Test on Lateral Resistance of Glulam Beam-to- Column Connections and Comparison of Ductility Analysis Methods

Transcription

1 Test on Lateral Resistance of Glulam Beam-to- Column Connections and Comparison of Ductility Analysis Methods Ph.D. Candidate: Huifen LIU Supervisor:Prof. Minjuan HE Department of Building Engineering Tongji University August.2013

2 Contents 1.Introduction 2.Test on Beam-to-Column Connections 3.Results and Discussion 4.Conclusion 1

3 1.Introduction Advantages: Easy-installed Elegant Transmit shear force directly Disadvantages: Poor ductility Low lateral resistance When subjected to load such as wind and earthquake, the connection may experience bending moments not intended in the design. 2

4 1.Introduction Two problems should be solved: How to improve the lateral resistance of Glulam beam-tocolumn bolted connection? How to define the ductility of beam-to-column bolted connection? 3

5 2.Test on Beam-to-Column Connections 2.1 Specimens Wood- steel-wood bolted connection Un-reinforced Reinforced Group Number of specimens/group NM2 3 NM3 3 SM2 3 SM3 3 Material Timber Bolt Steel Glulam M14 Q235B 4

6 2.Test on Beam-to-Column Connections 2.1 Specimens 4d 4d 5d 5d NM2 NM3 5

7 2.Test on Beam-to-Column Connections 2.1 Specimens Partial thread 130mm in length SM2 SM3 6

8 2.Test on Beam-to-Column Connections 2.2 Test Setup Electrohydraulic Servo Loading System Measuring Points 7

9 2.Test on Beam-to-Column Connections 2.3 Test procedure Monotonic test ASTM D Each specimen is subjected to a displacement-control at a rate of 5mm/min. (1) Pre-loading 10% of estimated ultimate load (2) Loading failure occurs or reaches 80% of estimated ultimate load 8

10 3.Results and Discussion 3.1 Failure Mode (1)Un-reinforced specimens Splitting Row shear-out Tension 9

11 3.Results and Discussion 3.1 Failure Mode (1)Un-reinforced specimens One plastic hinge Wood crushing in the compression region Slightly bending Wood crushing beneath the bolts 10

12 3.Results and Discussion 3.1 Failure Mode (2)Reinforced specimens Splitting Embedded 11

13 3.Results and Discussion 3.1 Failure Mode (2)Reinforced specimens Slightly bending One plastic hinge Wood crushing beneath the bolts 12

14 Moment / kn m 3.Results and Discussion 3.2 Load-Deformation Curve Rotation/ Notice: The capacity of SM3 exceeded the range of the loading system, it did not reach the ultimate moment and rotation 13

15 3.Results and Discussion 3.3 Bending Capacity and Stiffness Table 1. Capacity and stiffness NM2 NM3 SM2 SM3 Max Moment (kn m) >32.20 Failure Moment (kn m) >25.76 Elastic Stiffness (kn m/ ) Failure moment 80% of Max moment Elastic stiffness K Table2.Comparison between connections Bending capacity increment Elastic stiffness increment NM2&NM3 27% 7.3% SM2&SM3 >40% 18% NM2&SM2 12% None NM3&SM3 >23% 7.1% Increasing the number of bolts could improve the bending capacity and elastic stiffness obviously, especially when the connection was reinforced. Self-tapping screws did contribution to the bending capacity 14

16 3.Results and Discussion 3.4 Yield Point Based on energy equivalent Principle Assumed as bilinear curve (a)eeep Fig1.Definition methods for the yield point 15

17 3.Results and Discussion 3.4 Yield Point Offset Distance: Displacement : 0.1mm Rotation : radians Offset distance (b) Offest Method Fig1.Definition methods for the yield point 16

18 3.Results and Discussion 3.4 Yield Point Bilinear approaches (c) CEN Method (d) Y&K Method Fig1.Definition methods for the yield point 17

19 3.Results and Discussion 3.4 Yield Point Proportional limit approaches (e) K&C Method (f) CSIRO Method Fig1.Definition methods for the yield point 18

20 Moment / kn m 3.Results and Discussion 3.4 Yield Point The yield load determined by EEEP method was the highest, and the yield point was located off the loaddisplacement curve. There was big difference between CEN method and Y&K method. The yield point determined by Offset method, Y&C method and CSIRO method were basically in coincidence. Rotation/ Fig.2 Location of yield points on the loaddeformation curve(nm2) 19

21 Moment / kn m 3.Results and Discussion 3.4 Yield Point The results of NM3 is similar to NM2 Rotation/ Fig.3 Location of yield points on the load-deformation curve(nm3) 20

22 Moment / kn m 3.Results and Discussion 3.4 Yield Point Similar to un-reinforced connection except that the result of the two bilinear approaches (CEN and Y&K ) were basically coincided. Rotation/ Fig.4 Location of yield points on the loaddeformation curve(sm2) 21

23 Moment / kn m 3.Results and Discussion 3.4 Yield Point The results of SM3 is similar to SM2 Rotation/ Fig.5 Location of yield points on the load-deformation curve(sm3) 22

24 3.Results and Discussion 3.5 Classification of ductility Smith.I.(2006) Notice: μ= p max / yield NOTμ= fail / yield 23

25 3.Results and Discussion 3.5 Classification of ductility EEEP Bilinear approaches Proportional limit approaches CEN Y&K CSIRO K&C Offset NM2 NM3 SM2 SM3 Yield Rotation / Ductility Ratio Yield Rotation / % Ductility Ratio % Yield Rotation / Ductility Ratio Yield Rotation / Ductility Ratio >2.06 >2.70 >2.50 >3.51 >3.59 >

26 4.Conclusion (1) K&C method, CSIRO method and Offset method are generally coincided and could produce reasonable estimates of ductility. (2) Connections reinforced with self-tapping screws have an increased ductility ratio by a factor of 1.41 and an increased bending capacity by a factor of 1.12~1.23 when compared to un-reinforced connections. (3) When the number of bolts increases from 8 to 12, the bending capacity of reinforced connection increases by 40%, while that of un-reinforced connection increases by 27%,and the elastic stiffness of reinforced connection increases by 18%, while that of un-reinforced connection increases by 7.3%. That is to say, if we consider the timber reinforced by self-tapping screws as a new kind of composite material, it performs better than un-reinforced timber both in capacity and stiffness. 25

27 Thanks for your attention!