What is a Soft Story Building?

Soft story buildings are structures that are typically multi-level and have one or more floors with significantly less stiffness and lateral support than the floors above. These buildings are often constructed with large openings, such as commercial spaces on the first floor with parking above, which can weaken the building’s overall structural integrity and make it more susceptible to damage during earthquakes, high winds, or other natural disasters.

Soft story buildings are common in cities and urban areas, where land is at a premium and developers are looking to maximize their profits by building taller structures. However, these buildings pose a significant risk to occupants and nearby residents, particularly in areas with high seismic activity.

Soft story buildings can take many different forms, but there are a few common characteristics that can help identify them. Some of the most common features of soft story buildings include:

Definition of a Soft Story Building

Soft story buildings are typically multi-level structures with one or more floors that are significantly less stiff and have less lateral support than the floors above. This lack of stiffness and support can make these buildings more susceptible to damage during earthquakes, high winds, or other natural disasters.

Identification of Soft Story Buildings

Soft story buildings can be identified by several key features, including large openings on the first floor, such as parking garages or commercial spaces, and a lack of structural support in the walls or columns on the lower floors. These buildings may also have a distinctive “inverted T” shape, with a wider first floor than upper floors.

Soft story buildings may also have been constructed before modern building codes were established, which means they may not have been designed to withstand modern seismic or wind loads.

Common Features of Soft Story Buildings

Some common features of soft story buildings include:

• Large openings on the first floor, such as commercial spaces or parking garages, which can weaken the building’s overall structural integrity.
• A lack of structural support in the walls or columns on the lower floors, which can make the building more susceptible to damage during natural disasters.
• A distinctive “inverted T” shape, with a wider first floor than upper floors. This shape can make the building more vulnerable to collapse during an earthquake or high winds.

Soft story buildings can take many different forms, but they all share these common characteristics that make them more vulnerable to damage during natural disasters.

Risks and Dangers of Soft Story Buildings

Soft story buildings pose significant risks and dangers to occupants and nearby residents, particularly during natural disasters such as earthquakes or high winds. Some potential risks of soft story buildings include:

• Collapse: Soft story buildings are more vulnerable to collapse during an earthquake or high winds, which can result in significant property damage and loss of life.
• Injuries: Occupants of soft story buildings may be at an increased risk of injury during natural disasters, particularly if the building collapses or if there are falling objects or debris.
• Property damage: Soft story buildings are more likely to sustain significant damage during natural disasters, which can result in costly repairs or even demolition.

There have been numerous historical examples of soft story building failures, including the collapse of the Northridge Meadows apartment complex during the 1994 Northridge earthquake, which resulted in 16 deaths and numerous injuries.

Soft Story Building Retrofitting

One way to mitigate the risks and dangers of soft story buildings is through retrofitting. Retrofitting involves modifying the building’s existing structure to improve its overall structural integrity and resistance to natural disasters.

Retrofitting a soft story building typically involves adding new structural elements, such as steel frames or concrete walls, to strengthen the building’s lower floors. There are several different methods of retrofitting soft story buildings, including:

• Adding steel moment frames: Steel moment frames can be added to the building’s lower floors to provide additional lateral support.
• Installing concrete shear walls: Concrete shear walls can be added to the building’s lower floors to improve its overall stiffness and resistance to lateral forces.
• Strengthening existing walls: Existing walls can be strengthened by adding additional materials, such as plywood or steel, to improve their overall stiffness and resistance to lateral forces.

Retrofitting a soft story building can be a complex and expensive process, but it is a necessary step in ensuring the safety of occupants and nearby residents. In some cases, local governments may offer financial incentives or assistance to encourage building owners to retrofit their structures.

Soft Story Building Regulations

In response to the risks posed by soft story buildings, many cities and states have implemented regulations to require the retrofitting of existing structures and the construction of new buildings to meet stricter seismic and wind load standards. Here is an overview of the most common types of soft story building regulations:

Overview of Soft Story Building Regulations

Soft story building regulations typically require building owners to retrofit their structures to meet stricter seismic and wind load standards. These regulations may also require new buildings to be constructed with additional structural support in the lower floors.

In many cases, these regulations are established at the city or state level, and building owners are required to comply within a certain timeframe. Failure to comply with these regulations can result in fines or other penalties.

Comparison of Local and National Regulations

Soft story building regulations can vary significantly depending on the location and jurisdiction. Some states, such as California, have statewide regulations that require the retrofitting of certain types of soft story buildings. Other cities and states may have more specific regulations that apply only to certain types of structures or geographic areas.

It is important for building owners and developers to understand the regulations that apply to their specific location and project to ensure compliance with all applicable laws and codes.

The Role of Building Codes in Regulating Soft Story Buildings

Building codes play a critical role in regulating soft story buildings and ensuring that new structures are designed and constructed to withstand seismic and wind loads. These codes are typically established by the International Code Council (ICC) and adopted by cities and states across the country.

The most recent version of the International Building Code (IBC) includes specific requirements for soft story buildings, including provisions for retrofitting existing structures and designing new buildings to meet stricter seismic and wind load standards.

Conclusion

Soft story buildings pose a significant risk to occupants and nearby residents during natural disasters, particularly in areas with high seismic activity. These structures are often constructed with large openings and a lack of structural support in the lower floors, which can weaken the building’s overall structural integrity.

To address these risks, many cities and states have implemented regulations to require the retrofitting of existing soft story buildings and the construction of new buildings to meet stricter seismic and wind load standards. Building codes also play a critical role in regulating soft story buildings and ensuring that new structures are designed and constructed to withstand natural disasters.

By understanding the risks posed by soft story buildings and complying with all applicable laws and codes, building owners and developers can help keep their communities safe and secure.