Seismic Performance of Seismic Performance of Reinforced Concrete Columns Reinforced Concrete Columns Under Biaxial ExcitationUnder Biaxial Excitation

Tiffany McCarthy

Dept. of Civil & Environmental Engineering

University of Houston

NSF REU Program

August 2007

ContentsContents

IntroductionIntroduction Objectives and ScopeObjectives and Scope ExperimentExperiment ResultsResults AnalysisAnalysis ApplicationsApplications Closing StatementClosing Statement Questions? Questions?

IntroductionIntroduction

Seismic = Earthquake - RelatedSeismic = Earthquake - Related Reinforced = Strengthened/SupportedReinforced = Strengthened/Supported Biaxial = 2 Axes Biaxial = 2 Axes Excitation = Acceleration Excitation = Acceleration 1999 Taiwan Earthquake1999 Taiwan Earthquake

1999 Taiwan Earthquake1999 Taiwan Earthquake

Tungtow BridgeTungtow Bridge

Tungtow Close-UpTungtow Close-Up

Taichung BuildingTaichung Building

Changhwa BuildingChanghwa Building

Objectives and ScopeObjectives and Scope

Subject to biaxial loadsSubject to biaxial loads– Test using more realistic conditionsTest using more realistic conditions

DetermineDetermine– Effect of orientationEffect of orientation– Effect of shear reinforcement ratioEffect of shear reinforcement ratio

Experimental ProgramExperimental Program

Steel ReinforcementSteel Reinforcement

FormworkFormwork

Concrete ColumnConcrete Column

Shake TableShake Table

ResultsResults

Cracking and YieldingCracking and Yielding Failure ModesFailure Modes Ultimate ForcesUltimate Forces Steel YieldingSteel Yielding Energy DissipationEnergy Dissipation Hysteretic ResponseHysteretic Response

SH1 and SH4SH1 and SH4

SH2 and SH5SH2 and SH5

SH3 and SH6SH3 and SH6

Force v. DisplacementForce v. Displacement(SH1 [left] and SH5 [right])(SH1 [left] and SH5 [right])

SH1 @ 1200gal

-2.00E+05

-1.50E+05

-1.00E+05

-5.00E+04

0.00E+00

5.00E+04

1.00E+05

1.50E+05

2.00E+05

2.50E+05

-2.00E+01

-1.50E+01

-1.00E+01

-5.00E+00

0.00E+00

5.00E+00

1.00E+01

1.50E+01

2.00E+01

Displacement

Fo

rce

SH5 @ 1600 gal

-2.50E+05-2.00E+05

-1.50E+05-1.00E+05-5.00E+040.00E+00

5.00E+041.00E+051.50E+05

2.00E+052.50E+05

-3.00E+01

-2.00E+01

-1.00E+01

0.00E+00 1.00E+01 2.00E+01 3.00E+01

Displacement

Fo

rce

Experimental AnalysisExperimental Analysis

Symmetry significant toSymmetry significant to– StiffnessStiffness– StrengthStrength– DeformationDeformation

Lower Energy Dissipation Than UniaxialLower Energy Dissipation Than Uniaxial Cracking and YieldingCracking and YieldingStiffness decr.Stiffness decr. Stirrup Spacing affects energy dissipation Stirrup Spacing affects energy dissipation

at high excitationat high excitation

ApplicationsApplications

More Reinforcements=More ResistantMore Reinforcements=More Resistant Orientation to Force is KeyOrientation to Force is Key Symmetry MattersSymmetry Matters Reduce Spalling Reduce Spalling

ClosingClosing StatementStatement

Reinforcement and Biaxial Loads are Reinforcement and Biaxial Loads are significant topics to consider when significant topics to consider when developing better guidelines for concrete developing better guidelines for concrete structures. structures.

Questions?Questions?