predicting human induced vibration with gsa footfall

www.oasys-software.com

Predicting Human Induced Vibration with GSA Footfall


Today’s Team

Peter Debney

Application Specialist

Nigel ReesSales

Manager


Today’s Team

Peter Debney

Application Specialist

Rhys Lewis

Consultant


1. Viewer Window 2. Control Panel

Oasys Software : GSA Footfall

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Agenda

• Product Demonstration• GSA

• Questions and Answers

NB: this webinar is designed as an introduction to GSA and footfall and is designed to provide an overview.


Who is Oasys?

• Wholly owned by Arup• Formed in 1976 to develop software for in-house and external use

• Most developers are engineers who have moved to programming

• In recent years have added marketing and sales staff

• Since 2003 have expanded the development team worldwide

• Wide network of resellers and channel partners


Oasys Customers


Structural

Geotechnical

CAD

Document Management

Sustainability

Crowd simulation


The ProblemVibration


The effects of vibration

•Structural Damage• Inelastic response – overload• Fatigue

•Discomfort• Bouncy floors and stairs• Wind-induced sway of buildings• Ride comfort• Noise• Machine operation

•Machine operability• High precision manufacturing

facilities• Medical facilities• Laboratories


What is Footfall?

Human induced vibration


What is Footfall?


What is Footfall?

Vibration

(a) A bridge as a simply supported beam

(b) The first mode of vibration

(c) The displacement of mid-span after someone jumps once at mid-span


What is Footfall?

Vibration


Results

Velocities and Accelerations

f = 1 / T

ω = 2 π f

x = X sin ωt

v = Xω cos ωt

a = -Xω2 sin ωt


Results

What is R?

BS 6472 base curve for human perception


Modal mass

F = ma a = F/m


Resonance

1st harmonic


Resonance

2nd harmonic


Resonance

3rd harmonic


Resonance

4th harmonic


Damping

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25

Disp

lace

men

t

Time

Damped Free Vibration

Damping 0.1 of critical

Critical Damping


Steady State Resonant Amplification Factors for SDOF systems

0

5

10

15

20

25

0 0.5 1 1.5 2 2.5 3

(excitation frequency)/(natural frequency)

Am

plifi

catio

n Fa

ctor

0.02 damping0.05 damping0.10 damping0.20 damping

Resonance and DampingDynamic amplification under harmonic (single

frequency) loading

1 - staticexcitation too fast for any significant response

resonance


Resonance and DampingDynamic amplification with multiple

harmonics


Transient Response – Impulse loading


Footfall Design Guides


Footfall - Simple Method

f0 = 18 / √δ


Footfall - FEA Method


The Solution


Any Questions?


• Contact Details• Peter Debney – [email protected]• Nigel Rees – [email protected]

• Next Webinars• August 15th: Raft and Soil-Structure Interaction• September 19th: Concrete Design

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predicting human induced vibration with gsa footfall

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