Structural Analyser › ASCE 7-16 › Chapter 1 — General

Chapter 1 — General

Scope · Definitions · Risk Categories · Importance Factors · Notional Loads · §1.4.2, §1.5, §1.5.1
§1.5 & Table 1.5-1 — Risk Categories Table 1.5-1

Select a category to see the nature of occupancy, applicable importance factors, and example building types. Risk Category II is the default for most buildings.

Risk Category II — Importance Factors (Table 7.3-1, Table 11.5-1)

Is
1.00
Snow Importance Factor
§7.3.4 Table 7.3-1
Ie
1.00
Seismic Importance Factor
§11.5.1 Table 11.5-1
Iw
MRI-50
Wind Speed Map (MRI)
§26.5.1 Fig. 26.5-1

Risk Category II — Standard Occupancy

Applies to all buildings and structures not listed under Risk Categories I, III, or IV. This is the default category.

Table 1.5-1 — Importance Factors Summary §7.3.4 · §11.5.1 · §26.5.1
Risk Category Is — Snow Ie — Seismic Iw — Wind MRI Description
I 0.80 1.00 MRI-10 Low hazard (agricultural, minor storage)
II 1.00 1.00 MRI-50 Standard occupancy — default
III 1.10 1.25 MRI-100 Substantial hazard (schools, large assembly)
IV 1.20 1.50 MRI-700 Essential facilities (hospitals, emergency ops)
§1.2.2 — Load Symbols §2.2
Symbol Load Type Standard Reference Category
DDead load — permanent gravity§3.1Dead
LLive load — floor, occupancy§4.3, Table 4.3-1Live
LrRoof live load§4.8Live
SSnow load§7Snow
RRain load§8Rain
WWind load§26–31Wind
EEarthquake load = Eh + Ev§12.4Seismic
EhHorizontal seismic force effect§12.4.2Seismic
EvVertical seismic force effect = 0.2SDSD§12.4.2.2Seismic
HLateral earth pressure / groundwater§3.2Soil
FFluid load (well-defined pressure)§2.3.1Fluid
NNotional load — structural integrity§1.4.2, Eq.(1.4-1)Integrity
TSelf-straining (thermal / shrinkage / creep)§2.3.4Thermal
§1.4.2 — Notional Lateral Force (Structural Integrity) Eq. 1.4-1

Minimum Lateral Force for Structural Integrity

Applied at each story level to ensure minimum structural integrity and robustness against progressive collapse. The notional load acts independently of other lateral loads.

Fx = 0.01 × Wx
Fx = notional lateral force at level x (kN or kip)
Wx = gravity load assigned to level x (kN or kip)
Applied independently in both orthogonal directions

Notes: This 1% notional load applies to each floor level concurrently. It is not combined with wind (W) or seismic (E) loads in the same load combination. Per §1.4.2, the loads act simultaneously with the gravity load case that produces them.

Notional Load Calculator — §1.4.2 Eq.(1.4-1)

Enter story weight (Wx) for each level. The calculator applies Fx = 0.01 × Wx.

Notional Load Results — ASCE 7-16 §1.4.2 Eq.(1.4-1)

Fx = 0.01 × Wx
Story LevelHeight (assumed)Wx (kN)Fx = 0.01 Wx (kN)
Total
§1.3 — Design Basis & Key Definitions §1.2, §1.3
TermDefinitionReference
Strength Design (LRFD) Factored loads applied to member; member strength must exceed factored demand. Uses load factors ≥ 1.0 and resistance factors φ < 1.0. §2.3
Allowable Stress Design (ASD) Unfactored loads; stresses must remain below allowable values (nominal strength ÷ safety factor Ω). §2.4
Risk Category Classification I–IV based on hazard to human life and essential services. Governs importance factors for snow, wind, and seismic loads. §1.5, Table 1.5-1
Mean Recurrence Interval (MRI) Average number of years between occurrences of an event of a given magnitude. Wind speed maps in ASCE 7-16 are given for specific MRI periods by Risk Category. §26.5.1
Structural Integrity Ability of a structure to resist progressive collapse; ensured by minimum notional lateral forces (§1.4.2) and connection ductility requirements. §1.4
Load Effect (Q) Internal forces, moments, stresses, or deformations in structural members resulting from applied loads. §1.2.2

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