An important item which concerns moving-load analysis is that certain vehicle types, including the AASHTO double truck (HL-93S), apply only for negative moment at supports and for interior reactions. These response quantities are defined under Usage on the General Vehicle Data form shown in Figure 1:
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Figure 1 - General Vehicle Data
Next, structural objects which exhibit negative moment at supports or interior reactions should be designated using vehicle response components, as described in the
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CSI
Analysis Reference Manual (Vehicle Response Components, page 446) and the attached PDF.
To satisfy AASHTO requirements, HL-93S vehicles should be applied using either of the following two methods:
- Coordinate these response components with the HL-93S vehicle by assigning vehicle-response-component overwrites through Assign > Frame Loads or Area Loads > Vehicle Response Components. For complex models, however, this process may require significant effort.
- Generate conservative results by modifying the vehicle definition to include Usage > All Other Responses. As a result, the HL-93S vehicle is used for all response measures, which is appropriate when the positive moments induced by HL-93S vehicles are similar to those of HL-93K vehicles.