Report - PEER - University of California, Berkeley

study (No damage, Repairable, Irreparable and Severe damage states) associated withvarious performance levels of some structural systems such as nonductile and ductilemoment resisting frames and frames with infills and walls, is described as follows:(a) No damage: No structural damage is observed. Some fine cracks in plastermay exist.(b) Repairable damage:• Light damage. Initiation of hairline cracking in beams and columns nearjoints and in walls. Cracking at the interface between frame and infillsand near corners of openings. Start of spalling in walls.• Moderate damage. Flexural and shear cracking in beams, columns andwalls. Some elements may reach yielding of steel.(c) Irreparable damage: Yielding of steel reinforcement occurs in severalelements. Cracks are larger than 2 mm. Residual deflection may occur.Ultimate capacity is reached in some structural elements and walls. Failureof short columns may occur. Partial failure of infills and heavy damage toframe members may take place. Severe cracking and bucking of steel inboundary elements of walls occurs.(d) Extreme: Partial collapse of lateral and gravity load carrying elements of thestructures is observed. Shear failure of columns. Shear failure of beams andcolumns causing complete failure of infills. Some reinforced concrete wallsmay fail.(e) Collapse: The structure may be on the verge of collapse or may experiencetotal collapse.3. DRIFTFor the case of three performance levels (serviceability, damage control and lifesafety or collapse prevention), three corresponding structural characteristics (stiffness,strength and deformation capacity) dominate the performance. If more intermediateperformance levels are selected, then it becomes difficult to define which structuralcharacteristic dominate the performance. Different performance objectives mayimpose conflicting demands on strength and stiffness. The displacements or driftlimits are also function of the structural system and its ability to deform (ductility).Design criteria may be established on the basis of observation and experimental dataof deformation capacity. For example, near collapse the drift limits of ductilestructural system are different from that of nonductile systems, which suggest thatdifferent drift limits will correspond to different damage levels for different structuralsystems.3.1 Factors That Affect DriftThe displacements or drift of a structure are functions of several factors such as thestiffness or strength and the ability of the structural system to deform (ductility).324