Finite element analysis of vibrations on flexible structures due to turbulent wind
Bibliographic record
Abstract
Wind load effects have a major impact on the design of numerous civil engineering structures. Building codes such as the National Building Code of Canada (NBC, 2015), the American Society of Civil Engineers Standards (ASCE-7, 2016) and the Eurocodes (Eurocode 8, 2016) display great details about the static effect of wind on different building shapes, surfaces and isolated exposed components. However, these standards provide very limited guidance on dynamic effects and current design methods are limited in scope and applicability, since they are based on dating experimental data such as a research from Vickery and Basu (1983), which did not use sophisticated experimental techniques as available nowadays. This research presents a dynamic analysis of two flexible telecommunication monopoles and a cantilevered sign structure, under static, harmonic and random wind loads using the nonlinear finite element analysis software ADINA. The analysis does not consider wind-structure dynamic interactions. The objective of this study is to investigate the response of different structures to a combination of wind actions and monitor any excessive or dangerous vibrations that may be engendered by resonance phenomena. Furthermore, the cyclic vibrations produced by wind can be used to assess the vulnerability of the modelled structures to fatigue and approximate their useful fatigue life. By modelling existing structures, field data can eventually be used to validate and adjust the models in order to mimic reality as much as possible and minimize uncertainty related to numerical predictions.After applying 100 random wind time histories to the three structures, it was first found that, for monopole structures, the suggested gust factor of 2.0 by CAN/CSA S37-18 is accurate in predicting the dynamic amplification produced by natural wind gusts, with maximum tip displacements values found to be amplified by 51% and 98% in comparison with the maximum equivalent static load. With further analysis of the critical case, the stress range was determined and compared to the fatigue limit of the material according to the S-N curve method (Wohler, 1855). It was found that the stress range would not exceed 50% of the value of the endurance limit of steel after 108 cycles of vibration for both monopoles. Thus, according to this method and under normal operating conditions, these two telecommunication towers will not likely suffer fatigue damages. Ambient Vibration Measurements (AVMs) were taken on one monopole and the first three modes of vibration of the structure as well as the damping corresponding to the first mode were obtained. It was found that the numerical model was about 10% stiffer than its real-life rendering. As such, the numerical model was adjusted beforehand to erase that disparity. The cantilevered sign structure was subjected to the same 100 random wind time histories and the maximum displacement observed at the end of the cantilever was 25 mm. This value corresponds to a 150% dynamic amplification from the maximum equivalent static load of 10 mm. CAN/CSA S6-18 proposes a gust factor value of 2.5 which corresponds to the exact amplification value found through dynamic numerical analysis. Once again, fatigue analysis showed results of stress range under 30% of the endurance limit of steel for this particular cantilevered sign structure after 108 cycles of vibration. Therefore, according to the S-N method (Wohler, 1855) and under normal operating conditions, this cantilevered sign structure will not likely suffer fatigue damages. Ambient Vibration Measurements (AVMs) were also taken on the sign structure and the first 4 modes of vibration of the structure were obtained. It was found that the numerical model was about 13% stiffer than its real-life rendering. Therefore, the numerical model was once again adjusted beforehand to correspond to the actual values measured in-situ
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".