Download presentation
Presentation is loading. Please wait.
Published byJacey Brush Modified over 10 years ago
1
Quick-Release Field Experiments on Seismically Isolated Bridges Stuart S. Chen, Ph.D., P.E. Associate Professor, University at Buffalo (SUNY), Fulbright Senior Lecturer, ITU
2
Presentation Outline Comprehensive Study Overview Bridges Studied Loading and Instrumentation Apparatus Selected Results Anticipating Seismic Performance Summary, Conclusions, Recommendations Acknowledgements
3
Comprehensive Study!: Overview Two Similar Bridges, Before and After Seismic Retrofit with Isolation Bearings Field (System Quick-Release) and Laboratory (Component Reverse-Cyclic) Experiments Comparing Analytical vs. Experimental Dynamic Behavior Inferring Seismic Performance from Calibrated Models
4
Seismic Isolation Concept (Kelly, 2001)
5
Seismic Isolation Concept (cont’d) (Kelly, 2001)
6
Bridges’ Plan View
7
Bridges’ Elevation; Brg. Schedule
8
Bridge Cross Sections
9
Bridge Bearing Replacement (Abut.)
10
Bridge Bearing Replacement (Pier)
11
Installing Isolation Brgs at Abutments
12
Southbound Abutment Isolator Kelly, 2001
13
Southbound Pier Isolator
14
Northbound Expansion Bearing (non-seismic)
15
Northbound Bridge Bearings
16
Objectives Measure and assess in-situ dynamic behavior and performance of typical slab- on- girder bridge subjected to transverse quick-release loading (steel brgs vs. seismic isolation brgs vs. standard laminated elastomeric brgs) Quantify in-situ dynamic performance change attributable to bearing retrofits
17
Objectives, cont’d Quantify Winter-Weather Effects on In-Situ Performance of Isolation and Elastomeric Bearings Assess Relative Merits of Several Modeling Approaches (at varying levels of complexity) in predicting transverse transient dynamic behavior of straight skewed slab-on-girder bridge structures
18
Loading Scheme
19
Loading Scheme (cont’d)
24
(Under-Bridge) Loading Scheme!
25
Loading Scheme (cont’d)
26
Loading Scheme: The Importance of Genuinely Quick Release!
27
Loading Scheme: Mechanical Fuse
28
Loading Scheme: Mechanical Fuse in Place
29
Selected Instrumentation
30
Selected Instrumentation (cont’d)
35
Selected Results: Free Vib’n
36
Pre-Retrofit in Frequency Domain
37
1 st 2 Pre-Retrofit Mode Shapes
38
SAP Model
39
DRAIN-2DX Model
40
3 rd Pre- Retrofit Mode Shape
41
Seismic Isolation Concept: Recall! SaSa TT SdSd ξ +
42
Post- Retrofit Time- History at Abutment
43
Post-Retrofit SB (Linear: “Portion 2”)
44
Post-Retrofit SB cont’d (Linear: Portion 2)
45
Post-Retrofit NB (Linear: Portion 2)
46
Post-Retrofit NB cont’d (Linear: Portion 2)
47
Selected NB Post-Retrofit T-H’s
48
Post-Retrofit SB cont’d
49
Post-Retrofit SB (Nonlinear: Portion 1)
50
Time, Temperature, Setup Effects (SB)
51
Old Steel Bearings: Not So Bad After All!
52
C/D vs. PGA, Pre-Retrofitted
53
C/D vs. PGA, Post-Retrofitted
54
Summary, Conclusions, Recommendations Transverse Quick-Release Experiments are successfully executed using the deployed apparatus Replacement of the original steel bearings with seismic isolation bearings leads to substantial behavior changes (period shift, etc.) in the transverse direction, as predicted. However, –Due to reserve strength of columns and steel bearings, actual seismic resistance of the retrofitted southbound bridge is not greatly increased by its seismic isolation retrofit, and –The torsional behavior induced in the retrofitted northbound bridge nullifies the otherwise seismically beneficial effect of its standard (non-seismic) elastomeric bearing retrofit
55
Summary, Conclusions, and Recommendations (cont’d) Neither a 3D Model nor formal structural identification methods produce any significant advantages over 2D modeling as long as nonlinear behavior is incorporated into the model (DRAIN-2DX) Cold-weather effects in western NY are not sufficiently severe to have a significant influence on LRB seismic isolation behavior
56
Acknowledgements J. B. Mander, D. Wendichansky, G. Pekcan, D.-K. Kim, I.-S. Ahn, L. Zhang, P. Dreyer, etc. New York State Dept. of Transportation, Union Concrete and Construction Corp. U.S. D.O.T. / Federal Highway Administration funding through NCEER/MCEER at the University at Buffalo
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.