Presentationby Valentin Shustov

20 June, 2007

https://central.nees.org/activities/index.php?facility=UCSD

• The latest research activities at CSUN culminated in the innovative building technology called the Earthquake Protector. Its research, supported by NSF, Award No. 0618183, and entitled “SGER: Testing of a New Line of Seismic Base Isolators” is both analytical and experimental. For the Final Report to NSF, click on https://central.nees.org/data/get/NEES-2006-0283/Public/REPORT.pdf

• The reported research contains a lot of novelties including but not limited to the very concept of earthquake protection, metrics of building performance, physical and virtual experiments, hardware, software and, of course, conclusions.

• Software for analytical research called Earthquake Performance Evaluation Tool (EPET) enables virtual experiments on buildings with and without Earthquake Protectors. On demand, all virtual experiments are animated.

• Major building earthquake performance evaluation parameter for the testing is the Seismic Performance Ratio.

Physical model Mathematical model

Building models are the primary measuring tool in all experiments.

ev

v

• where Quality Factor Rw is understood as the ratio of the ultimate allowable story drift vu that can be tolerated by the structure without a collapse to the maximum elastic story drift ve.

For assessment or comparison of the anticipated building performance, the Story Performance Rating R will be used as a major criterion:

R = (1)

• where v = un - un-1 is an actual or calculated inter-story drift;

• ve is an inter-story drift at the assumed elastic limit of horizontal deformation.

The ultimate allowable value of R will occur when

R = Rw = (2)e

u

v

v

• The case R < 1 relates to a purely elastic performance of the structure.

• The case 1 < R < Rw defines how far the structure extends into the plastic range.

• The case R > Rw means a possibility of either collapse of the story or occurrence of other life threatening damage that will not, necessarily, result in losing full value of the structure.

• Ratio R/Rw is the Seismic Performance Ratio which controls the anticipated physical losses due to seismic exposure of the building structure.

• The anticipated damage due to a seismic exposure is defined by the Damage Ratio D.R. that may be related to R/Rw.

http://www.ecs.csun.edu/~shustov/000-EPF.html

http://www.ecs.csun.edu/~shustov/001-EPF-03.html

http://www.ecs.csun.edu/~shustov/EP-2004-1.htm

http://www.ecs.csun.edu/~shustov/EP-2005.htm

Main technical characteristics of the facility:• Platen 7.6 m x 12.2 m• Stroke 0.75 m

• Frequency 0-20 Hz • Peak velocity 1.8 m/s• Force capacity 6.8 MN • Vertical payload 20 MN

Performance testing of Earthquake Protectors took place at the UC San Diego Large High Performance Outdoor Shake Table (LHPOST).

LHPOST is a participant of the George E. Brown Jr. Network for Earthquake Simulation (NEES).

• Three 1/8th–scaled down building models of identical design were tested on the shake table, namely: 6-story, 12-story and 18-story ones.

• Those models were kinematically equivalent to the real building prototypes which meant they would deflect horizontally the same way under the same horizontal excitation.

• The “prestressing” concept of design was chosen to increase the models’ structural redundancy while preserving their visual sensitivity to any kind of lateral excitations.

• Earthquake Protector or EP (U.S. Patent pending) is a system of structural elements resting on a building footing and underpinning a building superstructure.

• This system, generically called base isolation, is intended to shield the building superstructure against lateral impacts of strong earthquakes.

• To withstand the real earthquake time-histories, the models of earthquake protectors had to have full scale horizontal dimensions.

• Unlike the active, hybrid or semi-active structural control hardware, it looks, apparently, simple and self-sufficient .

Each EP comprises: • Three properly configured

race pads 1, 2 and 3 mounted one over another with the lower pad 1 resting on the footing.

• Two circular-cylinder-shaped segmented slide tracks 4 and 5 which are sagged down, located between adjacent race pads and containing freely revolving parallel cylindrical rollers 6 with their axes being set horizontal and mutually orthogonal.

• a column stub 7 resting upon a spherical bearing 9 mounted centrically on the upper pad 3 with the top end of the column stub being framed rigidly into the supported superstructure 8.

• Assembly of four Earthquake Protectors in the process of assembly:

• The 6-story building model supported on four Earthquake Protectors:

http://www.ecs.csun.edu/~shustov/EP-2006.htm

Ground acceleration mitigation factor Fmit , that is the most simple performance parameter chosen for comparison with the field records, may be determined as a ratio of the maximum recorded horizontal acceleration on the ground (or on the shake table platen) to the maximum recorded horizontal acceleration on the building (or on the model structure).

