[LOAD]     The Lateral load profile for Wind or Seismic shows nothing, though the loads are defined. Why?

A: The Principle Axis of regular buildings are generally oriented towards the two mutually perpendicular horizontal directions i.e X-Y. However, this may not be the case of buildings with Plan Irregularity.

The Plan Irregularity is a condition when the plan arrangement of lateral load resisting elements providing stiffness in one direction of a building are not perpendicular to those providing stiffness in other direction. Hence the structure’s Principal Axes directions may not be parallel with the directions of the lateral load resisting elements.

It is very important to determine the Principal Axes directions because lateral loading in those directions would result in maximum values of lateral displacement and drift ratio.

Lateral forces in each lateral force-resisting element would achieve their maximum values when the lateral loading is applied in a particular direction. This direction is unique for each lateral force-resisting element.
In midas Gen, ‘Auto –Search Angle’ option automatically takes the excitation angle of response spectrum as the major-axis direction of a building.
From main menu select Load > Dynamic load > Response spectrum Load case

Major : Major-axis direction Ortho : Major-axis direction + 90˚

Creation date: 8/16/2017 12:39 PM      Updated: 9/5/2017 8:34 AM
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