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When youstatic applyloading staticis loadsapplied in the X direction, the net reaction will be zero in the Y direction. Dependingwill on the type of the structurebe zero, thethough individual reactions may be nonzero, depending buton the sumtype isof notstructure. (For example, considerwhen a single-story open-frame structuresystem with 4four columns, arranged in thea square layout.plan Thesewith columns are fixed at their base and connected by 4 interconnecting beams at theirthe toproof jointslevel, usingis one beam along each side of the square layout. Applying subjected to a horizontal point load alongin the major direction ofat the structure to a point  located on the top of one column will result in a torsion of the entire open frame structure and, torsion will cause horizontal support reactions in the direction orthogonal to theloading.

directionGiven ofa thedynamic loading.)

For dynamics, the condition, net reactionreactions isare in equilibrium notfor justboth with the applied loadloading (asand for static), but also with[inertial forces|kb:Time-history output-acceleration accuracy]. When the inertia forces. If the structural center of stiffness ofdiffers a structure is not from the same as the center of [mass|kb:Mass], loading thenin anthe X loadingdirection may generate motion in the Y motion,direction. whichThis inmotion turnwill generatescorrelate Ywith inertiaa forces.set Thatof isinertial whyforces theand reactionsupport mayreactions existorthogonal into athe direction different fromof loading. This
situation
exists forMost most non-symmetricalsymmetric structures. exhibit Thisorthogonal behaviorreactions isand notresponse aquantities fictionwhen ofsubjected theto model,either thestatic technique, or thedynamic softwareloading. This is the nature of dynamic behavior. These are the real forces that should be designed forbehavior naturally occurs as a structure establishes equilibrium. Design must account for these orthogonal forces, along with all others which result from load application.

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*Related IncidentsIncident:*

* {incident:no=31688|comment=Explanation of the effect described in this wiki page.} *\\
* {email:date=2/17/2011|from=bm|to=ok|subject=Coupling of longitudinal and transverse response in response spectrum analysis|comment=|id=6881762}
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h1. See alsoAlso

* [Base reactions for response -spectrum analysis|kb:Base reactions for response-spectrum analysis] article