BEHAVIOR OF DUCTILE STEEL RETROFITTED DECK-TRUSS BRIDGES
Bibliographic record
Abstract
Seismic evaluations of many existing deck truss bridges in recent years have revealed that in the event of a major earthquake, both substructure and superstructure would suffer damage. They are typically supported on non-ductile substructures and the superstructure lateral-load resisting system consisting of non-ductile bracing members and connections. The proposed seismic retrofit strategy includes replacing the existing non-ductile end and lower-end panel members with ductile steel frames, which can perform as ductile fuses. These fuses limit seismically induced forces exceeding capacities of both substructure and superstructure members, therefore allowing damage and energy dissipations to take place in a well predictable and ductile manner and only at the ductile retrofit panels. A performance-based seismic design procedure was developed and used to design retrofits for a 270-ft long prototype steel deck-truss bridge. The design procedure allows a special design of eccentrically braced frames, vertical shear-link and TADAS systems used as main ductile elements of the steel retrofit panels. The results of nonlinear time-history analyses of the as-built and retrofitted bridge indicated that the retrofitted bridge suffered no damage and the earthquake energy dissipated only through ductile retrofit devices. A series of pseudodynamic tests was performed on a 27-ft long, 1/10 scale, complete 3-dimensional model of the prototype steel deck-truss bridge fabricated at the University of Ottawa, to evaluate performance of both as-built and retrofitted conditions of the bridge model. A unique testing procedure was devised and the pertaining test set-up was designed and fabricated to simultaneously apply gravity and non-uniform lateral seismic forces. Test data confirmed the vulnerability of the bridge in the end and top lateral bracings, as well as in the intermediate cross frames. Two retrofits consisting of eccentrically braced frame and vertical shear link system were designed and implemented. Pseudo-dynamic testing of the retrofitted bridge proved the enhanced seismic performance and effectiveness of the proposed steel ductile retrofits. As the shape of hysteretic curves and test observations indicated, the steel shear-links of the retrofitted panels had a robust and ductile behavior. This paper explains the ductile steel retrofitting strategy for deck truss bridges. It presents a summary of test observations and data on seismic performance of a model deck-truss bridge in as-built and retrofitted conditions, as well as performance of ductile shear links used as main energy dissipating device in a deck-truss bridge.
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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 | 0.000 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".