3. Introduction
• Slotted-bolted connection (SBC)
– low-cost friction dampers
– simplicity
– effective to be used as seismic protection
devices (Fitzgerald et al., 1989; Grigorian et al.,
1993; Tremblay and Stiemer, 1993)
– suitable for developing countries
5. Problems
• Past studies:
– normally assume that sufficient slip length can
be provided.
• Earthquakes are unpredictable.
• Cannot guarantee that the bolts will slide
“freely” in the provided slot lengths.
• Not practical to provide very long slot.
7. Objectives
• Investigate behaviour of SBC in the event
of bolt impact.
• Model of SBC with limited slip length
• Analytical assessment of the seismic
performance of buildings equipped with
limited slip length SBC
8. Scopes
• Series of cyclic tests of SBC specimens
with bolt impacts
• 2-D nonlinear dynamic analyses
• Horizontal ground motions only
• Exclude environmental and long-term effect
• Buckling phenomena is neglected in
analyses.
9. Research Significance
• Performance and behaviour of SBC in the
event of bolt impacts
• Enhancement of the SBC device
• Mathematical model of the enhanced SBC
13. Central Plate & Cover Plate
All dimensions are in millimeter.All dimensions are in
millimeters.
All dimensions are in millimeter.All dimensions are in millimeters.
Central plate Cover plate
20. Loss of clamping forces
Specimen Frequency Clamping force (kN) Ratio
(Hz) Before test After test
BR-5 0.1 55 12 0.22
BR-12 0.5 55 23 0.42
BR-13 1 55 29 0.53
BR-11 2 55 53 0.96
22. Conventional SBC
• More than 50% loss of friction can occur
due to bolt impact.
• Some restraining mechanisms are obviously
required to prevent bolt impacts.
24. Enhanced SBC
• Concept: provide restrainers as another
source to resist bearing
• Restraining mechanism operates before bolt
impact occurs.
• Called “SBC with restrainers (SBC-R)”
25. SBC-R
• Desired behaviour:
– No loss of friction force
– Stable hysteresis
– Controllable max. restraining force
26. SBC-R
• Outer plates are fabricated to have wedge-
like ends providing restraints.
• Slope of wedge = 26.7 degree --> to limit
the maximum restraining force
• Freely slip travel = +/- 10 mm
29. Experimental Programs
• Cyclic tests at 0.01 Hz (displ. control)
• No wedge impact = 15 cycles
• 3 series of displacement histories for wedge
impact on both sides
35. SBC-R: Test results
• Proposed restraining mechanism can
effectively prevent damages of the bolts.
• No loss of frictions
• Hystereses are stable.
• Max. restraining force can be controlled.
36. Model of SBC-R
• Hysteresis of the enhanced SBC can be
divided into 2 parts:
– Hysteresis without wedge impact
– Hysteresis after wedge action occurs.
48. Conclusions
• Bolt impacts result in an unacceptable
behaviour of a conventional SBC.
• Proposed SBC-R can effectively prevent
loss of the design friction force.
• Slip limit friction damper provides more
safety to the retrofitted structure compared
with the conventional one.