Superstructure with fundamental

period Tf

Bearing type and its isolated

period Ti

Earthquake Mitigation

Factor Fmit 6-story building model, Tf = 0.6s

Earthquake Protector, Ti = 5s

300% Northridge Jan.17, 1994

4.78

12-story building model, Tf = 1.2s

Earthquake Protector, Ti = 5s

100% Northridge Jan.17, 1994

2.63

18-story building model, Tf = 1.8s

Earthquake Protector, Ti = 5s

120% Northridge

Jan.17, 1994

2.77

Facility Bearing Type Earthquake Mitigation

Factor Fmit Santa Ana RiverBridge

Lead-rubber Whittier Narrows Oct. 1,

1987

0.28

Sierra Point Overpass

Lead-rubber Loma Prieta Oct. 17,

1989

0.22

LA County FireCommand Facility

High-damping rubber

Northridge Jan.17, 1994

0.54

USC TeachingHospital

Rubber/Lead-rubber

Northridge Jan.17, 1994

0.89 – 1.76

Rockwell Intl.Headquarters

Lead-rubber Northridge Jan.17, 1994

0.53

3-story ResidenceBuilding

Spring & Viscodamper

Northridge Jan.17, 1994

0.70

See http://www.ecs.csun.edu/~shustov/Topic4.htm

1 - LA County Fire Command Facility

2 - USC Teaching Hospital

3 - 3-story Residence Building

4 - Rockwell Intl. Headquarters

See http://www.ecs.csun.edu/~shustov/Topic2.htm

• Software for analytical research called Earthquake Performance Evaluation Tool (EPET) enables virtual experiments on buildings with and without Earthquake Protectors. On demand, all virtual experiments are animated.

• Major building fitness evaluation parameter for the testing is the Seismic Performance Ratio R/Rw .

The software development source code: http://epet.space3d.biz/EPET_DEV.zip.

• Quantitative performance evaluation of a virtual building structure during a virtual earthquake excitation is done with the help of the nth story Seismic Performance Ratio R/Rw (or SPR):

SPR = vn/Rwnven (3)

• There will be the following three basic situations:• 0 < SPR < 1 Acceptable performance of a story, called: GOOD.• 1 < SPR < 1.5 Possibility of structural failure, called: FAILURE.• 1.5 < SPR Structural collapse, called: СOLLAPSE.

DAMAGE

INDEX0 1 2 3 4

DAMAGE

CATEGORYNo damage Slight Considerable Severe Collapse

SPR = R/Rw < 0.167 0.167 – 0.5 0.5 – 1.0 1.0 - 1.5 > 1.5

D.R. (%) < 0.14 0.14 - 3.75 3.75 – 30.00 30.00 – 100 > 100

http://www.ecs.csun.edu/~shustov/TEST_8_LARGE.wmv

FLOOR

NUMBER

EXPERIMENTAL STORY DRIFTS of 6-STORY BUILDING MODELS (cm)

Cone© maximum velocity = 16.96 cm/s

Cone© maximum velocity = 46.63 cm/s

Cone© maximum velocity = 89.48 cm/s

Fixed base On EP Fixed base On EP Fixed base On EP

6th 1.23 0.26 2.39 0.37 4.96 0.54

5th 2.82 0.25 6.46 0.39 6.90 0.62

4th 2.22 0.38 5.83 0.54 7.15 0.81

3rd 3.22 0.31 8.65 0.47 11.66 0.73

2nd 2.97 0.31 7.17 0.47 11.4 0.72

1st 2.12 0.24 4.29 0.37 13.46 0.59

Ave. drift

mitigation8.38 13.18 13.82

FLOOR

NUMBER

STORY DAMAGE INDEX and DAMAGE CATEGORY for 6-STORY BUILDING MODELS at SHAKE TABLE TESTING

Cone© maximum velocity = 16.96 cm/s

Cone© maximum velocity = 46.63 cm/s

Cone© maximum velocity = 89.48 cm/s

Fixed base On EP Fixed base On EP Fixed base On EP

6th 1slight

0no damage

2considerable

0no damage

4collapse

1slight

5th 3severe

0no damage

4collapse

0no damage

4collapse

1slight

4th 2considerable

0no damage

4collapse

1slight

4collapse

1slight

3rd 3severe

0no damage

4collapse

0no damage

4collapse

1slight

2nd 2considerable

0no damage

4collapse

0no damage

4collapse

1slight

1st 2considerable

0no damage

3severe

0no damage

4collapse

1slight

http://www.ecs.csun.edu/~shustov/TEST_5_LARGE.wmv

http://www.ecs.csun.edu/~shustov/TEST_6_LARGE.wmv

FLOOR

NUMBER

COMPARATIVE INDEX OF EARTHQUAKE PERFORMANCE FOR 6-STORY BUILDING MODELS: EP vs. Fixed base

Cone© maximum velocity = 16.96 cm/s

Cone© maximum velocity = 46.63 cm/s

Cone© maximum velocity = 89.48 cm/s

6th 0 - 1 0 - 2 1 - 4

5th 0 - 3 0 - 4 1 - 4

4th 0 - 2 1 - 4 1 - 4

3rd 0 - 3 0 - 4 1 - 4

2nd 0 - 2 0 - 4 1 - 4

1st 0 - 2 0 - 3 1 - 4

Damage Index: 0 – no damage; 1 – slight; 2 – considerable; 3 – severe; 4 - collapse

• Shake table experiments with Earthquake Protectors performed on the scaled-down building models were a full success.

• The stronger an earthquake the better Earthquake Protector’s mitigating performance.

• Taking ground acceleration mitigation factor Fmit as a criterion for performance comparison of different types of base isolators, Earthquake Protector is, at least, five times more effectively than any of the field-tested seismic base isolator in California.

• Earthquake Protector is simple, inexpensive to build and applicable to any size of the building structure.

Earthquake Performance Evaluation Tool (EPET) can accurately predict earthquake performance of a building, with or without Earthquake Protector, up to the point of its virtual state of “severe damage”.