EK149

If the beam was statically indeterminate, the plastic hinge does not reduce it to a mechanism, and it can support any additional load. This additional load causes a redistribution of the bending moment, during which the moment at the plastic hinge remains fixed, while the moment at another highly strained cross-section increases until it forms a plastic hinge. This process is repeated until enough plastic hinges have formed to reduce the beam to a mechanism. The beam is then unable to support any further increase in load, and its ultimate strength is reached.