Post on 09-Apr-2018
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FLOOR VIBRATIONSDUE TO HUMAN ACTIVITIES
TOOLS AND TIPS FOR
SATISFACTORY DESIGNS
PRESENTATION OVERVIEW
Introduction
Floor vibration basics
Current design practices
Basic computer modeling for vibrations
Q&A (please ask questions throughout!)
This presentation will focus on steel framed floors, butmany principles may be applied to other framing systems
Your speaker
Assistant Professor, MSOE, Architectural Engr.
>10 years experience as a structural engineer
Education:
. . , ,
M.S. Architectural Engineering, Penn State, 2000
Thesis: Development of an Experimental Protocol for FloorVibration Assessment
Ph.D. Civil Engineering, Marquette, current pursuit
Dissertation topic: Robustness of steel structures
Licensed P.E., S.E.
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Why are we talking about this?
Floor vibrations continue to be common
Efficient designs present new problemsvibrations!
g we g concre e
Stronger steel
Design techniques continue to improve
based on new research
PRESENTATION OVERVIEW
Introduction
Floor vibration basics
Current design practices
Case study: Kunkle Lounge at Penn State
Basic computer modeling for vibrations
Q&A (please ask questions throughout!)
Floor vibration basics
Why are vibrations objectionable? Our bodies are not comfortable when theyre
vibrating!
When are vibrations ob ectionable? When our internal organs go into resonance
This occurs when the floor has a fundamentalnatural frequency of approx. 7 Hz.
Will the floor collapse? Strength and serviceability are different things
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Whats a bad floor?
Experimental floor PennState
Whats a bad floor?
0.025
0.05
0.075
0.1
-0.1
-0.075
-0.05
-0.025
0 2 4 6 8 10 12 14
Time (s)
Floor vibration basics
Recommended peakaccelerationforhumancomfort
(AllenandMurray1993)
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Floor vibration basics
Floors have distributed mass, stiffness
Modal analysis can be used to determinenatural frequencies and mode shapes
Modal equation of motion
M* = Modal mass matrix
C* = Modal damping matrix
K* = Modal stiffness matrix
F(t) = Forcing function
T = Mode shape vector= Modal acceleration, velocity and displacement
&& &* * * * ( )TM Y C Y K Y F t
&&&Y,Y,Y
Floor vibration basics
The following parameters affect vibration:
Mass
Stiffness (natural frequency, actually)
amp ng
In order to improve a floor system, one (ormore) of these must be adjusted
Floor vibration basics
Things that affect vibration in a real system:
Depth of concrete slab (mass)
LW vs. NW concrete (mass)
ee ec pro e mass
Stiffer beams w/ the same spacing (stiffness)
Spacing beams closer (stiffness)
Longer/shorter beams and girders (stiffness)
Full height partitions (damping)
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Floor vibration basics
Things that DONT affect vibration:
Spacing or size of beams if they areefficiently designed
-
Strength of concrete
Strength of steel
Transient mass (people, desks, etc.)
PRESENTATION OVERVIEW
Introduction
Floor vibration basics
Current design practices
Case study: Kunkle Lounge at Penn State
Basic computer modeling for vibrations
Q&A (please ask questions throughout!)
Current design practices
AISC Design Guide 11 SJI Tech. Digest #5
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Initial assessment
Who (or what) will object to vibration?
(helps to define appropriate limits)
Who or what causes the vibration?(helps to define the expected dynamic forces)
What is the expected system response atthe location of those objecting?
Negotiating design
Consider the floor plan
Consider the system
Consider the framing selection
I know youre going to haveproblems if
The span of the open web steel joists isaround 28-0
0.6C deck with 2 total thickness
The ballroom floor has a fundamentalfrequency of around 3 hertz
The employee aerobics room is right next tothe office of the VP
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System-based approach
Slab assumed to continue to adjacent bays
Mass (weight) and stiffness determined on apanel basis
We assume fundamental frequencyparticipates the most (others negligible)
Assume composite action
Continuity and cantilevers are considered
What about damping?
Architectural elementsprovide most damping
Full height partitions?Use 3% damping (0.03)
Use 2% (0.02) for mostother scenarios
(Tedescoet.al1999)
PRESENTATION OVERVIEW
Introduction
Floor vibration basics
Current design practices Case study: Kunkle Lounge at
Penn State
Basic computer modeling for vibrations
Q&A (please ask questions throughout!)
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Case study: Kunkle Lounge
Pre-engineered frame
Second and thirdfloors hung from frame
Interior support by steelrods from beams
Exterior supportdirectly to columns
VERY bouncy floor
Case study: Kunkle Lounge
Case study: Kunkle Lounge
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Experimental analysis hardware
Proofmassactuator Accelerometer
0.005
0.01
0.015
0.02
0.025
0.03
0.035
tion(g)
Acceleration response
-0.035
-0.03
-0.025
-0.02
-0.015
-0.01
-0.005
0
0 1 2 3 4 5 6 7 8
Acceler
Time (sec)
Frequencies and mode shapes
Mode1:7.08Hz
=3.24%
Mode2:7.63Hz
=1.02%
Mode3:8.96Hz
=1.59%
Mode4:10.66Hz
=0.50%
(Excitationcenteredonthefloor)
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Frequencies and mode shapes
Mode1:7.09H z Mod e2:7.62H z M od e3:8.96H z Mod e4:10.66Hz
(Excitationoffsetfromcenter)
Results of Kunkle Lounge testing
Clearly the floor is not within allowablelimits per DG #11
Several natural frequencies within the
Active control tried to minimize vibration
Proof-mass actuator used
Floor was noticeably stiffer when actuatortuned to the floors vibration
PRESENTATION OVERVIEW
Introduction
Floor vibration basics
Current design practices Case study: Kunkle Lounge at Penn State
Basic computer modeling forvibrations
Q&A (please ask questions throughout!)
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Computer analysis
Packages with
vibration capabilities SAP 2000 / ETABS RAM
Others
Basic modelingusing availablepackages
Advanced modelingusing FE packages
Computer analysis
0.025
0.05
0.075
0.1
-0.1
-0.075
-0.05
-0.025
0
.
0 2 4 6 8 10 12 14
Time (s)
Computer analysis
Model slab usingplate elements
Model beams and
girders using shapedatabase
Superimpose DL and11 psf LL
DeflectedshapesfromRISA
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References and acknowledgments
Funding for this research provided (in part) by the National ScienceFoundation, grant no. CMS 9900099
Allen, D.E. and Murray, T.M. (1993). Design Criterion for Vibrations Due toWalking, AISC Engineering Journal, 4th Qtr., pp.117-129.
Hana an,L.M. 2003. Floor Vibration Serviceabilit : Ti s andTools for, . . . :Negotiating a Successful Design, Proceedings of the North American SteelConstruction Conference, Baltimore, MD.
Hanagan, L.M., Raebel, C.H. and Marsh, E. (2000). Modeling for ControllerDesign on a Steel Floor System, Proceedings of the 18th InternationalModal Analysis Conference, San Antonio, TX.
Raebel, C.H. (2000). Development of an Experimental Protocol for FloorVibration Assessment, M.S. Thesis, The Pennsylvania State University,University Park, PA.
References and acknowledgments
Murray, T.M., Allen, D.E. and Ungar, E.E. (1997). Floor Vibrations Due
to Human Activity, AISC Design Guide #11, American Institute of Steel
Construction, Chicago, IL.
Tedesco, J.W., et. al. (1999). Structural Dynamics: Theory and
, , , .