triangles to the outside or inside of a building. These are called trusses or braces. They help hold the building together and stop it from twisting.
- Shear Walls: Sometimes, new strong walls are added. These "shear walls" are like giant shields that resist the sideways pushing and pulling of an earthquake.
- Steel Jackets: For columns (the vertical supports), engineers might wrap them in steel or strong fabric. This is like giving the column a tough jacket to stop it from breaking apart.
Fixing Foundations
The foundation is the part of the building that sits on the ground. It's super important!
- Anchoring: Buildings can slide right off their foundations during an earthquake. Engineers can add strong bolts or anchors to tie the building firmly to its base.
- Cripple Walls: Many older houses have short walls under the first floor called "cripple walls." If these are weak, the house can collapse. Strengthening them with plywood or other materials makes the house much safer.
- Base Isolation: This is a very cool technique! Imagine putting big, flexible pads under the building. These pads let the ground shake, but the building above them moves much less. It's like the building is floating on a cushion.
Strengthening Materials
Sometimes, the materials themselves need to be made stronger.
- Reinforcing Concrete: Older concrete might not have enough steel bars inside it. Engineers can add more steel or special wraps to make concrete columns and beams stronger.
- Connecting Parts: Earthquakes can shake buildings apart at their joints. Retrofitting often involves making sure all the different parts of a building are strongly connected to each other.
Famous Retrofit Projects
Many important structures around the world have been retrofitted.
- Bridges: Large bridges, like the San Francisco-Oakland Bay Bridge, have been upgraded. They get new stronger parts to help them survive big quakes.
- Historic Buildings: Even very old buildings, like those in Charleston, South Carolina, have been made safer. After a big earthquake in 1886, people added "earthquake bolts" to many houses. These bolts helped hold the walls together.
Retrofitting is a vital part of living in earthquake-prone areas. It helps protect our communities and ensures our buildings can stand strong for years to come.
Images for kids
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Infill shear trusses — University of California dormitory, Berkeley
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External bracing of an existing reinforced concrete parking garage (Berkeley)
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Port Authority Bus Terminal in New York City
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One of many "earthquake bolts" found throughout period houses in the city of Charleston subsequent to the Charleston earthquake of 1886. They could be tightened and loosened to support the house without having to otherwise demolish the house due to instability. The bolts were directly loosely connected to the supporting frame of the house.
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Partial failure due to inadequate shear structure at garage level. Damage in San Francisco due to the Loma Prieta event.
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Corner joint steel reinforcement and high tensile strength rods with grouted anti-burst jacket below
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House slid off of foundation
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Low cripple wall collapse and detachment of structure from concrete stairway
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Jacketed and grouted column on left, unmodified on right
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Additional diagonals were inserted under both decks of this bridge
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Obsolete riveted lattice members
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Bolted plate lattice replacement, forming box members
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Cypress Freeway viaduct collapse. Note failure of inadequate anti-burst wrapping and lack of connection between upper and lower vertical elements.
See also
In Spanish: Refuerzo antisísmico para niños
