RCPier - Spread Footings on Rock vs Soil

Hi there,

I'm checking a design calculation for an abutment on spread footings done in LEAP RCPier. I couldn't find any information in the user manual or input/analysis tabs to determine how bearing pressure is calculated for a wall bearing on soil or rock. Note, depending on this criteria, AASHTO requires bearing stress to be determined based on a uniform distribution (soil) or linearly distributed (rock).  

Any help on this matter would be appreciated.

Thanks

  • Also if the user wants to input maximum Soil reaction manually then that information can be inputted in the Footing TAB --> Reaction Parameters --> user specified maximum Soil reaction.

    Whatever value inputted here by the user will be used for the design of the footing. Currently user cannot input if the spread footing is on Rock.

  • The design calculation for an abutment on spread footings done in LEAP RCPier will be similar to the spread footing design under a column.
    The footing can be defined only if user has selected Stem Wall option in abutment configuration screen. In this case, program assumes the footing is concentric with stem. If user wants to consider the effect of eccentricity, consider this effect during load definition.

    As per help file -- For isolated spread footings, forces and moments obtained from each load combination, at the top of the footing, are applied at the centroid of the footing. The footing is treated as a member with infinite stiffness. The bearing pressure at each corner is calculated, as follows: Q = (P/A) +- ( Mxx * Z / Ixx ) +- ( Mzz * x / Izz )