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ANTI SAG SUPPORT FOR WIND UPLIFT
In roof situations where the effect of uplift on the structure must be managed the use of anti sag components may be mandatory depending on the advice given in the load tables. These provide categorised load data for the uplift situation on the basis of the number of anti sag supports used. Where the values quoted stipulate the use of one or more supports these must be incorporated to achieve the loadings given. It must be noted that the function of assessing the need to make provision for managing uplift remains with the building design team and is not dealt with here. Outlined below are general details for the application of anti sag support. These apply where screw fixed steel sheeting is used which fully restrains the top flange of the purlin. Additional more job specific information may be obtained by contacting Duggan Profiles. 
 

Construction details

The general arrangement for anti sag members for uplift conditions is categorised by the quantity involved and illustrated in the diagrams below. Tube Struts should be used for this purpose.

Note: The number to use is specified in the uplift section of the load tables. The Load Data for the Tube Strut gives the strength of these components which the designer should take into account during the design process.
 
Single sag rod (Tube Strut)

For spans where a single row of anti sag supports are required they should be positioned at:
 Midspan Uplift
Mid span
 
2 sag rods (Tube Struts)

For spans where a double row of ties are required they should be positioned at:
 One Third Uplift
1/3 points