Higher strength cold-formed steel framed / steel shear walls for mid-rise construction
Bibliographic record
Abstract
The current North American Standards, AISI S240 (2015) & AISI S400 (2015), provide design information for steel sheathed shear walls having a maximum sheathing thickness of 0.84mm (0.33'') and a 1.37mm (0.54'') thick frame. The specimens tested as part of past research programs composed of these members developed a shear resistance close to 30 kN/m (2058lb/ft) (#10 screws @ 50 mm (2'') o.c.). There is a demand to be able to design all-steel shear walls that are capable of developing lateral resistance beyond 100 kN/m to bridge the gap between cold-formed steel and hot-rolled steel lateral framing shear wall systems. DaBreo (2012) showed that the full blocking increased the resistance of the shear walls by up to 25%.The objectives of the current research project are; 1) to analyze the influence of the wall length for shear walls designed and built with quarter point blocking elements, and 2) to determine the influence of the framing thickness on the performance of the shear walls. In total, 28 specimens (14 configurations) were tested under monotonic and CUREE reversed cyclic loading protocols. The data analysis conducted to extract various design parameters for Canada was based on the Equivalent Energy Elastic-Plastic (EEEP) methodology. The equivalent design parameters were also determined for the United States of America and Mexico.First, the results of this research program indicate that the shear resistance (normalized to length) is not be affected by the wall length for walls having an aspect ratio (h:w) less than (2:1). Walls having an aspect ratio (h:w) of 4:1 reached equivalent levels of ultimate resistance but had to be pushed to large displacement in order to attain those load levels. Second, the data collected showed that specimens constructed with a thicker framing developed a higher shear capacity. Lastly, the testing program showed that the quarter point blocking reinforcement reduced the distortion of the chord studs of the 2' (610 mm), 4' (1220 mm) and 6' (1830 mm) long walls. The full blocking did not restrict effectively the overall out-of-plane deformation of the 8' walls.The recommended Canadian limits states design resistance factor ϕ for shear walls with blocking reinforcement designed to carry lateral wind loads is 0.7. For the USA and Mexico, a resistance factor ϕ=0.6 was recommended. Further, the reduction factor of 2w/h listed in the AISI S400 (2015) Standard for high aspect ratio walls is applicable for the design of blocked shear walls. The recommended factors of safety, calculated for limit states design (LSD) and allowable strength design (ASD) are respectively 2.06 and 2.88. For Canada, an overstrength value of 1.4 was recommended for the blocked specimens. Finally, for CFS framed / steel sheathed shear walls, the measured “test based” Canadian seismic force modification factors for ductility are Rd=2.0 and for overstrength, Ro=1.3.The FEMA P795 methodology was applied in order to determine if the cold-formed steel shear walls designed with full frame blocking and thick sheathing / framing members is equivalent to line A.16 in Table 12.2-1 of ASCE/SEI (2010), which reads “Light-Frame (cold-formed steel) walls sheathed with wood structural panels rated for shear resistance or steel sheets.” The results obtained from the analysis were not conclusive, some of the requirements listed by the FEMA P-795 to confirm the equivalency were not met. It is recommended to apply the FEMA P-695 methodology, in which R values are evaluated using a non-linear response history dynamic analyses of representative structures, whose load-deformation response is modeled after the results of the shear wall tests.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 0.002 |
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".