Self centering steel frame systems
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Self-Centering Steel Frame Systems. NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems Project Team Richard Sause, James Ricles, David Roke, Choung-Yeol Seo, Michael Wolski, Geoff Madrazo ATLSS Center, Lehigh University Maria Garlock, Erik VanMarcke, Li-Shiuan Peh

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Self centering steel frame systems

Self-Centering Steel Frame Systems

NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

Project Team

Richard Sause, James Ricles, David Roke,

Choung-Yeol Seo, Michael Wolski, Geoff Madrazo

ATLSS Center, Lehigh University

Maria Garlock, Erik VanMarcke, Li-Shiuan Peh

Princeton University

Judy Liu

Purdue University

Keh-Chyuan Tsai

NCREE, National Taiwan University


Current neesr project neesr sg self centering damage free seismic resistant steel frame systems

Current NEESR ProjectNEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

This material is based on work supported by the National Science Foundation, Award No. CMS-0420974, in the George E. Brown, Jr. Network for Earthquake Engineering Simulation Research (NEESR) program, and Award No. CMS-0402490 NEES Consortium Operation.


Self centering steel frame systems

Motivation: Expected Damage for Conventional Steel Frames

Conventional Moment Resisting Frame System

Reduced beam section (RBS) beam-column test specimen with slab: (a) at 3% drift, (b) at 4% drift.


Self centering sc seismic resistant system concepts

M

Self Centering (SC) Seismic-Resistant System Concepts

  • Discrete structural members are post-tensioned to pre-compress joints.

  • Gap opening at joints at selected earthquake load levels provides softening of lateral force-drift behavior without damage to members.

  • PT forces close joints and permanent lateral drift is avoided.


Previous work on sc steel moment resisting mrf connections

Previous Work on SC Steel Moment Resisting (MRF) Connections

W24x62 (Fy 248 MPa),

or W36x150 (Fy 350 MPa)

W14x311, W14x398(Fy 350 MPa)

or CFT406x406x13 (Fy 345 MPa)

PT Strands

3660to

4120mm

MRF Subassembly with PT Connections

6100to8540mm


Initial stiffness is similar to stiffness of conventional systems

PT Steel MRF

D

H

Initial Stiffness Is Similar to Stiffness of Conventional Systems

Stiffness with welded connection

MRF subassembly with post-tensioned connections


Self centering steel frame systems

Lateral Force-Drift Behavior Softens Due to Gap Opening

Steel MRF subassembly with post-tensioned connections and angles at 3% drift


Self centering steel frame systems

Conventional steel MRFs soften by inelastic deformation, which damages main structural members and results in residual drift

SC steel MRF softens by gap opening and reduced contact area at joints

Welded Connection

D

H

Post-Tensioned Connection

Lateral Force-Drift Behavior Softens Without Significant Damage


Self centering steel frame systems

Steel MRF

D

H

Specimen PC2

L6x6x5/16, g/t = 4

Specimen PC4

L8x8x5/8, g/t = 4

Energy Dissipation from Energy Dissipation (ED) Elements

Steel MRF subassemblies with post-tensioned connections withdifferent size ED elements.


Limited repairable damage

Angle fracture

Limited, Repairable Damage

Before testing

@ 4% Drift

After testing


Summary of sc seismic resistant structural system behavior

Summary of SC Seismic-Resistant Structural System Behavior

  • Initial lateral stiffness is similar to that of conventional seismic-resistant systems.

  • Lateral force-drift behavior softens due to gap opening at selected joints and without significant damage to main structural members.

  • Lateral force-drift behavior softening due to gap opening controls force demands.

  • Energy dissipation provided by energy dissipation (ED) elements, not from damage to main structural members.


Neesr sg self centering damage free seismic resistant steel frame systems

NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

  • Project Scope.

  • Project Goals.

  • Status of Selected Research Tasks.

  • Summary.


Neesr sg sc steel frame systems project scope

NEESR-SG: SC Steel Frame Systems Project Scope

  • Develop two SC steel frame systems:

    • Moment-resisting frames (SC-MRFs).

    • Concentrically-braced frames (SC-CBFs).

  • Conduct large-scale experiments utilizing:

    • NEES ES (RTMD facility) at Lehigh.

    • non-NEES laboratory (Purdue).

    • international collaborating laboratory (NCREE)

  • Conduct analytical and design studies of prototype buildings.

