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This page was initially*NOTE:* While created for [SAP2000|sap2000:home], butthis thearticle same conceptalso applies also to [CSiBridge|csibridge:home].
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An important Initem which concerns moving [moving-load|kb:Moving-load analysis,] thereanalysis is one important item that youcertain should be aware of. Certain types of vehicles, such asvehicle types, including the AASHTO "double truck" (HL-93S), apply only for negative momentsmoment at supports and for interior reactions. ThisThese isresponse definedquantities byare checkingdefined theunder appropriateUsage items inon the UsageGeneral dataVehicle setData asform shown in Figure below1:

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!Vehicle_definition_usage_selection.png|align=center,border=0!

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Now, SAP2000 does not "know" what elements and their internal forces represent negative moments{center-text}Figure 1 - General Vehicle Data{center-text}

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Next, structural objects which exhibit negative moment at supports or interior reactions, unlessshould webe designate these elements for SAP2000 as such. For this purpose, the program uses the concept of designated using vehicle response components, which isas described in the {new-tab-link:http://www.csiberkeley.com/}CSI{new-tab-link} [_Analysis Reference Manual_|doc:CSI Analysis Reference Manual] (Bridge Analysis > Vehicle Response Components, page 446) and further explained in the attached notePDF.

DependingTo onsatisfy theAASHTO particular modelrequirements, youHL-93S mayvehicles considershould thebe followingapplied twousing approacheseither applyof the HL-93Sfollowing vehicletwo tomethods:
satisfy
the# AASHTOCoordinate requirements:these response (1)components Youwith couldthe assignHL-93S vehicle by assigning vehicle-response -component overwrites usingthrough "Assign > Frame Loads (_or_ Area Loads) > Vehicle Response Components" menu command to designate the response components which should be used for the HL-93S vehicle. However, for certain types of . For complex models, however, this process may require significant effort.

(2) You could simply obtain \\
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# Generate conservative results by modifying the vehicle definition to include "Usage > All Other Responses". inAs thea vehicle usage. This way result, the HL-93S vehicle would beis used for all responses.response Thismeasures, maywhich beis appropriate when the positive moments dueinduced toby HL-93S vehiclevehicles are expected to be similar to positive moments due tothose of HL-93K vehiclevehicles.


h1. AttachementsAttachments

* [Vehicle Response Components |^Vehicle_Response_Components.pdf] (PDF File, 122 KB)