Earthquakes, Records, and Nonlinear Responses

Abstract

The estimation of MDOF nonlinear structural response given an earth-quake of magnitude M at distance R is studied with respect to issues such as the benefits and harms of (1) first scaling the records, (2) selecting records from the “wrong” magnitude, (3) alternative choices for how to scale the records, and (4) scaling records to a significantly higher or lower intensity, etc. We find that properly chosen scaling can reduce the necessity of the number of nonlinear analyses by a factor of about four, and that proper scaling does not introduce any bias. Several global and local nonlinear damage measures are considered. A five-DOF model of a steel structure is used; other cases are under study. The paper finishes with a demonstration of the use of such results in the estimation of the annual probability of exceeding a specified interstory ductility (drift) or other damage measures.

Computational and rapid expected annual loss estimation methodologies for structures

“…An example of the former would be uncertainty in analytical modelling, and the latter would be the inherent record-to-record randomness of earthquake ground motions. As discussed earlier, previous studies [5,6,16] have shown that aleatory uncertainty approximately conforms to a lognormal distribution. For convenience, it is assumed here that epistemic uncertainties are also lognormally distributed.…”

“…This Rapid IDA-EAL methodology utilizes the customary assumption that variability conforms to a lognormal distribution [5,6,15,16], allowing fragility curves to be generated for discrete states of damage. The fragility curves are then transformed via the seismic hazard model into hazardsurvival curves for each damage state.…”

“…Choosing an appropriate IM is an important step, since it can have significant effect on the scatter of data. Current best practice for the first mode dominated structures is to use the 5% damped spectral acceleration at the fundamental period of the structure, which has been shown to be relatively 'efficient' and 'sufficient' compared to peak ground acceleration [16]. Due to the lack of large earthquakes in New Zealand over the past 100 years, despite its known large seismicity, there are insufficient regional ground motion records to use for the IDA.…”

“…β C = 0.2 and β U = 0.25. Although β D is difficult to quantify, it varies depending on the parameter used as the IM and the value of IM itself [16]. Using spectral acceleration at the natural period of the structure as the IM (i.e.…”

Simplified Seismic Collapse Assessment of Generic Frame Structures Subjected to Pdelta and Material Deterioration

“…For the same structural configurations, in Figure 7 the corresponding measure for the recordto-record dispersion σ = ln CC p84 /CC p16 [20], where CC p84 and CC p16 denotes the 84th and 16th percentile, respectively, of the collapse capacity, is depicted. σ is a meaningful measure of dispersion because the record-to-record variability of the collapse capacity can be in general approximated by a log-normal distribution [23], confirmed in [4,3] for PDelta sensitive structures. The outcomes show that σ is proportional to the building flexibility τ and the number of stories n, and it increases as τ and n increases.…”