Connection Design Examples

Transcription

1 Connection Design Examples Using the 2015 NDS (DES345) Lori Koch, P.E. Manager, Educational Outreach American Wood Council Adam Robertson, M.A.Sc., P.Eng. Manager, Codes and Standards Canadian Wood Council

2 COURSE DESCRIPTION With the variety of fasteners available for wood construction, this presentation will provide a basic understanding of connections that includes design examples based on the 2015 National Design Specification (NDS ) for Wood Construction. Solutions for nailed, screwed, and bolted connections will be presented, along with specific information on calculating shear capacity as well as withdrawal capacity. Multiple approaches to calculating capacity will be discussed, including tabulated references, calculation-based techniques, and computer program solutions (including WoodWorks Connections software). Material properties for fasteners as well as connected materials including wood-to-wood, wood-to-steel, and wood-to-concrete will be discussed. Disclaimer: Portions of this presentation were developed by a third party and are not funded by American Wood Council or the Softwood Lumber Board.

3 The American Wood Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider # Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-aia members are available upon request. Participants may download the presentation here: This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

4 LEARNING OBJECTIVES Upon completion, participants will be better able to identify: 1 Withdrawal and Shear Loading 3 Be familiar with NDS provisions for fastener withdrawal capacity and NDS and TR-12 provisions for fastener shear capacity Lateral Yield Modes Understand the 6 lateral design value yield modes and material properties used to calculate capacity 2 NDS-based Calculations 4 Learn various approaches in the NDS for calculating fastener capacity Software-based Solutions Understand the types of connections WoodWorks software designs, how to use the software, how to view the design results and the connection drawing output

5 OUTLINE 1 Introduction 3 NDS Provisions on Connection Design Shear Examples Force is applied perpendicular to the length of the fastener 2 Withdrawal Examples 4 Force is applied parallel to the length of the fastener Computer Aided Solutions Examples using WoodWorks software

6 POLLING QUESTION What is your profession? a) Engineer b) Architect c) Building Official d) Other 6

7 NDS CH. 11 MECHANICAL CONNECTIONS Design issues Reference design values Chapter 12 dowel-type connectors (nails, bolts, lag/wood screws) Chapter 13 split rings and shear plates Chapter 14 timber rivets Adjustment factors 7

8 NDS CH. 11 MECHANICAL CONNECTIONS 8

9 NDS CH. 12 DOWEL-TYPE FASTENERS Withdrawal Equations for Dowel-Type Fasteners Lag screws Wood screws W = 1800 G 3/2 D 3/4 W = 2800 G 2 D Smooth shank nails (bright or galvanized carbon steel) W = 1380 G 5/2 D Post-frame ring shank nails W = 1800 G 2 D 9

10 NDS CH. 12 DOWEL-TYPE FASTENERS Withdrawal Penetration Lag screws Do NOT include length of tapered fastener tip in penetration Wood screws, Nails/Spikes Include length of tapered fastener tip in penetration 10

11 NDS CH. 12 DOWEL-TYPE FASTENERS Withdrawal based on inches of penetration into main member 11

12 WITHDRAWAL EXAMPLES Withdrawal examples Smooth shank nail Lag screw 12

13 Withdrawal Design Value - Plain Shank Nail Using 2015 NDS section 12.2, calculate the Allowable Stress Design (ASD) reference withdrawal capacity of an 8d common plain shank nail in the connection below: Main member: Spruce-Pine-Fir Nominal 4x (Actual dimension 3.5 in.) (G = 0.42) Side member: 12 gage (0.105 in. thick) ASTM A653 Grade 33 steel side plate Fastener Dimensions: 8d nail (NDS Table L4) Length = 2.5 in. Diameter = in. D Fastener diameter (in.) G 0.42 L 2.5 L s Specific gravity (NDS Table A) Nail Length (in.) Side Member thickness (in.) p t L L s Nail penetration into main member (in.) p t W 1380G D NDS Equation W 20.7 Resistance Resistance 49 p t W Reference withdrawal design value. Compare to NDS Table 12.2C, W = 21 lbs/in Resistance based on main member penetration (lbs) AWC Online Connection Calculator gives identical result of 49 lbs See NDS Table for application of additional adjustment factors for connections based on end use conditions.

