Construction Engineering of Steel I-Girder Bridges

Thanh Nguyen Georgia Tech

Feb 27 2015

Why Steel I-Girder Bridges?

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What changed & not changed?• More flexible structures

o 70 grade steel

o Designers pushing geometry limits

• Designers doing what they have always

done o Mostly 1D Line Analysis & 2D Traditional Grid

o Selection of critical design parameters based on long-established practices

o Not accounting for Lack-of-fit effects. When they rarely do, it is often not rigorous

o Erection engineering left to erectors

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Key Objectives• Improved design guidelines to ensure

reliable fit-up

• Provide a clear understanding of

implications ofo Framing arrangements

o Cross-frame detailing methods

o Erection procedures

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Outline1. Fit conditions

2. Bridge Construction Simulations

3. Fit-up Estimation

4. Parametric Studies

o Selection of Bridges & Erection Sequences

o Variation of Framing Arrangements

o Variation of Detailing Methods

5. Synthesis of a few Results

6. Streamlined Calculation of the LOF effects

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1. Fit Conditions

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No Load Fit (NLF)

Steel Dead Load Fit (SDLF)

No Load

Steel Dead Load

Total Dead Load

No Load

Steel Dead Load

Total Dead Load

Total Dead Load Fit (TDLF)

No Load

Steel Dead Load

Total Dead Load

2. Bridge Construction Simulations

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Concrete Deck (S4R, Shell)

Flanges (B31, Beam)

Cross-frame Chords (B31, Beam)

Web(S4R, Shell)

Transverse Stiffener (B31, Beam)

Cross-frame Diagonals (T3D2, Truss)

Bearing Stiffener (B31, Beam)

3. Fit-Up Estimation• Fit-up forces: external forces required to put the

steels togethero CF Fit-up

o Field Splice Fit-up

• Unanticipated fit-up forces can lead to delay, increased cost & bridges not constructible

• First study to provide first-level of engineering estimates of fit-up

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3. Fit-Up Estimation• A simple span bridge erection sequence

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3. Fit-Up Estimation

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Stage 2-1 Stage 2-2

Stage 2-3 Stage 2-4

3. Fit-Up Estimation

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Stage 3-1 Stage 3-2

Stage 3-3 Stage 3-4

3. Fit-Up Estimation• Fit-up calculation: the forces developed at the

connection being made

• Elevations can be varied for holding cranes, lifting cranes and shoring towers

• Knocked-down CFs: Top and bottom connections

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3. Fit-Up Estimation• First and second connection fit-up forces (F1 &

F2)

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StageDetailingMethod

Holding Elevations

Minimum Fit-Up

Forces as a

Function of the

Crane Holding

Elevations

Comments on Configuration Pertaining to the Minimum Fit-Up Force

Holding Crane:

NLLifting

Crane: NL

Holding Crane:

SDLLifting

Crane: SDL

Holding Crane:

NLLifting

Crane: NL + 40

% SDL Camber

(upward)

Holding Crane:

NLLifting

Crane: NL + 80

% SDL Camber

(upward)

Holding Crane: NL

Lifting Crane: NL

- 40 % SDL Camber

(downward)

Holding Crane: NL

Lifting Crane: NL

+ 160 % SDL

Camber (upward)

F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 F1 F2

2-3A

NLF 0.4 NA 6.5 NA 0.9 NA 1.4 NA 0.9 NA 2.6 NA 0.4 NA Lift-off at G2 supports

SDLF 2.5 NA 8.5 NA 1.9 NA 1.5 NA 3.4 NA 1.1 NA 1.1 NA Lift-off at G2 supports

TDLF10.

2NA

14.6

NA 9.4 NA 8.8 NA10.6

NA 7.7 NA 7.7 NA Lift-off at G2 supports

2-3B

NLF 1.7 1.8 7.0 1.7 2.0 2.0 2.4 2.3 4.6 4.3 3.3 2.8 NA 1.7 Slack cables on lifting crane (G2)

SDLF 8.9 7.411.

