During pushover analysis, what does the term 'plastic hinge' represent, and why is its location significant?

During pushover analysis, a 'plastic hinge' represents a localized zone within a structural element (like a beam, column, or wall) where significant inelastic deformation occurs under increasing load. In simpler terms, it's a point where the material yields and starts to deform permanently, behaving like a hinge that can rotate without significant increase in resisting moment. The location of plastic hinges is significant because it indicates where the structure is experiencing the highest stress concentrations and where failure is most likely to initiate. The sequence in which plastic hinges form and their locations reveal the structure's failure mechanism and its ability to redistribute forces. If plastic hinges form in undesirable locations, like in columns before beams (in a moment frame), it can lead to a soft-story mechanism and premature collapse. Conversely, if plastic hinges form in a controlled manner in beams, the structure can exhibit more ductile behavior and dissipate energy effectively. Therefore, monitoring the location and sequence of plastic hinge formation is crucial for assessing the seismic performance of a structure during pushover analysis.