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CUREe-Caltech Woodframe Project, Element 1 - Research Meeting

CUREe-Caltech Woodframe Project, Element 1 - Research Meeting. Task 1.4.8.2 - Connections Ken Fridley, Ted Ryan, David Pollock, and Rafik Itani Washington State University January 12 & 13, 2001. Outline. I. Data Analysis a. Scenario 1 first cyclic test

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CUREe-Caltech Woodframe Project, Element 1 - Research Meeting

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  1. CUREe-Caltech Woodframe Project, Element 1 - Research Meeting Task 1.4.8.2 - Connections Ken Fridley, Ted Ryan, David Pollock, and Rafik Itani Washington State University January 12 & 13, 2001

  2. Outline I. Data Analysis a. Scenario 1 first cyclic test b. Scenario 1 second cyclic test II. Probabilistic Analysis of toe-nailed joint a. Derivation b. Results III. Suggested modification of Scenarios 7 & 8 a. Scenario 7 b. Scenario 8 IV. Observations and Questions

  3. I. Data Analysis

  4. Scenario #1 Cyclic test number #1 Load vs. Interstory slip --- Interstory slip Max absolute load: 6700 lbs.. Displacement at max load: 0.73 in

  5. Scenario #1 Cyclic test number #2 Load vs. Interstory slip --- Interstory slip Max absolute load: 6100 lbs. Displacement at max load: -0.84 in

  6. II. Probabilistic Analysis of toe-nailed joint

  7. Wall Elevation View Area of interest

  8. Failure line

  9. Procedure • Use NDS Yield Equations and Monte Carlo Simulation to predict yield load. • Bending yield strength of nails and dowel bearing strength of wood were considered as random variables. All other variables were assumed deterministic. • Distributions were fit to random variables and a single nail yield value was produced using a Weibull distribution (for both random variables) based on best-fit. • This was expanded to analyze the connection as a ductile parallel system.

  10. NDS Yield Equations For Nailed Connections Modes IIIs and IV generally control in nailed connections of this type

  11. Parallel System Yield Equation 1,2 1. Assuming same stiffness in each nailed connection 2. Data ranked in increasing order

  12. Predicted yield load (direct multiplication of single nail capacity and probabilistic value) Using the yield limit equations without safety factors (but including toenail factor): Z = 364 lbs. Mode Is Toenail factor 0.83 Z = 215 lbs. Mode IIIm Z= 144 lbs. Mode IIIs Z = 132 lbs. Mode IV <== controls There are 37 nails per connection (16 in rim joist and 3 in each of 7 floor joists) connection capacity = (132 lbs./nail)*(37nails) = 4883 lbs. Zsys(probabilistic method)=4249 lbs. (average over 1000 iterations)

  13. III. Suggestions for modification of Scenarios 7 & 8

  14. Original Scenario #7 Scenario #1 with a wall opening; rim joist serves as collector

  15. Modified Scenario #7 This will be a modification of Scenario #3 instead of collector elements a different size rim board will be used and compared to that done in scenario #3 *Drawings courtesy of Kelly Cobeen and Jim Russell

  16. Original Scenario #8 Scenario #2 with a wall opening; double 2x6 Douglas fir header provided in wall system to serve as collector

  17. Modified Scenario #8 This will be a modification of the baseline scenario with sheathing split at midpoint of rim joist instead of below and above rim joist connection *Drawings courtesy of Kelly Cobeen and Jim Russell

  18. Conclusions • NDS yield equations provide a conservative estimate of connection capacity. • Preliminary data suggests that inter-story drift may need to be emphasized in building design provisions. • Connection failure was consistent with controlling yield equation (ductile, yielding of nails). • Probabilistic analysis provides a comparison to conventional deterministic design procedures.

  19. Questions and Suggestions???

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