PDF - Centralia College

comprised of glass block. The east and west exterior walls are constructed of 4” concrete masonry blockwalls. Concrete masonry block walls also divide the classroom spaces. The floor framing consists of aconcrete slab on grade.Student CenterThe Student Center Building is made up of two main areas. The first area was originally designed as aclassroom area and is one story in height, approximately 50ft wide by 100ft long. At the north end of thisarea is the original library, which consists of two levels, each approximately 60ft by 60ft. The building wasoriginally designed and constructed in the early 1960’s. Since that point the classroom area has been changedto cafeteria/lounge, and the lower level of the library is utilized as the bookstore and the upper level as astudent resource center. The lower level of the library is set partially below grade. The roof framing overboth areas consists of 2x12 rafters spanning between steel beams supported on steel columns. The roofsheathing is 1x diagonal shiplap. The second floor of the library is structured with a thin metal pan deck andconcrete topping over open web bar joists spanning between steel beam girders on steel columns. The firstlevel exterior walls of the library are partial height concrete retaining walls with glazing up to the second levelon the east and west elevations, and a stud wall on the north elevation. The second level library walls consistof glass storefront windows on the north elevation, and solid stud walls on the east and west elevations. Theinterior stair core connecting the lower level and upper levels of the library is constructed of concretemasonry walls. The cafeteria exterior walls consist of glass storefront on both the west and east elevationsand a solid stud wall on the south elevation. The cafeteria area also includes a large light well, centered in thelower roof, which is covered with a skylight.Seismic Hazard and Past Performance:Western Washington is seismically active with the most recent major events being the 1949 OlympiaEarthquake (Mag 7.1), the 1965 SeaTac Earthquake (Mag 6.5), and the 2001 Nisqually Earthquake (Mag 6.8).Recent research indicates that there are three sources of strong ground motion in the Puget Sound region.The first is an interplate event off of the coast of Washington where the Juan de Fuca plate drives under(subducts) the North American plate. Earthquakes up to a Magnitude 9.0 and strong ground motion lastingseveral minutes are predicted from this source once every 500 years. The 1964 Alaska earthquake was causedby a similar mechanism. The second source is an intraplate event deep in the Juan de Fuca plate directlybeneath Puget Sound. This event is thought to be capable of producing a Mag 7.5 earthquake once every 500years. The 1949, 1965, and 2001 earthquakes are examples of this type of event. Strong ground motions areexpected to last 20 seconds. The third source is a crustal event occurring close to the surface, which mayoccur along known or unknown fault lines. The 1996 Duvall earthquake (Mag 5.7) is an example of this typeof event. Recent research has uncovered faults such as the Seattle and South Whidbey Island fault, whichmay be capable of producing a Mag 7+ event with 20 seconds of strong ground motion. Since these shallowearthquakes are much closer to the surface the ground motions are expected to be very intense.The buildings appear to have withstood the 1965 and 2001 events with some little structural damage. From ourconversation with the Maintenance Department, we understand that the roof structure of the library driftedsubstantially out of plumb during the 2001 Nisqually Earthquake and required repair following the event.Findings and Recommendations