With 39 of the 50 states in the nation at moderate to severe risk for seismic activity, earthquake protection is a high priority for most real estate developers – and a top concern for the affordable housing community. A Seismic Retrofit provides existing structures with more resistance to seismic activity due to earthquakes. In buildings, this process typically includes strengthening weaknesses found in wall connections, continuity ties and shear walls or geo stabilization.
In the affordable housing space there are added challenges to maintaining structural soundness. Buildings are often older within affordable housing communities compared to luxury developments. Housing authorities do not always have the financial means to update or maintain structural integrity and making structural upgrades can displace residents at a higher rate and for longer periods of time than other rehabilitation projects. Despite these challenges, seismic retrofitting is necessary to secure the foundation of properties and make homes safer.
Recently CPP along with our partner, Related Affordable, completed a seismic retrofit at our Northgate Terrace property in Oakland, Calif. Famous for its San Andreas Fault, California is home to some of the nation’s most powerful earthquakes, adding even greater urgency to the retrofit.
Northgate Terrace underwent a variety of structural improvements including column fiber wrapping (FRP) which uses fiber-reinforced polymer sheets to strengthen concrete columns and give them more mobility in the event of an earthquake.
Modifications to existing wall footing and grade beams will transmit the weight of the wall directing into the ground and reinforce the concrete beams in load bearing walls. This utilizes the strength of the concrete while preventing excessive settling, giving the building a new “back bone” to withstand the pressures of earthquakes.
Debonding the existing structural rebar and welding new grade compliant rebar within the structure will allow more flexibility in movement which discourages crumbling and breakage during seismic activity. The retrofit also shores up existing structural columns and adds new structural columns using shotcrete, a concrete or mortar sprayed at a high velocity reinforced by steel rods, beams, mesh or fiber which promotes better weight distribution throughout the structure during seismic disturbances.
Using FRP sheets and new light-weight composites in the retrofit provides increased durability and performance of the structure. These methods are being widely applied to overcome the shortcomings of conventional seismic strengthening methods along with other geo stabilization techniques like compaction grouting.
CPP is committed to preserving affordability and maintaining safe living spaces for residents. Markets at higher risk for seismic activity can certainly present additional challenges; however, CPP is committed to tackling these tasks and providing safe affordable housing options throughout the nation.