Report - PEER - University of California, Berkeley

The original concept is illustrated in Figure 1, above, whereby the range of periodswith displacement capacity below the displacement demand is obtained andtransformed into a range of heights using the aforementioned relationship betweenlimit state period and height. This range of heights is then superimposed on to thecumulative distribution function of building stock to find the proportion of buildingsfailing the given limit state. The inclusion of a probabilistic framework into themethod, however, has meant that the simple graphical procedure outlined in Figure 1that treated the beam- or column-sway RC building stock as single building classescan no longer be directly implemented, but instead, separate building classes based onthe number of storeys need to be defined, as noted in subsequent sections.2.1 Classification of Buildings2. DETERMINISTIC IMPLEMENTATIONThe initial step required in this method is the division of the building population intoseparate building classes. A building class is to be considered as a group of buildingsthat share the same construction material, failure mechanism and number of storeys;e.g., reinforced concrete moment resisting frames of 3 to 5 storeys, exhibiting a beamswayfailure mode. A decision regarding whether a moment resisting frame willexhibit a beam-sway or a column-sway mechanism may be made considering theconstruction type, construction year and presence of a weak ground floor storey.2.2 Structural and Non-Structural Limit StatesDamage to the structural (load-bearing) system of the building class is estimatedusing three limit states of the displacement capacity. The building class may thus fallwithin one of four discrete bands of structural damage: none to slight, moderate,extensive or complete. A qualitative description of each damage band for reinforcedconcrete frames is given in the work by Crowley et al. (2004) along with quantitativesuggestions for the definition of the mechanical material properties for each limitstate, taken from the work of Priestley (1997) and Calvi (1999).Damage to non-structural components within a building can be considered to beeither drift- or acceleration-sensitive (Freeman et al., 1985; Kircher et al., 1997).Drift-sensitive non-structural components such as partition walls can becomehazardous through tiles and plaster spalling off the walls, doors becoming jammedand windows breaking. Acceleration-sensitive non-structural components includesuspended ceilings and building contents. At present, only drift-sensitive nonstructuraldamage is considered within this methodology, using three limit states ofdrift capacity. Interstorey drift can be used to predict drift-sensitive non-structuraldamage. Freeman et al. (1985) report that studies on dry wall partitions indicate aninitial damage threshold at a drift ratio of 0.25%, and a threshold for significantdamage at drift ratios between 0.5 to 1.0%. However, to ensure three non-structural175