The powers of geology are awe inspiring. When plate tectonics are in motion, they can move cities. The people of San Francisco know this all too well the power of earthquakes. The famous 1906 earthquake and the more recent 1989 Loma Prieta earthquake have left their mark on the memories and architecture of our fine city. The latest of these marks is retrofitting. After the 1989 Loma Prieta earthquake, a common fault was discovered in a common architecture from. The city has taken measure, in the form of a new building code, to attempt to protect buildings and people from the damage caused by this fault. Retrofitting is a world unto itself, and if you are new to this world, you will find that people often take for granted that you are familiar with the vocabulary used by professionals in this field. When you work day in and day out in a field, it is easy to forget that not everyone knows what you know. In order to bridge this gap, we will cover some of the terminologies that you find on our blogs, on our site, and in any retrofitting-oriented publication. We are Consulting Engineering Corp, a leader in the retrofitting field. We are staffed by highly experienced and eminently qualified engineers.
Soft Story Buildings
These buildings were built mainly before 1978, have wooden frames and have bottom floors that consist of either garage space or commercial space with large windows. The bottom floor is weak and is more likely to collapse in earthquakes. Many of San Francisco’s famous and historic “Painted Ladies” fall into this category.
- The soft story is the bottom floor that has a large opening, either garage doors or windows. It supports the floors above it until it is acted upon by overwhelming forces from, for example, an earthquake or high winds. When the bottom floor collapses, the upper floors either fall as a whole or pancake down, potentially killing many of the inhabitants.
- The implementation of design modification to enable a structure to better withstand the forces unleashed during an earthquake. These forces can include ground motion and soil failure i.e.,., liquefaction.
- The phenomena where loosely compacted or partially or wholly saturated soil loses its strength and essential becomes liquid in that it behaves like a liquid. This has been observed during earthquakes and contributes to substantial damage of the buildings at the surface.
Steel Moment Frames
- This is a rectilinear assemblage of beams and columns, with the beams rigidly connected to the columns.For retrofitting, they must comply with strict regulations with regards to, among other things, construction, connection stiffness, and load path. Moment resisting frames strengthen the soft story enhancing its ability to withstand earthquakes.
- This is a wall that acts to strengthen a building’s ability to withstand shear forces, which are side to side forces as opposed to downward or purely vertical forces. In retrofitting, they are installed in soft story buildings to strengthen the bottom floor and enhance the ability of the entire structure to survive an earthquake.
This is by no means a complete list of common terminology, for more about seismic retrofitting, or to schedule a free telephone consultation, call us today.