Performance objectives in earthquake engineering shape how buildings respond to seismic events. They guide designers in creating structures that meet specific goals for safety and functionality during and after earthquakes, balancing risk and cost.

These objectives range from keeping buildings fully operational to preventing collapse. By setting clear targets, engineers can tailor designs to meet the unique needs of different structures, from critical facilities like hospitals to standard buildings like homes.

Performance Objectives in Earthquake Engineering

Role of performance objectives

• Performance objectives guide seismic design defining specific goals for building behavior during and after earthquakes
• Objectives expressed as acceptable damage levels and functionality (minor cracking, full operability)
• Framework for evaluating structural performance allowing customization based on building importance and owner requirements
• Key components include hazard levels (frequent, occasional, rare earthquakes) and performance levels (operational, immediate occupancy, life safety)

Levels of seismic design performance

• Operational performance level ensures minimal structural damage building remains fully functional (hospitals)
• Immediate occupancy level allows minor structural damage building safe to occupy may require repairs (schools)
• Life safety level permits significant structural damage no collapse occupants can safely evacuate (residential buildings)
• Collapse prevention level accepts severe structural damage but prevents collapse protects against loss of life building may be total economic loss (warehouses)

Performance objectives vs design criteria

• Performance objectives inform design criteria more stringent objectives lead to demanding criteria
• Design criteria translate objectives into measurable parameters (drift limits, strength requirements, ductility demands)
• Iterative process refines criteria based on analysis results and performance evaluations
• Criteria examples include story drift limits (0.5% immediate occupancy, 2% life safety) and strength requirements (base shear coefficients)

Application for earthquake-resistant structures

• Identify building importance and required performance level (critical facilities, standard occupancy)
• Determine seismic hazard level for site (probabilistic seismic hazard analysis)
• Select appropriate performance objectives based on building use and hazard level
• Translate objectives into design criteria:
  1. Set allowable story drift limits
  2. Determine strength requirements
  3. Specify ductility demands
  4. Consider non-structural components (acceleration limits for equipment)
• Implement in design process using pushover analysis or nonlinear time history analysis
• Iteratively refine design to meet performance objectives (adjust member sizes, reinforcement details)