ASCE 7 Chapter 11 addresses seismic design, establishing design earthquake parameters for buildings in seismically active regions. Seismic hazard levels are determined by location, with areas near major fault zones experiencing higher seismic activity. Seismic spectral response acceleration parameters at short periods (Ss) and 1-second period (S1) are determined from USGS maps or local seismic studies. Site classification considers soil properties, with soft clay sites (Site Class E or F) experiencing greater ground motion amplification than rock (Site Class A). Design spectral acceleration in the 0-0.5 second range determines lateral forces on tall buildings, while longer-period buildings experience more force at 1-second periods. Seismic design category is determined from spectral response acceleration and building importance factor, ranging from A (lowest seismic risk) to F (highest). Buildings in Design Category F may require nonlinear dynamic analysis and supplementary considerations. Response modification factor (R) accounts for structural ductility and energy dissipation capacity, with higher R-factors for more ductile systems. Moment-resisting frames with good ductility have R-factors of 8-9. Rigid systems like shear walls have lower R-factors of 5-6. Irregularities in plan or elevation increase design forces and may limit R-factors. Diaphragm flexibility affects load distribution to vertical elements.