Influence of column base fixity on the seismic response of single storey braced frames
Bibliographic record
Abstract
Gravity columns with exposed base plate connections are often assumed as pinned in both analysis and design. However, past experiments have shown that base plate connections can provide a significant level of flexural strength and stiffness depending on the depth of anchor rod embedment and the level of axial load carried by the gravity column. The goal of this study is to investigate the influence, if any, that the effect of base plate flexural strength and stiffness have on the global seismic response of single storey braced frames with flexible roof diaphragms. To capture the nonlinear response of exposed base plate connections, a simplified approach to model exposed base plate connections suitable for nonlinear time-history analysis is developed in OpenSees. The OpenSees model uses compression-only elements to model the contact between the base plate and grout, nonlinear fiber elements to capture the flexural response of the steel base plate and tension-only elements to model the nonlinear response of the anchor rods. To validate the proposed modeling approach it is compared with available experimental data in the literature and detailed finite element models developed in Abaqus. The results show that the OpenSees model can capture the nonlinear cyclic response of exposed column base connections and is suitable for conducting nonlinear time-history analysis. To investigate the influence of column base fixity on the system-level response of single-storey braced frames, the nonlinear dynamic response of two prototype single-storey steel concentrically braced frames with flexible roof diaphragms are investigated. The structures are designed for a site in Vancouver, British Columbia Canada and have different storey heights and footprints to investigate the influence that building geometry has on their response. Finite element models of each prototype structure are developed in OpenSees. The lateral load resisting system for the prototype structures is a tension-only braced frame system. The OpenSees model includes inelastic buckling of the tension-only X braces. The flexible steel deck roof diaphragm is modeled using shell elements in OpenSees. The developed models are subjected to a suite of 15 ground motion records representative of the regional seismicity in Western Canada. Each prototype structure is subjected to the series of earthquakes with three different assumptions for the degree of base fixity: (1) pinned, (2) fixed and (3) a realistic base plate connection. The simplified base plate model developed in OpenSees is shown to be able to accurately capture the strength and stiffness of exposed base plate connections and is suitable for nonlinear time-history analysis. The results of the study show that the degree of column base fixity does not have a significant influence on the maximum displacement response of single storey steel braced frames with flexible roof diaphragms. © The 17th World Conference on Earthquake Engineering.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".