Part II—Building

CHAPTER 5
STABILITY


  • SECTION 501
    STRUCTURAL FORCES

    501.1 Objective.
    To provide a desired level of structural performance when structures are subjected to the loads that are expected during construction or alteration and throughout their intended lives.

    501.2 Functional statements.

    501.2.1 Life safety and injury prevention.
    Structures shall be designed and constructed to prevent injury to occupants due to loading of a structural element or system consistent with the design performance level determined in Chapter 3.

    501.2.2 Property and amenity protection.
    Structures shall be designed and constructed to prevent loss of property and amenity consistent with the design performance level determined in Chapter 3.

    501.3 Performance requirements.

    501.3.1 Stability.
    Structures, or portions thereof, shall remain stable and not collapse during construction or alteration and throughout their lives.

    501.3.2 Disproportionate failure.
    Structures shall be designed to sustain local damage, and the structural system as a whole shall remain stable and not be damaged to an extent disproportionate to the original local damage.

    501.3.3 Loss of amenity.
    Structures, or portions thereof, shall have a low probability of causing damage or loss of amenity through excessive deformation, vibration or degradation during construction or alteration and throughout their lives.

    501.3.4 Expected loads.
    Structures, or portions thereof, shall be designed and constructed taking into account all expected loads, and combination of loads, associated with the event(s) magnitude(s) that would affect their performance, including, but not limited to:

    1. Dead loads.

    2. Live loads.

    3. Impact loads.

    4. Explosion loads.

    5. Soil and hydrostatic pressure loads.

    6. Flood loads (mean return period).

    Small: 100 years

    Medium: 500 years

    Large: Determined on a site-specific basis

    Very Large: Determined on a site-specific basis

    7. Wind loads (mean return period).

    Small: 50 years

    Medium: 75 years

    Large: 100 years

    Very Large: 125 years

    8. Wind-borne debris loads.

    9. Snow loads (mean return period).

    Small: 25 years

    Medium: 30 years

    Large: 50 years

    Very Large: 100 years

    10. Rain loads. See Table 501.3.4.

    11. Earthquake loads (mean return period).

    Small: 25 years

    Medium: 72 years

    Large: 475 years, but need not exceed two-thirds of the intensity of very large loads

    Very Large: 2,475 years. At sites where the 2,475-year, 5-percent damped spectral response acceleration at a 0.3-second period exceeds 1.5 g and at a 1-second period exceeds 0.6 g, very large ground shaking demands need not exceed a 5-percent damped response spectrum that at each period is 150 percent of the median spectral response acceleration ordinate resulting from a characteristic earthquake on any known active fault in the region.

    12. Ice loads, atmospheric icing (mean return period).

    Small: 25 years

    Medium: 50 years

    Large: 100 years

    Very Large: 200 years

    13. Hail loads.

    14. Thermal loads.

    TABLE 501.3.4
    RAIN LOADS

    MAGNITUDE OF EVENTDRAINAGE SYSTEMMRI (YEARS)STORM DURATION (MIN.)
    SmallPrimary2560
    SmallSecondary2515
    MediumPrimary5060
    MediumSecondary5015
    LargePrimary10060
    LargeSecondary10015
    Very LargePrimary10030
    Very LargeSecondary10010

    501.3.5 Safety factors.
    The design of buildings and structures shall consider appropriate factors of safety to provide adequate performance from:

    1. Effects of uncertainties resulting from construction activities.

    2. Variation in the properties of materials and the characteristics of the site.

    3. Accuracy limitations inherent in the methods used to predict the stability of the building.

    4. Self-straining forces arising from differential settlements of foundations and from restrained dimensional changes due to temperature, moisture, shrinkage, creep and similar effects.

    501.3.6 Demolition and alteration.
    The demolition or alteration of buildings and structures shall be carried out in a way that avoids the likelihood of premature collapse.

    501.3.7 Site work.
    Site work, where necessary, shall be carried out to provide stability for construction on the site and avoid the likelihood of damage to adjacent property.