carrier beam design
carrier beam design
(OP)
i am designing a steel structure that will be shipped as a "whole structure" using transporter. since i cannot use uniform support in staad i used pinned supports. but it is not acting the way i wanted.
anaylysis shows support reaction from 2 to 5 is under tension.
staad is neglecting the stiffness/rigidity of beam to make
all supports reaction under compression.
how do i do model it to simulate "actual" reaction where
all supports reaction are compression?
anaylysis shows support reaction from 2 to 5 is under tension.
staad is neglecting the stiffness/rigidity of beam to make
all supports reaction under compression.
how do i do model it to simulate "actual" reaction where
all supports reaction are compression?






RE: carrier beam design
Mike McCann
MMC Engineering
RE: carrier beam design
RE: carrier beam design
i did a test run where i used very thick concrete
(definitely rigid) against a relatively small
load at the ends and still getting tension on 2 to 5..
looks like the closest i could to "actual"
is remove 2 to 5..
unless any other good advice here..
RE: carrier beam design
STAAD is giving you the correct answer as you have it modeled.
My suggestion:
Add additional nodes. At least one in between each of the support nodes that you have.
Copy all support nodes down 3". These copied nodes will be your new supports.
Remove all support parameters.
Assigned "fixed" supports at the new support nodes.
Put stub columns in from the new support nodes to the old support nodes.
The two stub columns on either end should be fixed at the base, and pinned at the beam.
Assign "compression only" to the remaining stub columns. This is under Commands --> Member Specifications or the specification page icon.
Re-run it.
Let me know how it goes.
Chip
RE: carrier beam design
what am trying to do is for staad to consider the "rigidity" of carrier beam similar to when
you do mat foundation as assumed rigid..
RE: carrier beam design
DaveAtkins
RE: carrier beam design
as infinitely rigid?
RE: carrier beam design
Naturally, we know this is not true.
If the transporter is perfectly rigid and the beam is not, then supports 2 through 5 are in tension by inspection.
We know this is probably not true either.
What is true is that both the beam and the transporter are NOT perfectly rigid and the center of the beam may or may not lift off of the center of the transporter. The only way to approach this accurately is to model both the beam and transporter's stiffness correctly.
Two ways to get your arms around the problem: 1 - go ahead and assume that supports 1 and 6 support all of the load or 2 - make sure they put some wood blocks to support the beam on the transporter. This will allow the beam to flex and help redistribute some of the load towards the center.
If you "heard" it on the internet, it's guilty until proven innocent. - DCS
http://www.eng-tips.com/supportus.cfm
RE: carrier beam design
thanks all for your help..