CEE 4606 - Capstone II Structural Engineering

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Nov 29, 2013 (3 years and 7 months ago)

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Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

1

CEE 4606
-

Capstone II

Structural Engineering

Lecture 3

Seismology, Earthquakes, and Roof
Design

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

2

Earthquake Loads

“Earthquakes systematically bring out the
mistakes made in
design

and
construction

-

even the most minute mistakes; it is this aspect
of earthquake engineering that makes it an
educational value far beyond its immediate
objectives.”


-
Newmark and Rosenbluth

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

3

Ductile vs. Non
-
ductile Concrete Construction


Note the obvious
differences of capability of
concrete columns to take
load after earthquake
damage.


The spirally reinforced
column (ductile
reinforcing) has an
obvious capacity to carry
much more load than the
tied corner column (non
-
ductile reinforcing).

San Fernando, 1971

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

4

Ductile vs. Non
-
ductile Concrete Construction


This photo was taken while
looking at the exterior of a
damaged classroom building


The column suffered a shear
failure.


Note that the column did not
fail at the top (where
anticipated) due to combined
shear and bending

Peru, 1974

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

5

Photo of Column from the Inside


Note that at the top of the
column ductile reinforcing
was used (ties very close
together).


The failure occurred where
the spacing of ties was
expanded.


Ductile reinforcing of
concrete is a necessity.


Follow the IBC and ACI
codes for seismic detailing
requirements

Peru, 1974

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

6

Earthquake Design


Of course the degree of importance of
an earthquake loading in any given
location is related to the
seismicity

of
the region:


Likelihood of occurrence


Probable intensity of the earthquake

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

7

How is seismicity determined?


Historical records


China 3000 years


Middle East 2000 years


Latin America ???


In the 1960’s the US developed the
World Wide Standardized Network


120 stations in 60 different countries

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

8

Seismographs


Instrument that
records the earth’s
motion


North
-
South


East
-
West


Vertical


Pen
-
Plotter


Digital

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

9

What causes earthquakes?

The lithosphere is broken into rigid plates that move.

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

10

Arabian Plate

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

11

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

12

Seismic Waves


When the earth shakes it releases
seismic waves


Body waves pass through the “body” of
the planet (fastest waves and can be
refracted and reflected)


Surface waves stay near the surface


There are many different types of waves

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

13

Types of Seismic Waves

P Wave

S Wave

Love Wave

Rayleigh Wave

Body

Surface

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

14

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

15

Body Waves

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

16

Primary Waves


P
-
waves (body waves)


Are the fastest; consequently, they reach the
recording station first.


Move in a push
-
pull fashion, alternating
pulses of compression and tension


Can travel in any medium


Arrival at your site may be accompanied with
thunder
-
like noises and rattling windows
(similar to a sonic boom)

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

17

Like a slinky

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

18

Secondary Waves


S waves (body waves)


The second wave to reach the recording
station


Transverse waves that propagate by shearing
or shaking particles in their path at right
angles to the path of advance


Travel only through solids


The wave motion that is most damaging to
structures

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

19

Snapping a
piece of rope

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

20

Love Waves


Surface waves


Motion is essentially an S wave that has
no vertical displacement


Moves the ground from side to side 90
degrees to the direction of propagation


Can be very damaging to structures

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

21

Love Waves

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

22

Rayleigh Waves


Most common surface wave


Similar to water wave except they have
a backwards rotation


Cause horizontal and vertical movement


Slower than Love waves


Pass through ground and water


Long periods and travel a long way
(once they get started)

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

23

Being on
a ship

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

24

Waves

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

25

Waves

P waves travel approximately 1.7 times
faster than S waves

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

26

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

27

Locating the Source


The epicenter can be located using the
lengths of time the various seismic waves
take to reach a seismograph


P waves travel approximately 1.7 times faster
than S waves; therefore, the larger the
difference in arrival time, the farther away
from the epicenter you are


This gives you distance


What about direction?