14 Withdrawal Design Value - Lag Screw Using 2015 NDS provisions (NDS 12.2) calculate the Allowable Stress Design (ASD) withdrawal capacity of a lag screw in the connection below: Main member: Southern Pine Nominal 6x (Actual thickness = 5.5 in.) (G = 0.55) (NDS Table A) Side member: Southern Pine Nominal 2x (Actual thickness = 1.5 in.) (G = 0.55) (NDS Table A) Fastener Dimensions: 1/2 in. diameter lag screw (NDS Table L2) Length = 4 in. Tip Length = in. D 0.5 tip G 0.55 L 4 L s 1.5 Fastener diameter (in.) Fastener tapered tip length (in.) Specific gravity (NDS Table A) Lag screw length (in.) Side Member thickness (in.) p t L L s tip Lag screw penetration into main member (in.) p t W 1800G D NDS Equation W Resistance p t W Resistance 955 Compare to NDS Reference Withdrawal Design Value Table 12.2A, W = 437 lbs/in. Resistance based on main member penetration (lbs) AWC Online Connection Calculator gives identical result of 955 lbs See NDS Table for application of additional adjustment factors for connections based on end use conditions.

15 NDS CH. 12 DOWEL-TYPE FASTENERS 4 Yield Modes 6 Yield Equations Single & Double Shear Wood-to-Wood Wood-to-Steel Wood-to-Concrete Members must be in contact at shear plane NO GAPS! 13

16 YIELD MODES MODE I bearing-dominated yield of wood fibers MODE II pivoting of fastener with localized crushing of wood fibers MODE III fastener yield in bending at one plastic hinge and localized crushing of wood fibers MODE IV fastener yield in bending at two plastic hinges and localized crushing of wood fibers 14

17 POLLING QUESTION The NDS Yield Limit Equations for Modes II and III m do not apply to Single Shear connections. a) True b) False 15

18 DOWEL BEARING STRENGTH 16

19 FASTENER BENDING YIELD STRENGTH Load 17

20 FASTENER BENDING YIELD STRENGTH Fastener Bending Yield Strength (F yb ) sources: NDS Appendix I TR-12 Appendix A Manufacturer s data ICC Evaluation Service Report ASTM F1667 Appendix 18

21 NDS CH. 12 DOWEL-TYPE FASTENERS New 19

22 NDS CH. 12 DOWEL-TYPE FASTENERS New Nonuniform for CLT 20

23 NDS CH. 12 DOWEL-TYPE FASTENERS Adjust l m or l s to compensate for orthogonal grain orientations in adjacent layers Parallel to grain: F e /F eǁ Example: ½ bolt in southern pine 3-ply CLT with 1-½ laminations l m = t 1ǁ +t 2 +t 3ǁ = 3(1.5) = 4.5 l m-adj = t 1ǁ +t 2 (F e /F eǁ )+t 3ǁ = (3650/6150) +1.5 =

24 NDS CH. 12 DOWEL-TYPE FASTENERS 22

25 NDS CH. 12 DOWEL-TYPE FASTENERS Threaded length < lm/4 lm Dia. Fastener = D Threaded length < lm/4 lm Dia. Fastener = D 23

26 NDS CH. 12 DOWEL-TYPE FASTENERS lm Dia. Fastener = D r NDS Chapter 12 Tables use: D r for lateral yield equations for lag screws and wood screws D for bolts 24

27 FASTENER BEARING LENGTH Tapered tip length, E: Dimensions for Lag Screws in NDS Appendix L Wood screws, Nails/Spikes Tip length, E = 2D Bearing length = penetration E/2 6D minimum penetration for nails*, spikes, wood screws 4D minimum penetration for lag screws *Exception for double shear connections with clinched nails, D

28 TECHNICAL REPORT 12 Provide tools for the analysis of gaps between members various fastener bending moment configurations fasteners through hollow members fasteners with tapered tips Provides mechanics-based approach to Lateral Connection Design Calculate P value with TR-12 equations divide by R d (NDS Table B) to get Z equal to NDS values 26

