UTFSM 2014 Part I - Seismic Design - March 19

1Robert TremblayPolytechnique Montreal, QC Canada

Universidad Tecnica Federico Santa Maria Valparaiso, March 2014

Seismic Design and Global Stability Requirements for Steel Building

Structures in Canada and the U.S.

Part I

Seismic Design

R. Tremblay, Polytechnique Montreal, Canada 2

2 Introduction

Seismic Loading and Analysis(ASCE 7-10 vs NBCC & NCh codes)

Seismic Design of Steel Structures(AISC 341-10 vs CSA S16 & NCh codes)

Plan


Introduction


3h

h

W

T = 0.38 s5% damping

Elastic

0.0 10.0 20.0 30.0 40.0Time (s)

-0.5

0.0

0.5

ag (g)

-1.0

0.0

1.0

/ h (%)

Horizontal 90 deg.

0.0126 h-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

V / W

1.28 W

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ h (%)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

V / W

High ground motion levels considered for design can impose large force demands on structures:


0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.5

1.0

1.5

2.0

2.5

S a (g

) M 7.0-7.510-20 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.5

1.0

1.5

Sa

(g)

M 7.0-7.530-50 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.4

0.8

1.2

1.6

2.0

Sa

(g) M 6.5-7.0

10-20 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.5

1.0

S a (g

)

M 6.5-7.030-50 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.5

1.0

S a (g

)

M 6.5-7.070-100 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.5

1.0

S a (g

) M 6.0-6.530-50 km

Earthquakes in California Site Class B 5% damping

Ground motions may be caused by different earthquake scenarios and have difference characteristics


4Steel is a ductile material and this characteristic can be exploited by allowing structures to deform in the nonlinear range under rare, large seismic events

FF

Fracture,instability,etc.

Ductileresponse

y

u


0.0 10.0 20.0 30.0 40.0Time (s)

-0.5

0.0

0.5

ag (g)

-1.0

0.0

1.0

/ h (%)

Horizontal 90 deg.

0.0126 h-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

V / W

1.28 W

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ h (%)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

V / W

-1.0

0.0

1.0

/ h (%)

-0.017 h

-1.0

-0.5

0.0

0.5

1.0

V / W

0.33 W

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ h (%)

-1.0

-0.5

0.0

0.5

1.0

V /

W

h

h

h

W


Vy = 0.25 W

Elastic


5-0.06 -0.04 -0.02 0.00 0.02 0.04 0.06Plastic Rotation (rad.)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

M /

Mpr

M. Englehardt Ecole Polytechnique of Montreal, 1996

Ecole Polytechnique of Montreal, 1996


-8 -4 0 4 8

/ y-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

P / Py

HSS 102x76x6.4 - KL/r = 112

Tensionyielding (typ.)

Inelastic bucklingwith plastic hinge (typ.)

PPPlastic

Hinge

+

-

+


6h

h

W


Vy = 0.25 W

0.0 10.0 20.0 30.0 40.0Time (s)

-0.5

0.0

0.5

ag (g)

-1.0

0.0

1.0

/ h (%)

Horizontal 90 deg.

0.018 h-0.4

-0.2

0.0

0.2

0.4

V / W

-0.36 W -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0/ h (%)

-0.4

-0.2

0.0

0.2

0.4

V / W

-1.0

0.0

1.0

/ h (%)

-0.017 h

-0.4

-0.2

0.0

0.2

0.4

V / W

0.33 W

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ h (%)

-0.4

-0.2

0.0

0.2

0.4

V / W

h

Vy = 0.25 W


0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.4

0.8

1.2

1.6

2.0

S a (g

)

Los Angeles AreaSite Class B

M6.0 - M7.5Dist. = 10-100 km

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.4

0.8

1.2

1.6

S a (g

), C

s

Los Angeles AreaSite Class B

Sa (Elastic)Cs (OCBF - R = 6.0)

x 1/R

Resistance to seismic ground motions through inelastic deformations can represent an effective strategy :

Design forces can be reduced; Structure response, including forces, can be better

controlled.This approach has been adopted in codes. Design must however be performed to achieve the intended ductile response.


7R. Tremblay, Polytechnique Montreal, Canada 13


8Grav.

Grav.

