Static adaptive pushover analysis

Adaptive pushover analysis is employed in the estimation of the horizontal capacity of a structure, taking full account of the effect that the deformation of the latter and the frequency content of input motion have on its dynamic response characteristics. It may be applied in the assessment of both buildings [e.g. Antoniou et al. 2002; Antoniou and Pinho 2004a; Ferracuti et al. 2009] as well as bridge structures [e.g. Pinho et al. 2007; Casarotti and Pinho 2007; Pinho et al. 2009].

In the adaptive pushover approach, the lateral load distribution is not kept constant but rather continuously updated during the analysis, according to the modal shapes and participation factors derived by eigenvalue analysis carried out at each analysis step. This method is fully multi-modal and accounts for the softening of the structure, its period elongation, and the modification of the inertia forces due to spectral amplification (through the introduction of a site-specific spectrum).

Apart from force distributions, adaptive pushover is also able to efficiently employ deformation profiles [Antoniou and Pinho 2004b; Pinho and Antoniou 2005]. Due to its ability to update the lateral load patterns according to the constantly changing modal properties of the system, it overcomes the intrinsic weaknesses of fixed-pattern displacement pushover and provides a more accurate performance-oriented tool for structural assessment, providing better response estimates than existing conventional methods, especially in cases where strength or stiffness irregularities exist in the structure and/or higher mode effects might play an important role in its dynamic response [e.g. Pietra et al. 2006; Bento et al. 2008; Pinho et al. 2008b].

The adaptive algorithm, as implemented in SeismoStruct, is very flexible and can accept a number of different parameters that suit the specific requirements of each particular project. For example, both SRSS and CQC modal combination methods [e.g. Clough and Penzien, 1993; Chopra, 1995] are supported and the number of modes considered is explicitly defined, whereas users can also chose to update only the increment of loads applied at each step or the total loads already applied throughout the process up to the current point (see Adaptive Parameters).

The load control types available for the case of adaptive pushover are similar, in input and functionality, to those available for conventional pushover; adaptive load control, adaptive response control and automatic response control. For further information, users should refer to the Adaptive Parameters page and consult some of the many publications on this subject that are indicated above.