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Abstract
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 to negative 4th power 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 baes shear due to earthquake loading, regardless of the wind or seismic zone in which the manufacturered 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 properites 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 However, there are several alternative anchoring and support sytems 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.
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 to negative 4th power 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 baes shear due to earthquake loading, regardless of the wind or seismic zone in which the manufacturered 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 properites 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 However, there are several alternative anchoring and support sytems 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.
Date
8/1995
8/1995
Author(s)
Richard Marshall; Felix Yokel
Richard Marshall; Felix Yokel
Page(s)
61
61
Keyword(s)
earthquake; seismic load; foundation; soil anchor; windstorm; structural engineering; manufactured home; mobile home;
earthquake; seismic load; foundation; soil anchor; windstorm; structural engineering; manufactured home; mobile home;