29 TECHNICAL REPORT 12 TR-12 Appendix A Provides design values inputs for various materials Dowel bearing strengths (F e ) Fastener bending yield strengths (F yb ) 27

30 SINGLE SHEAR NAIL EXAMPLE Compare to NDS Table 12N value: Z = 121 lbs Single Nail Single Shear Nail Properties Yield Mode Calculations Nail Size 10d Mode I m 785 Diameter (in.) Mode I s 280 F yb (psi) Mode II 262 Length (in.) 3 Mode III m 272 Mode III s 121 Main Member Properties Mode IV 128 Main Member Thickness (in.) 2.5 Main Member Species Southern Pine Z (lbs) = 121 Main Member Dowel Bearing Strength (F em ) (psi) 5550 Side Member Properties Side Member Thickness (in.) 0.75 Side Member Species Southern Pine Side Member Dowel Bearing Strength (F es ) (psi) 5550 Calculated Inputs Side Member Bearing Length (L s ) (in.) 0.75 Main Member Penetration (p) (in.) 2.25 Tapered Tip Length (E) (in.) Main Member Bearing Length (L m ) (in.)

31 SHEAR EXAMPLES Additional shear examples Smooth shank nail single shear Wood Screw double shear Bolt single shear 29

32 Single Common Nail Lateral Design Value - Single Shear Wood-to-wood Connection Using the 2015 NDS yield limit equations in section 12.3, determine the Allowable Stress Design (ASD) reference lateral capacity of a single shear connection with the following configuration: Main member Nominal 3x Southern Pine (Actual thickness = 2.5 in.) (G = 0.55) (NDS Table A) Side member Nominal 1x Southern Pine (Actual thickness = 0.75 in.) (G = 0.55) (NDS Table A) Fastener Dimensions: 10d Common Nail (NDS Table L4) D = in. Length = 3 in. Define parameters: F em 5550 F es 5550 Main member Dowel Bearing Strength (NDS Table ) (psi) Side member Dowel Bearing Strength (NDS Table ) (psi) R e F em F es R e 1 F yb Fastener dowel bending yield strength (psi) (NDS Table I1) D Tip 2D Nail Diameter (in.) Length of tapered fastener tip (in.) (NDS b) L s 0.75 Side member Dowel Bearing Length (in.) (NDS ) Tip L m 3 L s Main member Dowel Bearing Length (in.) (NDS ) 2 L m 2.1 NDS Requires minimum main member penetration equal to 6D, L m > 0.89 in. R d 2.2 Reduction Term (NDS Table B)

33 Calculate k 1, k 2, and k 3 (NDS Table A) L m R t R L t s R e 2R e 1 R t R t R t Re k 1 1 R e R e 1 R t k k R e 2F yb 1 2R e D 2 2 3F em L m k k R e R e 2F yb 2 R e D 2 2 3F em L s k Yield Mode Calculations (NDS Table A) Mode I m Z Im DL m F em R d Z Im 785 Yield Mode I m Solution (lbs) Mode I s Z Is DL s F es R d Z Is 280 Yield Mode I s Solution (lbs)

34 Mode II Z II k 1 DL s F es R d Z II 262 Yield Mode II Solution (lbs) Mode III m Z IIIm k 2 DL m F em 1 2R e R d Z IIIm 272 Yield Mode III m Solution (lbs) Mode III s Z IIIs k 3 DL s F em 2 R e R d Z IIIs 121 Yield Mode III s Solution (lbs) Mode IV D 2 Z IV R d 2F em F yb 3 1 R e Z IV 128 Yield Mode IV Solution (lbs) Z dist Z Im Z Is Z II Z IIIm Z IIIs Z IV Z dist Creating an array with all Yield Mode Solutions

35 Z minz dist Z 121 Minimum value of all Yield Modes provides Z reference lateral design value (lbs). Mode III s controls. Compare to NDS Table 12N value = 121 lbs. See NDS Table for application of additional adjustment factors for connections based on end use conditions.

