monorail beam flange reinforcemen

huangyhg

monorail beam flange reinforcement
dear all,
in case the secondary stresses due to trolley and the load on it is high and trolley flange needs reinforcement do you use a flat bar underside of the flange to increase the stiffness? is there a supporting document to see what has been considered for the reinforcement calculation, and if available how can i reach that document? does have specific weld requirement?
i have a bhp brochure on monorail beam design which gives a type of reinforcement which consist of two bar ( rectangular or square ) elements. these stiffener bars are welded under the flange, and each one is located underside of the trolley wheels and continuously welded. all these works are based on bhp tests. however, this document does not support the full bar stiffener and beams with tapered flanges.
if you know the availability of this document please let me know asap. if the document is reasonable in size ( for you ) could you please forward on my e-mail address below.
thank you in advance.
ibrahim demir
design engineer
clyde babcock hitachi
for safety purposes, i personally would replaced the monorail beam (i suppose its removable) with a new one that can take the load.
kiss - keep it simple and safe
do you need to:
1. increase the moment capacity of overall section for strength,
2. increase the stiffness of overall section for deflection control, or
3. strengthen the the bottom flange for local bending due to the trolley wheel loads
if it is the latter, don't make the mistake of having a single flange "doubler" plate that spans between the lange toes, i.e.:
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in this arrangement the flange "doubler" plate won't contribute to resisting the cantilever bending moment due to the trolley wheel loads.
you may be able to replace the trolley with one that has more wheels to spread out the load. this works pretty well with relatively light systems.
thanks for your replies.
unfortunately, we are not able to replace the section size. the cross section (u beam)is the most suitable section for bending to a small radius in the weak axis direction. i tried to use universal column sections which does not require the stiffening. however, the manufacturer can not bend to the working radius that the client requires. additionally, built-in cross section becomes very expensive with bends. therefore, we need to use universal beam which have less flange width that does not cause problem during the bending. however, these beams do not have the required flange thickness.
i have made this kind of reinforcement by using the bhp reference earlier. however, we are trying to reduce the cost down, and additionally two stiffeners under the flange require more space to overcome the secondary stresses. this time, we wanted to try to use a single flat bar. however, we do not have any supporting document or tests at this stage. i am still trying to obtain it if available.
the bhp document i have has some references but i am not sure if they are suitable for my purpose. i am just guessing; if they were, the bhp would use the same method instead of using two bars under the flange.
thanks again.
ibrahim demir
torsional effects on a monorail beam curved in plan will further stress the flanges.
refer to bradford's design of steel i-beams curved in plan to as4100 (australian journal of structural engineering, 2000;3(1-2):85-98).
dbuzz,
thanks for your response. however, i disagree with your statement on the zero contribution of the doubler plate under the flange for the trolley wheel load. basically the resistance comes from the flextural stiffness in the longitudinal direction not in the transverse direction of the bar(s). the action is localised under the wheels. therefore, the remaining portions both side of the bars are stiil unloaded locally and have contribute by resisting flexurally in the longitudinal direction.
thanks again
edba and 49merc,
thanks for your response. however, the loads are very high and we need to keep the bend radius as i explained earlier. the only option we have is to reinforce the bottom flange by a method that i was explaining earlier.
our target is to use a single flat bar ( doubler plate ) underside the flange at this stage. otherwise, we will be forced to use the bhp reference for reinforcement with two bars.
thanks for your contribution.
ibrahim demir
dbuzz,
thanks for your reference. however, that is not the one i can use for the calculation for the resistance cantribution of the doubler plate to local bending.
thanks
ibrahim demir
the trolley wheel loads are transferred to the beam web from the point of load application by local bending of the bottom flange.
the bhp design guideline uses longitudial billets, which are quite stiff, to increase the effective width of flange resisting the local bending moment.
i would be wary of assuming that a flange doubler plate, of similar thickness to the bottom flange, will achieve the same result.  it simply isn't stiff enough.
the bradford reference is not a monorail design guide but it does advise on how to calculate the combined stress in the bottom flange from bending and torsion.  this effects the required thickness for your bottom flange for transfer of trolley wheel loads.  as 1418.18-2001 requires that if the horizontal radius of curvature is less than twice the distance between the supports, then the beam must be analysed as a curved beam.
dbuzz,
thanks for the details. i accept your concern about the beam with curvature. i do calculate the combined action on the curved beam and on the bottom flange. this is not my concern.
i understand that you know about the bhp guideline about stiffening. if you follow the examples in that booklet, you will see that those longitudinal billets have a contribution to the resistance against the localised wheel loads in addition to the overall bending. they act as a beam on an elastic foundation. if you write a spreadsheet for this calculation, you will see that you are able to play with the width and the depth of these billets.
so, my concern is to replace these two billets with a flat bar ( a doubler plate in your term ). this doubler plate will still act as the billets act against the load. my question is how? and, is there any supporting paper or test?
thanks for your input. i still believe it is very valuable for me.
ibrahim demir