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Composite and Modular Structures, Part 2

ACI Spring 2012 ConventionMarch 18 – 21, Dallas, TX

Steven J. Mitchell received his Bachelors of Science degree in Civil Engineering from Trine (formerly Tri-State) University in 2009. Before enrolling in graduate school at the University of Cincinnati in September, 2010, he worked

for a consulting firm in South Bend, IN, where he is originally from, called Lawson-Fisher Associates P.C. He is currently in his second year of graduate studies at the University of Cincinnati, pursuing his Masters of Science in Civil Engineering. A Research Experience for Undergraduates (REU) experience at UC during the summer of 2007 instilled in him the desire to pursue graduate studies, and most notably research within academics. Upon completion of his master’s degree, he is considering pursuing a doctorate degree at the University of Cincinnati, while at the same time searching for future employment as a civil engineer in the Midwest and elsewhere in the United States.

The development of a replaceable (steel fuse) coupling beam for coupled core wall systems

Steven J. Mitchell – Graduate student, University of Cincinnati

Gian A. Rassati – Associate professor, University of Cincinnati

Bahram M. Shahrooz – Professor, University of Cincinnati

Presentation Outline

• Background: Steel Coupling Beams (SCBs), and Steel Fuse Coupling Beams (SFCBs)

• Methodology of SFCBs

• Previous SFCB experiment

• Proposed design procedure

• Prototype Design and Analytical modeling

• Preliminary results

• Half-scale testing of SFCB

Background

• Efficient Lateral Force Resisting System (LFRS)

Background

• Efficient Lateral Force Resisting System (LFRS)

• Application to building structures

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Background

• Efficient Lateral Force Resisting System (LFRS)

• Application to building structures

• Types of coupling beams– Reinforced concrete

– Diagonally reinforced concrete

– Conventional steel

Background

• Efficient Lateral Force Resisting System (LFRS)

• Application to building structures

• Types of coupling beams – Conventional Steel

• Significant advantages include:– Superior strength and stiffness in

coupled core wall systems

– Ductility and energy dissipation capacities

– Performance under cyclic loads

Background

• Efficient Lateral Force Resisting System (LFRS)

• Application to building structures

• Types of coupling beams

• Methodology for a Steel Fuse Coupling Beam, how will it perform, and why is this desirable?

Methodology

• Seismic response of structures

– Localized, controlled damage

– Steel links in eccentrically braced frames (EBFs)

– Protect the elements surrounding the link from yielding

Methodology• Localize damage in a central ‘fuse’ section

• Surrounding beam components remain elastic

• Has the same advantages as conventional steel coupling beams

Previous SFCB Experiment• First generation developed at the University of Cincinnati

(Fortney, 2005)

• Design procedure based on ‘arbitrary’ strength values to achieve performance.

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Proposed Design Procedure

1. Determine the load demands on a single coupling beam, both shear and moment

a) The fuse section is designed to resist these forces and must be designed FIRST

2. Design the fuse

a) Shear Capacity:

b) Flexural Capacity:

wfwfynf thFV 6.0

fypfnf zFMM

Check limiting width-thickness

ratios:

Proposed Design Procedure

3. Determine fuse length to ensure it is shear-critical:

p

p

V

Me

)6.1(

nfp VV

pfp MM Where:

4. Use the EXPECTED shear strength of the fuse to determine the loadsimparted to the surrounding embedded beams:

Proposed Design Procedure

4. Use the EXPECTED shear strength of the fuse to determine the loadsimparted to the surrounding embedded beams:

nfyembuf VRVV 1.1,exp,

Proposed Design Procedure

5. Design the embedded beams

a) Shear Capacity:

b) Flexural Capacity:

6. Design the bolted and

welded connections

eyy SFM

Check limiting width-thickness

ratios:

weweyne thFV 6.0

Proposed Design Procedure7. Design the coupling beam within the reinforced concrete wall piers

a) Embedment length

b) Auxiliary transfer bars

c) Detailing

8. Perform necessary limit-state checks on beam elements and connecting elements.

Analytical Modeling

Elastic design/analysis completed using software package ETABS

Adaptive pushover analysis completed using the software package Ruaumoko.

