Development of Replaceable Steel Coupling Beams for ...risedr.tongji.edu.cn/7th_Kwang-Hua_Forum/files/Parallel_2B/... · Development of Replaceable Steel Coupling Beams for Enhanced

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Xiaodong JITsinghua University

Development of Replaceable Steel Coupling Beams for Enhanced Seismic

Resiliency of High-Rise Buildings

December 9, 2016

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Chile Earthquake (2010)

Wenchuan Earthquake（2008）

Kobe Earthquake(1995)

Loma Prieta Earthquake(1989)

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Replaceable steel coupling beam (RSCB)

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Replaceable steel coupling beam (RSCB)

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Tianjin 117 Tower(597 m)

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Beijing Sancai Building (48.5 m)

• Background & motivations• Seismic design of RSCBs• Performance assessment of RSCBs

Outlines

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Shear linkYield in shear

Beam segment

Flexural strength

Link-to-beam connection

e/(Mp/Vp)<1.6Vp=0.6fyAwYield strength

Mbp>0.5l·(ΩVp)Vbp> Ω VpShear strength

Vcp> Ω Vp

Mcp>0.5e’·(Ω Vp)Flexural strength

Shear strength

Capacity design philosophy

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• Very short shear links• Link-to-beam connections• RC slab

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e/(Mp/Vp) < 1.0 e/(Mp/Vp) ≈ 1.5Length ratio

RSCBs EBFs

Shear links （per AISC 341 & GB 50011）

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0.08 rad required by AISC 341

Test of very short shear links

e/(Mp/Vp) = 0.87Length ratio:

Ji X, Wang Y, Ma Q, Okazaki T. Cyclic behavior of very short steel shear links. Journal of Structural Engineering (ASCE), 2016, 142(2): 04015114.

Hybrid section: LY 225/Q235 for link web and Q345 for flanges

Overstrength Ω = Vmax/Vn

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n The very short shear links generated an overstrength factor of approximately 1.9, significantly exceeding the value of 1.5 assumed for EBF links in the AISC 341-10 provisions.

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I-shaped section linkCB1: End plate connection

I-shaped section link CB2: Splice plate connection

14Epoxy adhesive fv = 15 MPa

Double channel section link CB3: Bolted web connection

Double channel section linkCB4: Adhesive web connection

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Loading protocol

Phase I 0.02 radPhase II Fail

n Phase I: load to 0.02 rad rotation

n Phase II: load till failure

n Replacement of the shear link

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CB1 CB2

CB3 CB4

Phase I test

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CB1 CB2

CB3 CB4: Adhesive fracture

Phase I test

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n Coupling beam

n Shear link

Phase II test

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Spec. No.

Connection type

Ultimate rotation

(rad)

Residual rotation for replacement

(rad)

Replacement time

(hour)

CB1 End plate connection 0.06 0.0045 0.4

CB2 Splice plate connection 0.09 0.0045 2.6

CB3 Bolted web connection 0.06 0.0065 2.2

CB4 Adhesive web connection 0.003 —— ——

Replaceability

Xiaodong Ji, Yandong Wang, Qifeng Ma, Taichiro Okazaki. Cyclic behavior of replaceable steel coupling beams. Journal of Structural Engineering (ASCE), 2016. DOI: 10.1061/(ASCE)ST.1943-541X.0001661.

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CBS1: Composite slab

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Slab damage

• At 0.04 rad beam rotation, most of shear studs pulled out from the RC slab, and the rebars were exposed and buckled.

• Shear studs are NOT recommended for use between the RSCBs and their above slabs.

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CBS2: Isolated slab

CBS3: Bearing slab CBS4: Slotted slab

CBS1: Composite slab

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CBS2: Isolated slab (GOOD)

CBS3: Bearing slab (FAIR) CBS4: Slotted slab (FAIR)

CBS1: Composite slab (BAD)

• Background & motivations• Seismic design of RSCBs• Performance assessment of RSCBs

Outlines

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Damage state

Damage description Repair method Damage illustration

DS1 - Substantial slab damage

- Replacement of the portion of the slab above the

RSCB aDS2

- Web buckling- Flange buckling- Global buckling

- Heat straightening - Replacement of

shear link aDS3

- Web fracture- Flange fracture

- Replacement of the shear link a

Next generation performance assessment（FEMA P-58）

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Damage state

Link rotation (Mean ) Repair method Damage illustration

DS1 5%

- Replacement of the portion of the slab above the

RSCB aDS2 9%

- Heat straightening

- Replacement of shear link a

DS3 11% - Replacement of the shear link a

Fragility curve of RSCB

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Beijing Sancai Building (11 story, 48.5 m)

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n Design basis earthquake (DBE) PGA 0.2gn Period：1.57 s (Y)、1.53 s (X)、1.26 s (Torsion)n Seismic design: linear spectrum analysis under SLE n Interstory drift ratio (SLE) < 1/800

Xiaodong Ji, Dan Liu, Ya Sun, Carlos Molina Hutt. Seismic performance assessment of a hybrid coupled wall system with replaceable steel coupling beams versus traditional RC coupling beams. Earthquake Engineering and Structural Dynamics, DOI: 10.1002/eqe.2801, 2016.

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• Wall pier：

OpenSees model

Multi-layer shell element

Beam element + Nonlinear link element

• Coupling beam：

• Coupling ratio=0.43

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Ground motions

• Seismic motions: selected from PEER database using linear scaling method

Damping ζ = 5%

• Seismic intensities: SLE, DBE, MCE, VRE

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Interstory drift ratio

Coupling beam behavior

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Seismic performance: HCW V.S. RCW

Damage states of coupling beams

MCE

VRE

RSCBs RC coupling beams

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Thanks much for your attention!

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