When a simply supported (pin-pin) frame object is inserted with top center or bottom center insertion point, the program generates internal constraints that essentially have the effect of vertically offsetting the frame in the model that is used for analysis as illustrated in figure below. This results in longitudinal force acting on an arm about the neutral axis of the section. This is kinematically correct behavior. If this is not the desired behavior, changing one support from pin to roller will give you zero horizontal reactions and zero moments at the supports.

Similar behavior can be observed also for bridge objects that are supported by bearing links located at the bottom of the bridge girders.

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The screenshot below illustrates this behavior for the attached model.

Attachments

• [SAP2000 V14.2.3 Model|^model A V14.2.3.zip] (Zipped SDB file)