Page 16 - Advanced Design Examples of Seismic Retrofit of Structures

Introduction Chapter 1 7

Level drift. substantially stiffness. of partitions, as well as systems All normal to are damage and Power are possibly sources damage risk

Operational (1-A) light Very permanent No Structure original retains and strength cracking Minor facades, ¸ ceilings and structural elements. important operation functional Negligible occurs. utilities other available, standby from less Much lower and

and of structural be may lack risk
Occupancy drift. substantially strength cracking and can protection but to or failure lower and

Levels Immediate (1-B) permanent original Minor partitions, well as Elevators Fire Equipment and contents are secure, due operate mechanical utilities damage

Performance Level Light No Structure retains stiffness. facades, ¸ ceilings as elements. restarted. operable generally not of Less

Building and strength stories. all out- No or walls of drift. partitions. beyond be repair mitigated architectural, electrical and damaged damage risk higher

Target Level Safety residual in left Gravity-load-bearing function. failure parapets. of permanent to may economical hazards many mechanical, are more slightly

[6] Life (3-C) Moderate Some stiffness elements of-plane tipping Some Damage Building Falling but systems Somewhat and
Levels Level and permanent blocked. damage

Performance Prevention stiffness residual load-bearing but walls and Large exits Some unbraced and at or failed incipient failure. Building is collapse damage more risk greater

Structural Collapse (5-E) Severe Little strength, columns function. drifts. Infills parapets near Extensive Significantly and

of components for under design
Sample with intended designed (National Hazards Program) the

1.1 Damage Nonstructural NEHRP for
TABLE Overall General Comparison performance buildings the Earthquake Reduction provisions, earthquake