Where is the rebar?


The two massive recent earthquakes in Turkey and Syria, with magnitudes as high as 7.8 and 7.5, have claimed over 40,000 lives so far. This death toll is certain to rise as more bodies are discovered in the rubble of collapsed multistory concrete buildings. With the high frequency of California earthquakes, one can look at the Turkey and Syria earthquakes and draw some conclusions. Of course a more scientific study is necessary to fully pinpoint the specific causes of structural failure in each case, but an overall review of the footage released by the news outlets, showing collapse of these multistory concrete buildings, reveals some commonalities that are worth noticing.

The first floor of these buildings is usually composed of columns without adequate shear walls or lateral load resisting elements. This constitutes a phenomenon known as a soft story condition.

Similar conditions were revealed during the 1994 Northridge earthquake that caused buildings with tucked-in parking open space floor plans on the first floor to suffer extreme damage. In the case of Northridge earthquake, although numerous unreinforced masonry buildings (URM or UMB) suffered severe structural damage; most of the buildings were typically of wood framed stucco construction and much lighter than concrete buildings i.e. the damage and loss of life was far less than the Turkey/Syria Earthquake.

The failure of the first floor columns subsequently causes catastrophic failure of the upper floors to collapse in a pancake type manner maximizing loss of life.

Another point to notice when you look at the rubble of collapsed buildings is the fact that there are not enough steel reinforcing bars (rebars) in the columns, shear walls, floor slabs, and the connections between them. This is primarily due to lack of attention to current building codes or lack thereof.

Fortunately, there are ordinances in California to retrofit substandard buildings to prevent such catastrophic failures.

  • Division 88 of the Los Angeles building code addressed the unreinforced masonry buildings since the 80’s.
  • Division 91 has addressed retrofits of concrete tilt-up buildings since the 90’s.
  • LABC Ordinance 183893 addresses the soft story wood framed construction as well as non-ductile concrete frame buildings.

SKS Construction has been involved in all aspects of seismic retrofitting of all of the above types of buildings as well as general construction since 1987. Soft story retrofits are required by law to improve the safety of buildings and reduce the risk of damage and injury during earthquakes. These laws help ensure that buildings are better equipped to withstand seismic activity, that occupants are protected, and that property is better protected. If you own a soft story building, it's important to understand the requirements and to take the necessary steps to retrofit the building to help keep you and your property safe during an earthquake.

At SKS Construction, we provide our clients with a full-service package including initial assessment and survey, design, engineering, permits and construction. Having 36 years of experience in engineering and construction we are recognized as a leader in Industry. Our services include design and construction of ADU’s, Seismic Retrofitting, and Balcony Repairs. With our specialty in seismic retrofitting, over the years, we have been able to mold to the demands of the construction market.

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