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4-2017

Hyperelastic Structural Fuses for Steel BuildingsFrancys LópezUniversity of Nebraska-Lincoln, flopez-mosquera@huskers.unl.edu

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López, Francys, "Hyperelastic Structural Fuses for Steel Buildings" (2017). Civil Engineering Theses, Dissertations, and Student Research.110.http://digitalcommons.unl.edu/civilengdiss/110

Hyperelastic Fuses

Why to upgrade traditional systems? The FEMA P-58-1 listed some of the limitations in present-generation procedures:

Questions regarding the accuracy and reliability of available analytical procedures in predicting actual building response.

“High” level of conservatism underlying the acceptance criteria.

Inability to reliably and economically apply performance-based procedures to the design of new buildings; and

Lack of alternative ways of communicating performance to stakeholders that is more meaningful and useful for decision making purposes.

Performance based design (PBD) emerges as the methodology aiming to bridge this gap, raising the design level performance from life safety (traditional systems) to keep structures fully functional after strong EQ.

What is a traditional Structural Fuse?Structural element where inelastic deformation (damage) is intentionally concentrated.Preferably, disposable and easy to repair structural element.

Remain elastic when subjected to considerably large deformations

Hysteresis Hyperelastic

Why Hyperelasticity?No inelastic deformations, and thus no residual drifts / Resiliency

Fuse initial sketch

Hyperelastic Fuse

The internal elements have an small initial skew that assures that the elements’ buckling path remains through the cycles.

What is a Hyperelastic System?

Target Buildings

How did we address these issues?

The target behavior is represented as follow.

Where: fe = elastic buckling load Ductility = ration between the displacement needed to close the fuse’s gap and the buckling displacement

Alpha1 = ratio between the secondary and initial stiffness

Alpha2 = ratio between the third and initial stiffness

duct ∆= g∆ y

α1 0k= ==2k0

α2 k= 3k0

4

5

Author: Francys López, Graduate Studentfor Steel Buildings

Hyperelastic Structural Fuses

Adviser: Joshua Steelman, Phd.

55

10

4

15

10

Fmax

/fy

9

20

3 8

Fs/fy. .2

.... Tn= 0.05s Sam

=1.6 R=8

Alpha2

25

7

Duct

62

30

541 320 1

8

10

12

14

16

18

20

22

24

26

05

10

4

20

10

Cd

9

30

3 8

Cd. .2

.... Tn= 0.05s Sam

=1.6 R=8

Alpha2

40

7

Duct

62

50

541 320 1

5

10

15

20

25

30

35

40

Building Performance (Under Evaluation)

How does this response (displacement and acceleration)

Using the FEMA P-58 report the respeonse can be associated with fragility levels, which will be useful to compare performance outcomes between strucrures with traditional and hyperelastic fuses.

Conclusions (Under Evaluation)

elastic buckling elements Frame equiped with Hyperelastic Fuses

-5 -4 -3 -2 -1 0 1 2 3 4 5

Sd[in]

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Fs/w

[k]

Case B Ductility effects with alpha= 0.25

Duct= 1

Duct= 2

Duct= 3

Duct= 4

Duct= 5

Duct= 6

Duct= 7

Duct= 8

Duct= 9

Duct= 10

Duct= 11

Duct= 12

Duct= 13

Duct= 14

Duct= 15

Duct= 16

Duct= 17

Duct= 18

Duct= 19

Duct= 20

Hysteretic

Evaluate hyper elastic fuse potential for retrofitting existing structures.

6 References

R\Tn 0.17 0.356 A B

3.5 C D

It is vital to 3D print fuse samples to investigate geometric sensitivities, and define and analyze the elastic buckling mode (internal elements of the fuse).

FEMA 445 Next Generation Performance- Based Seismic Design Guidelines: Program Plan for New and Existing Buildings. (n.d.). Retrieved February 06,2017, from https://wbdg.org/ffc/dhs/criteria/fema445Goldsworthy, H. (2012). Lessons from the 22 February 2011 Christchurch earthquake. Australian Journal of Structural Engineering, 13(2). doi:10.7158/s11-136.2012.13.2

Parametric Study3Resilient Construction is Needed1

2

1.25

1.4

4

1.6

10

Drif

t [%

]

9

1.8

3 8

Drift. .2

.... Tn= 0.5s Rlim

=3 R=3

Alpha2

2

7

Duct

62

2.2

541 3

20 1

1.4

1.5

1.6

1.7

1.8

1.9

2

X: 8

Y: 3.05

Z: 1.912

05

2

4 10

4

Fmax

/fy

93 8

Fs/fy. .2

.... Tn= 0.5s Sam

=2.9 R=3

6

Alpha2

7

Duct

62

8

541 320 11

2

3

4

5

6

7

X: 2.5

Y: 1.75

Z: 1.534

For 3-story buildings, a ductility higher than 15 is needed to equal the force level on both systems (Hyst. vs Hyper)

translate into performance?