Undergraduate seismic design competition -2013

EERI Student Chapter – Rice University

Topic #1: Basic Earthquake Engineering Concepts

What happens during an Earthquake?

• Ground motion characteristics:– How long?– How strong?– Frequency content?

• Building response:– Strong vibrations – Large stresses and strains– Local Failure – Many local Failures Progressive Collapse

Building Collapse

Basic Design Concepts #1

• Avoid ‘soft-story’ ground floors!– Maintain uniformity throughout height – Provides braces at all storeys

‘Soft-story’ formation

Basic Design Concepts #2

• Avoid ‘soft-story’ upper floors!– Maintain uniformity throughout height – Provides braces at all storeys

‘Soft-story’ formation

Basic Design Concepts #3• Avoid non-symmetric bracing!

Bracings

Building Front View Building Top View

Non-symmetric Bracing

Symmetric Bracing

Basic Design Concepts #4

• Avoid discontinuities is stiffness and resistance

Basic Design Concepts #5

• Provide slender structural walls!– Structural walls along principal directions – Be as symmetric as possible

Basic Design Concepts #6

• Avoid short column!– Short columns often fail in shear

Basic Design Concepts #7

• Protect your foundations!

Basic Design Concepts #8

• Strong column weak beam theory!

Basic Design Concepts #9

• Avoid resonance!– We will need this at the

analytical/computer model building stage– We have to check and confirm that

dominant earthquake frequency and building frequency are different to avoid resonance

– Mention this point in the proposal!!

Basic Design Concepts #9

• Bracings and damping devices – Will be covered tomorrow!

Topic #2: Structural Systems for Tall Buildings

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Tall Buildings

• Skyscraper is the greatest architectural invention of America

• Steel frame structure for the 1st time used in England in 1792

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Problem of Size

• Increase in size: reduction in strength– The Euler buckling of the columns– Cannot directly employ the existing

models and magnify them

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Imhotep to Fazlur Rahman Khan

• "Einstein of structural engineering"

• His "tube concept," using all the exterior wall perimeter structure of a building to simulate a thin-walled tube, revolutionized tall building design

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Structural Systems

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Example of Bundle Tubes

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Truss Tube

Mode shapes

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Connections• Optimum seismic connection

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Failure Mechanism

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Failure Mechanism