COLD-FORMED STEEL RESEARCH CONSORTIUM SDII SDII Team and Partners: - - PowerPoint PPT Presentation

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COLD-FORMED STEEL RESEARCH CONSORTIUM SDII SDII Team and Partners: - - PowerPoint PPT Presentation

Jul 30, 2023 129 likes •339 views

Steel Diaphragm Innovation Initiative AISI COS/COFS Webinar B.W. Schafer 30 June 2020 COLD-FORMED STEEL RESEARCH CONSORTIUM SDII SDII Team and Partners: Management: COLD-FORMED STEEL RESEARCH CONSORTIUM Industry Sponsors:

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SDII

B.W. Schafer 30 June 2020

Steel Diaphragm Innovation Initiative AISI COS/COFS Webinar

COLD-FORMED STEEL RESEARCH CONSORTIUM

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SDII

SDII Team and Partners:

  • Management:
  • Industry Sponsors:
  • Government Sponsors:
  • Researchers:

COLD-FORMED STEEL RESEARCH CONSORTIUM

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Currently in its final year of primary research.

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SDII

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steeli.org

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SDII

ASCE 7 AISC 341 AISI S310 AISI S400 AISC 342 ASCE 41

Codes and Standards Efforts of SDII

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Background

  • ASCE7-16 introduces alt. diaphragm

design with Rs, but no steel provisions are included

  • FEMA P-1026 (2015) introduces alt.

RWFD design methods, but does not include steel deck in recommendations due to concerns

  • ASCE41-17 does not allow ductility to

be considered in bare or concrete-filled steel deck diaphragms

  • AISC 341-16 does not link to AISI S310

for capacity

  • AISI S310-16 provides a grossly

conservative prediction for strength of concrete-filled steel deck

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SDII

ASCE 7 AISC 360 AISC 341 AISI S310 AISI S400 AISC 342 ASCE 41

Codes and Standards Efforts of SDII

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  • Bare steel deck
  • seismic detailing for AISI S400
  • With PBD methods
  • Rs for ASCE 7
  • Rdiaph for RWFD in ASCE 7
  • m for AISC 342/ASCE 41
  • modeling for AISC 342/ASCE 41
  • Concrete-filled steel deck
  • strength for AISI S310
  • strength callout for AISC 360&341
  • Rs for ASCE 7
  • m for AISC 342/ASCE 41
  • modeling for AISC 342/ASCE 41
  • more coming… (shear studs,

reinforced concrete-filled)

Example of links Created by SDII Standards work

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SDII

Update on latest research

  • CFSRC Dspace provides public reports:

https://jscholarship.library.jhu.edu/handle/1774.2/40428

SelectedTopics

  • Concrete-filled steel deck cantilever

diaphragm testing and connection to final full-scale bay testing

  • 3D building modeling and assessment of

diaphragm design methodologies

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SDII

Concrete-filled steel deck cantilever testing

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W 24x84 (2 studs at 12 in.) W 24x84 (Studs at 12 in.) Deck Direction 15 ft. 12 ft. 17 ft. 13.3 ft. W 24x84 (Studs at 12 in.) W 24x84 (2 studs at 12 in.) Master Actuator in Displacement Control Slave Actuator in Force Control Stud spacing equal to approximately 36 in. for specimens designed to fail the perimeter fasteners

schematic: in the lab:

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SDII

Test matrix

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Test Specimen Concrete Type Steel Deck Height Total Thickness (in) Predicted Shear Strength (k/ft) Objective Failure Mode Status 3/6.25-4-L-NF-DT LW 3 6.25 9.1 Typical 2 Hr Fire Rating for LW Diagonal Tension Completed 3/7.5-4-N-NF-DT NW 3 7.5 14.6 Typical 2 Hr Fire Rating for NW Diagonal Tension Completed 2/4-4-L-NF-DT LW 2 4 5.5 Thin assembly using LW Diagonal Tension Completed (Fills LW gap in past testing) 3/6.25-4-L-NF-P LW 3 6.25 6.5 Fail Studs with LW Perimeter Fastener Completed 2/4.5-4-L-RS-DT LW 2 4.5 19 Include Reinforcing Steel Diagonal Tension Completed #4@12 each way 3/7.5-4-N-NF-P NW 3 7.5 6.6 Fail Studs with NW Perimeter Fastener In Progress* 3/6.25-4-L-RS-DT LW 3 6.25 17.2 Include Reinforcing Steel Diagonal Tension Future #4@18 each way 3/7.5-4-N-RS-DT NW 3 7.5 23.2 Include Welded wire fabric Diagonal Tension Future 6x6 W4.5xW4.5** *prior to March COVID shutdowns completion of last 3 specimens expected by December 2020, now ~ March 2021

