Open web crane girder suport conditions at column locations 1

[kvram]

Dear Members,

I am designing a crane girder "open web type " due to heavy crane loads and large spans. Crane capacities are two nos. of 50t and crane beam span is 24m. Crane beam has to design with top chord and bottom chord with web members. This crane girder will be supported by column in each end at both chord member points. To define the support points for these chord members , how define the type of supports for this crane beam?
Generally we define one end with Pin and other end with roller supports for a simply supported beam . Due to four types of support points , pl. suggest me the type of support which gives the best optimized design.

Thanking you.

Regards,
KVRam

 

[IJR]

dear Kvram

50ton crane girder is a serious business and 24m span will govern your design. You are going to have a deep girder.

My five cents worth:

1) You have a lateral buckling problem no matter what girder you will use. Brace the top chord or the top flange appropriately. If you use trusses then consider a 3D triangular prism truss with a flat top. this will resist lateral forces. If you use plate girders then I would suggest box sections.

2) You have a stiffness requirement. Usually under crane load your deflection is required to be below l/600.

3) You may have a fatigue problem. If your stresses govern then keep them well below your usual allowables and learn all you need to know on how fatigue is fought especially on weld details.

4) Your support conditions are simple. Usually sufficient rotations must be allowed at the end of girders by detailing properly, poor support details will eventually show themselves after a couple of crane runs.

If this is your first time with crane girders then I suggest you search for a typical girder and make sure you show your design to an experienced someone before application.

You may want to read AISE design of steel mill buildings further for basics of design.

respects
IJR

 

[kvram]

Dear Mr. IJR,

Thank you for your detailed reply and valuable guidance. Surely I will present my deign calcs. with an expert like you before application.

Sorry for late response.

Regards,

KVRam.