C

C' T

u

u y

Grav.

E

> E

> E

Grav.

Grav.

Grav.

Column designed for gravity plus expected brace tensilestrength

Gusset plates designed incompression for the expectedbrace compressive strength

2. Design other elements :

1. Select Braces:

Design for gravity + ECheck KL/r, b/t, etc. for ductile response

Gusset plate designed in tensionfor the expected brace tensilestrength

Two-Step Capacity Design Procedure (CBF example):


AISC 360-10

ASCE 7-10AISC 341-10

United StatesR. Tremblay, Polytechnique Montreal, Canada 16

9NBCC 2010

CSA S16-09

Canada


Seismic Force Resisting Systems

Plastic Hinge (typ.)

Shearyielding


Tensionyielding

Plastic HingeTension

yielding

Tensionyielding

Compressionyielding e


Plastic Hinge

End-plateBending

Shearyielding


10



11


NCh2369 (2003)


12

Structural damage & residual deformations are expected when applying this design strategy

Kobe, 1995 Kobe, 1995

C.-M. Uang, UCSDR. Tremblay, Polytechnique Montreal, Canada 23

Variability & Uncertainty

in Demand & Response

0 4 8 12 16Number of Storeys

0.0

1.0

2.0

3.0

4.0

/ h

s (%

)

84th percentile50th percentilePredictedIndividual Record

0.0 1.0 2.0 3.0 4.0Period (s)

0.0

0.5

1.0

1.5

S a (g

)

Historical Records

Ground MotionsDesign Spectrum


13

Bruneau, M., Sabelli, R., and Uang C.-M. (2003) Ductile Design of Steel Structures, 2nded., Wiley

AISC. (2013) Seismic Design Manual, 2nd ed., AISC

Filiatrault, A., Tremblay, R., Christopoulos, C., Foltz, B., and Pettinga, D. (2013)Elements of Earthquake Engineering and Structural Dynamics, 3rd ed.,Presses Internationales Polytechnique (PIP)


Seismic Loading and Analysis(ASCE 7-10 vs NBCC & NCh codes)


14

0.0 0.5 1.0 1.5 2.0 2.5 3.0Period, T (s)

0.0

0.4

0.8

1.2

1.6

2.0

S a (g

)

0.53 g

1.22 g

0.23 g

T = 1.0 s

T = 0.2 s

Absolute AccelerationResponse Spectrum

(5% damping)

T = 2.0 s

0.0 10.0 20.0 30.0 40.0Time (s)

-0.4

-0.2

0.0

0.2

0.4

ag (g)

-0.4-0.20.00.20.4

a (g)

-1.2-1.0-0.8-0.6-0.4-0.20.00.20.40.60.81.01.2

a (g)

0.53

1.22

0.57

-0.4

-0.2

0.0

0.2

0.4

a (g)

- 0.23

M6.7 1994 NorthridgeCastaic - Old Ridge Route St. 90o


Required Seismic Data

(from maps or GS websites)

MCER Spectral Valuesfor Site Class B:

SS (0.2s)

S1 (1.0s)

Long-period transition period:

TL


15

http://earthquake.usgs.gov/hazards/designmaps/usdesign.php


http://earthquake.usgs.gov/designmaps/us/application.php


16





17

http://earthquake.usgs.gov/hazards/designmaps/usdesign.php


http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/zoning-zonage/NBCC2010maps-eng.php


18

http://www.earthquakescanada.nrcan.gc.ca/hazard-alea/interpolat/index_2010-eng.php



19

MCER SS & S1 Spectral Valuesfor Site Class B



20

Importance Factor, IeDepends on the Occupancy Category:

I. Buildings that represent low hazardto human life in the event of failure

II. All buildings except those listed inOccupancy Categories I, III & IV

III. Buildings that represent substantial hazardto human life in the event of failure

IV. Essential facilities



21



22



23


T from: - T = Ta ; or- Dynamic analysis; except that T < CuTa for strength design


24


FF

VMx

i

xxhx hxh i


25



26



27

= redundancy factorEarthquake Effects:

Load combinations including E:

When combining the two above:

Amplified Earthquake Loads


P- effects can be neglected if < 0.1 Earthquake effects x 1/(1-) Nonlinear static or dynamic analysis


