STUDY ON SEISMIC PERFORMANCE OF ADJACENT BUILDINGS USING FVDs

CIV E 661- Dynamics of Structures

UNIVERSITY OF ALBERTA

Group Members

Course ID

Ayaz Malik Luong Hong

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OBJECTIVES

To study the effect of Fluid Viscous Dampers (FVDs)

on response of adjacent buildings during a past

earthquake (El Centro).

To perform Qualitative Damage Analysis of the

structure under earthquake excitation, with and

without FVDs.

SPECIFICATIONS FOR ANALYSIS AND DESIGN

ACI 318-08, Building Code Requirements for

Structural Concrete

AISC 360-05, Specification for Structural Steel

Buildings

IBC (International Building Code), 2009

ATC-40 Report on Seismic Evaluation and Retrofit of

Concrete Buildings, Volume 1

COMPUTER SOFTWARE USED: SAP 2000 Ver. 14

BUILDING MODEL

Number of Stories = 11

Storey height = 14 ft

Bay width = 20 ft

fc’ (Columns) = 4000 Psi

fc’ (Beams/Slabs) = 3000 Psi

fy (Reinforcement) = 60, 000 Psi

fy (Steel beams) = 250 MPa

Typical Beam Size = 18 x 21 in

Typical Column Size = 24 x 24 in

Slab Thickness = 6 in

LOADINGS FOR ANALYSIS

Partition load = 20 lb/ft2

Live Load = 80 lb/ft2

Earthquake load = El Centro

Step size = 0.1 sec , Number of steps = 3000 (Chopra)

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Acc

elera

tion

(g)

Time (sec)

ANALYSIS CASES

Case 1 Case 2

Case 3 Case 4

Building 2 Building 1

ANALYSIS CASES

Case 5 Case 6

Case 7

FVDs consist of a closed cylinder filled with viscous fluid.

The movement of a piston in that cylinder causes a

friction and energy of the motion can be dissipated. For

non-linear FVDs, the force (𝑓𝐷) - velocity (𝑢 ) relation is;

𝒇𝑫 = 𝒄𝜶𝒔𝒈𝒏(𝒖 ) 𝒖 𝜶 (Lin & Chopra, 2002)

Where: 𝒄𝜶 – damping coefficient (571 Kips-sec/in)

𝜶 – positive exponent, 0.35 – 1.0 (0.5 in model)

sgn(𝑢 ) – signum function

𝜶 = 1.0 represents the linear FVDs and 𝜶 = 0 represents

the pure friction damper.

FLUID VISCOUS DAMPERS (FVDs)

SAN FRANCISCO CIVIC CENTER DAMPER INSTALLATION (Tylor, Duflot)

Sa

(g)

Performance Point (Sd, Sa, D)

Sd

Family of Demand Spectra for

different values of damping

Single Demand Curve with

variable damping

Capacity Curve

Acceleration Displacement Response Spectrum

CAPACITY SPECTRUM METHOD ATC-40 Report on Seismic Evaluation and Retrofit of Concrete Buildings

Performance point;

(T = 2.85sec, D = 6.5in)

CAPACITY-DEMAND CURVES FOR MODEL BUILDING

ANALYSIS RESULTS FOR CASES

Case Deflection (in) No. of

Dampers Building 1 Building 2

1 12.93 12.93 0

2 7.58 10.95 30

3 6.58 12.39 36

4 5.45 11.54 66

5 7.38 7.39 60

6 6.76 6.78 72

7 5.91 5.9 132

COM

PARISON

Betw

een

1 a

nd 6

-15

-10

-5

0

5

10

15

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Roof

Dis

pla

cem

ent

(in

)

Time (Sec)

Without Damping

With Damping

ROOF DISPLACEMENT VS TIME

-40

-30

-20

-10

0

10

20

30

40

50

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Vel

oci

ty (

in/s

ec)

Time (sec)

With damping

Without Damping

VELOCITY VS TIME

-250

-200

-150

-100

-50

0

50

100

150

200

250

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Acc

eler

ati

on

(in

/sec

2)

Time (sec)

With damping

Without Damping

ACCELERATION VS TIME

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Base

Sh

ear

(Kip

s)

Time (sec)

With Damping

Without Damping

BASE SHEAR VS TIME

Immediate Occupancy, SP-l: A stage where very limited

structural damage has occurred.

Damage Control, SP-2: A range of post-earthquake damage

states that could vary from SP-I to SP-3.

Life Safety, SP-3: At this level the risk of life-

threatening injury from structural damage is very low.

Limited Safety, SP-4: A range of post-earthquake damage

states that are less than SP-3 and better than SP-5.

Structural Stability, SP-5: A level at which structure is on

the verge of experiencing partial or total collapse.

SEISMIC PERFORMANCE LEVELS ATC-40 Report on Seismic Evaluation and Retrofit of Concrete

Buildings, Volume 1

CASE 1 Roof Displacement > 10 inch

As expected from performance point

displacement, at displacements greater

than 6.5 inch the performance of the

structure became poor. Damage-level

hinges were formed for displacements

greater than 10in which means that the

structure is on the verge of global or

local failure under the given earthquake

load.

As the maximum displacement, i.e.

6.8 inch, was very close to

performance point displacement (6.5

inch), Only Immediate Occupancy

level hinges were formed for

displacements lesser than 7 inch.

Thus, for case-6, structure is safe

from stability as well as life safety

point of view under the given

earthquake load.

CASE 6 Roof Displacement < 7 inch

• Results showed a significant reduction in lateral

deflection and velocity of the structures when viscous

dampers were added. However, not much improvement

was observed in Acceleration and base shear.

• Their was a significant improvement in performance

level of the structure under earthquake when dampers

were added.

• Optimum level of performance depends on the type of

structure and the level of performance required by

the place holder.

CONCLUSIONS

(A California Structural Engineer)

“ WHEN IN DOUBT ……

DAMP IT OUT !! ”

ANY QUESTIONS