Design for Diaphragm Action - NEWBuildS: Strategic...
Transcript of Design for Diaphragm Action - NEWBuildS: Strategic...
Design for Diaphragm Action
Chun NiTerje Haukaas
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Outline
Diaphragm Flexibility
Collective Chord Design Method for Large Diaphragm
2
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Diaphragm Flexibility
Flexible▫ Diaphragm load is distributed to shear walls by
tributary area
Rigid▫ Diaphragm load is distributed to shear walls by
relative stiffness of walls
Semi-rigid
3
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
CIVL 435 Advanced Structural Analysis
4
u1,floor
u2,floor
u3,floor
u1
u2
u3
F
u1
u2
u3
u2
u3
u1
u1
u2
u3
Static indeterminacy stiffness influences force distribution
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Prescriptive Method (ASCE 7)
Wood diaphragms idealized as flexible if …
▫ … walls are steel braced frames, concrete, etc.
▫ … one- and two-family dwellings
▫ … no concrete structural topping
5
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Calculation Method (ASCE 7 , ASCE 41)
Flexible: MDD > 2 ADVE Rigid: MDD < 1/2 ADVE Otherwise semi-rigid
6
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Case Studies
7
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
NEWBuildS Funded MASc Theses
Xinlei Huang▫ Diaphragm Stiffness in Wood-frame Construction
Sepideh Ashtari▫ In-plane Stiffness of Cross-laminated Timber Floors
Sai Ganesh Sarvotham Pai▫ Force Transfer around Openings in CLT Shear Walls
www.circle.ubc.ca
8
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Embedment Properties, HYST (Xinlei)
9
Li, M. H., Foschi, R. O., and Lam, F. (2011). "Modeling Hysteretic Behavior of Wood Shear Walls with A Protocol-Independent Nail Connection Algorithm." ASCE, 138(1), 99-108.
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Laboratory Tests (Xinlei)
10
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Floor Model, FLOOR2D (Xinlei)
11
Bott, J. W. (2005). "Horizontal Stiffness of Wood Diaphragms". Master Degree. Virginia Polytechnic Institute and State University, Virginia, United States.
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Shear Modulus Values (Xinlei)
12
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Shear Wall Forces (Xinlei)
13
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
CLT Panel Connections (Sepideh)
14
Lam, F. (2011). "Cross Laminated Timber (CLT) Connection Tests for UBC Bioenergy Research & Demonstration Project Nexterra Building (Report prepared for CST Innovation
Ltd.)." Timber Engineering and Applied Mechanics (TEAM) Laboratory.
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
ANSYS Model (Sepideh)
15
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Shear Wall Forces (Sepideh)
16
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Observations
Wood-frame diaphragms were relatively rigid!
CLT diaphragms were relatively flexible!
Keyword: Relatively
17
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Transfer Forces (Sai)
18
2D Model 3D Model
Frame Model 2D Model with Tie-rods
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
ICASP12
12th International Conference on Applications of Statistics and Probability in Civil EngineeringVancouver, Canada, July 12-15, 2015
Coast Plaza Hotel & Suites on Denman Streetwww.icasp12.ubc.ca
19
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Collective Chord Design Method for Large Diaphragm - Background Traditional diaphragm
design method▫ assumes bending moment
resisted by diaphragm perimeter members
▫ Commonly used for small & moderate diaphragms
▫ Assumed to be a conservative when applied to large diaphragms
20
MT Cb
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Collective Chord Method (Lawson 2007)
21
6( )( 2 )o
sMFb s b s
Assume evenly spaced girders / purlins act as collective chord
Use strain compatibility to estimate axial forces of chord members
Significantly lower chord forces
s – girder / purlin spacing
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Examine applicability of the collective chord design methods in collaboration with Clemson Univ.
Evaluate shear force distribution along the depth of diaphragm
Study on Collective Chord Method
22
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Study on Collective Chord Method
23
Framing members Sheathing panels Connectors
▫ Panel-to-frame (P2F) –sheathing nails
▫ Frame-to-frame (F2F) –bearing contact between framing members, continuity ties, subpurlin-to-purlin connections
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Case Study Structure Single-story tilt-up concrete building Diaphragm consist of glulam girders, D.Fir lumber
purlins and sub-purlins, 15/32” OSB sheathing, 10d common nails at 6” o.c. around panel edges
24
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Base Case – Chord Force Distribution
25
-40 -30 -20 -10 0 10 20 30 400
500
1000
1500
Axial Force (kip)
Ver
tical
Dis
tanc
e (in
)
, p ,
-0.92
0.02
0.04
1.00
-0.03
-10 -5 0 50
500
1000
Axial Force (kip)
Ver
tical
Dis
tanc
e (in
)
-0.91-0.03
0.02
0.10
1.00
-0.03
0 1 2 3 4 5 6 70
50
100
150
Displacement at Mid-span (in)
Rea
ctio
n F
orce
(ki
p)
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Base Case – Shear Flow of Sheathing Nails
26
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Effect of Diaphragm Aspect Ratio –Chord Force Distribution
27
2:1 (Length:Width)1:24:1Collective Chord Model
2:11:2
4:1
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Effect of Diaphragm Aspect Ratio –Panel Shear Force Distribution
28
Aspect Ratio 2:1 Aspect Ratio 4:1
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
The distribution of chord forces and shear force is a function of the diaphragm aspect ratio
Where diaphragm aspect ratio is low, the chord force distribution approaches the assumption of the traditional method
Collective chord method works better for high aspect ratio diaphragms
In the range of the aspect ratios typical to large diaphragms, the collective chord method over-predicted the chord forces carried by the intermediate chords
Effect of Diaphragm Aspect Ratio –Summary
29
www.fpinnovations.ca
Follow us on
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Questions?
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Two-span diaphragm supported by three lateral load resisting members and subjected to a uniform load
Distribution of reaction forces with different stiffness ratios between ▫ diaphragm and supporting members ▫ central support and end supports
Study on Diaphragm Flexibility
31
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Study on Diaphragm Flexibility Reaction at the supports (same stiffness at supports)
True flexible diaphragm
True flexible diaphragm
True rigid diaphragm
32
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Study on Diaphragm Flexibility Flexible diaphragm
Center support:(a) a diaphragm with MDD /
ADVE = 2.0(b) a truly flexible diaphragm
Side supports:(a) a diaphragm with MDD /
ADVE = 2.0 (b) a truly flexible diaphragm
33
© 2014 FPInnovations. All rights reserved. Copying and redistribution prohibited. ® FPInnovations, its marks and logos are trademarks of FPInnovations.
Study on Diaphragm Flexibility Rigid diaphragm
Center support:(a) a diaphragm with MDD /
ADVE = 0.5(b) a truly rigid diaphragm
Side supports:(a) a diaphragm with MDD /
ADVE = 0.5 (b) a truly rigid diaphragm
34