Is there a reference to look at explaining the effect of bearing surface on loadpath?
For example, an existing structure has a suboptimal load transfer/distribution. A new support is added to add/improve integrity. How the loadpath will change, should the surface of the new support press hard against the existing structure or just slightly to guide the load?
See the diagram below.
Frame Action
If you attached the additional support snugly without releasing the built-in stresses in the original support structure, then the state of the bearing of the new support will depend on the load and the deformation that come after the addition. Note that the stresses in the original support will continue to increase, albeit at a reduced rate.
However, the entire load on the beam, including self-weight, will be shared equally by both the original and the additional supports, if the stress in the original support structure is fully released by "jacking" and "repositioning" operations prior to and after the addition is in place.
Composite Action
Another requirement to ascertain the proper transfer of loads from the existing structural element to the new element is to develop the composite action between the two elements through adding connectors/shear studs and careful grouting at the interface. Without such, while beam-column joint can be fully in contact, separation could occur in between the existing structure and the additional beam element, as they literally act independently from each other, thus the state of stress at the interface is highly uncertain.
