NSCP 2001: Selection of Lateral-Force Procedure & Seismic Design Vocabulary

27 vocabulary flashcards covering key seismic-design terms and provisions from NSCP 2001 Section 208 on selecting lateral-force procedures, calculating base shear, and accounting for site, occupancy, and structural factors.

Simplified Static Lateral-Force Procedure

A Section 208.5.2.3 method allowed for light-frame buildings ≤3 stories (Occ. Cat. IV–V) or other buildings ≤2 stories.

Static Lateral-Force Procedure

Section 208.5 analysis permitted for most regular/irregular structures in Seismic Zone 2, regular buildings <75 m tall, and certain flexible-upper/rigid-lower configurations.

Dynamic Lateral-Force Procedure

Section 208.6 method required for tall ≥75 m buildings and those with significant vertical, stiffness, weight, or geometric irregularities, or on Soil Profile SF with T > 0.7 s.

Design Base Shear (V)

Total horizontal seismic force at the base, calculated from specified equations and bounded by upper/lower limits.

Structure Period (T)

Fundamental elastic vibration period of the building used in base-shear and force distribution calculations.

Method A (Approximate Period)

Empirical formula to estimate T for all buildings; may use C₁ or 0.0743/√Ac for concrete/masonry shear-wall structures.

Method B (Analytical Period)

Substantiated analysis based on actual stiffness and mass; T cannot exceed Method A value by >30 % in Zone 4 or 40 % in Zone 2.

Occupancy Category

Classification (I–V) assigning importance and observation requirements per Table 103-1 and 208-1.

Seismic Importance Factor (I)

Multiplier reflecting occupancy risk (e.g., 1.50 for essential facilities, 1.25 for hazardous, 1.00 for standard/miscellaneous).

Soil Profile Type SA

Hard rock with Vs > 1500 m/s (best seismic performance).

Soil Profile Type SB

Rock with Vs = 760–1500 m/s.

Soil Profile Type SC

Very dense soil/soft rock; Vs = 360–760 m/s, N > 50, Su > 100 kPa.

Soil Profile Type SD

Stiff soil; Vs = 180–360 m/s, N 15–50, Su 50–100 kPa (default when soil unknown).

Soil Profile Type SE

Soft soil; Vs < 180 m/s, N < 15, Su < 50 kPa.

Soil Profile Type SF

Problematic soils requiring site-specific investigation (e.g., liquefiable, peat, very thick soft clays).

Seismic Zone Factor (Z)

Regional seismicity parameter (e.g., Z = 0.20 or 0.40) assigned from Figure 208-1 and Table 208-3.

Near-Source Factor Na

Multiplier modifying Ca based on proximity to seismic source (Table 208-5); capped at 1.1 if certain conditions are met.

Near-Source Factor Nv

Multiplier modifying Cv based on distance and source type (Table 208-6).

Seismic Coefficient C

Short-period design coefficient from Table 208-7, dependent on Z, soil type, and Na.

Seismic Coefficient C₂ (Cv)

Long-period design coefficient from Table 208-8, dependent on Z, soil type, and Nv.

Seismic Dead Load (W)

Total dead load plus portions of live and other loads (≥25 % warehouse live load, ≥0.5 kN/m² partitions, permanent equipment weight).

Numerical Coefficient R

Factor in Table 208-11 representing system overstrength and global ductility; used to reduce elastic forces.

Vertical Distribution of Force

Prescribed formula allocating base shear over building height, including top concentration Ft and story forces Fx.

Overstrength

Inherent reserve strength of a lateral-force system beyond design demand, reflected in coefficient R.

Global Ductility

Capacity of the overall lateral system to undergo inelastic deformation without loss of strength; also embodied in R.

Seismic Live-Load Portion

Requirement that at least 25 % of warehouse/storage live load be included in W for seismic design.

Partition Load Inclusion

Minimum 0.5 kN/m² partition weight that must be added to seismic dead load W when partitions are considered in floor design.

Flexible-Upper / Rigid-Lower Structure

Building with lower portion ≥10× stiffer than upper; qualifies for static procedure if period criteria (T ≤ 1.1 Tupper) are met.