Post on 13-Dec-2015
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Predicting Human Induced Vibration with GSA Footfall
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Today’s Team
Peter Debney
Application Specialist
Nigel Rees
SalesManager
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Today’s Team
Peter Debney
Application Specialist
Rhys Lewis
Consultant
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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.
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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
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Oasys Customers
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Structural
Geotechnical
CAD
Document Management
Sustainability
Crowd simulation
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The ProblemVibration
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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
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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
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What is Footfall?
Human induced vibration
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What is Footfall?
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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
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What is Footfall?
Vibration
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What is Footfall?
Vibration
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Results
Velocities and Accelerations
f = 1 / T
ω = 2 π f
x = X sin ωt
v = Xω cos ωt
a = -Xω2 sin ωt
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Results
What is R?
BS 6472 base curve for human perception
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Modal mass
F = ma a = F/m
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Resonance
1st harmonic
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Resonance
2nd harmonic
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Resonance
3rd harmonic
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Resonance
4th harmonic
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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
Dis
plac
emen
t
Time
Damped Free Vibration
Damping 0.1 of critical
Critical Damping
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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
pli
ficati
on
Facto
r
0.02 damping
0.05 damping
0.10 damping
0.20 damping
Resonance and DampingDynamic amplification under harmonic (single
frequency) loading
1 - staticexcitation too fast for any significant response
resonance
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Resonance and DampingDynamic amplification with multiple
harmonics
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Resonance and DampingDynamic amplification with multiple
harmonics
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Transient Response – Impulse loading
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Footfall Design Guides
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Footfall - Simple Method
f0 = 18 / √δ
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Footfall - FEA Method
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Footfall - FEA Method
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The Solution
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Any Questions?
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• Contact Details• Peter Debney – peter.debney@arup.com• Nigel Rees – nigel.rees@arup.com
• Next Webinars• August 15th: Raft and Soil-Structure Interaction• September 19th: Concrete Design
Webinar has now Ended