  • Develop design criteria and design procedures.


Neesr sg sc steel frame systems project goals

NEESR-SG: SC Steel Frame Systems Project Goals

  • Overall: self-centering steel systems that are constructible, economical, and structurally damage-free under design earthquake.

  • Specific:

    • Fundamental knowledge of seismic behavior of SC-MRF systems and SC-CBF systems.

    • Integrated design, analysis, and experimental research using NEES facilities.

    • Performance-based, reliability-based seismic design procedures.


Neesr sg self centering damage free seismic resistant steel frame systems1

NEESR-SG: Self-Centering Damage-Free Seismic-Resistant Steel Frame Systems

  • Project Scope.

  • Project Goals.

  • Status of Selected Research Tasks.

  • Summary.


Neesr sg sc steel frame systems project research tasks

NEESR-SG: SC Steel Frame Systems Project Research Tasks

  • Develop reliability-based seismic design and assessment procedures.

  • Develop SC-CBF systems.

  • Further develop SC-MRF systems.

  • Develop energy dissipation elements for SC-MRFs and SC-CBFs.

  • Develop sensor networks for damage monitoring and integrity assessment.

  • Design prototype buildings.

  • Perform nonlinear analyses of prototype buildings.

  • Conduct large-scale laboratory tests of SC-MRFs and SC-CBFs.

  • Collaborate on 3-D large-scale laboratory tests on SC-MRF and SC-CBF systems.


Task 2 develop sc cbf systems sc cbf system concept

Task 2. Develop SC-CBF Systems: SC-CBF System Concept

Rocking behavior of simple SC-CBF system.


More complex sc cbf configurations being considered

P01+P

P02+P

roof

P02

P01

g

g

g

g

V

g

g

g

g

g

g

g

g

base

base

col

V

More Complex SC-CBF Configurations Being Considered


Self centering steel frame systems

Lateral Force

MCE

DBE

Failure of Frame Members

PT Yielding

Significant Yielding of Frame Members

Δgap

IO

LS

CP

Column Decompression

PT steel yields

Member yields

Roof Drift

SC-CBF Design Criteria


Current work on sc cbf systems

Current Work on SC-CBF Systems

  • Evaluate frame configurations.

  • Evaluate effect of energy dissipation (ED) elements.

  • Develop and evaluate performance-based design approach.


Sc cbf configurations studied

SC-CBF Configurations Studied

PT

PT

PT

ED

ED

Frame A

Frame B12

Frame B12ED


Dynamic analysis results dbe

2.7%

1.4%

2.7%

2.4%

Dynamic Analysis Results (DBE)

  • Roof drift:

    • Effect of frame configuration.

    • Effect of ED elements.


Pushover analysis results

PT Yield

Base Shear (V/Vdes)

Decompression

Roof Drift (%)

Pushover Analysis Results


Preliminary results for sc cbf

Preliminary Results for SC-CBF

  • Dynamic analysis results indicate self-centering behavior is achieved under DBE.

  • Frame A has lower drift capacity before PT yielding than Frame B:

    • PT steel is at column lines rather than mid-bay.

  • Frame A also has lower drift demand.

  • Energy dissipation helps to reduce drift demand and improve response.


Task 3 further develop sc mrf systems current work

Task 3. Further Develop SC-MRF Systems: Current Work

  • Study of interaction between SC-MRFs and floor diaphragms by Princeton and Purdue.

  • SC column base connections for SC-MRFs being studied by Purdue.


Interaction of sc mrfs and floor diaphragms princeton

2Dgap

Dgap

Dgap

2Dgap

qr

Collector Beams

Interaction of SC-MRFs and Floor Diaphragms (Princeton)

Approach 1. Transmit inertial forces from floor diaphragm without excessive restraint of connection regions using flexible collectors.


Interaction of sc mrfs and floor diaphragms purdue

Interaction of SC-MRFs and Floor Diaphragms (Purdue)

Approach 2. Transmit inertial forces from floor diaphragm within one (composite) bay for each frame.


Sc column base connections for sc mrfs purdue

SC Column Base Connectionsfor SC-MRFs (Purdue)

Post-Tensioned Bars

Reinforcing Plate

Energy Dissipation Plate

Slotted Keeper Angle

Beam at Grade


Moment rotation response at column base

Moment-Rotation Response at Column Base

Identifying appropriate level of column base moment capacity and connection details, leading to laboratory experiments.