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SDII

Unreinforced Concrete-filled steel deck (3/6.25-4-L-NF-DT)

  • Hysteresis
  • Cracking at peak load

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peak matches well with AISI S310-22 Stiffness is challenging to measure, a little low

  • vs. AISI S310-22

Observed hysteresis part of the justification for Rs proposals in ASCE 7, and used in modeling of buildings

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SDII

Test matrix

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Test Specimen Concrete Type Steel Deck Height Total Thickness (in) Predicted Shear Strength (k/ft) Objective Failure Mode Status 3/6.25-4-L-NF-DT LW 3 6.25 9.1 Typical 2 Hr Fire Rating for LW Diagonal Tension Completed 3/7.5-4-N-NF-DT NW 3 7.5 14.6 Typical 2 Hr Fire Rating for NW Diagonal Tension Completed 2/4-4-L-NF-DT LW 2 4 5.5 Thin assembly using LW Diagonal Tension Completed (Fills LW gap in past testing) 3/6.25-4-L-NF-P LW 3 6.25 6.5 Fail Studs with LW Perimeter Fastener Completed 2/4.5-4-L-RS-DT LW 2 4.5 19 Include Reinforcing Steel Diagonal Tension Completed #4@12 each way 3/7.5-4-N-NF-P NW 3 7.5 6.6 Fail Studs with NW Perimeter Fastener In Progress* 3/6.25-4-L-RS-DT LW 3 6.25 17.2 Include Reinforcing Steel Diagonal Tension Future #4@18 each way 3/7.5-4-N-RS-DT NW 3 7.5 23.2 Include Welded wire fabric Diagonal Tension Future 6x6 W4.5xW4.5** *prior to March COVID shutdowns completion of last 3 specimens expected by December 2020, now ~ March 2021

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SDII

Reinforced Concrete-filled steel deck (2/4.5-4-L-RS-DT)

  • Hysteresis
  • Reinforcing

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SDII

Reinforced Concrete-filled steel deck (2/4.5-4-L-RS-DT)

  • Hysteresis
  • Cracking at peak load

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peak matches reasonably with additive strength Including reinforcing.

High strength, excellent distributed cracking, essentially ideal concrete response for the load, but…

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SDII

Reinforced Concrete-filled steel deck (2/4.5-4-L-RS-DT)

  • Hysteresis
  • Cracking at peak load

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peak matches reasonably with additive strength Including reinforcing.

rib shear failure Geometric and/or reinforcing details exist to avoid this limit state, but are not currently in AISC 360/341 or AISI S310 or ACI

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Full Building Bay Diaphragm Testing

Quick Facts: Stroke: +/- 10” Force: 724 kip each direction combined total Steel framing: 20’ x 28’ Concrete: Lightweight, 6.25” thick total, 3” deck Concrete edge dims: 32’ x 24’ Concrete Reinforcement: wwf only

  • Important realistic building features
  • floor framing stiffness included
  • deck fill can bear into columns
  • To be tested at STRESS lab at Northeastern
  • Parallel cantilever diaphragm specimen test at VT
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SDII

Update on latest research

  • CFSRC Dspace provides public reports:

https://jscholarship.library.jhu.edu/handle/1774.2/40428

SelectedTopics

  • Concrete-filled steel deck cantilever

diaphragm testing and connection to final full-scale bay testing

  • 3D building modeling and assessment of

diaphragm design methodologies

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SDII

BRB Building Study

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Seismic Behavior of Steel BRBF Buildings Including Consideration of Diaphragm Inelasticity

