Building Design and Construction Handbook - Merritt - Ventech!

STRUCTURAL THEORY 5.3
Torsional loads are forces that are offset from the shear center of the section
under consideration and are inclined to or in the plane of the section, thus twisting
the supporting member (see Arts. 5.4.2 and 5.5.19).
Also, building codes classify loads in accordance with the nature of the source.
For example:
Dead loads include materials, equipment, constructions, or other elements of
weight supported in, on, or by a building, including its own weight, that are intended
to remain permanently in place.
Live loads include all occupants, materials, equipment, constructions, or other
elements of weight supported in, on, or by a building and that will or are likely to
be moved or relocated during the expected life of the building.
Impact loads are a fraction of the live loads used to account for additional
stresses and deflections resulting from movement of the live loads.
Wind loads are maximum forces that may be applied to a building by wind in
a mean recurrence interval, or a set of forces that will produce equivalent stresses.
Snow loads are maximum forces that may be applied by snow accumulation in
a mean recurrence interval.
Seismic loads are forces that produce maximum stresses or deformations in a
building during an earthquake.
5.1.2 Service Loads
In designing structural members, designers should use whichever is larger of the
following:
1. Loadings specified in the local or state building code.
2. Probable maximum loads, based not only on current site conditions and original
usage of proposed building spaces but also on possible future events. Loads that
are of uncertain magnitude and that may be treated as statistical variables should
be selected in accordance with a specific probability that the chosen magnitudes
will not be exceeded during the life of the building or in accordance with the
corresponding mean recurrence interval. The mean recurrence interval generally
used for ordinary permanent buildings is 50 years. The interval, however, may
be set at 25 years for structures with no occupants or offering negligible risk to
life, or at 100 years for permanent buildings with a high degree of sensitivity
to the loads and an unusually high degree of hazard to life and property in case
of failure.
In the absence of a local or state building code, designers can be guided by
loads specified in a national model building code or by the following data:
Loads applied to structural members may consist of the following, alone or in
combination: dead, live, impact, earth pressure, hydrostatic pressure, snow, ice, rain,
wind, or earthquake loads; constraining forces, such as those resulting from restriction
of thermal, shrinkage, or moisture-change movements; or forces caused by
displacements or deformations of members, such as those caused by creep, plastic
flow, differential settlement, or sideways (drift).
Dead Loads. Actual weights of materials and installed equipment should be used.
See Tables 5.1 and 5.2c.