Multiaxial fatigue life assessment of complex connections using sparse response-only vibration measurements
Puerto Tchemodanova, Sofia.
2021
-
Thesis
(Ph.D.)--Tufts University, 2021.
Submitted to the Dept. of Civil Engineering.
Advisor: Masoud Sanayei.
Committee: Babak Moaveni, Erin Bell, Eleni Chatzi, and Guillermo Riveros.
Keywords: Civil engineering, and Engineering.
Civil engineering structures grow more complex as engineers push innovation boundaries using new structural systems. ... read moreLoad complexity, costs, construction and maintenance efficiency, among other things, can lead to unique designs that are often excluded in current design codes and evaluation standards. Complex structures are subject to different types of cyclic loading such as vehicular, mechanical, seismic, and wind. Continuous application of this types of stresses may induce microcracking that can eventually propagate and produce fatigue failure of the member, connection, or structure. Fatigue-induced damage is currently one of the most common types of damage experienced by ordinary and complex civil engineering structures subjected to cyclic loading. However, current fatigue evaluation and design standards provide limited guidance on how to approach complex welded connections. A methodology for the evaluation of remaining fatigue life of connections that experience multiaxial non-proportional load histories (common in complex connections) is proposed. Furthermore, the estimation of fatigue life of a structure or structural component requires availability of strain time histories at critical locations. However, these time histories are commonly unavailable due to the pointwise nature of typical wired sensing systems, their limited coverage, and their inaccessible location or difficulties in instrumentation placement. Therefore, the possibility to reliably estimating strain time histories (in place of directly measuring) are essential for remining fatigue life predictions under realistic conditions of operation. The Augmented Kalman Filter (AKF) is combined with a substructuring approach for the estimation of strain time histories at unmeasured locations of a rollercoaster connection, with the purpose of predicting remaining fatigue life. In addition, a new scheme is proposed for the improvement of AKF strain predictions. Strain predictions can reliably be used for dynamic evaluation of the state of stresses and multiaxial fatigue life predictions of complex structures such as rollercoasters, bridges, wind turbines, etc.read less - ID:
- 6108vs063
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