A Quantitative Super‐Sensitivity Photogrammetry Method for Interstory Drift Measurements of Buildings Under Seismic Excitation

ABSTRACT Interstory drift is a fundamental parameter in earthquake engineering to characterize damage states and performance levels of buildings. Defined as the relative displacement between adjacent floors, it is nearly impossible to measure directly in practice and must be derived from absolute displacement measurements. Among various displacement measurement techniques, photogrammetry has emerged as a prominent method for displacement and drift measurements owing to its full‐field, noncontact incoherent optical characteristics. However, the sensitivity of the existing photogrammetry method is significantly lower than required by precise drift measurements due to the following: (1) much smaller drift magnitudes than displacement itself, requiring higher measurement precision; and (2) quantization‐limited low sensitivity of photogrammetry, especially under large meters per pixel (MPP) conditions in field applications. In this work, we address quantitatively the challenge of precise interstory drift measurement under seismic excitation by exceeding the theoretical sensitivity limit inherent in photogrammetry. Specifically, we leverage the recent advances in breaking the theoretical measurement sensitivity limit in photogrammetry, and adapt a super‐sensitivity photogrammetry method for precise interstory drift measurements. Furthermore, we derive a mathematical model based on rigorous uncertainty propagation theory, for the first time, to quantify the achievable photogrammetry sensitivity for interstory drift, as ; it reveals not only the quantitative relation between the achievable interstory drift measurement sensitivity and that of the displacement , but also the parametric dependence on the key factors: the number of effective spatial pixels , the imaging noise level , the effective rank of the dominant modes , the digital camera bit depth B , and the MPP. Extensive numerical simulations and laboratory shake table tests on a building structure model under representative seismic excitation are conducted and discussed. The results indicate that the adopted method achieves super‐sensitivity interstory drift measurements, which even approach the performance of the coherent laser displacement sensors as the number of effective pixels increases; in addition, observations on the tests are found to be consistent, quantitatively, with the derived mathematical model. This work provides a quantitative super‐sensitivity photogrammetry method for interstory drift measurements.