28



29


2011 Decreto

2011 Decreto


30


Fk

Zk

h

2011 Decreto


31


RASCE/SEI 7-10

3-1/468

3-1/24-1/2

87


32


Seismic Design of Steel Structuresin accordance with AISC 341-10


33

Inelastic response of framesPlastic

Hinge (typ.)Shearyielding


Tensionyielding

Plastic HingeTension

yielding

Tensionyielding

Compressionyielding e


Plastic Hinge

End-plateBending

Shearyielding


16 seismic forceresisting systemsdetailed for ductileseismic response

+

SFRS not specificallydetailed for seismic resistance


34

VeR

V =

Perimetermembers

RoofDiaphragm

Braceconnections

Bracingmembers

Anchor rods

Foundations

V V

Capacity DesignPoutrelle(typ.) Poutre de toit

(typ.)

Poteau(typ.)

Feuille de tablier mtall ique

typ.)

Contreventement (typ.)


Control ofLocal Buckling


35

Expected (probable)material strength

Liu, J. et al. (2007). AISC Eng.


Concentrically Braced Frames (SCBFs)

Energy dissipated in bracing members through tensile yielding and flexural hinging

Connections and other members expected to remain essentially elastic

Tensionyielding (typ.)

Inelastic bucklingwith plastic hinge (typ.)


36

Kobe 1995



37

Uriz and Mahin (2004) Univ. of California, Berkeley

Fracture in1st cycle at1 2% hs1

2


Northridge 1994Photos from Peter Maranian, Brandow and Associates (P. Uriz Thesis, 2005)


38

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

P /

AgF

y

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

HSS 254 x 254 x 12b/t = 18, KL/r = 42



39


-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

P /

Py

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

RHS-4KL/r = 40b0/t = 17

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

RHS-2KL/r = 40b0/t = 13

RHS-19KL/r = 60b0/t = 13

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

P /

Py

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

CHS-1KL/r = 42b0/t = 30

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 / hs (%)

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0

/ LH (%)-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 / hs (%)

CHS-2KL/r = 62b0/t = 31

W-6KL/r = 67b0/t = 5.9


40

W4

W6

W4 W660004000

2000

0

2000

4000

6000

3 2 1 0 1 2 3

Interstorey Drift Angle (%)P

(kN)


0.0 0.5 1.0 1.5 2.0 2.5

Brace Slenderness, = (Fy / Fe)0.50

5

10

15

20

25

Duc

tility

at F

ract

ure,

f

f = 2.4 + 8.3

y

-6 -4 -2 0 2 4 6

-10 -8 -6 -4 -2 0 2 4 6 8 10

.

KL/r = 93HSS 127x76x4.8

KL/r = 142HSS 76x76x4.8

f f

yy

-6 -4 -2 0 2 4 6

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

P /

A gF y

KL/r = 42HSS 254x254x12

f


41

Design Bracing Configuration Along any braced line, between 30% & 70% of lateral

load is resisted by tension braces Tension-only braced frames not permitted K-bracing not permitted



42

Design Bracing Members Braces must resist gravity + lateral loads Pn in tension and compression as per AISC 360-10 KL/r < 200 Section must meet seismic hd limits For built-up sections, individual components must

meet KL/r limits and stitch subjected to shear under buckling must meet minimum shear strength


L

L

H

N

KLout 0.9 LHKLin 0.5 LN

KLout 0.5 LHKLin 0.5 LN


43

Bracing ConfigurationTension-only braced frames permitted

Bracing MembersSection must meets b/t limits that vary with KL/r


Cexp

Cexp

Design Expected Brace Strengths

P/P

y

Texp


44


0.0 0.5 1.0 1.5 2.0 2.5

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Cu

/ AgF

y

Cu (S16-01, n = 1.34)Cu (AISC 1999)

0 50 100 150 200KL/r

0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

C' u

/ A

gFy

(Duc

tility

= 1

.0)

Cu (S16-01, n = 1.34)

0 50 100 150 200KL/r

0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

C' u

/ A

gFy

(Duc

tily

= 3.

