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Aluminium Shear Yielding Damper as Energy Dissipation DevicesAlok RajDual degree, Civil EngineeringIndian Institute of Technology Kanpur

Thesis Supervisor: Prof. Durgesh C Rai1ContentsIntroductionObjectiveLiterature review3.1 Al-SYD for passive control of seismic response of Truss Moment Frame (TMFs) - Ankit Sachan, 20113.2 Placement of bilinear hysteretic energy dissipation devices for passive control of RC structures - Puneet Chugh, 2013Conclusions Future scope

Introduction Truss Moment Frame AdvantagesBetter option for large spansVery economicalSimple detailing of moment connectionsDucts and pipes can be installed through web openingsHigh strength to weight ratio, large ductility, ease of fabrication and erection

DisadvantagesPoor seismic performance

AL-SYD as an Energy dissipatorUtilises metallic hysteresis for enhanced seismic energy dissipationDesigned to yield in shear modeVery ductile and very large deformations possible without tearing or buckling.

ObjectiveImprove the performance of TMFs by introducing a device that can absorb seismic energyEnhance energy dissipation without considerable decrease in stiffness of structureTo develop a design methodology for the designing of Al-SYD for the TMFTo develop a methodology to determine optimal location of Al-SYDsTo determine optimal number of dampers needed in a structure

Al-SYD for passive control of seismic response of Truss Moment Frame (TMFs) - Sachan,2011

Designed so as to allow inelastic activity in Al-SYDAl-SYD was modelled as link element and designed using design lateral load as per IS1893 and Energy based designExperimental ProcedurePrototype Structure and Al-SYD was scaled down to 1/6thTwo types of specimen: Specimen 1 (Al-SYD TMF) & Specimen 2 (TMF)Free vibration tests: Impact hammer test and snap back tests were performed to evaluate model dynamic properties.For dynamic loading, TaftN21E component of 1952 kern Country earthquake was used.Loading sequence of specimen started with Taft (PGA 0.05g) up to Taft (PGA 2.40g).White noise (0.05g) was applied before and after the application of each Taft motions to investigate the change in stiffness of structure.

Test Specimen (Al-SYD TMF) (Sachan,2011)Results

After Taft Motion with PGA 1.65gAfter Taft Motion with PGA 2.25g (Sachan,2011)Change in variation of natural frequency in specimen 1 and Specimen 2 (Sachan,2011)Sl. No.Loading StageFrequency (Hz)ObservationSpecimen 1Specimen 2Specimen 1Specimen 210.05g3.134.2120.10g - 0.30g3.134.19Loosening of welds30.45g -0.90g2.494.12Yielding of shear linkLoosening of welds41.05g - 1.35g2.494.1Loosening of welds51.50 g2.494.1Onset of buckling61.65g2.494All shear link buckledInitiation of inelastic activity in columns71.80g - 2.10g2.344Tearing in one of the link82.25g2.14Excessive tearing in all shear linksComparison of results

Natural frequency observed for Specimen 1 was lower

For all ground motion, roof acceleration, base shear and base overturning moment reduced significantly for Al-SYD TMF

Roof drift for both specimen was mostly same.

Hysteretic plots for specimen 1 was observed to be smaller than TMF

Comparison of average Peak roof acceleration Comparison of average Peak roof acceleration Comparison of average Peak roof acceleration (Sachan,2011)Analytical StudyAl-SYD TMF and TMF was modelled in SAP 2000Shear link was modelled as two link elementNon-linear static pushover analysis was performed in both modelNon-linear direct integration analysis was performed using Taft MotionBase shear obtained analytically was found to match closely with experimental result

Load displacement using Pushover analysisBase shear comparison Sachan (2011)Placement of bilinear Hysteretic Energy dissipation devices for passive control of RC structures - Puneet Chugh, 2013

Analytical StudyThree different 2D frames of 4, 6 and 10 storeys were consideredSimplified Sequential Search Algorithm (SSSA) with Optimal Location Index was used to obtain optimal or most efficient configurationNonlinear direct integration time history analysis was performed on considered framesRMS value of peak interstorey drift (i, RMS) was obtained and Optimal Location index (i)value was found

Analysis was repeated with the first damper in place and the optimal location of next damper was sequentially found

Optimal Damper Locations (Chugh,2013)FrameNumber of DampersDamper Locations4-Storeys32-1-36-Storeys52-1-3-4-210-Storeys84-3-2-5-2-6-3-7Performance at desired seismicityEach frames were subjected to another set of (scaled) ground motion.Peak RMS floor displacement is less than target displacement (i) for DBE (calculated from FEMA 356 (2000)).

Peak floor displacement comparison

Peak RMS floor displacement for DBE (Chugh, 2013)Near Field MotionsNear Field MotionsFar Field MotionsFar Field MotionsSSSA on 3D structuresInterstory translational displacement and torsional response of floor contributes to interstory drifts.Along with optimal location of floor, optimal location index for all the floors of each frame was found.After placing the damper at this location, the SSSA process is repeated.

Target displacementTarget displacement (t) for DBE and MCE at node was calculated using Displacement Coefficient Method described in FEMA 356 (2000).

C0, C1, C2, C3 = Modification FactorsSa = Response spectrum accelerationTe = Effective fundamental periodConclusionsIn Al-SYD TMF, reduction in base shear in the range of 36% to 82%.Peak roof accelerations experienced in Al-SYD TMF was 40%-80% lower than that in TMF.SSSA with proposed Optimal Location Index can efficiently determine the location of dampers.Performance of damper added frames satisfy the acceptability limits of roof drift and interstory drifts.

Future ScopeApplication of damper at any other location in Al-SYD TMF can be studied.Pseudo dynamic testing on full scale model of Al-SYD TMF will provide confidence on working of shear link in Al-SYD TMF.Efficiency of SSSA procedure can be tested on other structures.Modification in the procedure due to mass and Stiffness distribution can be investigated.

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