36 Single Wood Screw Lateral Design Value - Double Shear Wood-to-wood Connection Using 2015 NDS yield limit equations in section 12.3, determine the allowable stress design reference lateral design value of a double shear connection with the following configuration: Main member Actual 3 in. Structural Composite Lumber Member (G = 0.5) (NDS ) Side members Nominal 2x Douglas Fir-Larch (DF-L) (Actual thickness = 1.5 in.) (G = 0.5) (NDS A) Fastener Dimensions: Number 10 Wood Screw (NDS Table L3) D = 0.19 in. D r = in. Length = 6 in. Define parameters: F em 4650 F es 4650 Main member Dowel Bearing Strength (NDS Table ) (psi) Side member Dowel Bearing Strength (NDS Table ) (psi) F em R e R F e 1 es t m 3.0 Main Member thickness (in.) t s 1.5 Side Member thickness (in.) F yb Fastener dowel bending yield strength (psi) (NDS Table I1) D 0.19 D r L screw 6 Screw Diameter (in.) Screw Root Diameter (in.) Screw Length (in.) Tip 2D L m t m L m 3 Length of tapered fastener tip (in.) (NDS b) Main member Dowel Bearing Length (in.) (NDS ) Tip L s L screw L m t s Side member Dowel Bearing Length (in.) (NDS ) 2 L s 1.31 NDS requires minimum 6D penetration, L s >1.14 in. R d 10D 0.5 R d 2.4 Reduction Term (NDS Table B)

37 Calculate k 3 (NDS Table A) (k 1 and k 2 not used) k R e R e 2F yb 2 R e D 2 r 2 3F em L s k Yield Mode Calculations (NDS Table A) Mode I m Z Im D r L m F em R d Z Im 883 Yield Mode I m Solution (lbs) Mode I s Z Is 2D r L s F es R d Z Is 772 Yield Mode I s Solution (lbs) Mode III s Z IIIs 2k 3 D r L s F em 2 R e R d Z IIIs 286 Yield Mode III s Solution (lbs) Mode IV 2 2D r Z IV R d 2F em F yb 3 1 R e Z IV 214 Yield Mode IV Solution (lbs)

38 Z dist Z Z Im Z Is Z IIIs Z IV minz dist Z dist Creating an array with all Yield Mode Solutions Z 214 Minimum value of all Yield Modes provides Z reference lateral design value (lbs). Mode IV controls. There are no tabulated values in the NDS to compare. See NDS Table for application of additional adjustment factors for connections based on end use conditions.

39 Single Bolt Lateral Design Value - Single Shear Wood-to-Wood Connection Using the 2015 NDS Yield Limit Equations (NDS 12.3), determine the Allowable Stress Design (ASD) reference lateral capacity of a single shear connection with the following configuration: Main member Nominal 4x Hem-Fir (Actual thickness = 3.5") Side member Nominal 4x Hem-Fir (Actual thickness = 3.5") Both members loaded parallel to grain G = 0.43 for Hem-Fir (NDS Table A) Fastener Dimensions: 1/2 in. diameter bolt 8 in. Bolt with 1.5 in. thread length (NDS Table L1) Define parameters: F em 4800 F es 4800 Main member Dowel Bearing Strength (NDS Table ) (psi) Side member Dowel Bearing Strength (NDS Table ) (psi) R e F em F es R e 1 F yb Fastener dowel bending yield strength (psi) (NDS Table I1) D 0.5 Bolt Diameter (in.) Per NDS , check that threads are less than 1/4 the bearing length in the member holding the threads. In this case, 3.5 in./4 > 0.5 in. Therefore, OK to use D instead of D r in calculations. L s 3.5 Side member Dowel Bearing Length (in.) (NDS ) L m 3.5 Main member Dowel Bearing Length (in.) (NDS ) R d1 4.0 R d2 3.6 Reduction Terms (NDS Table B) R d3 3.2

40 Calculate k 1, k 2, and k 3 (NDS Table A) L m R t R L t 1 s R e 2R e 1 R t R t R t Re k 1 1 R e R e 1 R t k k R e 2F yb 1 2R e D 2 2 3F em L m k k R e R e 2F yb 2 R e D 2 2 3F em L s k Yield Mode Calculations (NDS Table A) Mode I m Z Im DL m F em R d1 Z Im 2100 Yield Mode I m Solution (lbs) Mode I s Z Is DL s F es R d1 Z Is 2100 Yield Mode I s Solution (lbs)

