DESIGN OF BEAMS IN BRIDGES

[harmsgundam]

Hi all,

I am new in the design of bridges and I would like to ask for opinions regarding the design of longitudinal beams directly supporting the slab above. Is it fine to subject the longitudinal beam to the full load of an MS18 truck loading/ lane loading for example (i.e. 324kN gross weight). Well not the full gross weight depending on the distance between abutments/ piers, but since a truck loading/ lane loading will cover a 3m lane width, normally there are several longitudinal beams within that 3m span. So should I design 1 longitudinal beam subjecting it to the full truck/ lane loading or will the load be shared with the adjacent longitudinal beams? Thanks in advance for those who can response.

 

[bridgebuster]

If you're using AASHTO LRFD you apply the full lane load to the stringer plus distribution; no impact is applied to the lane load if it's part of the HL-3 loading.

Under the AASHTO Standard Specifications, it's the same thing except you include impact.

 

[yakpol]

The longitudinal beam in multi-beam bridge will carry a fraction of total truck/lane loading. Look in AASHTO section 4.6.2.2 (Beam-slab bridges) for an appropriate distribution factor. Alternatively distribution factor can be found from grillage or FE analysis which are more precise but require more efforts.

 

[harmsgundam]

@bridgebuster and yakpol - Thank you very much for your replies.