The tripod structure show in the
figure(http://home.attbi.com/~josephsieh/Picture1.jpg) is made of
steel tubes
and has a triangular transient loading applied at its top as shown.The
load
direction is parallel to the 8 inch dimension. Dimensions are in
inches. The frame is made of 5/16 inch steel tubes (0.095 inch wall
thickness) that have been welded together. The 8 inch and 12 inch legs
are at 90 degrees with respect to one another. Consider the triangular
base to be completely fixed. Use PIPE16 elements in ANSYS(it is an
engineering software). Because of the symmetry of the cross section, a
PIPE16 element orientation is defined merely by the two nodes it
connects, and the required real constants are just the steel and wall
thickness.
(a)Use single degree  of freedom response  spectrum method to estimate
   the maximum displacement in the direction of the load for a load
amplitude
   Po=0.07656 pounds,t=(T2)/2 sec where T2 is the period of the second
mode.
   Neglect damping
(b)Use modal analysis coupled with numerical integration methods to
verify
   your result found in (a).How many modes do you think are necessary
to get
   a good answer?Remeber that if you normalize the modes n the
matrix,the
   generalized masses all have unit values.
(c)Find the amplitude of steady state response of the problem describe
in (a)
   if the load is applied as a harmonic loading at frequency equal to
the
   average of the first two natural frequencies.(omega1+omega2)/2
   Do you think damping is important in this problem?Explain how to
include a
   damping of 2 percent  critical in each mode but don't do the
calculation
PS:Please show me the ANSYS code

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Clarification of Question by wjs-ga on 01 May 2003 14:34 PDT

td=(T2)/2 sec

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Clarification of Question by wjs-ga on 01 May 2003 23:28 PDT

1.The frame is made of 5/16 inch outer diameter steel tubes (0.095 inch wall
  thickness) that have been welded together
2.please use ANSYS to set the model and solve in (a)