Figure: Vertical frame bridge, Perspective view. See the sloping case.

Each wing of the abutment can be in any angle depending on terrain condition or they are parallel as the center part supporting the deck. In this example the vertical wings are all opening in 45°.

Figure: Vertical frame bridge, South view. See the sloping case.

Figure: Vertical frame bridge, Section1 (or Left View). See the sloping case.

Section1 shows the deck is casting directly on the abutment at the center, and the wings are casting vertically to the center abutment.

Figure: Vertical frame bridge, 3D View. See the sloping case.

Thus, earth pressures from the abutments will act on the deck. Oppositely, the bracing forces from the deck will be transferred to the soil as an attraction for the frame bridge.

Sloping Frame Bridge

The frame bridge is called ‘sloping’ in ICDAS COB when the abutments are sloping outwards at the bottom, as shown in figures below.

Figure: Sloping frame bridge, Floor Plan view with Section1 (on the left). See the Vertical case.

Figure: Sloping frame bridge, Perspective view. See the vertical case.

The sloping abutments open wider at the bottom giving additional 2x3.5m traffic lanes underpass compared to the vertical frame bridge.

Figure: Sloping frame bridge, South view. See the vertical case.

The above Perspective and the South view shows the sloping abutments are designed to stop 846mm below top of the edge beam of the deck, then two small triangle concrete boxes are casting above. Thus, the sloping abutments run directly under the deck to support the deck.

Figure: Sloping frame bridge, Section1 (or Left View). See the vertical case.

The Left view (Section1) shows the sloping abutments are continued to top of the deck edge beams by the to the two triangles casting above the abutments. These two top triangles 846mm height are only intended to prevent the soil fall on the underpass.

Figure: Sloping frame bridge, 3D View. See the vertical case.

Once create the soil in Revit, one has the quantity of the soil on the foundation for LUSAS FEM model. To drag the soil along and below the bridge overpass, one has the quantity of the soil needed for the overpass construction work if the soil is not existing in terrain condition.

LUSAS FEM model

Frame bridge has a simple structural geometry, so the wings can be easily modelled manual in LUSAS from the Revit model geometry. The user can run ICDAS to automate the deck, loads and combinations of loads on it. The case of sloping frame bridge, the user needs to ensure traffic loads act the sloping abutments. Truck on the deck have been automated from ICDAS, also the parts outside the deck. The user needs to define and assign ‘Search Area’ to the sloping abutments so they can detect the traffic loads on it.

Verification of concrete and reinforcement for the long sloping abutments will take time as for the deck, unlike a normal slab bridge with short abutments. Consider the support conditions at bottom of the sloping abutments. Big spring stiffnesses assumed in the abutment direction (at the foundation) will require reinforcement due to the temperature expansion load case. 

ICDAS COB for Slab-Beam Bridges