Safety Assessment Program Evaluator Student Manual

CA Emergency Mgmt. Agency Safety Assessment Program Evaluator Manual April 2011Chimney failures are common in areas with moderate ground motion, as chimneys usually aremade of unreinforced masonry and are often not braced or reinforced at the roof line. In areaswith strong ground motion, the chimneys are often snapped off and laying on the ground.2.2 Windstorm and Flood EffectsDamage from lateral forces due to wind and moving floodwater is the most common structurefailure mechanism in these types of disasters. Lateral forces from strong winds can be asdamaging to a structure as those from earthquake forces. There are recorded examples ofhurricane force winds that have destroyed unreinforced masonry buildings, and the violent windsof strong tornados can completely decimate structures.In floods, it is not uncommon for buildings to be floated off their foundations and swept away.In the most extreme cases, it does not matter if the building is attached firmly to a concrete slabfoundation; there are numerous examples from the 2005 Hurricane Katrina event of entire wellbuilthomes being raised out of the ground with their slab foundations by storm surge floodingand pushed some distance from their original location.Floods can also undermine foundations by scouring the soil out from under them. Additionally,both strong winds and floods can send large objects such as cars, appliances, etc. into buildingsand cause additional damage.Photo courtesy Raymond Lui, SEAFigure 2-13 – Unreinforced masonry building failure due to storm surge, 2005 HurricaneKatrinaThis photo shows an unreinforced masonry garage in the process of failure. Note the water linejust below the top of the windows; the force of the water caused the damage shown.39