Dynamic response history analyses completedusing the software package Ruaumoko,with the following ground motions considered (further records to be added later):

RuaumokoBuilding Model

Dynamic ForcesAnalysis Time (s)

Peak Acceleration (g)

1 Adaptive Pushover 100 N/A

2 ASCE Design Earthquake 30 1.050

3 ASCE MC Earthquake 30 1.575

4 El Centro Earthquake 20 0.348

5Northridge Earthquake @ 

Sylmar Hospital40 0.798

6Northridge Earthquake @ 

Pacoima Dam60 1.492

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Analytical Modeling

The following response quantities are of interest in the analyses:

1. Building drift information – residual effects

2. Status of coupling beams throughout the ground motion

3. Peak rotations witnessed by coupling beams

4. Load demands on wall piers – base shears and moments

Prototype Building Design

0

2

4

6

8

10

12

14

16

18

20

0 100 200 300 400 500 600 700

Flo

or L

evel

Shear (Kips)

Coupling Beam Shear Demand Vs. Capacity

Shear Demands

Fuse Shear Capacities

Embedded Beam ShearCapacities

1.1RyVn, Fuses

Each floor level coupling beam is designed such that the fuse is capable of resisting design-level demands.

Prototype Building DesignEach floor level coupling beam is designed such that the fuse is capable of

resisting design-level demands.

0

2

4

6

8

10

12

14

16

18

20

0 200 400 600 800 1000 1200 1400 1600 1800

Flo

or L

evel

Moment (Kip-Feet)

Coupling Beam Moment Demand Vs. Capacity

MomentDemands

Fuse MomentCapacities

EmbeddedBeam MomentCapacities

0

2

4

6

8

10

12

14

16

18

20

0.00% 0.20% 0.40% 0.60% 0.80% 1.00% 1.20% 1.40%

Flo

or L

evel

Inter-story Drift (% Story Height)

Normalized Story Drift

Prototype Building Design

Analytical Modeling –Pushover Analysis

0

2

4

6

8

10

12

14

16

18

20

0.00% 0.10% 0.20% 0.30% 0.40% 0.50% 0.60% 0.70%

Flo

or L

evel

Inter-story Drift (% Story Height)

Normalized Story Drift Fuse yield progression during pushover:

Fuses at level 4 Fuses at level 20

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

200%

0.00% 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%

Per

cent

of

EL

F B

ase

Shea

r (%

)

Roof Deflection (% of Building Height)

Progression of Fuses Yielding

Base Shear Vs. RoofDeflection

Fuses Yielding

Analytical Modeling –Pushover Analysis

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Analytical Modeling – Response Histories

Earthquake Ground Motions:

-0.4

-0.2

0

0.2

0.4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Acc

eler

atio

n (

g)

Time Step (seconds)

El Centro Record

Peak Acceleration = 0.348 g

-1

-0.5

0

0.5

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Acc

eler

atio

n (

g)

Time Step (seconds)

Northridge (Sylmar) Record

Peak Acceleration = 0.798 g

Analytical Modeling –Response Histories

Artificial Earthquake Ground Motions:

-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6Acc

eler

atio

n (

g)

Time Step (seconds)

Design Earthquake Record

Peak Acceleration = 1.04 g

-1

-0.5

0

0.5

1

1.5

2

0 1 2 3 4 5 6

Acc

eler

atio

n (

g)

Time Step (seconds)

MC Earthquake Record

Peak Acceleration = 1.54 g

Analytical Modeling –Response Histories

Top Floor Drifts – All Earthquakes:

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

0 2.5 5 7.5 10 12.5 15

Top

Flo

or D

rift

(in

ches

)

Time Step (Seconds)

Top Floor Drifts

El Centro

Design EQ

Northridge

MC Earthquake

Peak Drift = -29.8 IN (2.48 FT) = 1.38% Building Height

Analytical Modeling –Response Histories

Steel Fuses Shear Performance:

-2000

-1500

-1000

-500

0

500

1000

1500

2000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Sh

ear

(Kip

s)

Time Step (seconds)

EC Shear Analysis, Floors 5-8

Pos Design Shear Strength

Neg Design Shear Strength

Floor 8

Floor 7

Floor 6

Floor 5

Pos Expected Shear Strength

Neg Expected Shear Strength

-3000-2500-2000-1500-1000

-5000

50010001500200025003000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Sh

ear

(Kip

s)

Time Step (seconds)

Northridge Shear Analysis, Floors 5-8

Pos Design Shear Strength

Neg Design Shear Strength

Floor 8

Floor 7

Floor 6

Floor 5

Pos Expected Shear Strength

Neg Expected Shear Strength

Analytical Modeling –Response Histories

Steel Fuses Shear Performance:

-2500-2000-1500-1000

-5000

500100015002000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Sh

ear

(Kip

s)

Time Step (seconds)

Design EQ Shear Analysis, Floors 5-8

Pos Design Shear Strength

Neg Design Shear Strength

Floor 8

Floor 7

Floor 6

Floor 5

Pos Expected Shear Strength

-3000-2500-2000-1500-1000

-5000

5001000150020002500

0 1 2 3 4 5 6 7 8 9 10

Sh

ear

(Kip

s)

