Building with base isolation techniques exhibit less lateral deformation if exposed to seismic load.

1. BUILDINGS WITH BASE
ISOLATION TECHNIQUES
Mahmoud SAYED AHMED
m.sayedahmed@ryerson.ca

2. Overview
Introduction
Literature Review
Case Study: Base Isolated Building
Case Study: Fixed Base Building
Conclusions and Recommendations

3. Introduction
NBCC 2010 specifies that
buildings and their
structural members shall be
designed by one of the
following methods:
 analysis based on generally
established theory,
 evaluation of a given full-scale
structure or a prototype by
loading tester or
 studies of model analogues .

4. Literature review
Earthquake
Structural bearing
Base Isolation
Design requirements
Construction of base isolated building

5. Earthquake
Tectonic plate movement

6. Cont.
0.8
0.7
Spectral Response Acceleration,S
0.6
0.5
Toronto
0.4
Alexandria
0.3
White River
0.2
0.1
0
0 0.5 1 1.5 2 2.5
Period, T
 Seismic map in Canada
 The four Sa 0.2, 0.5, 1.0 and 2.0 seconds (equivalent to frequencies of 5, 2, 1, and 0.5 Hertz)
[Source: www.earthquakescanada.nrcan.gc.ca]

7. Structural bearing
The CHBDC standards recognized
the bearing as follows:
 Plain elastomeric
 Natural Rubber
 Neoprene
 Steel reinforced elastomeric
 Roller bearing Elastomeric Roller
 Rocker bearing
 Pot bearing
 Disc bearing
 Spherical and cylindrical bearing
 Other (require approval)
Rapolla seismic isolated building, Potenza, Italy
LBRtest
Rocker Pot

8. Rubber bearing
Lift-off: bearing behavior assumed in :
Internal forces which act to displace the rubber from the vertical height “seismic linear model”
lost in deflection to the unloaded sides
Load-deflection for one and three layer units reinforced with steel plate [Farat]

9. Base isolation
 Add your procedure
here
 Key assumptions
 Add your assumptions
here
Building movement
Base-Isolation Building [Lu et al 2012]

10. Building movement
Press to run Video
Press to run Video

11. Damping
0.001 g (0.01 m/s²) – perceptible by people
0.02 g (0.2 m/s²) – people lose their balance
0.50 g – very high; well-designed buildings can
survive if the duration is short

12. Design requirements


13. Cont.,


14. Construction of base isolation
 Friction Pendulum
System
 Pasadena City Hall

15. Pasadena City Hall

17. Parametric study
Finite element modeling
Gravity loads
Isolated base building
Fixed base building
Results

18. Finite element modeling
Table 3. 1 High damping bearing Properties
Vertical (axial) stiffness 10,000 k/in
(linear)
Initial shear stiffness in each 10 K/in
direction
Shear yield force in each 5 kips
direction B.1
Ratio of post yield shear 0.2
stiffness to initial shear
stiffness
Figure 3. 1 3D Finite element model

19. Gravity loads & forces
Moment 3-3 Diagram
Axial Force Diagram
Figure 3. 3 Combo (Dead plus live load) effect on the N-S for Grid A.1 or A.4

20. Isolated base building
Response histories
(a) displacement of column
(joint 15, 13),
(b) displacement of column
w.r.t. base,
(c) displacement of base shear

21. MODAL 1
 Moment 3-3 Diagram
(MODAL) Model 1 –
Period 2.81065
 Deformation shape
(MODAL) – Mode 1 –
Period 2.81065

22. MODAL 2
 Moment 3-3 Diagram
(MODAL) Model 2 –
Period 2.7975
 Deformation shape
(MODAL) – Mode 2 –
Period 2.7975

23. MODAL 3
 Moment 3-3 Diagram
(MODAL) Model 3 –
Period 2.42137
 Deformation shape
(MODAL) – Mode 3 –
Period 2.42137

24. MODAL 4
 Moment 3-3 Diagram
(MODAL) Model 4 –
Period 0.32664
 Deformation shape
(MODAL) – Mode 4 –
Period 0.32664

25. MODAL 5
 Moment 3-3 Diagram
(MODAL) Model 5 –
Period 0.24728
 Deformation shape
(MODAL) – Mode 5 –
Period 0.24728

26. Fixed base building
 Response histories
(a) displacement of column
(joint 15, 13),
(b) displacement of column w.r.t.
base,
(c) displacement of base shear

