The growth in computer processing power has made possible a continuous drive towards increasingly accurate but at the same time more complex analysis methods. Thus, the state of the art has progressively moved from elastic static analysis to dynamic elastic, non-linear static and ;nally non-linear dynamic analysis. In the last case, the convention has been to run one to several di4erent records, each once, producing one to several ‘single-point’ analyses, mostly used for checking the designed structure. On the other hand, methods like the non-linear static pushover (SPO) [1] or the capacity spectrum method [1] o4er, by suitable scaling of the static force pattern, a ‘continuous’ picture as the complete range of structural behaviour is investigated, from elasticity to yielding and ;nally collapse, thus greatly facilitating our understanding. By analogy with passing from a single static analysis to the incremental SPO, one arrives at the extension of a single time-history analysis into an incremental one, where the seismic ‘loading’ is scaled. The concept has been mentioned as early as 1977 by Bertero [2], and has been cast in several forms in the work of many researchers, including Luco and Cornell [3; 4], Bazurro and Cornell [5; 6], Yun and Foutch [7], Mehanny and Deierlein [8], Dubina et al. [9], De Matteis et al. [10], Nassar and Krawinkler [11, pp 62–155] and Psycharis et al. [12]. Recently, it has also been adopted by the U.S. Federal Emergency Management Agency (FEMA) guidelines [13; 14] as the incremental dynamic analysis (IDA) and established as the state-of-the art method to determine the global collapse capacity. The IDA study is now a multi-purpose and widely applicable method and its objectives, only some of which are evident in Figure 1(a) and 1(b), include:
1. thorough understanding of the range of response or ‘demands’ versus the range of potential levels of a ground motion record,
2. better understanding of the structural implications of rarer=more severe ground motion levels,
3. better understanding of the changes in the nature of the structural response as the intensity of ground motion increases (e.g. changes in peak deformation patterns with height, onset of sti4ness and strength degradation and their patterns and magnitudes),
4. producing estimates of the dynamic capacity of the global structural system and
5. ;nally, given a multi-record IDA study, understanding how stable (or variable) all these items are from one ground motion record to another.
Our goal is to provide a basis and terminology to unify the existing formats of the IDA study and set up the essential background to achieve the above-mentioned objectives.
معرفی کتاب Incremental dynamic analysis