Time Step (seconds)

MCE Shear Analysis, Floors 5-8

Pos Design Shear Strength

Neg Design Shear Strength

Floor 8

Floor 7

Floor 6

Floor 5

Pos Expected Shear Strength

Neg Expected Shear Strength

Analytical Modeling – Response HistoriesSteel Fuses Time of First Yielding:

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0123456789

1011121314151617181920

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Acc

eler

atio

n (

g)

Flo

or L

evel

Time Step (seconds)

El Centro Ground Motion

Peak Acceleration = 0.348 g

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Analytical Modeling – Response HistoriesSteel Fuses Time of First Yielding:

-0.80

-0.60

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

0123456789

1011121314151617181920

0 1 2 3 4 5 6 7 8 9 10

Acc

eler

atio

n (

g)

Flo

or L

evel

Time Step (seconds)

Northridge (Sylmar) Ground Motion

Peak Acceleration = 0.798 g

Analytical Modeling – Response HistoriesSteel Fuses Time of First Yielding:

-0.40

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0123456789

1011121314151617181920

0 1 2 3 4

Acc

eler

atio

n (

g)

Flo

or L

evel

Time Step (seconds)

Design Earthquake Ground Motion

Peak Acceleration = 1.04 g

Analytical Modeling – Response HistoriesSteel Fuses Time of First Yielding:

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

0123456789

1011121314151617181920

0 1 2 3 4

Acc

eler

atio

n (

g)

Flo

or L

evel

Time Step (seconds)

MC Earthquake Ground Motion

Peak Acceleration = 1.54 g

Analytical Modeling –Response Histories

Wall Pier Integrity – El Centro Earthquake:

The outline represents a ‘yield surface’ for the wall piers at the floor levels presented at the top of the plot.

-60,000

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000 -150,000 -100,000 -50,000 0 50,000 100,000 150,000 200,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Base Level Wall Pier Demands

Left Pier Demands

Right Pier Demands

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000 -150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 5 Wall Pier Demands

Left Pier Demands

Right Pier Demands

-20,000

-10,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

-150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 13 Wall Piers Demands

Left Pier Demands

Right Pier Demands

Analytical Modeling –Response Histories

Wall Pier Integrity – Northridge (Sylmar) Earthquake:

The outline represents a ‘yield surface’ for the wall piers at the floor levels presented at the top of the plot.

-60,000

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000-150,000-100,000 -50,000 0 50,000 100,000 150,000 200,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Base Level Wall Pier Demands

Left Pier Demands

Right Pier Demands

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000-150,000-100,000-50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 5 Wall Pier Demands

Left Pier Demands

Right Pier Demands

-20,000

-10,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

-150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 13 Wall Piers Demands

Left Pier Demands

Right Pier Demands

Analytical Modeling –Response Histories

Wall Pier Integrity – Design Earthquake:

The outline represents a ‘yield surface’ for the wall piers at the floor levels presented at the top of the plot.

-60,000

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000-150,000-100,000 -50,000 0 50,000 100,000 150,000 200,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Base Level Wall Pier Demands

Left Pier Demands

Right Pier Demands

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000 -150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 5 Wall Pier Demands

Left Pier Demands

Right Pier Demands

-20,000

-10,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

-150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 13 Wall Piers Demands

Left Pier Demands

Right Pier Demands

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Analytical Modeling –Response Histories

Wall Pier Integrity – MC Earthquake:

-60,000

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-500,000 -400,000 -300,000 -200,000 -100,000 0 100,000 200,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Base Level Wall Pier Demands

Left Pier Demands

Right Pier Demands

-40,000

-20,000

0

20,000

40,000

60,000

80,000

-200,000 -150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 5 Wall Pier Demands

Left Pier Demands

Right Pier Demands

-20,000

-10,000

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

-150,000 -100,000 -50,000 0 50,000 100,000 150,000

Axi

al L

oad

(k

ips)

Moment (k-ft)

Floor 13 Wall Piers Demands

Left Pier Demands

Right Pier Demands

The outline represents a ‘yield surface’ for the wall piers at the floor levels presented at the top of the plot.

Half-Scale Experimental Test

• Half-scale test coupling beam designed from floors 5-8 of the prototype structure

• Experimental steel fuse coupling beam already fabricated

Half-Scale Experimental Test

• Half-scale test coupling beam designed from floors 5-8 of the prototype structure

• Experimental steel fuse coupling beam already fabricated

• Instrumentation packages will be used on the fuses, and the embedded beams both outside and inside the reinforced concrete walls

• Testing schedule is likely for April-May, 2012

• Data from experiment will help guide future analytical modeling

Previous test at the University of Cincinnati

Large Scale Testing Facility

Questions ?