41 Mode II Z II k 1 DL s F es R d2 Z II 966 Yield Mode II Solution (lbs) Mode III m Z IIIm k 2 DL m F em 1 2R e R d3 Z IIIm 957 Yield Mode III m Solution (lbs) Mode III s Z IIIs k 3 DL s F em 2 R e R d3 Z IIIs 957 Yield Mode III s Solution (lbs) Mode IV D 2 Z IV R d3 2F em F yb 3 1 R e Z IV 663 Z dist Z Im Z Is Z II Z IIIm Z IIIs Z IV Z min Z dist Z 663 Yield Mode IV Solution (lbs) Creating an array with all Yield Mode Solutions Minimum value of all Yield Modes provides Z reference lateral design value (lbs). Mode IV controls.

42 Repeat same problem, but solve using Technical Report 12 - General Dowel Equations for Calculating Lateral Connection Values (TR-12) Equations for comparison q s F es D Side member dowel bearing resistance, lbs/in. q m F em D Main member dowel bearing resistance, lbs/in. M F yb D 3 6 Side and Main member dowel resistance (equal due to equivalent dowel diameter in both members), in.-lbs gap 0 Gap between member shear planes, in. The limiting wood stresses used in the yield model are based on the load at which the load-deformation curve from a fastener embedment test intersects a line represented by the initial tangent modolus offset 5%of the fastener diameter. The reduction term, Rd, reduces the values calculated using the yield limit equations to approximate estimates of the nominal proportional limit design valuesin previous NDS editions. Yield Mode Calculations (TR-12 Table 1-1) Mode I m P Im q m L m P Im 8400 TR-12 Yield Mode I m Solution (lbs) Mode I s P Is q s L s P Is 8400 TR-12 Yield Mode I s Solution (lbs)

43 Mode II 1 A II 4q s 1 4q m L s L m B II gap 2 2 C II 2 q s L s 4 2 q m L m 4 P II 2 B II B II 4A II C II 2A II P II 3479 TR-12 Yield Mode II Solution (lbs) Mode III m 1 1 A IIIm 2q s 4q m L m B IIIm gap 2 C IIIm M 2 q m L m 4 P IIIm 2 B IIIm B IIIm 4A IIIm C IIIm 2A IIIm P IIIm 3062 TR-12 Yield Mode III m Solution (lbs) Mode III s 1 A IIIs 4q s 1 2q m B IIIs gap C IIIs M L s 2 2 q s L s 4

44 P IIIs 2 B IIIs B IIIs 4A IIIs C IIIs 2A IIIs P IIIs 3062 TR-12 Yield Mode III s Solution (lbs) Mode IV 1 A IV 2q s B IV gap 1 2q m C IV M M P IV 2 B IV B IV 4A IV C IV 2A IV P IV 2121 TR-12 Yield Mode IV Solution (lbs) Z dist2 P Im R d1 P Is R d1 P II R d2 P IIIm R d3 P IIIs R d3 P IV R d3 Z dist Converting from TR-12 "P" values to NDS "Z" values and creating an array. Shows TR-12 results equal NDS results for each Yield Mode. All values in units of lbs. Z 2 Z minz dist2 Z value from TR-12 equations is equivalent to Z value from NDS equations and comparable to NDS Table 12A value Z parallel = 660 lb. See NDS Table for application of additional adjustment factors for connections based on end use conditions.

45 Z dist Z dist Z dist is NDS equation result, Z dist2 is TR-12 equation result, for Modes I m, I s, II, III m, III s, and IV, respectively. All values in units of lbs.

46 POLLING QUESTION Technical Report 12 can be used to calculate a doweltype connection s: a) Reference withdrawal design values b) Reference lateral design values c) Combined lateral and withdrawal reference design values d) Maximum fastener sizes 30

47 2018 NDS CHANGES WHAT S COMING? Revised withdrawal equations for deformed-shank nails Inclusion of Roof Sheathing Ring Shank (RSRS) nail Removal of generic threaded nail withdrawal provision New equation for stainless steel smooth shank nails Round-head fastener pull-through December webinar on 2018 NDS changes! 31