0)

Cu (S16-01, n = 1.34)C'u (mean)

0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

C' u

/ A

gFy

(Duc

tility

= 5

.0)

Cu (S16-01, n = 1.34)C'u (mean)


Texp = A RyFy

Cexp = A (1.12 Fcr) where Fcre = Fcr with RyFy< A RyFy

Cexp = 0.3 Cexp

Cexp

Cexp

Texp

45

Texp = A RyFyCexp = A (1.12 Fcr) ,Fcre = Fcr with RyFy

< A RyFyCexp = 0.3 Cexp


Schimdt and Bratlett (2002)


46


Design Brace ConnectionMust resist brace Texp & 1.1 Cexp

Must allow for ductile rotational behavior or resist 1.1 x brace expected flexural strength


47

Net Section Fracture(HSS Braces)

Kobe 1995

Archambault et al. (1995)Tremblay and Bolduc (2002)

cole Polytechnique,Montreal


Kobe1995


48

Yang and Mahin (2004) Univ. of California, Berkeley


Kanwinde and Fell (2005) Univ. of California, Berkeley


49



50

Sabelli (2003) Sabelli (2005)

Sabelli (2003)


Prototype Test Specimen

Attachment toload frame:

LW

LW

LC-C

LTS

2 t 2 t g g

Gussetplate

Gussetplate

35O

Coverplate

Coverplate

5182

(min

) @

793

7 (m

ax)

102

290

35O

Elevation

Specimen

End Restraint

Side View

EndHinge


51



Design Columns and BeamsMust resist gravity loads plus two brace force scenarios:

Upon first buckling & yielding (Texp & Cexp) In post-buckling range (Texp & Cexp)

Beams in V and inverted-V bracing must be continuous between columns

Column sections must meet hdBeam sections must meet md

52


At Buckling Post-Buckling

T T

T T

T T CC

CC

CCexp,1 exp,1

exp,2 exp,2

exp,3 exp,3 exp,3exp,3

exp,2exp,2

exp,1exp,1

F3 F3F3

F2 F2F2

F1 F1F1

W W WW W WW W W

Brace force scenarios for columns:

Northridge 1994Photos from Finley 1999(P. Uriz Thesis, 2005)


53

Taiwan 1999



54

MRF

(typ

.)

BF (typ.)

5 @ 9000 = 45 000

[mm]PLAN

300(slab edge)

5 @

900

0 =

45 0

00

Gravity loads: Roof: Dead = 3.2 kPa Live = 1.0 kPa Floor: Dead = 3.5 kPa Partitions = 1.0 kPa Live = 3.8 kPa Exterior walls = 1.5 kPa

Seismic Load Data (NCh433): Zone 2 Soil Type C A= 0.30 g In-plane torsion omitted

Load Combinations: 1.2D + 1.6L 1.2D + 1.0L + 1.4E 0.9D + 1.4E

Seismic weight: P = 7720 kN (Level 9) 12635 kN (Levels 2-8) 12840 kN (Level 1)

Steel: BRB cores: Fyc = 260-290 MPa Other members: Fy = 345 MPa

Note: Redundancy factor, ,and seismic load effectswith overstrength factor, 0,are not considered.

SCBF

5500

EBF BRBF

4 @

400

0=

16 0

00

[mm]ELEVATIONS



55

Static method of analysis


SAP2000Analysis


56

Brace Design

Brace Expected Strengths


At Buckling

Column Design

1103

4890

4092 47492492

7916 791625914437

+ 1.2 x 644 (D)+ 1.0 x 372 (L)= 5893

-0.9 x 644 (D)= 1913

1103

4092

2001 4890

29072907

70077007

599

169 169169

599599 599

1692001


57

Post-Buckling

Column Design

1103

4890

1227 5136662

6085 60867774437

+ 1.2 x 644 (D)+ 1.0 x 372 (L)= 6280

-0.9 x 644 (D)= 82

331

1227

600 4890

29072907

70077007

856

812 812812

856856 856

812600


Column Design


58

At Buckling Post-Buckling

Beam Design

1103 331

4092 1227

2001 600

2001 600

1103 331

1498 1210

939 556

1498 1210

939 556

1077 842

2907 2907

7007 7007

4890 4890

4890 4890

2907 2907

-1498 -1210

-939 -556

-2800 -2565

M = 243 M = 243

M = 759 M = 3896

M = 2785 M = 3939

1498 1210

939 556

1077 842

1.2 w + 1.0 w = 8.71

1.2 w + 1.0 w = 24.0

1.2 w + 1.0 w = 24.0

1.2 w + 1.0 w = 8.71

1.2 w + 1.0 w = 24.0

1.2 w + 1.0 w = 24.0

D

D

D

u u

u u

u u

D

D

D

L

L

L

L

L

L

[kN,m]


