I am undertaking a check for a 4 span steel box girder footbridge with a curved soffit. The southern abutment of the bridge will form an integral connection with lateral and flexural displacements being accommodated by the piles. The northern abutment will be allowed to freely moved in longitudinal and transverse directions by providing elastomeric bearings.
The superstructure of the bridge was modelled with plate elements. The southern abutment (as shown below) was modelled with 3D solid elements and the piles was modelled with beam elements. The soil structure interaction was modelled by applying soil springs to the abutment and piles.
At the northern abutment, supports that is vertically fixed and have soft springs in longitudinal and transverse directions were used to model the bearings.
My colleague has also created a LUSAS model for this bridge using similar approach.
We are getting similar axial force in piles (Fx), however our Shear Forces (Fy and Fz) and Bending Moments are different. My maximum shear forces Fy and Fz are 189 and 61kN respectively. The results from Lusas model are 280 kN and 113 kN. Similarly the bending moment from STAAD is 164kNm which is a lot smaller than 380kNm from Lusas.
We compared the geometry, loadings, spring stiffness etc. and they are all similar. I am running out of things to compare. The only possibility might be the way that I connect piles to the pile cap in STAAD. At the moment it is just beam elements connected directly to solid elements.
Your comments on this would be appreciated.
Thanks
Harry
Image may be NSFW.
Clik here to view.
