While minor tremors are common across much of the globe and rarely result in serious damage or physical injury, major earthquakes are a much more dangerous threat. During a major earthquake, energy is released deep with the earth as tectonic plates move against each other and create friction. The release of waves of energy resulting from the friction of the plates then creates the moving sensation that can be felt on the earth's surface. Buildings and infrastructure that are not specifically designed to resist damage from this type of movement are the ones most likely to receive severe damage or even collapse during an earthquake.
Some types of buildings, especially those that are now several decades old, were likely not built to specifications that would make them capable of surviving an earthquake without incurring damage. Soft story retrofitting is a process that can be used on some of these buildings to stabilize their structures beyond the scope of their original design so that they are more likely to remain standing after a major earthquake occurs.
The importance of steel framing
One of the most commonly used techniques in soft story retrofitting projects is the addition of steel framing. Much of the damage that wooden structures incur during an earthquake is related to stress on the structure as it is forced to move during the quake. By adding steel to support and stabilize the structure, some of the shock from the quake can be better absorbed so that movement to the structure and the resulting amount of damage are more apt to be lessened.
The importance of joining the steel to the foundation
While strong in its own right, steel must still be joined securely to the foundation of the building in order for the soft story retrofit to have the best chance of being successful. Instead of just bolting the steel to the surface of the foundation, however, it is best to ensure that the steel is firmly affixed to the foundation deep below the surface of the soil. To accomplish this, most soft story retrofit projects require drilling into the existing concrete and using a combination of epoxy and rebar to join the steel to the foundation. Once completed, a new layer of concrete is added to add even more stability.
Once the steel has been added to the structure and firmly affixed to the foundation, the retrofit process may also include the use of draglines to add further strength and resistance to movement. Property owners who want to learn more about this process to help protect their structures will want to discuss their situation with a reputable contractor who specializes in soft story retrofitting.