48 WOODWORKS DESIGN OFFICE 11 SOFTWARE SIZER Gravity Design Concept mode Beam mode Column mode SHEARWALLS Lateral Design (Wind and Seismic) CONNECTIONS Fasteners DATABASE EDITOR Add proprietary products woodworks-software.com 32

49 SINGLE SHEAR NAIL EXAMPLE Choose connection geometry: Lapped shear Wood-to-wood Splice, two member 33

50 SINGLE SHEAR NAIL EXAMPLE Choose fastener type: Nails 34

51 SINGLE SHEAR NAIL EXAMPLE Specify properties of main member: Database editor 35

52 SINGLE SHEAR NAIL EXAMPLE Database editor: 36

53 SINGLE SHEAR NAIL EXAMPLE Specify properties of side member: Database editor Manual input section sizes 37

54 SINGLE SHEAR NAIL EXAMPLE Wet service factor (C M ) Specify additional parameters: Temperature factor (C t ) Fire retardant treatment (C ft ) (Unique to WoodWorks not in NDS) Frequently used load duration factor (C D ) 38

55 SINGLE SHEAR NAIL EXAMPLE Specify fastener properties: 39

56 SINGLE SHEAR NAIL EXAMPLE Preliminary connection layout: 40

57 SINGLE SHEAR NAIL EXAMPLE Results: 41

58 SINGLE SHEAR NAIL EXAMPLE Results: 42

59 SINGLE SHEAR BOLT EXAMPLE Choose connection geometry: Lapped shear Wood-to-wood Splice, two member 43

60 SINGLE SHEAR BOLT EXAMPLE Choose fastener type: Bolts 44

61 SINGLE SHEAR BOLT EXAMPLE Specify properties of main and side members: 45

62 SINGLE SHEAR BOLT EXAMPLE Wet service factor (C M ) Specify additional parameters: Temperature factor (C t ) Fire retardant treatment (C ft ) (Unique to WoodWorks not in NDS) Frequently used load duration factor (C D ) 46

63 SINGLE SHEAR BOLT EXAMPLE Specify fastener properties: 47

64 SINGLE SHEAR BOLT EXAMPLE Preliminary connection layout: 48

65 SINGLE SHEAR BOLT EXAMPLE Results: 49

66 SINGLE SHEAR BOLT EXAMPLE Results: 50

67 SINGLE SHEAR BOLT EXAMPLE Results: 51

68 LAG SCREW WITHDRAWAL EXAMPLE Choose connection geometry: Post and Beam Beam-to-beam One-sided 52

69 LAG SCREW WITHDRAWAL EXAMPLE Choose fastener type: Lag screws 53

70 LAG SCREW WITHDRAWAL EXAMPLE Specify properties of main and side members: 54

71 LAG SCREW WITHDRAWAL EXAMPLE Wet service factor (CM) Specify additional parameters: Temperature factor (Ct) Fire retardant treatment (Cft) (Unique to WoodWorks not in NDS) Frequently used load duration factor (CD) 55

72 LAG SCREW WITHDRAWAL EXAMPLE Specify fastener properties: 56

73 LAG SCREW WITHDRAWAL EXAMPLE Preliminary connection layout: Export to CAD file (.DXF format) 57

74 LAG SCREW WITHDRAWAL EXAMPLE Results: 58

75 LAG SCREW WITHDRAWAL EXAMPLE Results: 59

76 LAG SCREW WITHDRAWAL EXAMPLE Results: 60

77 LAG SCREW WITHDRAWAL EXAMPLE Results: 61

78 ADDITIONAL CONNECTION TYPES Wood-to-wood: Wood-to-steel: Export as DXF Wood-to-concrete: 62

79 WOODWORKS DESIGN OFFICE 11 SOFTWARE SIZER Gravity Design Concept mode Beam mode Column mode DATABASE EDITOR Add proprietary products 10% discount for AWC members SHEARWALLS Lateral Design (Wind and Seismic) CONNECTIONS Fasteners For more information contact: or 63

80 POLLING QUESTION The WoodWorks Design Office software has versions for both US and Canadian standards. a) True b) False 64

81 This concludes the American Institute of Architects Continuing Education Systems Course This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of American Wood Council (AWC) is prohibited. American Wood Council 2017