View
213
Download
0
Category
Preview:
Citation preview
Off-Diagonal 2-4 Damping Technology using Off-Diagonal 2-4 Damping Technology using Semi-Active Resetable DevicesSemi-Active Resetable Devices
Geoffrey W RodgersGeoffrey W Rodgers, Kerry J Mulligan, J Geoffrey Chase, John B Mander, , Kerry J Mulligan, J Geoffrey Chase, John B Mander,
Bruce L Deam, and Athol J CarrBruce L Deam, and Athol J Carr
End Cap
Cylinder
Piston
Seal
Device DesignDevice Design
Valvea)
Valves
Cylinder Piston
b)
Cylinder Piston
Independent two chamber design allows broader range of control laws
Overall Customised HysteresisOverall Customised Hysteresis
Only the 2 - 4 control law does not increase base-shear
Viscous Damper
1-4 Resetable
1-3 Resetable
2-4 Resetable
Resist all motion
Resist motionaway from 0
Resist motiontoward 0
Resist all velocity
Semi-Active Resetable Device ModelSemi-Active Resetable Device Model
-15 -10 -5 0 5 10 15-3000
-2000
-1000
0
1000
2000
3000
4000
For
ce (
N)
Piston Displacement from Centre Position (mm)
Experimental Test Results
-15 -10 -5 0 5 10 15-3000
-2000
-1000
0
1000
2000
3000
4000
For
ce (
N)
Piston Displacement from Centre Position (mm)
Simulink Models
-20 -15 -10 -5 0 5 10 15-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
For
ce (
N)
Piston Displacement from Centre Position (mm)-20 -15 -10 -5 0 5 10 15
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
Forc
e (
N)
Piston Displacement from Centre Position (mm)
Simplified Linear ModelSimplified Linear Model
Less computationally expensive, with no anticipatedloss of accuracy or generality
1-3 control 2-4 control
1-4 control
Response SpectraResponse Spectra
Average response spectra for different control laws
How do the different control laws perform relative to one another?
Reduction FactorsReduction Factors
More clearly represent reductions achieved with each control law
Note the apparent invariance to the type of ground motion encountered
Divide results with additional stiffness by the uncontrolled case
Largest reductions seen for the 1-4 device – This device acts over a larger percentage of each cycle and will consequently
have longer active strokes
Suite DependenceSuite DependenceNormalise the average reduction factor from each suite
to the reduction factors for all ground motions to investigate suite dependence
Values close to unity across the spectrum indicates an invariance to the type of ground motion (near field vs. far field) encountered – indicating a robustness of this form of control
Spread of ResultsSpread of Results
Log-normal co-efficient of variation or dispersion factor- Indicates the spread of the results within a ground motion suite- Largest spread is seen for the 1-4 device indicating more variability- Both the 1-3 and 2-4 device show a tighter spread
Structural ForceStructural ForceThe base-shear force for a linear, un-damped structure - Gives an indication of the required column strength
Largest reductions for the 1-4 device – consistent with other metricSimilar performance for the 1-3 and 2-4 devices
Base-ShearBase-ShearThe sum of the structural force and the resetable device force - Gives an indication of the required foundation strength
Only the 2-4 device reduces base shear across the entire spectrum
The 1-3 and 1-4 devices increase base-shear by as much as 60%
The 2-4 device provides similar reductions in displacement and structural force as the 1-3 device, and also reduces base-shear
Control laws comparedControl laws comparedAveraging across suites more clearly indicates
the relative advantage of the control laws
Structural Force Base-Shear Force
1-3 and 2-4 show similar reductions in structural force, but are outperformed by the 1-4 device
Only the 2-4 device reduces base-shear, whereas both the 1-3 and 1-4 increase base-shear by as much as 60%
Displacement Spectral AreaDisplacement Spectral AreaNumerically integrate the area under the response spectra in the seismically
important T = 0.5 to 2.5 second range.
An indication of the average displacement reduction factor in the constant velocity region of the spectra
Fit empirical equations to estimate damping reduction factors
BR /1 wherestructural
resetable
K
KCB 1
where C = 1.43, 1.59, and 5.75 for the 1-3, 2-4 and 1-4 devices
How accurate are these equations?How accurate are these equations?
Re-plot the displacement reduction factors, with the reduction factors from the empirical equations
Although variations can be seen above T = 3.0seconds, equations are appropriate over the constant velocity region from T = 0.5 – 3.0 secs
Black Line is Empirical Equation
ADRS ADRS Acceleration-Displacement Response Spectra
Relate additional resetable stiffness to design guidelines
Empirical reduction factor equations create a “standard design platform” for a structural engineer to safely and
effectively add resetable devices to their design.
SummarySummary
• The 1-4 device outperforms both the 1-3 and 2-4 device for displacement response and structural force as it acts over the full response cycle, has longer active strokes, and consequently higher energy dissipation
• Both the 1-3 and 1-4 devices provide a reduction in structural force and displacement response, but increase base-shear up to 60%
• The 2-4 device reduces both structural force and base-shear
• All three control laws are suite invariant indicating a robustness to the type of ground motion encountered
• Empirical equations to approximate reduction factors allow incorporation into accepted performance based design metrics
ConclusionsConclusions
• Semi-active control enables customisation of overall structural hysteresis in novel ways not available with passive systems
• The most applicable control law (of the selected few presented) depends on the application
• New purpose designed structure • Retrofit application with limited foundation strength• Thus, device selection and implementation is a structural design problem rather
than a control systems problem
• The overall approach presented can be used to develop standard design metrics for any similar novel semi-active or passive systems/devices, thus creating a bridge to the design profession and a greater likelihood of uptake.
Experimental WorkExperimental WorkOne fifth scale building fitted with pneumatic
semi-active resetable devices
Experimental and Analytical Experimental and Analytical ComparisonComparison
10 15 20 25 30-20
-15
-10
-5
0
5
10
15
20
time (s)
Dis
pla
cem
en
t (m
m)
El Centro 70% - Displacement Structural Response
Valves Open1-4 Control Law2-4 Control Law
Reductions seen in shake table tests are close to those predicted by the analytical study
AcknowledgementsAcknowledgements
Special thanks to Ms Kerry Mulligan and Professors Special thanks to Ms Kerry Mulligan and Professors Chase and Mander for their assistance with this research, Chase and Mander for their assistance with this research,
as well as to our co-authorsas well as to our co-authors
This research was funded by the NZ Earthquake Commission This research was funded by the NZ Earthquake Commission (EQC) Research Foundation and the New Zealand Tertiary (EQC) Research Foundation and the New Zealand Tertiary Education Commission (TEC) Bright Futures Top Achievers Education Commission (TEC) Bright Futures Top Achievers
Doctoral Scholarship SchemeDoctoral Scholarship Scheme
Recommended