Task 4 develop energy dissipation elements for sc mrfs

Task 4. Develop Energy Dissipation Elements for SC-MRFs

  • SC systems have no significant energy dissipation from main structural elements:

    • Behavior of energy dissipation elements determined SC system energy dissipation.

  • Energy dissipation elements may be damaged during earthquake and replaced.

  • For SC-MRFs, energy dissipation elements are located at beam-column connections.


Quantifying energy dissipation

Area of yellow

bE = x 100(%)

Area of blue

Quantifying Energy Dissipation

  • Define relative hysteretic ED ratio bE

bE: Relative ED capacity

For SC systems: 0 ≤ bE ≤ 50%

Target value:bE = 25%

Hysteresis Loop


Ed element assessment

ED Element Assessment

  • Consider several ED elements:

    • Metallic yielding, friction, viscoelastic, elastomeric, and viscous fluid.

  • Evaluation criteria:

    • Behavior, force capacity versus size, constructability, and life-cycle maintenance.

  • Friction ED elements selected for further study.


Bottom flange friction device

Slotted plate

Friction bolts

Friction PL

Col. angle bolts

Column angle

Bottom Flange Friction Device

W36x300


Bffd moment contribution

COR+

COR-

BFFD Moment Contribution

  • BFFD contribution to connection moment capacity

MFf+ = Ff ∙r+

MFf- = Ff ∙r -

MFf = Ff∙r

|MFf+ | > |MFf- |


Test setup

Test Setup

W21x111

Beam

Bracing

Bracing

PT Strands

Column

3/5 Scale

BFFD

Test setup elevation

Test setup


Test matrix

Test Matrix

CS: Cyclic SymmetricEQ: Chi-Chi MCE Level Earthquake Response


Test 2 design friction force

Test 2: Design Friction Force

Beginning of Test 2

qr = +0.03 rads

qr = -0.03 rads


Test 2 response

1.0

+

-

q

M

+

q

-

r

M

r

p,n

0.5

imminent gap opening

stiffness

reduction

theoretical decompression

0.0

Normalized Moment, M/M

stiffness

theoretical decompression

reduction

-0.5

imminent gap opening

-1.0

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

q

Rotation,

(rads)

r

Test 2: Response


Test 2 comparison with simplified model

Axial stiffness of PT

strands & beam

1

2M+Ff

Md + M+Ff

2M-Ff

Md + M-Ff

Test 2: Comparison with Simplified Model


Results for ed elements for sc mrfs

Results for ED Elements for SC-MRFs

  • Friction ED element:

    • Reliable with repeatable and predictable behavior.

    • Large force capacity in modest size.

  • BFFD:

    • Provides needed energy dissipation for SC-MRF connections.

    • When anticipated connection rotation demand is exceeded, friction bolts can be designed to fail in shear without damage to other components.


Task 8 conduct large scale laboratory tests

Task 8. Conduct Large-Scale Laboratory Tests

  • Two specimens, one SC-MRF and one SC-CBF, tested at Lehigh NEES ES (RTMD facility).

  • 2/3-scale 4 story frame.

  • Utilize hybrid test method (pseudo dynamic with analytical and laboratory substructures).

  • Utilize real-time hybrid test method, if energy dissipation elements are rate-sensitive.


9 collaborate on 3 d large scale laboratory tests

9. Collaborate on 3-D Large-Scale Laboratory Tests

  • Large-scale 3-D SC steel frame system tests at NCREE in Taiwan under direction of Dr. K.C. Tsai.

  • Interaction of SC frame systems with floor diaphragms and gravity frames will be studied.

  • 3-D tests are part of Taiwan program on SC systems.

  • Project team is collaborating with Taiwan researchers:

    • US-Taiwan Workshop on Self-Centering Structural Systems, June 6-7, 2005, at NCREE.

    • 2nd workshop planned for October 2006 at NCREE.


Summary

Summary

  • Two types of SC steel frame systems are being developed:

    • Moment-resisting frames (SC-MRFs).

    • Concentrically-braced frames (SC-CBFs).

  • Research plan includes 9 major tasks:

    • Significant work completed on 7 tasks.

    • Numerous conference publications available from current project.

  • Large-scale experiments utilizing NEES ES at Lehigh are being conducted.

  • Ongoing collaboration with NCREE in Taiwan.


Self centering steel frame systems1

Self-Centering Steel Frame Systems

Thank you.


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