Introduction  to  Engineering

Tzuyang Yu Assistant Professor, Ph.D.

Department of Civil and Environmental Engineering University of Massachusetts Lowell (UML)

March 6, 2009 Lowell High School

1

Outline

n  What is Engineering?

n  Scope and Process of Engineering

n  Great Engineering Achievements in the 20th Century

n  Example of Engineering Design

n  Engineering Research Approach

n  Summary

2

What is Engineering?

n  If it is green, it is biology.

n  If it stinks, it is chemistry.

n  If it doesn’t work, it is physics.

n  If it works but no one knows why, it is engineering. – Anonymous

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What is Engineering? n  “The scientist explains that which exists; the

engineer creates that which never was.” –– Theodore von Karman (1881~1963), a Hungarian-German-American engineer and physicist who was active primarily in the fields of aeronautics and astronautics

von Karman at the California Institute of Technology Vortex 4

What is Engineering?

Engineers

Engineering science Engineering problem

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What is Engineering? n  Engineering involves:

n Science n Math n Writing n Problem solving n Speaking n Teamwork n etc…

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What is Engineering? n  Engineer, as a noun, is from French “to contrive”. n  Engineers: “One who contrives, designs, or

invents; an author, designer (const. of); also absol. an inventor, a plotter, a layer of snares.” –– Oxford English Dictionary

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Scope of Engineering

n  If Engineering = Problem Solving,

– Does this mean any problem? – or only problems dealing with a technology

component?

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Process of Engineering n  Invention n  Research n  Design n  Development n  Production/Realization

Cost Cycle

Risk Mitigation

I-35 Minneapolis Bridge Collapse, MN (2007) 9

Great Engineering Achievements in the 20th Century

n  Electrification n  Automobile n  Airplane n  Safe and abundant water n  Electronics n  Radio and TV n  Agricultural

Mechanization n  Computers n  Telephone n  Air Conditioning and

Refrigeration

n  Interstate Highways n  Space Exploration n  Internet n  Imaging Technologies n  Household Appliance n  Health Technologies n  Petroleum and Gas

Technologies n  Laser and Fiber Optics n  Nuclear Technologies n  High Performance

Materials 10

n  A clear classification of high-rise buildings with respect to their structural system is difficult.

n  A rough classification can be made with respect to effectiveness in resisting lateral loads.

Example of Engineering Design – Design of High-rise Buildings

Structural Systems: n  Moment resisting frame systems n  Braced frame, shear wall systems n  Core and outrigger systems n  Tubular systems

¨ Framed tubes ¨ Trussed tubes ¨ Bundled tubes

n  Hybrid systems 11

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20 30

40

50 60

70

80

90

100

110

Type I Shear Frames Type II Interacting Systems Type III Partial Tubular Systems Type IV Tubular Systems

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Type II Type III

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Type IV

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Sem

i-Rig

id

Fram

e

Rig

id F

ram

e

Fram

e w

ith S

hear

Tru

ss

Fram

e w

ith S

hear

ban

d an

d

Out

rigge

r Tru

sses

End

Cha

nnel

Fra

med

Tub

e w

ith

Inte

rior S

hear

Tru

sses

End

Cha

nnel

and

Mid

dle

I Fr

amed

Tub

es

Exte

rior F

ram

ed T

ube

Bun

dled

Fra

med

Tub

e

Exte

rior D

iago

naliz

ed T

ube

# of Floors

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Development of Structural Systems

50 100 150 200 250 300 350 400 450 500 550

m

Frame Systems Tube in Tube

Bundled Tube

Tubular Systems Hybrid Systems

World’s Tallest Buildings by Year

(Figure source: www.skyscrapers.com) 13

Structural Loads n  Gravity loads

¨ Dead loads ¨ Live loads ¨ Snow loads

n  Lateral loads ¨ Wind loads ¨ Seismic loads

n  Special load cases ¨  Impact loads ¨ Blast loads

Earthquake Load

Snow Load

Wind Load

Dead Loads

Live Loads

Blast Load

Impact Load

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Gravity Loads n  Floor systems account for a major portion of the gravity loads n  Selection of the floor system may influence structural behavior

and resistance n  Structural use plays a major role in selection of the floor system

¨  Office buildings n  large simply supported spans

¨  Residential and hotel buildings n  short continuous spans

Types of floor systems •  Concrete •  Steel •  Composite •  Prestressed concrete

Composite floor systems

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Wind Loads

Plan view

Wind

zQ

hQzQ

hQ

hQ hQ

2zQ KV I=

z

h z z HQ Q

==

H

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Seismic Loads

Spe

ctra

l res

pons

e

acce

lera

tion

(g)