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

28

Use Multiple Seismographs

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

29

Example Problem

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Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

30

Example Problem continued

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

31

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

32

We use that procedure for all earthquakes

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

33

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

34

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

35

Magnitudes of Earthquakes


The magnitude is an estimate of the
relative size (amplitude) of an earthquake
measured from a seismogram

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

36

Richter Scale


1935, Charles Richter of CIT defined
the magnitude of an earthquake

Magnitude
-

the logarithm to the base ten of the
maximum seismic wave amplitude (in thousandths of
a millimeter) recorded on a standard seismograph at a
distance of 100 kilometers from the earthquake center



For every tenfold increase in amplitude
on the seismogram, the Richter Number
increases by 1.0

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

37

Magnitudes


Earthquakes of
magnitude < 5.0 are
not expected to
cause structural
damage


Earthquakes > 5.0
are potentially very
damaging

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

38

Procedure for Measuring Magnitude


S
-

P = 24 sec


Max height = 23 mm


Connect points with
a straight line


Read intersection


Magnitude = 5.0

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

39

Earthquake Intensity


Intensity is the severity of the ground
motion at any point


The measuring scale is the Modified
Mercalli (MM)


Scale of I to XII


I
-

Nothing to XII
-

Total Destruction

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

40

Relating Richter to Mercalli

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

41

El Salvador


7.6 magnitude quake


January 2001


Centered off the Salvadoran coast
about 65 miles southwest of San Miguel


There were pockets of destruction, with
destroyed towns next to areas that were
completely unscathed

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

42

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

43

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

44

Tremors were felt at our site

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

45

Earthquakes Over 5.0 Richter in Honduras, 1900
-

1980

Structural damage would
be expected in structures
designed in accordance
with
US codes

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

46

Earthquake Design

Section 1613

Definitions

Section 1614

General


Exceptions


Additions and/or alterations


Change of use

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

47

Earthquake Design


Considerations

are similar to wind


site characteristics


occupancy


structural configuration and system


height and weight


zoning (wind speed vs. ground
acceleration)


Section 1615


Site Ground Motion


Figures 1615 (1) through (10)

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

48

Figure 1615(1)


East Coast


Contours


Acceleration in
% of gravity


Linear
interpolation


Specific time of
response (.2
sec)


Assumption of
5% damping


Site Class

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

49

Section 1616


EQ Load Criteria
Selection


Seismic Design Criteria


Lateral resisting systems


Continuous path


Seismic Use Group and Importance
Factors (I, II, or III)


Table 1604.5


Same as for wind design



Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

50

Section 1616.3


Seismic Design
Category


Design Categories A


F (used to be
Zones 1


4) impacts:


Structural system


Height and plan limitations


Components design


Types of analysis


Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

51


Section 1617


EQ Loads


Minimum
Design Lateral Force and Related
Effects


1617.4 Equivalent Lateral Force Procedure


Equation 16
-
34


Base Shear, V = C
s
W


1617.5 “Simplified” Procedure


Equation 16
-
49


Base Shear, V = 1.2S
DS
W/R

Types of Analysis

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

52


Based on calculating the base shear, V,
of the structure and distributing the load
vertically to the different story heights

Static Procedures

m
2

m
1

F
2

F
1

V

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

53

1618
-

Dynamic Analysis Procedures


Modal Response Spectrum Analysis


Linear Time
-
History Analyses


Nonlinear Time
-
History Analyses


Alternative Advanced Analyses


Generally, the simple analyses
provide more conservative designs

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

54

Other Sections


1619


Soil Structure Interaction Effects


1620


Design, Detailing Requirements
and Structural Component Load Effects


1621


Architectural, Mechanical, and
Electrical Component Requirements


1622


Nonbuilding Structures

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

55

Some Information Sources


www.usgs.gov


www.nhc.noaa.gov


www.eeri.org


Compendix
-

Database of engineering
journals (thru VU library)

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

56

Chapter 15

Roof Assemblies and Rooftop Structures


1501


General


1502


Definitions


1503


Weather
Protection


1504


Performance
Requirements


1505


Fire
Classification


1506


Materials


1507


Requirements for
Roof Coverings (largest
section)


1508


Roof Insulation


1509


Rooftop
Structures


1510
-

Reroofing

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

57

Roof Design


Constraints


Material availability


No lifting equipment


Typical construction practice


Structural Layout


Critical Loads

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

58

Truss Questions


Are the trusses supported by the
columns on the porch?


Trusses should be supported by columns


Do the walls extend to the roof or to the
base of the truss?


Trusses will be exposed on the interior of
the structure


Truss information?


Constructed from 2
-

5”x2”x1/16” channels
welded together

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

59

Truss Construction

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

60

Trusses

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

61

Connection Detail

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

62

Homework


Continue research on wind and
seismicity of Honduras


Determine a design wind speed


Determine the ground acceleration


Determine the loads for your roof design

Villanova University

Dept. of Civil & Environmental Engineering

CEE 4606
-

Capstone II

Structural Engineering

63

Next Lecture


Load paths


Construction considerations


Design guides


Review of Progress Report #1
Requirements