85.5 7.2 6.1 7.2 6.3

11.9

10.0

7.2 6.9 NA 5.5 Slack cables on lifting crane (G2)

TDLF28.

622.

327.

517.

328.

622.

325.

619.

728.6

22.3

24.6

19.6

NA 17.3 Slack cables on lifting crane (G2)

3-3A

NLF 2.8 NA 4.9 NA 3.3 NA 3.5 NA 2.3 NA 3.7 NA 2.3 NA Lift-off at G3 supports

SDLF 0.7 NA 6.6 NA 0.6 NA 0.9 NA 1.1 NA 1.3 NA 0.6 NA Lift-off at G3 supports

TDLF10.

0NA

10.4

NA 9.3 NA 8.7 NA10.0

NA 7.5 NA 7.5 NA Slack cables on lifting crane (G3)

3-3B

NLF 3.3 2.3 4.7 0.2 3.6 1.9 3.8 1.7 3.2 2.7 4.0 1.9 NA 0.2 No slack cables or lift-off

SDLF 7.0 6.7 9.5 4.9 6.2 6.1 5.7 5.7 7.7 7.2 5.2 5.2 NA 4.9Slack cables on lifting crane (G3) and on

holding crane (G1)TDLF24.

019.

123.

517.

724.

019.

124.

019.

124.0

19.1

22.5

18.2

NA 17.7

3. Fit-Up Estimation• Critical fit-up forces

• Critical crane loads

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Detailing Method

F1 F2 Fmax

NLF 2.3 1.7 2.3

SDLF 1.1 5.5 5.5

TDLF 7.7 17.7 17.7

DetailingMethod

Lifting Crane Holding Crane

MaxLoad

Min Load

Max Load

Min Load

NLF 22.8 0 22.5 0.2

SDLF 21.2 0 18.7 0

TDLF 12.4 0 12.2 0

4. Parametric Studies 4.1. Bridges & Erection Schemes

• Leveraging NCHRP 12-79 research

• Selection of a subset of bridge designs & erection schemes from 12-79o From inside to outside vs. outside to inside on several curved

spans

o Phased construction

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4.1.A. Curved Radially-Supported Bridges

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Ls = 90 ft Ls = 150 ft Ls = 150 ft

Ls = 225 ft

Ls = 329 ft

Ls = 350 ft

4.1.B. Straight Skewed Bridges

Looc = 211 ft Ls= 150 ft

Ls= 300 ft

Ls= 150 ft

Ls= 150 ft

Looc = 259 ft17

4.1.C. Curved and Skewed Bridges

Lmax= 340 ft

Lmax= 366 ft

Lmax= 164 ft

Lmax= 195 ft

Lmax= 192 ft

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4.1.C. Curved and Skewed Bridges

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Lmax= 214 ft

Lmax= 279 ft

Lmax= 326 ft

4.2. Variation in Framing Arrangements

• Offsets & CF spacing near skewed bearing lines

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4.2. Variation in Framing Arrangements

• Avoid connecting intermediate CFs directly into bearing locations

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4.2. Variation in Framing Arrangements

• Stagger the intermediate CFs along lines parallel to the skew

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4.2. Variation in Framing Arrangements

• Continuous CFs in curved-radially supported and curved and skewed bridges

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4.3. Variation of CF Detailing Methods• All 3 detailing methods considered for the

completed bridges

• NLF is not considered for erection studies of straight skewed bridges

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5. Synthesis of a few Results• Max Fit-up forces, curved radially-supported bridges