Beam Design


Next Steps:

Verify drifts and P-delta effectsPerform 3D analysis for in-plane torsionDesign connections

59

9000

O41.6 W610 Beam

Bolted EndPlate Connection

750 +

/-

4500 +

/-602

1

Hinge

4000

Once member sizes are known, more realistic, shorter, brace effective lengths can be used to assess brace resistances. Brace sizes may be reduced, which would diminish the force demand on beams and columns and, possibly, member sizes.

Period T* will increase if member sizes are reduced, which may lead to lower seismic loads and allow further reduction in member sizes.


SCBF

5500

2 @ 4000= 8000

For this example:

T* = 0.55 s -> 0.65 sC = 0.119 -> 0.093 (22% reduction)


60

Assignment no. 1

Redo the design of the braced frameconsidering that KL for braces are 5600 mm at Level 1

and 4500 mm at levels 2&3.

You may use/refer to the SAP2000 model & the spreadsheet that were used in the preliminary design


Moment Resisting FramesEnergy dissipated by plastic hinging in beams and limited shear yielding in column panel zones. Plastic hinging in columns permitted at the base and in single-storey structures.

Connections and other members expected to remain essentially elastic


61

Section must meet hdMust resist expected shear demand upon hingingMust be laterally braced

Design Beams

L'

L

L' = L - 2 x - d c

wpb

1.1 R My pb

1.1 R My pb

V = wL' / 2 + 2.2 R M / L'h y pb

Vh Vh


Section must meet hdMust satisfy weak beam-strong column criteriaexcept for:

Columns with Puc < 0.3 AcFy in single-storey buildings or at the top storey of multi-storey buildings;Columns with Puc < 0.3 AcFy when their total shear contribution < 20% of total storey shear resistance and 33% of storey shear resistance along their MF line; orColumns that have shear capacity to demand ratio 50% gretaer than in the storey above.

Design Columns


62

L'

L

L' = L - 2 x - d c x + d /2c x + d /2c

ww w

1.1 R My pb

1.1 R My pb

1.1 R My pb

1.1 R My pb

V = wL' / 2 + 2.2 R M / L'h y pb

Vh Vh

Vh

Vh

M'rc, i+1

M'rc, iCf, i

Cf, i+1

Weak beam-strong column criteria:

M*: projected at membercenter lines



Member forcesupon beam hinging:

63


x + d /2c x + d /2c

1.1 R My pb

1.1 R My pb Vh

Vh

V

V

Must meet: t > (dz + wz)/90Shear strength, Rn:

Design Column panel zone


64

Design Beam-to-column connections

Must accommodate 4% storey drift angleMeasured flexural resistance at column face (Mcf) at 4% storey drift angle > 80% MpbPerformance considered as demonstrated if pre-qualified connections are used; otherwise must be demonstrated through physical cyclic testing:


http://www.aisc.org

Design requirements

Welding requirements

Bolting requirements

Requirements for 6pre-qualified connections


65

Welded Unreinforced FlangeWelded Web

Bolted End Plate

Kaiser Bolted Bracket

Bolted Flange PlateReduced Beam Section

Conxtech Conxl



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MRF

Example



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From analysis:

b) Moments from response spectrum analysis

c) Maximum probable bending moments and shear forces at plastic hinge locations

d) Beam induced forces imposed at column faces

e) Beam induced forces at column centerlines


RBS:

> 682 kN-m => OK!

> 442 kN => OK!

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At Level 1:

M*pb = 656 + 738 = 1394 kN-m



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371 kN & 354 kNshears in columns (see above)

1992 kN force from Mcf = 1319 kN-m :1992 = 1319/(678-16.3)

17 kN force induced by floor diaphragm (from equilibrium of the two column shears)


UTFSM 2014 Part I - Seismic Design - March 19

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Transcript of UTFSM 2014 Part I - Seismic Design - March 19