Gengrui Wei, Matthew R. Eatherton, Hamid Foroughi, Shahab Torabian, Benjamin W. Schafer March 2020 COLD-FORMED STEEL RESEARCH CONSORTIUM REPORT SERIES CFSRC R-2020-04

https://jscholarship.library.jhu.edu/handle/1774.2/62366

(a) 1-story building (b) 4-story building (c) 8-story building (d) 12-story building Figure 4 3D OpenSees models of archetype buildings

  • Perimeter BRB
  • 1,4,8 and 12 stories
  • Diaphragm designs
  • Traditional ASCE 7
  • Alt. Rs (1, 2/2.5)
  • Vibration - Period
  • Pushover - Ductility
  • NL time history – Collapse
  • Across models
  • Across EQ and EQ levels
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SDII

  • 0.15
  • 0.1
  • 0.05

0.05 0.1

Typical Floor Diaphragm Truss Deformation (in)

  • 100
  • 50

50 100

Typical Floor Diaphragm Truss Force (kip)

  • 1
  • 0.5

0.5 1

Roof Diaphragm Truss Deformation (in)

  • 20
  • 10

10 20

Roof Diaphragm Truss Force (kip)

Example Building Response (1 EQ, MCE level)

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10 20 30 40 50

Time (sec)

2 4 6 8 10 12

Story Drift (SRSS) (%)

  • 4
  • 2

2 4

BRB Deformation (in)

  • 600
  • 400
  • 200

200 400 600

BRB Force (kip)

building drift in time BRB floor concrete-filled steel deck roof bare steel deck response at peak drift Δ(𝑢) 𝑄 − 𝜀 𝑄 − 𝜀 𝑄 − 𝜀

  • Vertical and horizontal LFRS contribute

to the inelastic response

  • BRB dominates inelastic response, and

story drift is the limiting demand

  • Drift is 3D Δ! and Δ" separately do not

effectively capture the actual response

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SDII

Collapse probability across models (ACMR level)

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𝑆! = 1 𝑆! = 2.5 𝑈𝑠𝑏𝑒. 𝐹𝑀𝐺 1 story (bare deck roof) 1 story (conc.-filled deck roof) 4 story (conc.-filled deck floors bare deck roof) 8 story 𝑆! = 1 𝑆! = 2 𝑈𝑠𝑏𝑒. 𝐹𝑀𝐺 𝑆! = 1 𝑆! = 2/2.5 𝑈𝑠𝑏𝑒. 𝐹𝑀𝐺 𝑆! = 1 𝑆! = 2/2.5 𝑈𝑠𝑏𝑒. 𝐹𝑀𝐺 𝑆! = 1 𝑆! = 2/2.5 𝑈𝑠𝑏𝑒. 𝐹𝑀𝐺

predicted collapse (%)

diaphragm design:

  • Traditional ASCE 7 diaphragm design and the alternative diaphragm design method with Rs=2 for

concrete-filled steel deck and 2.5 for bare steel deck result in the same diaphragm designs

  • Performance of the buildings is dominated by story drift and response of the BRB. Collapse

probabilities are acceptable or nearly so for Rs=2/2.5 designed diaphragms

  • Increasing this diaphragm demand forces with an Rs=1 design does not typically result in

improved collapse probabilities for this building system.

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SDII

Conclusions

  • SDII has provided a pathway for modernizing codes and standards related to the seismic

design of bare and concrete-filled steel deck diaphragms, this has lead to a wide array of improvements across multiple standards

  • SDII has increased our state of knowledge with respect to the performance of steel deck

diaphragms and has key final tests and analyses in place to answer critical remaining questions: strength and stiffness contributions as well as load path in real floors, insight on seismic detailing in concrete-filled steel deck diaphragms

  • Technology transfer and outreach will be a big part of the SDII effort in the coming years –

anticipate evolving the effort and website in that direction over next few years

  • Important future questions (irregularities, detailed modeling guidance, integration of seismic

fuses in diaphragms) will remain and be worth pursuing.

  • Ack

Acknowledgments/Discl claimer: This work was supported by the Steel Diaphragm Innovation Initiative which is funded by NSF, AISC, AISI, SDI, SJI, and MBMA. Any opinions expressed in this presentation are those of the authors alone, and do not necessarily reflect the views of the sponsors.

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