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NLF SDLF TDLF

(A) EISCR1 90 17.5 200 3 0.45 5.1 3.3 7.4 22.3

(B) NISCR2,

Scheme 1150 24.0 438 4 0.34 6.2 16.6 28.7 54.0

(B) NISCR2,

Scheme 2A" " " " " " 84.4 82.5 80.2

(B) NISCR2,

Scheme 2B" " " " " " 40.4 19.4 50.5

(C) NISCR7 150 74.0 280 9 0.54 2.0 21.3 35.9 75.3

(D) NISCR10 225 74.0 705 9 0.32 3.0 18.6 20.4 21.8

(E) EICCR11 322/417/329 40.4 4 0/0/0.80 8.0/10.3/8.1 37.5 86.3 130.0

(F) NICCR12 350/350/280 74.0 909 9 0.39/0.39/0.31 4.7/4.7/3.8 28.4 38.6 57.4

(G) EICCR4219/260/211/

162/256/19036.7

968/3@1108

/968/4

0.198/0.235/0.190/

0.146/0.264/0

6.0/7.1/5.7/

4.4/7.0/5.212.3 12.6 16.0

Max Fit-Up Forces (kip)Bridge Ls (ft) wg (ft) R (ft) ng Ls/R Ls/wg

5. Synthesis of a few Results• Max Fit-up forces, straight skewed bridges

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SDLF TDLF

(H1) EISSS57 211 63 61.0 69.5/-4.4 7 0.77 3.5 1.0 5.0 15.0

(H2) EISSS57 " " " " " " " " 5.0 14.2

(I1) NISSS14 150 150 74.0 70 9 1.36 2.0 2.0 3.6 15.3

(I2) NISSS14 " " " " " " " " 2.5 7.5

(J1) NISSS54 300 300 74.0 70 9 0.68 4.1 4.1 9.2 73.5

(J2) NISSS54 " " " " " " " " 8.4 47.9

(K1) EICSS12 150/139 150/139 41.0 59.6 6 0.47/0.50 3.7/3.4 3.7/3.4 0.6 6.3

(K2) EICSS12 " " " " " " " " 0.4 7.7

(K3) EICSS12 " " " " " " " " 1.2 17.0

(L) NICSS16 120/150/150 120/150/150 74.0 70 9 1.69/1.36/1.36 1.6/2.0/2.0 1.6/2.0/2.0 0.8 36.9

(M1) EICSS2 259/255/220 241/183/220 66.6 58/61.8/38/38 8 0.48/0.49/0.23 3.9/3.8/3.3 3.6/2.7/3.3 4.9 46.9

(M2) EICSS2 " " " " " " " " 0.8 2.8

Max Fit-Up

Forces (kip)Bridge Lmax (ft) Lmin (ft) wg (ft) q (deg) ng Is Lmax/wg Lmin/wg

5. Synthesis of a few Results• Final girder elevations

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Curved radially-supported bridge Straight skewed bridge

6. Streamlined Calculation of LOF effects

• Due to SDLF and TDLF

• Engineers rarely include these effects

• Most rigorous & accurate method is to calculate the initial strains

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-10

-5

0

5

10

15

20

25

30

0 0.2 0.4 0.6 0.8 1

fl(k

si)

Normalized Length

TDLF SDLF NLF

6. Streamlined Calculation of LOF effects

Engineering strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 =𝐿2 ∗cos(α)−𝐿1

𝐿1

Rotated engineering strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 =𝐿2 −𝐿1

𝐿1

Log strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 = 𝑙𝑛𝐿2

𝐿1

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𝐿1 𝐿2

6. Streamlined Calculation of LOF effects

• Time consuming by hands

• Considerable efforts via analysis software

• A tool has been developedo Efficient and accurate

o Gives the same results as analysis software

• Tool features:o Curved and/or skewed bridges

o Common CF types

o Common strain types

o Variation in bridge geometries (section changes, number of spans...)

o Bearing fixities

o 2D grid (fixed end forces) and 3D FEA (initial strains)

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Final Observations• Supports some of the current industry

recommendations

• Understanding of curved and/or skewed

bridge behavior

• Recommendations/guidelines on:o CF framing arrangements

o Detailing methods

o Erection sequence

• First study that provides detailed first-level estimates of fit-up

• Tool for streamline calculation of LOF effects

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Questions?