User note:
About this chapter: Chapter 5 provides the requirements for the structural design of buildings and other structures. Section 501 specifies the forces for which structures need to be designed and the required performance. This chapter requires a structure to be designed for the expected forces it will be subjected to throughout its life. This is the same requirement found in Chapter 16 of the International Building Code®.
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.
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.
Structures, or portions thereof, shall remain stable and not collapse during construction or alteration and throughout their lives.
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.
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.
Structures, or portions thereof, shall be designed and constructed taking into account expected loads, and combination of loads, associated with the event(s) magnitude(s) that would affect their performance, including, but not limited to:
- Dead loads.
- Live loads.
- Impact loads.
- Explosion loads.
- Soil and hydrostatic pressure loads.
- 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
- Wind loads (mean return period).
- Small: 50 years
- Medium: 75 years
- Large: 100 years
- Very Large: 125 years
- Windborne debris loads.
- Snow loads (mean return period).
- Small: 25 years
- Medium: 30 years
- Large: 50 years
- Very Large: 100 years
- Rain loads. See Table 501.3.4.
- 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.
- Ice loads, atmospheric icing (mean return period).
- Small: 25 years
- Medium: 50 years
- Large: 100 years
- Very Large: 200 years
- Hail loads.
- Thermal loads.
[BS] TABLE 501.3.4
RAIN LOADS
| MAGNITUDE OF EVENT | DRAINAGE SYSTEM | MRI (YEARS) | STORM DURATION (MIN.) |
| Small | Primary | 25 | 60 |
| Small | Secondary | 25 | 15 |
| Medium | Primary | 50 | 60 |
| Medium | Secondary | 50 | 15 |
| Large | Primary | 100 | 60 |
| Large | Secondary | 100 | 15 |
| Very Large | Primary | 100 | 30 |
| Very Large | Secondary | 100 | 10 |
The design of buildings and structures shall consider appropriate factors of safety to provide adequate performance from:
- Effects of uncertainties resulting from construction activities.
- Variation in the properties of materials and the characteristics of the site.
- Accuracy limitations inherent in the methods used to predict the stability of the building.
- Self-straining forces arising from differential settlements of foundations and from restrained dimensional changes due to temperature, moisture, shrinkage, creep and similar effects.
The demolition or alteration of buildings and structures shall be carried out in a way that avoids the likelihood of premature collapse.
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.