On January 17, 1994, an earthquake of magnitude 6.7 struck the neighborhood of Los Angeles. This earthquake exposed the major structural flaws that plagued most of the buildings of America at that time. As the earthquake hit Reseda, a neighborhood in Los Angeles, the bottom floor of Northridge Meadows collapsed, and the two floors above it fell on it, causing more than 20 deaths. This building collapse raised a question: Why Northridge Meadows collapsed while many other buildings survived during the Northridge Earthquake.
What is soft-story seismic retrofitting?
The main reason for the collapse of Northridge Meadows during the Northridge Earthquake was soft-story building. This earthquake exposed that most houses in earthquake-prone cities such as California, Oakland, Los Angles, and Sans Fransisco have a soft or less rigid basement or bottom floor. According to the study conducted by the California Institute of Technology, there are more than 20,000 soft-story buildings in Los Angles and 10,800 soft-story buildings in Sans Francisco. The same reason-soft-story building- caused the collapse of Northridge Meadows during the Northridge Earthquake. The less rigid basement or bottom floor could not withstand the lateral force generated by the seismic waves. When the bottom floor collapses due to lateral seismic waves, the portions of the building above it pancake down upon it, crushing everything underneath it. Now, the important question is how to protect soft-story buildings from an earthquake? Dr. Scott Adan, Founder of Adan Engineering, says that the only viable and easy seismic retrofit solution to prevent buildings from such disaster is soft-story seismic retrofitting-giving lateral stiffness to make building safe from the earthquake.
Protecting Soft-story Buildings From Earthquakes
The first step of the seismic retrofit solution is to analyze the building to determine the best possible way to give it lateral support- soft-story seismic retrofitting. The first simple and easy way to retrofit the soft-story building is to fill the ground floor opening space with braces and walling the openings in the ground floor walls. The second way to retrofit the building is to add accessory dwelling units (ADU’s) in the existing buildings. ADU is the addition of small additional independent residential units in the existing buildings. This process helps reinforce the strength of the building. Most people in San Francisco and Oakland are using this technique to retrofit the soft-story building to protect it from earthquakes.
How Much Will Cost to Retrofit a Soft-Story Building?
The average cost of retrofitting a soft-story building varies and depends upon the complexity of the building and the scope of the project. The retrofitting of the large and complex building can cost up to USD 100,000. Although retrofitting the building is not cheap; however, it is necessary to ensure the safety of the residents of the building during earthquakes.
In conclusion, the soft-story building is a serious issue in the earthquake-prone zones of the US like Sans Francisco, Oakland, and Loss Angles. There is a dire need to retrofit these buildings to make them safe from an earthquake.