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TR.27.2 Inclined Support Specification

These commands may be used to specify supports that are inclined with respect to the global axes.

General Format

joint-list INCLINED { f1 f2 f3 | REF  f4 f5 f6 | REFJT f7 } { PINNED | FIXED ( BUT release-spec (spring-spec) ) | ENFORCED ( BUT release-spec) }   


f1, f2, f3 x, y, z relative distances from the joint in the global directions to the reference point
f4, f5, f6 x, y, z global coordinates of an arbitrary reference point
f7 a joint number whose x, y, z global coordinates are the reference point

A vector from the joint location to the reference point location serves to define a local coordinate system (same as member with BETA = 0).  The inclined support directions are in this local  "Inclined Support Axis System" (see more below).

Note: The release-spec and spring-spec are the same as in the Global Supports (See TR.27.1 Global Support Specification).  However, FX through MZ and KFX through KMZ refer to forces/moments and spring constants in the "Inclined Support Axis System" (see below).

Inclined Support Axis System

The INCLINED support specification is based on the "Inclined Support axis system." The local x-axis of this system is defined by assuming the inclined support joint as the origin and joining it with a "reference point" with coordinates of f1, f2, and f3 (see the following figure) measured from the inclined support joint in the global coordinate system.

Reference point for defining an inclined support angle

The Y and Z axes of the inclined support axis system have the same orientation as the local Y and Z axes of an imaginary member whose BETA angle is zero and whose incidences are defined from the inclined support joint to the reference point. G.4.3 Relationship Between Global and Local Coordinates for more information on these concepts.

Note: Inclined support directions are assumed to be same as global when computing some dynamic and UBC intermediate results (e.g., global participation factors).  If masses and/or forces in the free directions at inclined supports are a relatively small portion of the overall forces, then the effect should be very small.