Adaptive Pushover

In addition to the parameters defined in the Adaptive Parameters module, some advanced settings can be selected in this window. These settings are:

Type of Updating
This adaptive option defines how the load distribution profile is updated at each analysis step. Four alternatives are available:

Total Updating. The load vector for the current step is obtained through a full substitution of the existing balanced loads (load vector at previous step) by a newly derived load vector, computed as the product between the current total load factor, the current modal scaling vector and the initial user-defined nominal load vector. This updating option is not recommended, since it features limited theoretical support.
Incremental Updating. The load vector for the current step is obtained by adding to the load vector of the previous step (existing balanced loads), a newly derived load vector increment, computed as the product between the current load factor increment, the current modal scaling vector and the initial user-defined nominal load vector. Incremental Updating usually is conceptually sounder than total updating, for which reason it is the default option.
Hybrid Updating. With this third load vector updating option, the possibility of combining the two methods described above, is provided. In this manner, the load vector for the current step is obtained through partial substitution of the existing balanced load vector by a newly derived load vector and by the partial addition of a newly derived load vector increment. The percentage ratios that may lead to an optimum solution, in terms of accuracy and numerical stability, obviously vary according to the model characteristics, the type of loading it is subjected to (displacements or forces), and the response spectra used in the determination of the modal scaling vector (if one is being used).
Fully Incremental Updating. The load vector for the current step is obtained by adding to the load vector of the previous step (existing balanced loads), a newly derived load vector increment, that reflects the changes in the current modal properties of the structure.

Frequency
This parameter defines how and when the modal scaling vector is updated during the analysis. Any integer larger than zero can be used. The default is 1, which means that the load distribution is updated at every analysis step, with the exception of steps where the analysis increment has been reduced due to convergence difficulties (automatic step adjustment). In those cases where a very large number of analysis steps have been defined by the user (i.e. the load is being applied in very small increments), it might be advantageous to use a frequency value that is larger than 1 (i.e. the modal scaling vector does not come updated at every step) so as to reduce the duration of the analysis without loss of accuracy.

Modal Combination method
Three modal combination rules can currently be utilised in the computation of the modal scaling vector, consisting of (i) the well-known Square Root of the Sum of Squares (SRSS), (ii) the Complete Quadratic Combination (CQC) and (iii) the Complete Quadratic Combination with three components (CQC3) methods [see e.g. Clough and Penzien, 1993; Chopra, 1995; Menun and Der Kiureghian 1998]. It is acknowledged that there are conspicuous limitations associated to the use of these always-additive modal combination methods, as discussed by many researchers [e.g. Kunnath, 2004; Lopez, 2004; Antoniou and Pinho, 2004a], and an optimum ideal methodology is yet to be identified. Such limitations, however, may be partially overcome with the employment of Displacement-based Adaptive Pushover, as shown by Antoniou and Pinho [2004b] and Pinho and Antoniou [2005], amongst others.
In addition, users may also employ a Single-Mode in the computation of the modal scaling vector, in which case they are asked to define the mode number and corresponding degree of freedom to be used. This may come particularly handy on those situations where the user does not have ways to estimate/represent the expected/design input motion at the site in question, in which case he/she should use DAP-1st mode (for buildings only).