27. MODAL 1
 Moment 3-3
Diagram (MODAL)
Model 1 – Period
0.49310
 Deformation shape
(MODAL) – Mode 1
– Period 0.49310

28. MODAL 2
 Moment 3-3 Diagram
(MODAL) Model 2 –
Period 0.35973
 Deformation shape
(MODAL) – Mode 2 –
Period 0.35973

29. MODAL 3
 Moment 3-3 Diagram
(MODAL) Model 3 –
Period 0.35117
 Deformation shape
(MODAL) – Mode 3 –
Period 0.35117

30. MODAL 4
 Moment 3-3 Diagram
(MODAL) Model 4 –
Period 0.19916
 Deformation shape
(MODAL) – Mode 4 –
Period 0.19916

31. MODAL 5
 Moment 3-3 Diagram
(MODAL) Model 5 –
Period 0.14006
 Deformation shape
(MODAL) – Mode 5 –
Period 0.14006

32. Results
Modal participating mass ratio (MPMR)
Period, T [seconds] Frequency, ƒ [Hz]
Modal
Fixed Base Isolated Base Fixed Isolated
Mode
Base Base
1 0.49310 2.81065 2.0279 0.35578
2 0.35973 2.79750 2.7799 0.35746
3 0.35117 2.42137 2.8476 0.41298
4 0.19916 0.32664 5.0211 3.06147
5 0.14006 0.24728 7.1397 4.04399
Where ƒ ≥ 1 Hz for rigid building, ƒ < 1 Hz for flexible building
6
5
MODAL, mode
4
3
Fixed base
2
Isolated base
1
0
0 2 4 6 8
frequency, Hz

33. Modal moment and shear values for edge column B.1
Modal 1 Modal 2 Modal 3 Modal 4 Modal 5
H Moment Shear Moment Shear Moment Shear Moment Shear Moment Shear
Minor (V3 , M2)
288 10.95 -0.146 -0.012 2.4E-4 -3.452 0.047 1104.155 -15.399 -423.458 5.990
144 -10.06 -0.146 0.022 2.4E-4 3.375 0.047 -1110.116 -15.399 437.875 5.990
Isolated-Base
144 29.27 -0.411 -0.035 5.2E-4 -8.186 0.115 1431.488 -20.376 -536.685 7.627
0 -29.27 -0.411 0.040 5.2E-4 8.403 0.115 -1502.657 -20.376 561.644 7.627
Major (V2, M3)
288 4.5E-3 2.3E-4 14.804 -0.19 22.168 -0.28 -0.246 0.022 2765.094 -37.176
144 0.038 2.3E-4 -12.55 -0.19 -18.120 -0.28 2.864 0.022 -2588.261 -37.176
144 -0.086 1.4E-3 32.193 -0.457 49.083 -0.698 -4.993 0.072 3107.763 -45.283
0 0.112 1.4E-3 -33.644 -0.457 -51.388 -0.698 5.389 0.072 -3413.022 -45.283
288 562.661 -7.645 245.464 -3.435 1.067 -0.023 -2586.53 38.47 944.549 -13.976
Minor (V3 , M2)
144 -538.23 -7.645 -249.23 -3.435 -2.209 -0.023 2921.005 38.47 -1068.03 -13.976
144 1133.21 -16.52 403.782 -5.849 2.217 -0.023 1862.977 -25.378 -691.367 9.451
0 -1245.9 -16.52 -438.537 -5.849 -1.082 -0.023 -1791.469 -25.378 669.645 9.451
Fixed-Base
288 -0.315 0.021 -1569.76 20.652 -1477.36 19.656 3.372 -0.038 -6329.895 94.133
Major (V2, M3)
144 2.776 0.021 1404.12 20.652 1353.073 19.656 -2.092 -0.038 7225.272 94.133
144 -3.192 0.031 -2430.91 37.054 -2251.60 34.076 0.841 -8.2E-3 4966.383 -66.903
0 1.321 0.031 2904.87 37.054 2655.291 34.076 -0.348 -8.2E-3 -4667.693 -66.903

34. Lateral displacement for B.1
Modal Mode Joint Fixed Base Isolated Base
[Height] U1 U2 U3 U1 U2 U3
15 [288] -9.2E-14 -0.7459 -0.0032 -2.2E-11 -0.4699 -0.0001
1 14 [144] -5.4E-14 -0.4597 -0.0025 -2.2E-11 -0.4642 -0.0001
13 [0.00] 0.00 0.00 0.00 -2.2E-11 -0.4518 -4.8E-5
15 [288] 0.8412 -0.2804 -0.0026 -0.4659 1.9E-11 2.3E-5
2 14 [144] 0.4806 -0.1602 0.0021 -0.4625 1.8E-11 2.1E-5
13 [0.00] 0.00 0.00 0.00 -0.456 1.8E-11 1.1E-5
15 [288] 0.7684 1.6E-13 -0.0013 -0.5141 0.1714 6.7E-5
3 14 [144] 0.4362 9.0E-14 -0.001 -0.5088 0.1696 6.0E-5
13 [0.00] 0.00 0.00 0.00 -0.4987 0.1662 2.9E-5
15 [288] 1.19E-14 0.5858 0.0073 -3.3E-14 -0.6543 -0.0086
4 14 [144] -1.03E-14 0.5853 0.0043 -1.8E-15 -0.1044 -0.0073
13 [0.00] 0.00 0.00 0.00 2.6E-14 0.5306 -0.0031
15 [288] 0.6114 -0.2038 -0.0062 -0.727 0.2423 0.0066
5 14 [144] -0.6612 0.2204 -0.0034 -0.1064 0.0355 0.0056
13 [0.00] 0.00 0.00 0.00 0.0025 -0.1926 0.5778
Where U1, U2, U3 are displacement in x, y, z directions respectively in [in]; Height in [in]

