Recommended Performance-Based Criteria for the Design of Manufactured Home Foundation Systems to Resist Wind and Seismic Loads.
Recommended Performance-Based Criteria for the Design of
Manufactured Home Foundation Systems to Resist Wind and
Marshall, R. D.; Yokel, F. Y.
NISTIR 5664; 74 p. August 1995.
Sponsor:Department of Housing and Urban Development, Washington,
Available from: National Technical Information Service
Order number: PB96-128111
building technology; codes; standards; earthquake
engineering; foundations; manufactured housing; mobile
homes; soil anchors; structural engineering; wind
engineering; wind loads; windstorm protection;
This report addresses the issue of tornadoes as a basis
for the design of manufactured homes and compares base
shears due to wind loading with base shears due to
earthquake excitation for various wind and seismic
zones. Only for annual exceedance probabilities less
than about 2.5 x 10-4 will tornadic wind speeds govern
the design for wind loading. In view of the accepted
probabilities of attaining or exceeding design limit
states for ordinary buildings, it is concluded that
tornadoes should not be a part of the wind load design
criteria for manufactured homes. Also, it is concluded
that transverse base shear due to wind loading will
always exceed the base shear due to earthquake loading,
regardless of the wind or seismic zone in which the
manufactured home is sited. In the longitudinal
direction the ranges of base shear for wind and
earthquake are approximately equal. These comparisons
are based on the assumption that the structural system
is properly detailed to resist earthquake forces and is
capable of accommodating inelastic deformations several
times greater than the deformation at first yield. In
view of the uncertainty regarding the dynamic properties
of manufactured homes and their support systems, a
simplified equation for the determination of seismic
base shear is proposed. Traditional anchor/tie/pier
systems and current installation practice do not provide
adequate windstorm protection for manufactured homes.
Even with preloading, the effectiveness of traditional
shallow, helix-plate soil anchors is limited to basic
wind speeds of approximately 44.7 m/s (100 mph).
However, there are several alternative anchoring and
support systems on the market or under development that
can provide the required resistance to wind and
earthquake loads. Finally, a set of performance-based
criteria for anchoring manufactured homes against wind
and earthquake loads is proposed.