Static pushover analysis

Conventional (non-adaptive) pushover analysis is employed in the estimation of the horizontal capacity of structures implying a dynamic response that is not significantly affected by the levels of deformation incurred (i.e. the shape of the horizontal load pattern, which aims at simulating dynamic response, can be assumed as constant).

The applied incremental load P is kept proportional to the pattern of nominal loads () initially defined by the user: . The load factor is automatically increased by the program until a user-defined limit, or numerical failure, is reached. For the incrementation of the loading factor, different strategies may be employed, since three types of control are currently available: load, response and automatic response.

• Load control refers to the case where the load factor is directly incremented and the global structural displacements are determined at each load factor level.
• Response control refers to direct incrementation of the global displacement of one node and the calculation of the loading factor that corresponds to this displacement.
• Automatic response control refers to a procedure in which the loading increment is automatically adjusted by SeismoStruct, depending on the convergence conditions at the previous step.

A more detailed description of the three types of control in pushover analysis is given in Loading Phases.

Note: Conventional pushover analysis features an inherent inability to account for the effects that progressive stiffness degradation, typical in structures subjected to strong earthquake loading, has on the dynamic response characteristics of structures, and thus on the patterns of the equivalent static loads applied during a pushover analysis. Indeed, the fixed nature of the load distribution applied to the structure ignores the potential redistribution of forces during an actual dynamic response, which pushover tries to somehow reproduce. Consequently, the resulting changes in the modal characteristics of the structure (typically period elongation) and consequent variation in dynamic response amplification are not accounted for, which might introduce non-negligible inaccuracies, particularly in those cases where the influence higher mode is, or becomes, significant. These effects can only be accounted for by means of Adaptive Pushover.