35. Cont.,
350 350
300 300
250 250
Mode 1
200 200
Height, in
Height, in
Mode 2
Mode 1
150 150 Mode 3
Mode 2
Mode 4
Mode 3 100 100
Mode 5
Mode 4
50 50
Mode 5
0 0
-1 -0.5 0 0.5 1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6
Displacment, in Displacement, in
 Movement in U2 direction for fixed & isolated base buildings under
the first five MODAL modes

36. Base shear
 SRSS; square
root of sum
of squares

37. Cont.,
Structure Joint reaction @ B.1 [kip]
Type
Type 1 2 3
Modal1 0.000 0.678 0.480
Modal 2 0.684 0.000 -0.108
Isolated Modal 3 0.748 -0.249 -0.291
Base Modal 4 0.000 -0.796 31.454
Modal 5 -0.867 0.289 -24.722
Gravity 0.000 0.000 361.487
Modal 1 -3.134E-2 16.522 13.514
Modal 2 37.054 5.849 10.948
Modal 3 -34.076 2.291E-2 5.603
Fixed Base
Modal 4 8.258E-3 25.378 -22.900
Modal 5 66.903 -9.451 18.251
Gravity 0.179 0.404 360.799

38. Conclusions
 The main observation from the modeling study on the accuracy of seismic
effect and lateral load patterns utilized in the Multi-Modal Pushover
analysis (MPA) in predicting earthquake effect showed that the accuracy of
the pushover results depends strongly on the load path, properties of the
structure and the characteristics of the ground motion.
 The lateral deflection for MDOF for multi-story building can be represented
as SDOF once the equivalent mass and stiffness is obtained.
 The plastic hinge location varies by the type of loading, and the change in
MODAL period. It can be located at any point along the span of member
as well as the end of the member.
 Drift index and inter-story drift should be predicted using the multi-modal
(SRSS) and the elastic first mode with long period for the lateral load
pattern which corresponds to the average in most cases.
 Base-isolated structure exhibit less lateral deflection, as the lateral
displacement at the base never equals to zero, and less moment values than
the fixed base structure.

39. Cont.,
 The base isolation decouples the building from the
earthquake-induced load, and maintain longer
fundamental lateral period than that of the fixed base.
 Base-isolated structure exhibit less lateral deflection, as
the lateral displacement at the base never equals to
zero, and less moment values than the fixed base
structure.
 The base isolation decouples the building from the
earthquake-induced load, and maintain longer
fundamental lateral period than that of the fixed base.

40. Recommendations
 Study the influence of the structural bearing
properties and the stresses generated from tilting of
the superstructure due to lateral loading.
 Study the potential for liquefaction of the soil and
its consequences on base-isolated buildings.
 Establish design procedures and guidelines for
Base-Isolation structure.

41. References
 Chopra, A.R., “Dynamics of structures,” Prentice-Hall, New
Jersy, USA, 2001.
 CSI, “base reactions for response spectrum,” website:
https://wiki.csiberkeley.com/display/kb/Base+reactions+fo
r+response+spectrum+analysis, accessed March 2012.
 Eggert, H., Kauschke, W., “Structural Bearings,” Ernst & Sohn,
Germany, 2002.
 NRCC, “National Building Code of Canada,” Associate
Committee on the National Building Code, National
Research Council of Canada, Ottawa, ON, 2005.
 Tedesco, J.W., McDougal, W.G., and Ross C.A., “Structural
dynamics: Theory and applications,” Prentice Hall, USA,
1998.

42.  DRAMATIC BUILDING COLLAPSE CAUGHT ON TAPE!
 http://www.youtube.com/watch?v=tzGJs-
uyaSY&feature=related
 Earthquake causes building to collapse
 http://www.youtube.com/watch?v=NqRN63iDTqA
 Rapolla seismic isolated building, Potenza, Italy
 http://www.youtube.com/watch?v=1oGkM1QpL3M
 LBRtest
 http://www.youtube.com/watch?v=2yXgu4aS8HE

43. Questions and Discussion