graef vibration presentation 07-09 - handouts

8/8/2019 GRAEF Vibration Presentation 07-09 - Handouts

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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


Introduction



Case study: Kunkle Lounge at Penn State




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)


Recommended peakaccelerationforhumancomfort

(AllenandMurray1993)


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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


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


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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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.)


Introduction



Case study: Kunkle Lounge at Penn State




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)


Introduction


Current design practices Case study: Kunkle Lounge at

Penn State




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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




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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


Introduction


Current design practices Case study: Kunkle Lounge at Penn State

Basic computer modeling forvibrations



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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

, , , .

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