Period (sec)

0 2 4 6 8

Response with increasing damping

Decreasing V/W

sV C W= ¥

V

W

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Final Design – Design of Member Dimensions

s max."6

Bottom of bend

Max. slope1:6

sSpecial tiesto resistoutward thrust

max. to bottomof beam bars

"3

12s

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Construction – Before

Royal Albert Bridge, UK (1859)

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Construction – Now

Lavant viaduct (Talubergang P19 Lavant), Austria (1985) 20

Steps in Engineering Research

n  Observe n  Simplify n  Analyze n  Model n  Experiment

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Engineering Research Approaches

n  Theoretical investigation (e.g., formulation, derivation, proof)

( ) [ ], 2,

1, expc

c

B

s js j B

S r t d i tR

ω π

ω π

ω ω+

−

= ⋅∫

( ) ( )2

,0 0

, , ,sR

sj i j i s j

RD t dr d G r S r tt

π

ξ φ φ⎛ ⎞− = ⋅⎜ ⎟

⎝ ⎠ ∫ ∫

, ,s sbp

R RF t C D tt t t

ξ ξ∂⎛ ⎞ ⎛ ⎞− = ⋅ −⎜ ⎟ ⎜ ⎟∂⎝ ⎠ ⎝ ⎠

( )

( )

0

0

, ,

,

s

s

Rtt

s s

Rtt

s

R RD t dt D t M t tt t t t

Rdt D t M t tt t

ξ ξ

ξ

−

−

∂ ∂⎛ ⎞ ⎛ ⎞ʹ′ ʹ′− = ⋅ − ⋅ −⎜ ⎟ ⎜ ⎟∂ ∂⎝ ⎠ ⎝ ⎠

∂⎛ ⎞ʹ′ ʹ′= ⋅ − ⋅ −⎜ ⎟ ∂⎝ ⎠

∫

∫ ( )int

0

, ,sR

sRI r d F tt

θ

φ ξ ξ⎛ ⎞= ⋅ −⎜ ⎟

⎝ ⎠∫22

Engineering Research Approaches

n  Numerical Simulation

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Y (m

)

Hx at time = 17 ns

1 1.2 1.4

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Y (m

)Hx at time = 20 ns

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Y (m

)

Hx at time = 23 ns

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Y (m

)

Hx at time = 26 ns

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Y (m

)

Hx at time = 29 ns

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Y (m

)Hx at time = 32 ns

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Y (m

)

Hx at time = 35 ns

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Y (m

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Hx at time = 38 ns

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Y (m

)

Hx at time = 41 ns

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X (m)

Y (m

)

Hx at time = 44 ns

1 1.2 1.4

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X (m)

Y (m

)

Hx at time = 47 ns

1 1.2 1.4

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X (m)

Y (m

)

Hx at time = 50 ns

1 1.2 1.4

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Y (m

)

Hx at time = 17 ns

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Y (m

)

Hx at time = 20 ns

1 1.2 1.4

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Y (m

)

Hx at time = 23 ns

1 1.2 1.4

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Y (m

)Hx at time = 26 ns

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Y (m

)

Hx at time = 29 ns

1 1.2 1.4

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Y (m

)

Hx at time = 32 ns

1 1.2 1.4

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Y (m

)

Hx at time = 35 ns

1 1.2 1.4

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1

Y (m

)Hx at time = 38 ns

1 1.2 1.4

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1

Y (m

)

Hx at time = 41 ns

1 1.2 1.4

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1

X (m)

Y (m

)

Hx at time = 44 ns

1 1.2 1.4

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0.9

1

X (m)

Y (m

)

Hx at time = 47 ns

1 1.2 1.4

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1

X (m)

Y (m

)Hx at time = 50 ns

1 1.2 1.4

0.6

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0.9

1

Engineering Research Approaches

n  Experimentation

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15.7 cm 15.2 cm

(Concrete core)

3.8 cm 3.8cm

2.5 cm 30.4 cm

Summary

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n  Engineering is the backbone of every civilization. n  Engineering is an applied science. n  Engineering includes a number of very diverse disciplines. Each

discipline usually includes several specialized areas. à Engineers are differentiated by the material or the structure or the property they study.

n  Engineering is about how to make things or how to make things work, which is very practical.

n  For whichever research topic engineers investigate, there must be a practical problem behind it.

n  Good engineers must have learned from their practical experience.